cargo fmt

Cargo.lock

@@ -493,7 +493,7 @@ checksum = "d71b6127be86fdcfddb610f7182ac57211d4b18a3e9c82eb2d17662f2227ad6a"
 
 [[package]]
 name = "canvas"
-version = "0.6.3"
+version = "0.6.7"
 dependencies = [
  "anyhow",
  "async-trait",
@@ -512,6 +512,7 @@ dependencies = [
  "tracing",
  "tracing-subscriber",
  "unicode-width 0.2.0",
+ "validation-core",
 ]
 
 [[package]]
@@ -585,7 +586,7 @@ dependencies = [
 
 [[package]]
 name = "client"
-version = "0.6.3"
+version = "0.6.7"
 dependencies = [
  "anyhow",
  "async-trait",
@@ -641,7 +642,7 @@ dependencies = [
 
 [[package]]
 name = "common"
-version = "0.6.3"
+version = "0.6.7"
 dependencies = [
  "prost 0.13.5",
  "prost-build 0.14.1",
@@ -3116,7 +3117,7 @@ checksum = "1c107b6f4780854c8b126e228ea8869f4d7b71260f962fefb57b996b8959ba6b"
 
 [[package]]
 name = "search"
-version = "0.6.3"
+version = "0.6.7"
 dependencies = [
  "anyhow",
  "common",
@@ -3215,7 +3216,7 @@ dependencies = [
 
 [[package]]
 name = "server"
-version = "0.6.3"
+version = "0.6.7"
 dependencies = [
  "anyhow",
  "bcrypt",
@@ -3252,7 +3253,9 @@ dependencies = [
  "tonic-reflection",
  "tracing",
  "tracing-subscriber",
+ "unicode-width 0.2.0",
  "uuid",
+ "validation-core",
  "validator",
 ]
 
@@ -4544,6 +4547,16 @@ dependencies = [
  "wasm-bindgen",
 ]
 
+[[package]]
+name = "validation-core"
+version = "0.6.7"
+dependencies = [
+ "regex",
+ "serde",
+ "thiserror 2.0.12",
+ "unicode-width 0.2.0",
+]
+
 [[package]]
 name = "validator"
 version = "0.20.0"

Cargo.toml

@@ -1,11 +1,11 @@
 [workspace]
-members = ["client", "server", "common", "search", "canvas"]
+members = ["client", "server", "common", "search", "canvas", "validation-core"]
 resolver = "2"
 
 [workspace.package]
 # TODO: idk how to do the name, fix later
 # name = "komp_ac"
-version = "0.6.3"
+version = "0.6.7"
 edition = "2021"
 license = "GPL-3.0-or-later"
 authors = ["Filip Priečinský <filippriec@gmail.com>"]
@@ -53,3 +53,4 @@ toml = "0.8.20"
 unicode-width = "0.2.0"
 
 common = { path = "./common" }
+validation-core = { path = "./validation-core" }

common/build.rs

@@ -24,6 +24,14 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
             ".komp_ac.table_validation.PatternRule",
             "#[derive(serde::Serialize, serde::Deserialize)]",
         )
+        .type_attribute(
+            ".komp_ac.table_validation.PatternPosition",
+            "#[derive(serde::Serialize, serde::Deserialize)]",
+        )
+        .type_attribute(
+            ".komp_ac.table_validation.CharacterConstraint",
+            "#[derive(serde::Serialize, serde::Deserialize)]",
+        )
         .type_attribute(
             ".komp_ac.table_validation.PatternRules",
             "#[derive(serde::Serialize, serde::Deserialize)]",
@@ -32,6 +40,14 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
             ".komp_ac.table_validation.CustomFormatter",
             "#[derive(serde::Serialize, serde::Deserialize)]",
         )
+        .type_attribute(
+            ".komp_ac.table_validation.FormatterOption",
+            "#[derive(serde::Serialize, serde::Deserialize)]",
+        )
+        .type_attribute(
+            ".komp_ac.table_validation.AllowedValues",
+            "#[derive(serde::Serialize, serde::Deserialize)]",
+        )
         .type_attribute(
             ".komp_ac.table_validation.UpdateFieldValidationRequest",
             "#[derive(serde::Serialize, serde::Deserialize)]",
@@ -40,11 +56,91 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
             ".komp_ac.table_validation.UpdateFieldValidationResponse",
             "#[derive(serde::Serialize, serde::Deserialize)]",
         )
+        .type_attribute(
+            ".komp_ac.table_validation.ReplaceTableValidationRequest",
+            "#[derive(serde::Serialize, serde::Deserialize)]",
+        )
+        .type_attribute(
+            ".komp_ac.table_validation.ReplaceTableValidationResponse",
+            "#[derive(serde::Serialize, serde::Deserialize)]",
+        )
+        .type_attribute(
+            ".komp_ac.table_validation.ValidationRuleDefinition",
+            "#[derive(serde::Serialize, serde::Deserialize)]",
+        )
+        .type_attribute(
+            ".komp_ac.table_validation.ValidationSetDefinition",
+            "#[derive(serde::Serialize, serde::Deserialize)]",
+        )
+        .type_attribute(
+            ".komp_ac.table_validation.UpsertValidationRuleRequest",
+            "#[derive(serde::Serialize, serde::Deserialize)]",
+        )
+        .type_attribute(
+            ".komp_ac.table_validation.UpsertValidationRuleResponse",
+            "#[derive(serde::Serialize, serde::Deserialize)]",
+        )
+        .type_attribute(
+            ".komp_ac.table_validation.ListValidationRulesRequest",
+            "#[derive(serde::Serialize, serde::Deserialize)]",
+        )
+        .type_attribute(
+            ".komp_ac.table_validation.ListValidationRulesResponse",
+            "#[derive(serde::Serialize, serde::Deserialize)]",
+        )
+        .type_attribute(
+            ".komp_ac.table_validation.DeleteValidationRuleRequest",
+            "#[derive(serde::Serialize, serde::Deserialize)]",
+        )
+        .type_attribute(
+            ".komp_ac.table_validation.DeleteValidationRuleResponse",
+            "#[derive(serde::Serialize, serde::Deserialize)]",
+        )
+        .type_attribute(
+            ".komp_ac.table_validation.UpsertValidationSetRequest",
+            "#[derive(serde::Serialize, serde::Deserialize)]",
+        )
+        .type_attribute(
+            ".komp_ac.table_validation.UpsertValidationSetResponse",
+            "#[derive(serde::Serialize, serde::Deserialize)]",
+        )
+        .type_attribute(
+            ".komp_ac.table_validation.ListValidationSetsRequest",
+            "#[derive(serde::Serialize, serde::Deserialize)]",
+        )
+        .type_attribute(
+            ".komp_ac.table_validation.ListValidationSetsResponse",
+            "#[derive(serde::Serialize, serde::Deserialize)]",
+        )
+        .type_attribute(
+            ".komp_ac.table_validation.DeleteValidationSetRequest",
+            "#[derive(serde::Serialize, serde::Deserialize)]",
+        )
+        .type_attribute(
+            ".komp_ac.table_validation.DeleteValidationSetResponse",
+            "#[derive(serde::Serialize, serde::Deserialize)]",
+        )
+        .type_attribute(
+            ".komp_ac.table_validation.ApplyValidationSetRequest",
+            "#[derive(serde::Serialize, serde::Deserialize)]",
+        )
+        .type_attribute(
+            ".komp_ac.table_validation.ApplyValidationSetResponse",
+            "#[derive(serde::Serialize, serde::Deserialize)]",
+        )
         // Enum -> readable strings in JSON ("BYTES", "DISPLAY_WIDTH")
         .type_attribute(
             ".komp_ac.table_validation.CountMode",
             "#[derive(serde::Serialize, serde::Deserialize)] #[serde(rename_all = \"SCREAMING_SNAKE_CASE\")]",
         )
+        .type_attribute(
+            ".komp_ac.table_validation.PatternPositionKind",
+            "#[derive(serde::Serialize, serde::Deserialize)] #[serde(rename_all = \"SCREAMING_SNAKE_CASE\")]",
+        )
+        .type_attribute(
+            ".komp_ac.table_validation.CharacterConstraintKind",
+            "#[derive(serde::Serialize, serde::Deserialize)] #[serde(rename_all = \"SCREAMING_SNAKE_CASE\")]",
+        )
         .type_attribute(
             ".komp_ac.table_definition.ColumnDefinition",
             "#[derive(serde::Serialize, serde::Deserialize)]",
@@ -61,6 +157,18 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
             ".komp_ac.table_definition.TableDefinitionResponse",
             "#[derive(serde::Serialize, serde::Deserialize)]"
         )
+        .type_attribute(
+            ".komp_ac.table_definition.GetColumnAliasRenameHistoryRequest",
+            "#[derive(serde::Serialize, serde::Deserialize)]"
+        )
+        .type_attribute(
+            ".komp_ac.table_definition.ColumnAliasRenameHistoryEntry",
+            "#[derive(serde::Serialize, serde::Deserialize)]"
+        )
+        .type_attribute(
+            ".komp_ac.table_definition.GetColumnAliasRenameHistoryResponse",
+            "#[derive(serde::Serialize, serde::Deserialize)]"
+        )
         .type_attribute(
             ".komp_ac.table_definition.RenameColumnAliasRequest",
             "#[derive(serde::Serialize, serde::Deserialize)]"

common/proto/table_definition.proto

@@ -22,6 +22,9 @@ service TableDefinition {
   // Pure data retrieval - no business logic.
   rpc GetProfileDetails(GetProfileDetailsRequest) returns (GetProfileDetailsResponse);
 
+  // Returns the stored rename history for column aliases in one profile.
+  rpc GetColumnAliasRenameHistory(GetColumnAliasRenameHistoryRequest) returns (GetColumnAliasRenameHistoryResponse);
+
   // Renames a user-visible column alias while keeping the physical column unchanged.
   rpc RenameColumnAlias(RenameColumnAliasRequest) returns (RenameColumnAliasResponse);
 
@@ -138,6 +141,31 @@ message GetProfileDetailsResponse {
   repeated TableDetail tables = 2;
 }
 
+// Request to fetch recorded column alias rename history for one profile.
+message GetColumnAliasRenameHistoryRequest {
+  string profile_name = 1;
+
+  // Optional filter. When omitted, returns all tables in the profile.
+  optional int64 table_definition_id = 2;
+}
+
+// One recorded column alias rename.
+message ColumnAliasRenameHistoryEntry {
+  int64 id = 1;
+  string profile_name = 2;
+  int64 table_definition_id = 3;
+  string table_name = 4;
+  string old_column_name = 5;
+  string new_column_name = 6;
+  string created_at = 7;
+}
+
+// Response with stored column alias rename history rows.
+message GetColumnAliasRenameHistoryResponse {
+  string profile_name = 1;
+  repeated ColumnAliasRenameHistoryEntry entries = 2;
+}
+
 // Describes a table with its columns and associated scripts.
 message TableDetail {
   string name = 1;

common/proto/table_validation.proto

@@ -2,31 +2,55 @@
 syntax = "proto3";
 package komp_ac.table_validation;
 
+// This proto is the canonical server-side storage and distribution contract for
+// client validation configuration.
+//
+// Design goals:
+// - The server stores the entire field validation definition in one structured payload.
+// - Clients fetch the validation rules for a table in one batch and map them to
+//   their local validation/runtime system (for example canvas).
+// - Common validation must be represented as typed data, not as string mini-languages.
+//
+// Important split:
+// - limits / pattern / allowed_values / required are validation rules.
+// - mask / formatter are presentation and input-shaping metadata for clients.
+
 // Request validation rules for a table
 message GetTableValidationRequest {
   string profileName = 1;
   string tableName = 2;
 }
 
-// Response with field-level validations; if a field is omitted,
-// no validation is applied (default unspecified).
+// Response with field-level validations for the whole table.
+// If a field is omitted, no validation configuration exists for that field.
 message TableValidationResponse {
   repeated FieldValidation fields = 1;
 }
 
-// Field-level validation (extensible for future kinds)
+// Field-level validation definition stored on the server and distributed to clients.
 message FieldValidation {
   // MUST match your frontend FormState.dataKey for the column
   string dataKey = 1;
 
-  // Current: only CharacterLimits. More rules can be added later.
+  // Validation 1: length and counting rules.
   CharacterLimits limits = 10;
-  // Future expansion:
-  PatternRules pattern = 11; // Validation 2
-  optional CustomFormatter formatter = 14; // Validation 4 – custom formatting logic
+
+  // Validation 2: position-based character constraints.
+  PatternRules pattern = 11;
+
+  // Exact-value whitelist.
+  AllowedValues allowed_values = 12;
+
+  // Client-side hint that this field participates in external/asynchronous validation UI.
+  bool external_validation_enabled = 13;
+
+  // Client-side formatter metadata. This is intentionally data-only, not executable code.
+  optional CustomFormatter formatter = 14;
+
+  // Client-side display mask metadata. The server stores raw data without mask literals.
   DisplayMask mask = 3;
-  // ExternalValidation external = 13;
-  // CustomFormatter formatter = 14;
+
+  // Field must be provided / treated as required by clients and server enforcement layers.
   bool required = 4;
 }
 
@@ -38,7 +62,8 @@ enum CountMode {
   DISPLAY_WIDTH = 3;
 }
 
-// Character limit validation (Validation 1)
+// Character limit validation (Validation 1).
+// These rules map directly to canvas CharacterLimits.
 message CharacterLimits {
   // When zero, the field is considered "not set". If both min/max are zero,
   // the server should avoid sending this FieldValidation (no validation).
@@ -51,39 +76,91 @@ message CharacterLimits {
   CountMode countMode = 4; // defaults to CHARS if unspecified
 }
 
-// Mask for pretty display
+// Mask for pretty display only.
+//
+// This is not a validation rule by itself. It exists so clients can render and
+// navigate masked input while still storing raw values server-side.
 message DisplayMask {
   string pattern = 1; // e.g., "(###) ###-####" or "####-##-##"
   string input_char = 2; // e.g., "#"
   optional string template_char = 3; // e.g., "_"
 }
 
-// One position‑based validation rule, similar to CharacterFilter + PositionRange
-message PatternRule {
-  // Range descriptor: how far the rule applies
-  // Examples:
-  //  - "0"        → Single position 0
-  //  - "0-3"      → Range 0..3 inclusive
-  //  - "from:5"   → From position 5 onward
-  //  - "0,2,5"    → Multiple discrete positions
-  string range = 1;
-
-  // Character filter type, case‑insensitive keywords:
-  // "ALPHABETIC", "NUMERIC", "ALPHANUMERIC",
-  // "ONEOF(<chars>)", "EXACT(:)", "CUSTOM(<name>)"
-  string filter = 2;
+// Which positions a pattern rule applies to.
+// This exists instead of a string syntax like "0-3" so the server can validate
+// the structure directly and clients do not need to parse a DSL.
+message PatternPosition {
+  PatternPositionKind kind = 1;
+  uint32 single = 2;
+  uint32 start = 3;
+  uint32 end = 4;
+  repeated uint32 positions = 5;
 }
 
+enum PatternPositionKind {
+  PATTERN_POSITION_KIND_UNSPECIFIED = 0;
+  PATTERN_POSITION_SINGLE = 1;
+  PATTERN_POSITION_RANGE = 2;
+  PATTERN_POSITION_FROM = 3;
+  PATTERN_POSITION_MULTIPLE = 4;
+}
+
+// What type of character constraint a pattern rule applies.
+// This mirrors the typed character filters used by canvas.
+message CharacterConstraint {
+  CharacterConstraintKind kind = 1;
+
+  // Used when kind == CHARACTER_CONSTRAINT_EXACT.
+  optional string exact = 2;
+
+  // Used when kind == CHARACTER_CONSTRAINT_ONE_OF.
+  repeated string one_of = 3;
+
+  // Used when kind == CHARACTER_CONSTRAINT_REGEX.
+  optional string regex = 4;
+}
+
+enum CharacterConstraintKind {
+  CHARACTER_CONSTRAINT_KIND_UNSPECIFIED = 0;
+  CHARACTER_CONSTRAINT_ALPHABETIC = 1;
+  CHARACTER_CONSTRAINT_NUMERIC = 2;
+  CHARACTER_CONSTRAINT_ALPHANUMERIC = 3;
+  CHARACTER_CONSTRAINT_EXACT = 4;
+  CHARACTER_CONSTRAINT_ONE_OF = 5;
+  CHARACTER_CONSTRAINT_REGEX = 6;
+}
+
+// One position-based validation rule, similar to canvas PositionFilter.
+message PatternRule {
+  PatternPosition position = 1;
+  CharacterConstraint constraint = 2;
+}
+
+// Client-side formatter metadata.
+// The formatter "type" is intended to be resolved by a client-side formatter registry.
 message CustomFormatter {
   // Formatter type identifier; handled client‑side.
   // Examples: "PSCFormatter", "PhoneFormatter", "CreditCardFormatter", "DateFormatter"
   string type = 1;
 
-  // Optional free‑text note or parameters (e.g. locale, pattern)
-  optional string description = 2;
+  repeated FormatterOption options = 2;
+  optional string description = 3;
 }
 
-// Collection of pattern rules for one field
+message FormatterOption {
+  string key = 1;
+  string value = 2;
+}
+
+// Exact-value whitelist configuration.
+// This maps to canvas AllowedValues semantics.
+message AllowedValues {
+  repeated string values = 1;
+  bool allow_empty = 2;
+  bool case_insensitive = 3;
+}
+
+// Collection of pattern rules for one field.
 message PatternRules {
   // All rules that make up the validation logic
   repeated PatternRule rules = 1;
@@ -92,11 +169,28 @@ message PatternRules {
   optional string description = 2;
 }
 
-// Service to fetch validations for a table
+// Service for storing and fetching field-validation definitions.
 service TableValidationService {
   rpc GetTableValidation(GetTableValidationRequest) returns (TableValidationResponse);
 
+  // Upsert a single field validation definition.
   rpc UpdateFieldValidation(UpdateFieldValidationRequest) returns (UpdateFieldValidationResponse);
+
+  // Replace the full validation definition set for a table in one transaction.
+  rpc ReplaceTableValidation(ReplaceTableValidationRequest) returns (ReplaceTableValidationResponse);
+
+  // Reusable named rule fragments.
+  rpc UpsertValidationRule(UpsertValidationRuleRequest) returns (UpsertValidationRuleResponse);
+  rpc ListValidationRules(ListValidationRulesRequest) returns (ListValidationRulesResponse);
+  rpc DeleteValidationRule(DeleteValidationRuleRequest) returns (DeleteValidationRuleResponse);
+
+  // Reusable named sets composed from rules.
+  rpc UpsertValidationSet(UpsertValidationSetRequest) returns (UpsertValidationSetResponse);
+  rpc ListValidationSets(ListValidationSetsRequest) returns (ListValidationSetsResponse);
+  rpc DeleteValidationSet(DeleteValidationSetRequest) returns (DeleteValidationSetResponse);
+
+  // Snapshot a reusable set onto a concrete table field.
+  rpc ApplyValidationSet(ApplyValidationSetRequest) returns (ApplyValidationSetResponse);
 }
 
 message UpdateFieldValidationRequest {
@@ -110,3 +204,102 @@ message UpdateFieldValidationResponse {
   bool success = 1;
   string message = 2;
 }
+
+message ReplaceTableValidationRequest {
+  string profileName = 1;
+  string tableName = 2;
+
+  // Full replacement set. Fields omitted here are removed from the stored config.
+  repeated FieldValidation fields = 3;
+}
+
+message ReplaceTableValidationResponse {
+  bool success = 1;
+  string message = 2;
+}
+
+message ValidationRuleDefinition {
+  string name = 1;
+  optional string description = 2;
+
+  // Reusable rule fragment. dataKey is ignored by the server for reusable rules.
+  FieldValidation validation = 3;
+}
+
+message ValidationSetDefinition {
+  string name = 1;
+  optional string description = 2;
+  repeated string ruleNames = 3;
+
+  // Server-resolved snapshot of all rules in ruleNames order.
+  FieldValidation resolvedValidation = 4;
+}
+
+message UpsertValidationRuleRequest {
+  string profileName = 1;
+  ValidationRuleDefinition rule = 2;
+}
+
+message UpsertValidationRuleResponse {
+  bool success = 1;
+  string message = 2;
+}
+
+message ListValidationRulesRequest {
+  string profileName = 1;
+}
+
+message ListValidationRulesResponse {
+  repeated ValidationRuleDefinition rules = 1;
+}
+
+message DeleteValidationRuleRequest {
+  string profileName = 1;
+  string name = 2;
+}
+
+message DeleteValidationRuleResponse {
+  bool success = 1;
+  string message = 2;
+}
+
+message UpsertValidationSetRequest {
+  string profileName = 1;
+  ValidationSetDefinition set = 2;
+}
+
+message UpsertValidationSetResponse {
+  bool success = 1;
+  string message = 2;
+}
+
+message ListValidationSetsRequest {
+  string profileName = 1;
+}
+
+message ListValidationSetsResponse {
+  repeated ValidationSetDefinition sets = 1;
+}
+
+message DeleteValidationSetRequest {
+  string profileName = 1;
+  string name = 2;
+}
+
+message DeleteValidationSetResponse {
+  bool success = 1;
+  string message = 2;
+}
+
+message ApplyValidationSetRequest {
+  string profileName = 1;
+  string tableName = 2;
+  string dataKey = 3;
+  string setName = 4;
+}
+
+message ApplyValidationSetResponse {
+  bool success = 1;
+  string message = 2;
+  FieldValidation validation = 3;
+}

common/src/proto/komp_ac.table_definition.rs

@@ -125,6 +125,44 @@ pub struct GetProfileDetailsResponse {
     #[prost(message, repeated, tag = "2")]
     pub tables: ::prost::alloc::vec::Vec<TableDetail>,
 }
+/// Request to fetch recorded column alias rename history for one profile.
+#[derive(serde::Serialize, serde::Deserialize)]
+#[derive(Clone, PartialEq, ::prost::Message)]
+pub struct GetColumnAliasRenameHistoryRequest {
+    #[prost(string, tag = "1")]
+    pub profile_name: ::prost::alloc::string::String,
+    /// Optional filter. When omitted, returns all tables in the profile.
+    #[prost(int64, optional, tag = "2")]
+    pub table_definition_id: ::core::option::Option<i64>,
+}
+/// One recorded column alias rename.
+#[derive(serde::Serialize, serde::Deserialize)]
+#[derive(Clone, PartialEq, ::prost::Message)]
+pub struct ColumnAliasRenameHistoryEntry {
+    #[prost(int64, tag = "1")]
+    pub id: i64,
+    #[prost(string, tag = "2")]
+    pub profile_name: ::prost::alloc::string::String,
+    #[prost(int64, tag = "3")]
+    pub table_definition_id: i64,
+    #[prost(string, tag = "4")]
+    pub table_name: ::prost::alloc::string::String,
+    #[prost(string, tag = "5")]
+    pub old_column_name: ::prost::alloc::string::String,
+    #[prost(string, tag = "6")]
+    pub new_column_name: ::prost::alloc::string::String,
+    #[prost(string, tag = "7")]
+    pub created_at: ::prost::alloc::string::String,
+}
+/// Response with stored column alias rename history rows.
+#[derive(serde::Serialize, serde::Deserialize)]
+#[derive(Clone, PartialEq, ::prost::Message)]
+pub struct GetColumnAliasRenameHistoryResponse {
+    #[prost(string, tag = "1")]
+    pub profile_name: ::prost::alloc::string::String,
+    #[prost(message, repeated, tag = "2")]
+    pub entries: ::prost::alloc::vec::Vec<ColumnAliasRenameHistoryEntry>,
+}
 /// Describes a table with its columns and associated scripts.
 #[derive(Clone, PartialEq, ::prost::Message)]
 pub struct TableDetail {
@@ -383,6 +421,36 @@ pub mod table_definition_client {
                 );
             self.inner.unary(req, path, codec).await
         }
+        /// Returns the stored rename history for column aliases in one profile.
+        pub async fn get_column_alias_rename_history(
+            &mut self,
+            request: impl tonic::IntoRequest<super::GetColumnAliasRenameHistoryRequest>,
+        ) -> std::result::Result<
+            tonic::Response<super::GetColumnAliasRenameHistoryResponse>,
+            tonic::Status,
+        > {
+            self.inner
+                .ready()
+                .await
+                .map_err(|e| {
+                    tonic::Status::unknown(
+                        format!("Service was not ready: {}", e.into()),
+                    )
+                })?;
+            let codec = tonic::codec::ProstCodec::default();
+            let path = http::uri::PathAndQuery::from_static(
+                "/komp_ac.table_definition.TableDefinition/GetColumnAliasRenameHistory",
+            );
+            let mut req = request.into_request();
+            req.extensions_mut()
+                .insert(
+                    GrpcMethod::new(
+                        "komp_ac.table_definition.TableDefinition",
+                        "GetColumnAliasRenameHistory",
+                    ),
+                );
+            self.inner.unary(req, path, codec).await
+        }
         /// Renames a user-visible column alias while keeping the physical column unchanged.
         pub async fn rename_column_alias(
             &mut self,
@@ -486,6 +554,14 @@ pub mod table_definition_server {
             tonic::Response<super::GetProfileDetailsResponse>,
             tonic::Status,
         >;
+        /// Returns the stored rename history for column aliases in one profile.
+        async fn get_column_alias_rename_history(
+            &self,
+            request: tonic::Request<super::GetColumnAliasRenameHistoryRequest>,
+        ) -> std::result::Result<
+            tonic::Response<super::GetColumnAliasRenameHistoryResponse>,
+            tonic::Status,
+        >;
         /// Renames a user-visible column alias while keeping the physical column unchanged.
         async fn rename_column_alias(
             &self,
@@ -724,6 +800,60 @@ pub mod table_definition_server {
                     };
                     Box::pin(fut)
                 }
+                "/komp_ac.table_definition.TableDefinition/GetColumnAliasRenameHistory" => {
+                    #[allow(non_camel_case_types)]
+                    struct GetColumnAliasRenameHistorySvc<T: TableDefinition>(
+                        pub Arc<T>,
+                    );
+                    impl<
+                        T: TableDefinition,
+                    > tonic::server::UnaryService<
+                        super::GetColumnAliasRenameHistoryRequest,
+                    > for GetColumnAliasRenameHistorySvc<T> {
+                        type Response = super::GetColumnAliasRenameHistoryResponse;
+                        type Future = BoxFuture<
+                            tonic::Response<Self::Response>,
+                            tonic::Status,
+                        >;
+                        fn call(
+                            &mut self,
+                            request: tonic::Request<
+                                super::GetColumnAliasRenameHistoryRequest,
+                            >,
+                        ) -> Self::Future {
+                            let inner = Arc::clone(&self.0);
+                            let fut = async move {
+                                <T as TableDefinition>::get_column_alias_rename_history(
+                                        &inner,
+                                        request,
+                                    )
+                                    .await
+                            };
+                            Box::pin(fut)
+                        }
+                    }
+                    let accept_compression_encodings = self.accept_compression_encodings;
+                    let send_compression_encodings = self.send_compression_encodings;
+                    let max_decoding_message_size = self.max_decoding_message_size;
+                    let max_encoding_message_size = self.max_encoding_message_size;
+                    let inner = self.inner.clone();
+                    let fut = async move {
+                        let method = GetColumnAliasRenameHistorySvc(inner);
+                        let codec = tonic::codec::ProstCodec::default();
+                        let mut grpc = tonic::server::Grpc::new(codec)
+                            .apply_compression_config(
+                                accept_compression_encodings,
+                                send_compression_encodings,
+                            )
+                            .apply_max_message_size_config(
+                                max_decoding_message_size,
+                                max_encoding_message_size,
+                            );
+                        let res = grpc.unary(method, req).await;
+                        Ok(res)
+                    };
+                    Box::pin(fut)
+                }
                 "/komp_ac.table_definition.TableDefinition/RenameColumnAlias" => {
                     #[allow(non_camel_case_types)]
                     struct RenameColumnAliasSvc<T: TableDefinition>(pub Arc<T>);

common/src/search.rs

@@ -1,8 +1,8 @@
 use std::path::{Path, PathBuf};
 
 use tantivy::schema::{
-    Field, IndexRecordOption, JsonObjectOptions, Schema, TextFieldIndexing, Term, INDEXED,
-    STORED, STRING,
+    Field, IndexRecordOption, JsonObjectOptions, Schema, Term, TextFieldIndexing, INDEXED, STORED,
+    STRING,
 };
 use tantivy::tokenizer::{
     AsciiFoldingFilter, LowerCaser, NgramTokenizer, RawTokenizer, RemoveLongFilter,
@@ -67,11 +67,7 @@ pub fn create_search_schema() -> Schema {
     schema_builder.build()
 }
 
-fn json_options(
-    tokenizer_name: &str,
-    with_positions: bool,
-    stored: bool,
-) -> JsonObjectOptions {
+fn json_options(tokenizer_name: &str, with_positions: bool, stored: bool) -> JsonObjectOptions {
     let index_option = if with_positions {
         IndexRecordOption::WithFreqsAndPositions
     } else {

search/src/lib.rs

@@ -5,8 +5,8 @@ use std::path::Path;
 use std::sync::{Arc, Mutex};
 
 use common::proto::komp_ac::search::searcher_server::Searcher;
-use common::proto::komp_ac::search::{search_response::Hit, SearchRequest, SearchResponse};
 pub use common::proto::komp_ac::search::searcher_server::SearcherServer;
+use common::proto::komp_ac::search::{search_response::Hit, SearchRequest, SearchResponse};
 use common::search::{register_tokenizers, search_index_path, SchemaFields};
 use query_builder::{build_master_query, ConstraintMode, SearchConstraint};
 use sqlx::{PgPool, Row};
@@ -34,7 +34,10 @@ impl SearcherService {
         }
     }
 
-    async fn run_rpc(&self, request: Request<SearchRequest>) -> Result<Response<SearchResponse>, Status> {
+    async fn run_rpc(
+        &self,
+        request: Request<SearchRequest>,
+    ) -> Result<Response<SearchResponse>, Status> {
         let req = request.into_inner();
         let normalized = normalize_request(req)?;
 
@@ -276,7 +279,9 @@ fn normalize_request(req: SearchRequest) -> Result<NormalizedSearchRequest, Stat
         });
     }
 
-    let limit = req.limit.map(|value| (value as usize).min(HARD_RESULT_LIMIT));
+    let limit = req
+        .limit
+        .map(|value| (value as usize).min(HARD_RESULT_LIMIT));
 
     Ok(NormalizedSearchRequest {
         profile_name: profile_name.to_string(),
@@ -335,8 +340,13 @@ async fn run_search(
     must: &[SearchConstraint],
     limit: usize,
 ) -> Result<Vec<Hit>, Status> {
-    let master_query =
-        build_master_query(&profile.index, &profile.fields, free_query, must, table_filter)?;
+    let master_query = build_master_query(
+        &profile.index,
+        &profile.fields,
+        free_query,
+        must,
+        table_filter,
+    )?;
 
     let searcher = profile.reader.searcher();
     let top_docs = searcher

search/src/query_builder.rs

@@ -34,7 +34,9 @@ pub fn build_master_query(
 
     for constraint in must {
         let predicate = match constraint.mode {
-            ConstraintMode::Exact => exact_predicate(fields, &constraint.column, &constraint.query)?,
+            ConstraintMode::Exact => {
+                exact_predicate(fields, &constraint.column, &constraint.query)?
+            }
             ConstraintMode::Fuzzy => {
                 fuzzy_predicate_scoped(fields, &constraint.column, &constraint.query)?
             }
@@ -157,7 +159,10 @@ fn fuzzy_predicate_scoped(
             .collect();
         layers.push((
             Occur::Should,
-            Box::new(BoostQuery::new(Box::new(BooleanQuery::new(ngram_clauses)), 1.0)),
+            Box::new(BoostQuery::new(
+                Box::new(BooleanQuery::new(ngram_clauses)),
+                1.0,
+            )),
         ));
     }
 

validation-core/Cargo.toml

@@ -0,0 +1,18 @@
+[package]
+name = "validation-core"
+version.workspace = true
+edition.workspace = true
+license.workspace = true
+authors.workspace = true
+description = "Shared validation primitives, rules, and sets."
+repository.workspace = true
+
+[dependencies]
+serde = { workspace = true }
+thiserror = { workspace = true }
+unicode-width = { workspace = true }
+regex = { workspace = true, optional = true }
+
+[features]
+default = []
+regex = ["dep:regex"]

validation-core/docs/validation_architecture.md

@@ -0,0 +1,493 @@
+# Validation
+
+This document is the frontend guide for the validation system.
+
+The important idea: reusable validation is built from **rules** and **sets**.
+The frontend creates and manages those. When a set is applied to a table field,
+the server resolves it into the existing `FieldValidation` shape, and the form
+runtime continues to work through the normal table-validation flow.
+
+## Ownership
+
+```mermaid
+flowchart LR
+    Core[validation-core<br/>validation meaning<br/>rule/set merge rules]
+    Server[server<br/>stores rules/sets<br/>applies sets<br/>enforces writes]
+    Common[common/proto<br/>gRPC contract]
+    Client[client/frontend<br/>rule/set UI<br/>calls gRPC]
+    Canvas[canvas<br/>field editing<br/>mask display<br/>local feedback]
+
+    Server --> Core
+    Canvas --> Core
+    Client --> Common
+    Server --> Common
+    Client --> Canvas
+```
+
+`server` stores simple serializable settings. `validation-core` owns how those
+settings combine. `canvas` uses resolved field validation to guide editing.
+
+## Terms
+
+| Term | Meaning |
+| --- | --- |
+| `FieldValidation` | Existing per-column validation config from `common/proto/table_validation.proto`. This is what forms/canvas already consume. |
+| `ValidationRule` | One named reusable fragment, for example `digits-only`, `phone-length`, or `required`. Stored by the server as a `FieldValidation` fragment with no meaningful `dataKey`. |
+| `ValidationSet` | Ordered collection of rule names, for example `phone = [required, phone-length, digits-only, phone-mask]`. |
+| Applied validation | A resolved snapshot of a set written to `table_validation_rules` for a concrete `(table, dataKey)`. |
+| Snapshot | Applying a set copies the resolved config to a field. Later edits to the set do not automatically update fields that were already applied. |
+
+## What Backend Enforces
+
+Backend write validation enforces only server-relevant parts:
+
+| FieldValidation part | Backend | Canvas/frontend |
+| --- | --- | --- |
+| `required` | Yes | Yes |
+| `limits` | Yes | Yes |
+| `pattern` | Yes | Yes |
+| `allowed_values` | Yes | Yes |
+| `mask` | Partly: raw value length/literals | Yes: display/editing mask |
+| `formatter` | No | Yes |
+| `external_validation_enabled` | No | Yes/UI hint |
+
+`mask` is visual metadata, but the backend still uses it to reject incorrectly
+submitted raw values. Example: if the mask is `(###) ###-####`, the backend
+expects the stored value to be raw digits, not `(123) 456-7890`.
+
+## Main User Flow
+
+```mermaid
+sequenceDiagram
+    participant UI as Frontend UI
+    participant API as TableValidationService
+    participant DB as Server DB
+    participant Form as Existing Form Runtime
+
+    UI->>API: UpsertValidationRule(required)
+    UI->>API: UpsertValidationRule(digits-only)
+    UI->>API: UpsertValidationRule(phone-length)
+    UI->>API: UpsertValidationSet(phone: [required, phone-length, digits-only])
+    UI->>API: ApplyValidationSet(profile, table, dataKey, phone)
+    API->>DB: write resolved FieldValidation snapshot
+    Form->>API: GetTableValidation(profile, table)
+    API->>Form: resolved FieldValidation for dataKey
+```
+
+After `ApplyValidationSet`, the existing form code does not need to know that a
+set was used. It receives normal `FieldValidation`.
+
+## API
+
+All APIs live on `TableValidationService`.
+
+### Rules
+
+Create or update one reusable rule:
+
+```text
+UpsertValidationRule(UpsertValidationRuleRequest)
+```
+
+Request shape:
+
+```text
+profileName: string
+rule:
+  name: string
+  description: optional string
+  validation: FieldValidation
+```
+
+Frontend rules:
+
+- `rule.name` is required and unique inside a profile.
+- `rule.validation.dataKey` is ignored by the server.
+- A rule should usually configure one logical fragment.
+- Examples: `required`, `phone-length`, `digits-only`, `phone-mask`.
+
+List rules:
+
+```text
+ListValidationRules({ profileName })
+```
+
+Delete rule:
+
+```text
+DeleteValidationRule({ profileName, name })
+```
+
+Deleting a rule removes it from future reusable composition. Already applied
+field snapshots are not changed.
+
+### Sets
+
+Create or update one reusable set:
+
+```text
+UpsertValidationSet(UpsertValidationSetRequest)
+```
+
+Request shape:
+
+```text
+profileName: string
+set:
+  name: string
+  description: optional string
+  ruleNames: repeated string
+```
+
+Frontend rules:
+
+- `set.name` is required and unique inside a profile.
+- `ruleNames` must contain at least one rule.
+- `ruleNames` are ordered.
+- Every rule name must already exist.
+- Duplicate rule names in the same set are rejected.
+- Conflicting singleton fragments are rejected.
+
+Singleton fragments are:
+
+```text
+limits
+allowed_values
+mask
+formatter
+```
+
+That means a set cannot currently contain two rules that both define `limits`.
+Pattern rules are additive: multiple rules with `pattern` are merged into one
+combined pattern.
+
+List sets:
+
+```text
+ListValidationSets({ profileName })
+```
+
+Response includes each set plus `resolvedValidation`, so the frontend can show
+what the set expands to.
+
+Delete set:
+
+```text
+DeleteValidationSet({ profileName, name })
+```
+
+Deleting a set does not change already applied fields.
+
+### Apply Set To Field
+
+Apply a reusable set to one field:
+
+```text
+ApplyValidationSet(ApplyValidationSetRequest)
+```
+
+Request shape:
+
+```text
+profileName: string
+tableName: string
+dataKey: string
+setName: string
+```
+
+Server behavior:
+
+1. Loads the set.
+2. Loads its ordered rules.
+3. Resolves/merges them through `validation-core`.
+4. Validates that `dataKey` exists in the table definition.
+5. Writes the resolved config into existing `table_validation_rules`.
+
+This is a snapshot. If the user later edits the `phone` set, fields that already
+used `phone` keep their old resolved config until the set is applied again.
+
+## FieldValidation Guide
+
+Rules and direct field validation both use `FieldValidation`.
+
+### Required
+
+```text
+required: true
+```
+
+Backend rejects missing or empty values.
+
+### Limits
+
+```text
+limits:
+  min: 10
+  max: 10
+  warnAt: optional
+  countMode: CHARS | BYTES | DISPLAY_WIDTH
+```
+
+Backend enforces `min` and `max`. `warnAt` is mainly UI feedback.
+
+### Pattern
+
+Pattern rules validate characters at positions.
+
+Example digits-only:
+
+```text
+pattern:
+  rules:
+    - position:
+        kind: PATTERN_POSITION_FROM
+        start: 0
+      constraint:
+        kind: CHARACTER_CONSTRAINT_NUMERIC
+```
+
+Useful constraints:
+
+```text
+CHARACTER_CONSTRAINT_ALPHABETIC
+CHARACTER_CONSTRAINT_NUMERIC
+CHARACTER_CONSTRAINT_ALPHANUMERIC
+CHARACTER_CONSTRAINT_EXACT
+CHARACTER_CONSTRAINT_ONE_OF
+CHARACTER_CONSTRAINT_REGEX
+```
+
+Pattern fragments from multiple rules are merged.
+
+### Allowed Values
+
+```text
+allowed_values:
+  values: ["open", "closed"]
+  allow_empty: false
+  case_insensitive: true
+```
+
+Backend rejects values not in the list.
+
+### Mask
+
+```text
+mask:
+  pattern: "(###) ###-####"
+  input_char: "#"
+  template_char: "_"
+```
+
+Canvas uses this for display/editing. Backend expects raw values without mask
+literals.
+
+### Formatter
+
+```text
+formatter:
+  type: "PhoneFormatter"
+  options: []
+  description: optional
+```
+
+Formatter is resolved client-side. Backend stores it but does not execute it.
+
+### External Validation
+
+```text
+external_validation_enabled: true
+```
+
+This is a frontend/UI hint. Backend stores it but does not perform external
+validation.
+
+## Recommended Frontend Screens
+
+### Rule List
+
+Show all rules for a profile.
+
+Actions:
+
+```text
+create rule
+edit rule
+delete rule
+preview rule config
+```
+
+### Rule Editor
+
+Build a `ValidationRuleDefinition`.
+
+Recommended UI:
+
+```text
+name
+description
+required toggle
+limits section
+pattern section
+allowed values section
+mask section
+formatter section
+external validation toggle
+```
+
+For v1, encourage one fragment per rule. Example: create `phone-length` and
+`digits-only` separately, instead of one huge rule.
+
+### Set List
+
+Show all sets for a profile.
+
+Use `ListValidationSets`, because it returns `resolvedValidation`.
+
+Actions:
+
+```text
+create set
+edit set
+delete set
+preview resolved validation
+```
+
+### Set Editor
+
+Build a `ValidationSetDefinition`.
+
+Recommended UI:
+
+```text
+name
+description
+ordered rule picker
+resolved preview
+```
+
+When rule ordering changes, call `UpsertValidationSet` and then refresh
+`ListValidationSets`.
+
+### Apply Set
+
+On the table/field validation screen, add:
+
+```text
+Apply validation set
+```
+
+Flow:
+
+1. Load sets with `ListValidationSets`.
+2. User selects a set.
+3. Call `ApplyValidationSet(profileName, tableName, dataKey, setName)`.
+4. Refresh `GetTableValidation(profileName, tableName)`.
+
+The field should now behave exactly like a directly configured field validation.
+
+## Example: Phone
+
+Create rule `required`:
+
+```text
+validation:
+  required: true
+```
+
+Create rule `phone-length`:
+
+```text
+validation:
+  limits:
+    min: 10
+    max: 10
+    countMode: CHARS
+```
+
+Create rule `digits-only`:
+
+```text
+validation:
+  pattern:
+    rules:
+      - position:
+          kind: PATTERN_POSITION_FROM
+          start: 0
+        constraint:
+          kind: CHARACTER_CONSTRAINT_NUMERIC
+```
+
+Create rule `phone-mask`:
+
+```text
+validation:
+  mask:
+    pattern: "(###) ###-####"
+    input_char: "#"
+```
+
+Create set `phone`:
+
+```text
+ruleNames:
+  - required
+  - phone-length
+  - digits-only
+  - phone-mask
+```
+
+Apply set:
+
+```text
+profileName: "default"
+tableName: "customers"
+dataKey: "customer_phone"
+setName: "phone"
+```
+
+Then refresh:
+
+```text
+GetTableValidation(default, customers)
+```
+
+The response contains a normal `FieldValidation` for `customer_phone`.
+
+## Important UX Notes
+
+- Applying a set is not a live link.
+- Editing a rule or set does not mutate fields where it was already applied.
+- To update a field after set changes, apply the set again.
+- If a set has conflicting singleton rules, the server rejects it.
+- For now, the system does not store field metadata like `sourceSetName` on
+  applied fields. The field only stores the resolved validation snapshot.
+
+## Files
+
+Core model:
+
+```text
+validation-core/src/set.rs
+validation-core/src/config.rs
+```
+
+Wire contract:
+
+```text
+common/proto/table_validation.proto
+```
+
+Server implementation:
+
+```text
+server/src/table_validation/get/service.rs
+server/src/table_validation/post/repo.rs
+server/src/table_validation/config.rs
+```
+
+Storage:
+
+```text
+server/migrations/20260506170000_create_validation_rules_and_sets.sql
+```

validation-core/src/config.rs

@@ -0,0 +1,311 @@
+use crate::rules::{
+    CharacterFilter, CharacterLimits, DisplayMask, PatternFilters, PositionFilter, PositionRange,
+};
+use serde::{Deserialize, Serialize};
+use std::sync::Arc;
+use thiserror::Error;
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct AllowedValues {
+    pub values: Vec<String>,
+    pub allow_empty: bool,
+    pub case_insensitive: bool,
+}
+
+impl AllowedValues {
+    pub fn new(values: Vec<String>) -> Self {
+        Self {
+            values,
+            allow_empty: true,
+            case_insensitive: false,
+        }
+    }
+
+    pub fn allow_empty(mut self, allow_empty: bool) -> Self {
+        self.allow_empty = allow_empty;
+        self
+    }
+
+    pub fn case_insensitive(mut self, case_insensitive: bool) -> Self {
+        self.case_insensitive = case_insensitive;
+        self
+    }
+
+    pub fn matches(&self, text: &str) -> bool {
+        if self.case_insensitive {
+            self.values
+                .iter()
+                .any(|allowed| allowed.eq_ignore_ascii_case(text))
+        } else {
+            self.values.iter().any(|allowed| allowed == text)
+        }
+    }
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct FormatterSettings {
+    pub formatter_type: String,
+    pub options: Vec<FormatterOption>,
+    pub description: Option<String>,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct FormatterOption {
+    pub key: String,
+    pub value: String,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub enum CharacterFilterSettings {
+    Alphabetic,
+    Numeric,
+    Alphanumeric,
+    Exact(char),
+    OneOf(Vec<char>),
+    Regex(String),
+}
+
+impl CharacterFilterSettings {
+    pub fn resolve(&self) -> CharacterFilter {
+        match self {
+            Self::Alphabetic => CharacterFilter::Alphabetic,
+            Self::Numeric => CharacterFilter::Numeric,
+            Self::Alphanumeric => CharacterFilter::Alphanumeric,
+            Self::Exact(ch) => CharacterFilter::Exact(*ch),
+            Self::OneOf(chars) => CharacterFilter::OneOf(chars.clone()),
+            Self::Regex(pattern) => {
+                #[cfg(feature = "regex")]
+                {
+                    match regex::Regex::new(pattern) {
+                        Ok(regex) => CharacterFilter::Custom(Arc::new(move |ch| {
+                            regex.is_match(&ch.to_string())
+                        })),
+                        Err(_) => CharacterFilter::Custom(Arc::new(|_| false)),
+                    }
+                }
+                #[cfg(not(feature = "regex"))]
+                {
+                    let _ = pattern;
+                    CharacterFilter::Custom(Arc::new(|_| false))
+                }
+            }
+        }
+    }
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct PositionFilterSettings {
+    pub positions: PositionRange,
+    pub filter: CharacterFilterSettings,
+}
+
+impl PositionFilterSettings {
+    pub fn resolve(&self) -> PositionFilter {
+        PositionFilter::new(self.positions.clone(), self.filter.resolve())
+    }
+}
+
+#[derive(Debug, Clone, Default, Serialize, Deserialize)]
+pub struct PatternSettings {
+    pub filters: Vec<PositionFilterSettings>,
+    pub description: Option<String>,
+}
+
+impl PatternSettings {
+    pub fn resolve(&self) -> PatternFilters {
+        PatternFilters::new().add_filters(
+            self.filters
+                .iter()
+                .map(PositionFilterSettings::resolve)
+                .collect(),
+        )
+    }
+}
+
+#[derive(Debug, Clone, Default, Serialize, Deserialize)]
+pub struct ValidationSettings {
+    pub required: bool,
+    pub character_limits: Option<CharacterLimits>,
+    pub pattern: Option<PatternSettings>,
+    pub allowed_values: Option<AllowedValues>,
+    pub display_mask: Option<DisplayMask>,
+    pub formatter: Option<FormatterSettings>,
+    pub external_validation_enabled: bool,
+}
+
+impl ValidationSettings {
+    pub fn resolve(&self) -> ValidationConfig {
+        ValidationConfig {
+            required: self.required,
+            character_limits: self.character_limits.clone(),
+            pattern_filters: self.pattern.as_ref().map(PatternSettings::resolve),
+            allowed_values: self.allowed_values.clone(),
+            display_mask: self.display_mask.clone(),
+            formatter: self.formatter.clone(),
+            external_validation_enabled: self.external_validation_enabled,
+        }
+    }
+
+    pub fn merge_rules<'a>(
+        rules: impl IntoIterator<Item = &'a ValidationSettings>,
+    ) -> Result<Self, ValidationMergeError> {
+        let mut merged = ValidationSettings::default();
+
+        for rule in rules {
+            merged.merge_rule(rule)?;
+        }
+
+        Ok(merged)
+    }
+
+    pub fn merge_rule(&mut self, rule: &ValidationSettings) -> Result<(), ValidationMergeError> {
+        self.required |= rule.required;
+        self.external_validation_enabled |= rule.external_validation_enabled;
+
+        merge_singleton(
+            "character_limits",
+            &mut self.character_limits,
+            &rule.character_limits,
+        )?;
+        merge_singleton(
+            "allowed_values",
+            &mut self.allowed_values,
+            &rule.allowed_values,
+        )?;
+        merge_singleton("display_mask", &mut self.display_mask, &rule.display_mask)?;
+        merge_singleton("formatter", &mut self.formatter, &rule.formatter)?;
+
+        if let Some(pattern) = &rule.pattern {
+            match &mut self.pattern {
+                Some(existing) => {
+                    existing.filters.extend(pattern.filters.clone());
+                    if existing.description.is_none() {
+                        existing.description = pattern.description.clone();
+                    }
+                }
+                None => self.pattern = Some(pattern.clone()),
+            }
+        }
+
+        Ok(())
+    }
+}
+
+fn merge_singleton<T: Clone>(
+    field_name: &'static str,
+    target: &mut Option<T>,
+    source: &Option<T>,
+) -> Result<(), ValidationMergeError> {
+    if let Some(source) = source {
+        if target.is_some() {
+            return Err(ValidationMergeError::DuplicateSingleton { field_name });
+        }
+
+        *target = Some(source.clone());
+    }
+
+    Ok(())
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Error)]
+pub enum ValidationMergeError {
+    #[error("validation set contains more than one rule configuring {field_name}")]
+    DuplicateSingleton { field_name: &'static str },
+}
+
+#[derive(Debug, Clone, Default)]
+pub struct ValidationConfig {
+    pub required: bool,
+    pub character_limits: Option<CharacterLimits>,
+    pub pattern_filters: Option<PatternFilters>,
+    pub allowed_values: Option<AllowedValues>,
+    pub display_mask: Option<DisplayMask>,
+    pub formatter: Option<FormatterSettings>,
+    pub external_validation_enabled: bool,
+}
+
+impl ValidationConfig {
+    pub fn validate_content(&self, text: &str) -> ValidationResult {
+        if text.is_empty() {
+            if self.required {
+                return ValidationResult::error("Value required");
+            }
+
+            if let Some(allowed_values) = &self.allowed_values {
+                if !allowed_values.allow_empty {
+                    return ValidationResult::error("Empty value is not allowed");
+                }
+            }
+
+            return ValidationResult::Valid;
+        }
+
+        if let Some(limits) = &self.character_limits {
+            if let Some(result) = limits.validate_content(text) {
+                if !result.is_acceptable() {
+                    return result;
+                }
+            }
+        }
+
+        if let Some(pattern_filters) = &self.pattern_filters {
+            if let Err(message) = pattern_filters.validate_text(text) {
+                return ValidationResult::error(message);
+            }
+        }
+
+        if let Some(allowed_values) = &self.allowed_values {
+            if !allowed_values.matches(text) {
+                return ValidationResult::error("Value must be one of the allowed options");
+            }
+        }
+
+        ValidationResult::Valid
+    }
+
+    pub fn has_validation(&self) -> bool {
+        self.required
+            || self.character_limits.is_some()
+            || self.pattern_filters.is_some()
+            || self.allowed_values.is_some()
+            || self.display_mask.is_some()
+            || self.formatter.is_some()
+            || self.external_validation_enabled
+    }
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum ValidationResult {
+    Valid,
+    Warning { message: String },
+    Error { message: String },
+}
+
+impl ValidationResult {
+    pub fn is_acceptable(&self) -> bool {
+        matches!(self, Self::Valid | Self::Warning { .. })
+    }
+
+    pub fn is_error(&self) -> bool {
+        matches!(self, Self::Error { .. })
+    }
+
+    pub fn message(&self) -> Option<&str> {
+        match self {
+            Self::Valid => None,
+            Self::Warning { message } | Self::Error { message } => Some(message),
+        }
+    }
+
+    pub fn warning(message: impl Into<String>) -> Self {
+        Self::Warning {
+            message: message.into(),
+        }
+    }
+
+    pub fn error(message: impl Into<String>) -> Self {
+        Self::Error {
+            message: message.into(),
+        }
+    }
+}

validation-core/src/lib.rs

@@ -0,0 +1,14 @@
+pub mod config;
+pub mod rules;
+pub mod set;
+
+pub use config::{
+    AllowedValues, CharacterFilterSettings, FormatterOption, FormatterSettings, PatternSettings,
+    PositionFilterSettings, ValidationConfig, ValidationMergeError, ValidationResult,
+    ValidationSettings,
+};
+pub use rules::{
+    count_text, CharacterFilter, CharacterLimits, CountMode, DisplayMask, LimitCheckResult,
+    MaskDisplayMode, PatternFilters, PositionFilter, PositionRange,
+};
+pub use set::{AppliedValidation, ValidationRule, ValidationSet};

validation-core/src/rules/character_limits.rs

@@ -0,0 +1,452 @@
+// src/validation/limits.rs
+//! Character limits validation implementation
+
+use crate::ValidationResult;
+use serde::{Deserialize, Serialize};
+use unicode_width::UnicodeWidthStr;
+
+/// Character limits configuration for a field
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct CharacterLimits {
+    /// Maximum number of characters allowed (None = unlimited)
+    max_length: Option<usize>,
+
+    /// Minimum number of characters required (None = no minimum)
+    min_length: Option<usize>,
+
+    /// Warning threshold (warn when approaching max limit)
+    warning_threshold: Option<usize>,
+
+    /// Count mode: characters vs display width
+    count_mode: CountMode,
+}
+
+/// How to count characters for limit checking
+#[derive(Debug, Clone, Copy, Serialize, Deserialize, Default)]
+pub enum CountMode {
+    /// Count actual characters (default)
+    #[default]
+    Characters,
+
+    /// Count display width (useful for CJK characters)
+    DisplayWidth,
+
+    /// Count bytes (rarely used, but available)
+    Bytes,
+}
+
+/// Result of a character limit check
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum LimitCheckResult {
+    /// Within limits
+    Ok,
+
+    /// Approaching limit (warning)
+    Warning { current: usize, max: usize },
+
+    /// At or exceeding limit (error)
+    Exceeded { current: usize, max: usize },
+
+    /// Below minimum length
+    TooShort { current: usize, min: usize },
+}
+
+impl CharacterLimits {
+    /// Create new character limits with just max length
+    pub fn new(max_length: usize) -> Self {
+        Self {
+            max_length: Some(max_length),
+            min_length: None,
+            warning_threshold: None,
+            count_mode: CountMode::default(),
+        }
+    }
+
+    /// Create new character limits with min and max
+    pub fn new_range(min_length: usize, max_length: usize) -> Self {
+        Self {
+            max_length: Some(max_length),
+            min_length: Some(min_length),
+            warning_threshold: None,
+            count_mode: CountMode::default(),
+        }
+    }
+
+    /// Create new character limits with just minimum length
+    pub fn new_min(min_length: usize) -> Self {
+        Self {
+            max_length: None,
+            min_length: Some(min_length),
+            warning_threshold: None,
+            count_mode: CountMode::default(),
+        }
+    }
+
+    /// Create new character limits with only a warning threshold.
+    pub fn new_warning(threshold: usize) -> Self {
+        Self {
+            max_length: None,
+            min_length: None,
+            warning_threshold: Some(threshold),
+            count_mode: CountMode::default(),
+        }
+    }
+
+    /// Set warning threshold (when to show warning before hitting limit)
+    pub fn with_warning_threshold(mut self, threshold: usize) -> Self {
+        self.warning_threshold = Some(threshold);
+        self
+    }
+
+    /// Set count mode (characters vs display width vs bytes)
+    pub fn with_count_mode(mut self, mode: CountMode) -> Self {
+        self.count_mode = mode;
+        self
+    }
+
+    /// Get maximum length
+    pub fn max_length(&self) -> Option<usize> {
+        self.max_length
+    }
+
+    /// Get minimum length
+    pub fn min_length(&self) -> Option<usize> {
+        self.min_length
+    }
+
+    /// Get warning threshold
+    pub fn warning_threshold(&self) -> Option<usize> {
+        self.warning_threshold
+    }
+
+    /// Get count mode
+    pub fn count_mode(&self) -> CountMode {
+        self.count_mode
+    }
+
+    /// Count characters/width/bytes according to the configured mode
+    fn count(&self, text: &str) -> usize {
+        match self.count_mode {
+            CountMode::Characters => text.chars().count(),
+            CountMode::DisplayWidth => text.width(),
+            CountMode::Bytes => text.len(),
+        }
+    }
+
+    /// Check if inserting a character would exceed limits
+    pub fn validate_insertion(
+        &self,
+        current_text: &str,
+        position: usize,
+        character: char,
+    ) -> Option<ValidationResult> {
+        let mut new_text = String::with_capacity(current_text.len() + character.len_utf8());
+        let mut chars = current_text.chars();
+
+        let clamped_pos = position.min(current_text.chars().count());
+        for _ in 0..clamped_pos {
+            if let Some(ch) = chars.next() {
+                new_text.push(ch);
+            }
+        }
+
+        new_text.push(character);
+
+        for ch in chars {
+            new_text.push(ch);
+        }
+
+        let new_count = self.count(&new_text);
+        let current_count = self.count(current_text);
+
+        if let Some(max) = self.max_length {
+            if new_count > max {
+                return Some(ValidationResult::error(format!(
+                    "Character limit exceeded: {new_count}/{max}"
+                )));
+            }
+
+            if let Some(warning_threshold) = self.warning_threshold {
+                if new_count >= warning_threshold && current_count < warning_threshold {
+                    return Some(ValidationResult::warning(format!(
+                        "Approaching character limit: {new_count}/{max}"
+                    )));
+                }
+            }
+        }
+
+        None // No validation issues
+    }
+
+    /// Validate the current content
+    pub fn validate_content(&self, text: &str) -> Option<ValidationResult> {
+        let count = self.count(text);
+
+        if let Some(min) = self.min_length {
+            if count < min {
+                return Some(ValidationResult::warning(format!(
+                    "Minimum length not met: {count}/{min}"
+                )));
+            }
+        }
+
+        if let Some(max) = self.max_length {
+            if count > max {
+                return Some(ValidationResult::error(format!(
+                    "Character limit exceeded: {count}/{max}"
+                )));
+            }
+
+            if let Some(warning_threshold) = self.warning_threshold {
+                if count >= warning_threshold {
+                    return Some(ValidationResult::warning(format!(
+                        "Approaching character limit: {count}/{max}"
+                    )));
+                }
+            }
+        }
+
+        None // No validation issues
+    }
+
+    /// Get the current status of the text against limits
+    pub fn check_limits(&self, text: &str) -> LimitCheckResult {
+        let count = self.count(text);
+
+        if let Some(max) = self.max_length {
+            if count > max {
+                return LimitCheckResult::Exceeded {
+                    current: count,
+                    max,
+                };
+            }
+
+            if let Some(warning_threshold) = self.warning_threshold {
+                if count >= warning_threshold {
+                    return LimitCheckResult::Warning {
+                        current: count,
+                        max,
+                    };
+                }
+            }
+        }
+
+        // Check min length
+        if let Some(min) = self.min_length {
+            if count < min {
+                return LimitCheckResult::TooShort {
+                    current: count,
+                    min,
+                };
+            }
+        }
+
+        LimitCheckResult::Ok
+    }
+
+    /// Get a human-readable status string
+    pub fn status_text(&self, text: &str) -> Option<String> {
+        match self.check_limits(text) {
+            LimitCheckResult::Ok => {
+                // Show current/max if we have a max limit
+                self.max_length
+                    .map(|max| format!("{}/{}", self.count(text), max))
+            }
+            LimitCheckResult::Warning { current, max } => {
+                Some(format!("{current}/{max} (approaching limit)"))
+            }
+            LimitCheckResult::Exceeded { current, max } => {
+                Some(format!("{current}/{max} (exceeded)"))
+            }
+            LimitCheckResult::TooShort { current, min } => Some(format!("{current}/{min} minimum")),
+        }
+    }
+    pub fn allows_field_switch(&self, text: &str) -> bool {
+        if let Some(min) = self.min_length {
+            let count = self.count(text);
+            // Allow switching if field is empty OR meets minimum requirement
+            count == 0 || count >= min
+        } else {
+            true // No minimum requirement, always allow switching
+        }
+    }
+
+    /// Get reason why field switching is not allowed (if any)
+    pub fn field_switch_block_reason(&self, text: &str) -> Option<String> {
+        if let Some(min) = self.min_length {
+            let count = self.count(text);
+            if count > 0 && count < min {
+                return Some(format!(
+                    "Field must be empty or have at least {min} characters (currently: {count})"
+                ));
+            }
+        }
+        None
+    }
+}
+
+pub fn count_text(text: &str, mode: CountMode) -> usize {
+    match mode {
+        CountMode::Characters => text.chars().count(),
+        CountMode::DisplayWidth => text.width(),
+        CountMode::Bytes => text.len(),
+    }
+}
+
+impl Default for CharacterLimits {
+    fn default() -> Self {
+        Self {
+            max_length: Some(30), // Default 30 character limit as specified
+            min_length: None,
+            warning_threshold: None,
+            count_mode: CountMode::default(),
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_character_limits_creation() {
+        let limits = CharacterLimits::new(10);
+        assert_eq!(limits.max_length(), Some(10));
+        assert_eq!(limits.min_length(), None);
+
+        let range_limits = CharacterLimits::new_range(5, 15);
+        assert_eq!(range_limits.min_length(), Some(5));
+        assert_eq!(range_limits.max_length(), Some(15));
+    }
+
+    #[test]
+    fn test_default_limits() {
+        let limits = CharacterLimits::default();
+        assert_eq!(limits.max_length(), Some(30));
+    }
+
+    #[test]
+    fn test_character_counting() {
+        let limits = CharacterLimits::new(5);
+
+        // Test character mode (default)
+        assert_eq!(limits.count("hello"), 5);
+        assert_eq!(limits.count("héllo"), 5); // Accented character counts as 1
+
+        // Test display width mode
+        let limits = limits.with_count_mode(CountMode::DisplayWidth);
+        assert_eq!(limits.count("hello"), 5);
+
+        // Test bytes mode
+        let limits = limits.with_count_mode(CountMode::Bytes);
+        assert_eq!(limits.count("hello"), 5);
+        assert_eq!(limits.count("héllo"), 6); // é takes 2 bytes in UTF-8
+    }
+
+    #[test]
+    fn test_insertion_validation() {
+        let limits = CharacterLimits::new(5);
+
+        // Valid insertion
+        let result = limits.validate_insertion("test", 4, 'x');
+        assert!(result.is_none()); // No validation issues
+
+        // Invalid insertion (would exceed limit)
+        let result = limits.validate_insertion("tests", 5, 'x');
+        assert!(result.is_some());
+        assert!(!result.unwrap().is_acceptable());
+    }
+
+    #[test]
+    fn test_content_validation() {
+        let limits = CharacterLimits::new_range(3, 10);
+
+        // Too short
+        let result = limits.validate_content("hi");
+        assert!(result.is_some());
+        assert!(result.unwrap().is_acceptable()); // Warning, not error
+
+        // Just right
+        let result = limits.validate_content("hello");
+        assert!(result.is_none());
+
+        // Too long
+        let result = limits.validate_content("hello world!");
+        assert!(result.is_some());
+        assert!(!result.unwrap().is_acceptable()); // Error
+    }
+
+    #[test]
+    fn test_warning_threshold() {
+        let limits = CharacterLimits::new(10).with_warning_threshold(8);
+
+        // Below warning threshold
+        let result = limits.validate_insertion("123456", 6, 'x');
+        assert!(result.is_none());
+
+        // At warning threshold
+        let result = limits.validate_insertion("1234567", 7, 'x');
+        assert!(result.is_some()); // This brings us to 8 chars
+        assert!(result.unwrap().is_acceptable()); // Warning, not error
+
+        let result = limits.validate_insertion("12345678", 8, 'x');
+        assert!(result.is_none());
+    }
+
+    #[test]
+    fn test_status_text() {
+        let limits = CharacterLimits::new(10);
+
+        assert_eq!(limits.status_text("hello"), Some("5/10".to_string()));
+
+        let limits = limits.with_warning_threshold(8);
+        assert_eq!(
+            limits.status_text("12345678"),
+            Some("8/10 (approaching limit)".to_string())
+        );
+        assert_eq!(
+            limits.status_text("1234567890x"),
+            Some("11/10 (exceeded)".to_string())
+        );
+    }
+
+    #[test]
+    fn test_field_switch_blocking() {
+        let limits = CharacterLimits::new_range(3, 10);
+
+        // Empty field: should allow switching
+        assert!(limits.allows_field_switch(""));
+        assert!(limits.field_switch_block_reason("").is_none());
+
+        // Field with content below minimum: should block switching
+        assert!(!limits.allows_field_switch("hi"));
+        assert!(limits.field_switch_block_reason("hi").is_some());
+        assert!(limits
+            .field_switch_block_reason("hi")
+            .unwrap()
+            .contains("at least 3 characters"));
+
+        // Field meeting minimum: should allow switching
+        assert!(limits.allows_field_switch("hello"));
+        assert!(limits.field_switch_block_reason("hello").is_none());
+
+        // Field exceeding maximum: should still allow switching (validation shows error but doesn't block)
+        assert!(limits.allows_field_switch("this is way too long"));
+        assert!(limits
+            .field_switch_block_reason("this is way too long")
+            .is_none());
+    }
+
+    #[test]
+    fn test_field_switch_no_minimum() {
+        let limits = CharacterLimits::new(10); // Only max, no minimum
+
+        // Should always allow switching when there's no minimum
+        assert!(limits.allows_field_switch(""));
+        assert!(limits.allows_field_switch("a"));
+        assert!(limits.allows_field_switch("hello"));
+
+        assert!(limits.field_switch_block_reason("").is_none());
+        assert!(limits.field_switch_block_reason("a").is_none());
+    }
+}

validation-core/src/rules/display_mask.rs

@@ -0,0 +1,348 @@
+// src/validation/mask.rs
+//! Pure display mask system - user-defined patterns only
+
+use serde::{Deserialize, Serialize};
+
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize, Default)]
+pub enum MaskDisplayMode {
+    /// Only show separators as user types
+    /// Example: "" → "", "123" → "123", "12345" → "(123) 45"
+    #[default]
+    Dynamic,
+
+    /// Show full template with placeholders from start
+    /// Example: "" → "(___) ___-____", "123" → "(123) ___-____"
+    Template {
+        /// Character to use as placeholder for empty input positions
+        placeholder: char,
+    },
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+pub struct DisplayMask {
+    /// Mask pattern like "##-##-####" where # = input position, others are visual separators
+    pattern: String,
+    /// Character used to represent input positions (usually '#')
+    input_char: char,
+    /// How to display the mask (dynamic vs template)
+    display_mode: MaskDisplayMode,
+}
+
+impl DisplayMask {
+    /// Create a new display mask with dynamic mode (current behavior)
+    ///
+    /// # Arguments
+    /// * `pattern` - The mask pattern (e.g., "##-##-####", "(###) ###-####")  
+    /// * `input_char` - Character representing input positions (usually '#')
+    ///
+    /// # Examples
+    /// ```
+    /// use validation_core::DisplayMask;
+    ///
+    /// // Phone number format
+    /// let phone_mask = DisplayMask::new("(###) ###-####", '#');
+    ///
+    /// // Date format  
+    /// let date_mask = DisplayMask::new("##/##/####", '#');
+    ///
+    /// // Custom business format
+    /// let employee_id = DisplayMask::new("EMP-####-##", '#');
+    /// ```
+    pub fn new(pattern: impl Into<String>, input_char: char) -> Self {
+        Self {
+            pattern: pattern.into(),
+            input_char,
+            display_mode: MaskDisplayMode::Dynamic,
+        }
+    }
+
+    /// Set the display mode for this mask
+    ///
+    /// # Examples
+    /// ```
+    /// use validation_core::{DisplayMask, MaskDisplayMode};
+    ///
+    /// let dynamic_mask = DisplayMask::new("##-##", '#')
+    ///     .with_mode(MaskDisplayMode::Dynamic);
+    ///     
+    /// let template_mask = DisplayMask::new("##-##", '#')
+    ///     .with_mode(MaskDisplayMode::Template { placeholder: '_' });
+    /// ```
+    pub fn with_mode(mut self, mode: MaskDisplayMode) -> Self {
+        self.display_mode = mode;
+        self
+    }
+
+    /// Set template mode with custom placeholder
+    ///
+    /// # Examples
+    /// ```
+    /// use validation_core::DisplayMask;
+    ///
+    /// let phone_template = DisplayMask::new("(###) ###-####", '#')
+    ///     .with_template('_');  // Shows "(___) ___-____" when empty
+    ///     
+    /// let date_dots = DisplayMask::new("##/##/####", '#')
+    ///     .with_template('•');  // Shows "••/••/••••" when empty
+    /// ```
+    pub fn with_template(self, placeholder: char) -> Self {
+        self.with_mode(MaskDisplayMode::Template { placeholder })
+    }
+
+    /// Apply mask to raw input, showing visual separators and handling display mode
+    pub fn apply_to_display(&self, raw_input: &str) -> String {
+        match &self.display_mode {
+            MaskDisplayMode::Dynamic => self.apply_dynamic(raw_input),
+            MaskDisplayMode::Template { placeholder } => {
+                self.apply_template(raw_input, *placeholder)
+            }
+        }
+    }
+
+    /// Dynamic mode - only show separators as user types
+    fn apply_dynamic(&self, raw_input: &str) -> String {
+        if raw_input.is_empty() {
+            return String::new();
+        }
+
+        let mut result = String::new();
+        let mut raw_chars = raw_input.chars();
+
+        for pattern_char in self.pattern.chars() {
+            if pattern_char == self.input_char {
+                // Input position - take from raw input
+                if let Some(input_char) = raw_chars.next() {
+                    result.push(input_char);
+                } else {
+                    // No more input - stop here in dynamic mode
+                    break;
+                }
+            } else {
+                // Visual separator - always show
+                result.push(pattern_char);
+            }
+        }
+
+        // Append any remaining raw characters that don't fit the pattern
+        for remaining_char in raw_chars {
+            result.push(remaining_char);
+        }
+
+        result
+    }
+
+    /// Template mode - show full pattern with placeholders
+    fn apply_template(&self, raw_input: &str, placeholder: char) -> String {
+        let mut result = String::new();
+        let mut raw_chars = raw_input.chars().peekable();
+
+        for pattern_char in self.pattern.chars() {
+            if pattern_char == self.input_char {
+                // Input position - take from raw input or use placeholder
+                if let Some(input_char) = raw_chars.next() {
+                    result.push(input_char);
+                } else {
+                    // No more input - use placeholder to show template
+                    result.push(placeholder);
+                }
+            } else {
+                // Visual separator - always show in template mode
+                result.push(pattern_char);
+            }
+        }
+
+        // In template mode, we don't append extra characters beyond the pattern
+        // This keeps the template consistent
+        result
+    }
+
+    /// Check if a display position should accept cursor/input
+    pub fn is_input_position(&self, display_position: usize) -> bool {
+        self.pattern
+            .chars()
+            .nth(display_position)
+            .map(|c| c == self.input_char)
+            .unwrap_or(true) // Beyond pattern = accept input
+    }
+
+    /// Map display position to raw position
+    pub fn display_pos_to_raw_pos(&self, display_pos: usize) -> usize {
+        let mut raw_pos = 0;
+
+        for (i, pattern_char) in self.pattern.chars().enumerate() {
+            if i >= display_pos {
+                break;
+            }
+            if pattern_char == self.input_char {
+                raw_pos += 1;
+            }
+        }
+
+        raw_pos
+    }
+
+    /// Map raw position to display position
+    pub fn raw_pos_to_display_pos(&self, raw_pos: usize) -> usize {
+        let mut input_positions_seen = 0;
+
+        for (display_pos, pattern_char) in self.pattern.chars().enumerate() {
+            if pattern_char == self.input_char {
+                if input_positions_seen == raw_pos {
+                    return display_pos;
+                }
+                input_positions_seen += 1;
+            }
+        }
+
+        // Beyond pattern, return position after pattern
+        self.pattern.len() + (raw_pos - input_positions_seen)
+    }
+
+    /// Find next input position at or after the given display position
+    pub fn next_input_position(&self, display_pos: usize) -> usize {
+        for (i, pattern_char) in self.pattern.chars().enumerate().skip(display_pos) {
+            if pattern_char == self.input_char {
+                return i;
+            }
+        }
+        // Beyond pattern = all positions are input positions
+        display_pos.max(self.pattern.len())
+    }
+
+    /// Find previous input position at or before the given display position
+    pub fn prev_input_position(&self, display_pos: usize) -> Option<usize> {
+        // Collect pattern chars with indices first, then search backwards
+        let pattern_chars: Vec<(usize, char)> = self.pattern.chars().enumerate().collect();
+
+        // Search backwards from display_pos
+        for &(i, pattern_char) in pattern_chars.iter().rev() {
+            if i <= display_pos && pattern_char == self.input_char {
+                return Some(i);
+            }
+        }
+        None
+    }
+
+    /// Get the display mode
+    pub fn display_mode(&self) -> &MaskDisplayMode {
+        &self.display_mode
+    }
+
+    /// Check if this mask uses template mode
+    pub fn is_template_mode(&self) -> bool {
+        matches!(self.display_mode, MaskDisplayMode::Template { .. })
+    }
+
+    /// Get the pattern string
+    pub fn pattern(&self) -> &str {
+        &self.pattern
+    }
+
+    /// Get the input placeholder character
+    pub fn input_char(&self) -> char {
+        self.input_char
+    }
+
+    /// Get the position of the first input character in the pattern
+    pub fn first_input_position(&self) -> usize {
+        for (pos, ch) in self.pattern.chars().enumerate() {
+            if ch == self.input_char {
+                return pos;
+            }
+        }
+        0
+    }
+}
+
+impl Default for DisplayMask {
+    fn default() -> Self {
+        Self::new("", '#')
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_user_defined_phone_mask() {
+        // User creates their own phone mask
+        let dynamic = DisplayMask::new("(###) ###-####", '#');
+        let template = DisplayMask::new("(###) ###-####", '#').with_template('_');
+
+        // Dynamic mode
+        assert_eq!(dynamic.apply_to_display(""), "");
+        assert_eq!(dynamic.apply_to_display("1234567890"), "(123) 456-7890");
+
+        // Template mode
+        assert_eq!(template.apply_to_display(""), "(___) ___-____");
+        assert_eq!(template.apply_to_display("123"), "(123) ___-____");
+    }
+
+    #[test]
+    fn test_user_defined_date_mask() {
+        // User creates their own date formats
+        let us_date = DisplayMask::new("##/##/####", '#');
+        let eu_date = DisplayMask::new("##.##.####", '#');
+        let iso_date = DisplayMask::new("####-##-##", '#');
+
+        assert_eq!(us_date.apply_to_display("12252024"), "12/25/2024");
+        assert_eq!(eu_date.apply_to_display("25122024"), "25.12.2024");
+        assert_eq!(iso_date.apply_to_display("20241225"), "2024-12-25");
+    }
+
+    #[test]
+    fn test_user_defined_business_formats() {
+        // User creates custom business formats
+        let employee_id = DisplayMask::new("EMP-####-##", '#');
+        let product_code = DisplayMask::new("###-###-###", '#');
+        let invoice = DisplayMask::new("INV####/##", '#');
+
+        assert_eq!(employee_id.apply_to_display("123456"), "EMP-1234-56");
+        assert_eq!(product_code.apply_to_display("123456789"), "123-456-789");
+        assert_eq!(invoice.apply_to_display("123456"), "INV1234/56");
+    }
+
+    #[test]
+    fn test_custom_input_characters() {
+        // User can define their own input character
+        let mask_with_x = DisplayMask::new("XXX-XX-XXXX", 'X');
+        let mask_with_hash = DisplayMask::new("###-##-####", '#');
+        let mask_with_n = DisplayMask::new("NNN-NN-NNNN", 'N');
+
+        assert_eq!(mask_with_x.apply_to_display("123456789"), "123-45-6789");
+        assert_eq!(mask_with_hash.apply_to_display("123456789"), "123-45-6789");
+        assert_eq!(mask_with_n.apply_to_display("123456789"), "123-45-6789");
+    }
+
+    #[test]
+    fn test_custom_placeholders() {
+        // User can define custom placeholder characters
+        let underscores = DisplayMask::new("##-##", '#').with_template('_');
+        let dots = DisplayMask::new("##-##", '#').with_template('•');
+        let dashes = DisplayMask::new("##-##", '#').with_template('-');
+
+        assert_eq!(underscores.apply_to_display(""), "__-__");
+        assert_eq!(dots.apply_to_display(""), "••-••");
+        assert_eq!(dashes.apply_to_display(""), "-----"); // Note: dashes blend with separator
+    }
+
+    #[test]
+    fn test_position_mapping_user_patterns() {
+        let custom = DisplayMask::new("ABC-###-XYZ", '#');
+
+        // Position mapping should work correctly with any pattern
+        assert_eq!(custom.raw_pos_to_display_pos(0), 4); // First # at position 4
+        assert_eq!(custom.raw_pos_to_display_pos(1), 5); // Second # at position 5
+        assert_eq!(custom.raw_pos_to_display_pos(2), 6); // Third # at position 6
+
+        assert_eq!(custom.display_pos_to_raw_pos(4), 0); // Position 4 -> first input
+        assert_eq!(custom.display_pos_to_raw_pos(5), 1); // Position 5 -> second input
+        assert_eq!(custom.display_pos_to_raw_pos(6), 2); // Position 6 -> third input
+
+        assert!(!custom.is_input_position(0)); // A
+        assert!(!custom.is_input_position(3)); // -
+        assert!(custom.is_input_position(4)); // #
+        assert!(!custom.is_input_position(8)); // Y
+    }
+}

validation-core/src/rules/mod.rs

@@ -0,0 +1,7 @@
+pub mod character_limits;
+pub mod display_mask;
+pub mod pattern_rules;
+
+pub use character_limits::{count_text, CharacterLimits, CountMode, LimitCheckResult};
+pub use display_mask::{DisplayMask, MaskDisplayMode};
+pub use pattern_rules::{CharacterFilter, PatternFilters, PositionFilter, PositionRange};

validation-core/src/rules/pattern_rules.rs

@@ -0,0 +1,330 @@
+// src/validation/patterns.rs
+//! Position-based pattern filtering for validation
+
+use serde::{Deserialize, Serialize};
+use std::sync::Arc;
+
+/// A filter that applies to specific character positions in a field
+#[derive(Debug, Clone)]
+pub struct PositionFilter {
+    /// Which positions this filter applies to
+    pub positions: PositionRange,
+    /// What type of character filter to apply
+    pub filter: CharacterFilter,
+}
+
+/// Defines which character positions a filter applies to
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub enum PositionRange {
+    /// Single position (e.g., position 3 only)
+    Single(usize),
+    /// Range of positions (e.g., positions 0-2, inclusive)
+    Range(usize, usize),
+    /// From position onwards (e.g., position 4 and beyond)
+    From(usize),
+    /// Multiple specific positions (e.g., positions 0, 2, 5)
+    Multiple(Vec<usize>),
+}
+
+/// Types of character filters that can be applied
+pub enum CharacterFilter {
+    /// Allow only alphabetic characters (a-z, A-Z)
+    Alphabetic,
+    /// Allow only numeric characters (0-9)
+    Numeric,
+    /// Allow alphanumeric characters (a-z, A-Z, 0-9)
+    Alphanumeric,
+    /// Allow only exact character match
+    Exact(char),
+    /// Allow any character from the provided set
+    OneOf(Vec<char>),
+    /// Custom user-defined filter function
+    Custom(Arc<dyn Fn(char) -> bool + Send + Sync>),
+}
+
+// Manual implementations for Debug and Clone
+impl std::fmt::Debug for CharacterFilter {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            CharacterFilter::Alphabetic => write!(f, "Alphabetic"),
+            CharacterFilter::Numeric => write!(f, "Numeric"),
+            CharacterFilter::Alphanumeric => write!(f, "Alphanumeric"),
+            CharacterFilter::Exact(ch) => write!(f, "Exact('{ch}')"),
+            CharacterFilter::OneOf(chars) => write!(f, "OneOf({chars:?})"),
+            CharacterFilter::Custom(_) => write!(f, "Custom(<function>)"),
+        }
+    }
+}
+
+impl Clone for CharacterFilter {
+    fn clone(&self) -> Self {
+        match self {
+            CharacterFilter::Alphabetic => CharacterFilter::Alphabetic,
+            CharacterFilter::Numeric => CharacterFilter::Numeric,
+            CharacterFilter::Alphanumeric => CharacterFilter::Alphanumeric,
+            CharacterFilter::Exact(ch) => CharacterFilter::Exact(*ch),
+            CharacterFilter::OneOf(chars) => CharacterFilter::OneOf(chars.clone()),
+            CharacterFilter::Custom(func) => CharacterFilter::Custom(Arc::clone(func)),
+        }
+    }
+}
+
+impl PositionRange {
+    /// Check if a position is included in this range
+    pub fn contains(&self, position: usize) -> bool {
+        match self {
+            PositionRange::Single(pos) => position == *pos,
+            PositionRange::Range(start, end) => position >= *start && position <= *end,
+            PositionRange::From(start) => position >= *start,
+            PositionRange::Multiple(positions) => positions.contains(&position),
+        }
+    }
+
+    /// Get all positions up to a given length that this range covers
+    pub fn positions_up_to(&self, max_length: usize) -> Vec<usize> {
+        match self {
+            PositionRange::Single(pos) => {
+                if *pos < max_length {
+                    vec![*pos]
+                } else {
+                    vec![]
+                }
+            }
+            PositionRange::Range(start, end) => {
+                let actual_end = (*end).min(max_length.saturating_sub(1));
+                if *start <= actual_end {
+                    (*start..=actual_end).collect()
+                } else {
+                    vec![]
+                }
+            }
+            PositionRange::From(start) => {
+                if *start < max_length {
+                    (*start..max_length).collect()
+                } else {
+                    vec![]
+                }
+            }
+            PositionRange::Multiple(positions) => positions
+                .iter()
+                .filter(|&&pos| pos < max_length)
+                .copied()
+                .collect(),
+        }
+    }
+}
+
+impl CharacterFilter {
+    /// Test if a character passes this filter
+    pub fn accepts(&self, ch: char) -> bool {
+        match self {
+            CharacterFilter::Alphabetic => ch.is_alphabetic(),
+            CharacterFilter::Numeric => ch.is_numeric(),
+            CharacterFilter::Alphanumeric => ch.is_alphanumeric(),
+            CharacterFilter::Exact(expected) => ch == *expected,
+            CharacterFilter::OneOf(chars) => chars.contains(&ch),
+            CharacterFilter::Custom(func) => func(ch),
+        }
+    }
+
+    /// Get a human-readable description of this filter
+    pub fn description(&self) -> String {
+        match self {
+            CharacterFilter::Alphabetic => "alphabetic characters (a-z, A-Z)".to_string(),
+            CharacterFilter::Numeric => "numeric characters (0-9)".to_string(),
+            CharacterFilter::Alphanumeric => "alphanumeric characters (a-z, A-Z, 0-9)".to_string(),
+            CharacterFilter::Exact(ch) => format!("exactly '{ch}'"),
+            CharacterFilter::OneOf(chars) => {
+                let char_list: String = chars.iter().collect();
+                format!("one of: {char_list}")
+            }
+            CharacterFilter::Custom(_) => "custom filter".to_string(),
+        }
+    }
+}
+
+impl PositionFilter {
+    /// Create a new position filter
+    pub fn new(positions: PositionRange, filter: CharacterFilter) -> Self {
+        Self { positions, filter }
+    }
+
+    /// Validate a character at a specific position
+    pub fn validate_position(&self, position: usize, character: char) -> bool {
+        if self.positions.contains(position) {
+            self.filter.accepts(character)
+        } else {
+            true // Position not covered by this filter, allow any character
+        }
+    }
+
+    /// Get error message for invalid character at position
+    pub fn error_message(&self, position: usize, character: char) -> Option<String> {
+        if self.positions.contains(position) && !self.filter.accepts(character) {
+            Some(format!(
+                "Position {} requires {} but got '{}'",
+                position,
+                self.filter.description(),
+                character
+            ))
+        } else {
+            None
+        }
+    }
+}
+
+/// A collection of position filters for a field
+#[derive(Debug, Clone, Default)]
+pub struct PatternFilters {
+    filters: Vec<PositionFilter>,
+}
+
+impl PatternFilters {
+    /// Create empty pattern filters
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// Add a position filter
+    pub fn add_filter(mut self, filter: PositionFilter) -> Self {
+        self.filters.push(filter);
+        self
+    }
+
+    /// Add multiple filters
+    pub fn add_filters(mut self, filters: Vec<PositionFilter>) -> Self {
+        self.filters.extend(filters);
+        self
+    }
+
+    /// Validate a character at a specific position against all applicable filters
+    pub fn validate_char_at_position(
+        &self,
+        position: usize,
+        character: char,
+    ) -> Result<(), String> {
+        for filter in &self.filters {
+            if let Some(error) = filter.error_message(position, character) {
+                return Err(error);
+            }
+        }
+        Ok(())
+    }
+
+    /// Validate entire text against all filters
+    pub fn validate_text(&self, text: &str) -> Result<(), String> {
+        for (position, character) in text.char_indices() {
+            self.validate_char_at_position(position, character)?
+        }
+        Ok(())
+    }
+
+    /// Check if any filters are configured
+    pub fn has_filters(&self) -> bool {
+        !self.filters.is_empty()
+    }
+
+    /// Get all configured filters
+    pub fn filters(&self) -> &[PositionFilter] {
+        &self.filters
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_position_range_contains() {
+        assert!(PositionRange::Single(3).contains(3));
+        assert!(!PositionRange::Single(3).contains(2));
+
+        assert!(PositionRange::Range(1, 4).contains(3));
+        assert!(!PositionRange::Range(1, 4).contains(5));
+
+        assert!(PositionRange::From(2).contains(5));
+        assert!(!PositionRange::From(2).contains(1));
+
+        assert!(PositionRange::Multiple(vec![0, 2, 5]).contains(2));
+        assert!(!PositionRange::Multiple(vec![0, 2, 5]).contains(3));
+    }
+
+    #[test]
+    fn test_position_range_positions_up_to() {
+        assert_eq!(PositionRange::Single(3).positions_up_to(5), vec![3]);
+        assert_eq!(PositionRange::Single(5).positions_up_to(3), vec![]);
+
+        assert_eq!(PositionRange::Range(1, 3).positions_up_to(5), vec![1, 2, 3]);
+        assert_eq!(PositionRange::Range(1, 5).positions_up_to(3), vec![1, 2]);
+
+        assert_eq!(PositionRange::From(2).positions_up_to(5), vec![2, 3, 4]);
+
+        assert_eq!(
+            PositionRange::Multiple(vec![0, 2, 5]).positions_up_to(4),
+            vec![0, 2]
+        );
+    }
+
+    #[test]
+    fn test_character_filter_accepts() {
+        assert!(CharacterFilter::Alphabetic.accepts('a'));
+        assert!(CharacterFilter::Alphabetic.accepts('Z'));
+        assert!(!CharacterFilter::Alphabetic.accepts('1'));
+
+        assert!(CharacterFilter::Numeric.accepts('5'));
+        assert!(!CharacterFilter::Numeric.accepts('a'));
+
+        assert!(CharacterFilter::Alphanumeric.accepts('a'));
+        assert!(CharacterFilter::Alphanumeric.accepts('5'));
+        assert!(!CharacterFilter::Alphanumeric.accepts('-'));
+
+        assert!(CharacterFilter::Exact('x').accepts('x'));
+        assert!(!CharacterFilter::Exact('x').accepts('y'));
+
+        assert!(CharacterFilter::OneOf(vec!['a', 'b', 'c']).accepts('b'));
+        assert!(!CharacterFilter::OneOf(vec!['a', 'b', 'c']).accepts('d'));
+    }
+
+    #[test]
+    fn test_position_filter_validation() {
+        let filter = PositionFilter::new(PositionRange::Range(0, 1), CharacterFilter::Alphabetic);
+
+        assert!(filter.validate_position(0, 'A'));
+        assert!(filter.validate_position(1, 'b'));
+        assert!(!filter.validate_position(0, '1'));
+        assert!(filter.validate_position(2, '1')); // Position 2 not covered, allow anything
+    }
+
+    #[test]
+    fn test_pattern_filters_validation() {
+        let patterns = PatternFilters::new()
+            .add_filter(PositionFilter::new(
+                PositionRange::Range(0, 1),
+                CharacterFilter::Alphabetic,
+            ))
+            .add_filter(PositionFilter::new(
+                PositionRange::Range(2, 4),
+                CharacterFilter::Numeric,
+            ));
+
+        // Valid pattern: AB123
+        assert!(patterns.validate_text("AB123").is_ok());
+
+        // Invalid: number in alphabetic position
+        assert!(patterns.validate_text("A1123").is_err());
+
+        // Invalid: letter in numeric position
+        assert!(patterns.validate_text("AB1A3").is_err());
+    }
+
+    #[test]
+    fn test_custom_filter() {
+        let pattern = PatternFilters::new().add_filter(PositionFilter::new(
+            PositionRange::From(0),
+            CharacterFilter::Custom(Arc::new(|c| c.is_lowercase())),
+        ));
+
+        assert!(pattern.validate_text("hello").is_ok());
+        assert!(pattern.validate_text("Hello").is_err()); // Uppercase not allowed
+    }
+}

validation-core/src/set.rs

@@ -0,0 +1,118 @@
+use crate::{ValidationConfig, ValidationMergeError, ValidationSettings};
+use serde::{Deserialize, Serialize};
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct ValidationRule {
+    pub name: String,
+    pub description: Option<String>,
+    pub settings: ValidationSettings,
+}
+
+impl ValidationRule {
+    pub fn resolve(&self) -> ValidationConfig {
+        self.settings.resolve()
+    }
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct ValidationSet {
+    pub name: String,
+    pub description: Option<String>,
+    pub rules: Vec<ValidationRule>,
+}
+
+impl ValidationSet {
+    pub fn resolve_settings(&self) -> Result<ValidationSettings, ValidationMergeError> {
+        ValidationSettings::merge_rules(self.rules.iter().map(|rule| &rule.settings))
+    }
+
+    pub fn resolve(&self) -> Result<ValidationConfig, ValidationMergeError> {
+        Ok(self.resolve_settings()?.resolve())
+    }
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct AppliedValidation {
+    pub set_name: Option<String>,
+    pub settings: ValidationSettings,
+}
+
+impl AppliedValidation {
+    pub fn resolve(&self) -> ValidationConfig {
+        self.settings.resolve()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::{
+        CharacterFilterSettings, CharacterLimits, PatternSettings, PositionFilterSettings,
+        PositionRange,
+    };
+
+    #[test]
+    fn validation_set_merges_rule_fragments() {
+        let set = ValidationSet {
+            name: "phone".to_string(),
+            description: None,
+            rules: vec![
+                ValidationRule {
+                    name: "phone-length".to_string(),
+                    description: None,
+                    settings: ValidationSettings {
+                        character_limits: Some(CharacterLimits::new_range(10, 15)),
+                        ..ValidationSettings::default()
+                    },
+                },
+                ValidationRule {
+                    name: "digits-only".to_string(),
+                    description: None,
+                    settings: ValidationSettings {
+                        pattern: Some(PatternSettings {
+                            filters: vec![PositionFilterSettings {
+                                positions: PositionRange::From(0),
+                                filter: CharacterFilterSettings::Numeric,
+                            }],
+                            description: None,
+                        }),
+                        ..ValidationSettings::default()
+                    },
+                },
+            ],
+        };
+
+        let settings = set.resolve_settings().expect("set should resolve");
+
+        assert!(settings.character_limits.is_some());
+        assert_eq!(settings.pattern.expect("pattern").filters.len(), 1);
+    }
+
+    #[test]
+    fn validation_set_rejects_duplicate_singleton_rules() {
+        let set = ValidationSet {
+            name: "conflict".to_string(),
+            description: None,
+            rules: vec![
+                ValidationRule {
+                    name: "short".to_string(),
+                    description: None,
+                    settings: ValidationSettings {
+                        character_limits: Some(CharacterLimits::new(10)),
+                        ..ValidationSettings::default()
+                    },
+                },
+                ValidationRule {
+                    name: "long".to_string(),
+                    description: None,
+                    settings: ValidationSettings {
+                        character_limits: Some(CharacterLimits::new(20)),
+                        ..ValidationSettings::default()
+                    },
+                },
+            ],
+        };
+
+        assert!(set.resolve_settings().is_err());
+    }
+}