validation of characters length is finished

canvas/Cargo.toml

@@ -33,7 +33,6 @@ default = []
 gui = ["ratatui"]
 autocomplete = ["tokio"]
 cursor-style = ["crossterm"]
-regex = ["dep:regex"]
 validation = ["regex"]
 
 [[example]]
@@ -45,3 +44,7 @@ path = "examples/autocomplete.rs"
 name = "canvas_gui_demo"
 required-features = ["gui"]
 path = "examples/canvas_gui_demo.rs"
+
+[[example]]
+name = "validation_1"
+required-features = ["gui", "validation"]

canvas/examples/validation_1.rs

@@ -0,0 +1,831 @@
+// examples/validation_1.rs
+//! Demonstrates field validation with the canvas library
+//!
+//! This example REQUIRES the `validation` feature to compile.
+//!
+//! Run with:
+//! cargo run --example validation_1 --features "gui,validation"
+//!
+//! This will fail without validation:
+//! cargo run --example validation_1 --features "gui"
+
+// REQUIRE validation feature - example won't compile without it
+#[cfg(not(feature = "validation"))]
+compile_error!(
+    "This example requires the 'validation' feature. \
+     Run with: cargo run --example validation_1 --features \"gui,validation\""
+);
+
+use std::io;
+use crossterm::{
+    event::{
+        self, DisableMouseCapture, EnableMouseCapture, Event, KeyCode, KeyModifiers,
+    },
+    execute,
+    terminal::{
+        disable_raw_mode, enable_raw_mode, EnterAlternateScreen, LeaveAlternateScreen,
+    },
+};
+use ratatui::{
+    backend::{Backend, CrosstermBackend},
+    layout::{Constraint, Direction, Layout, Rect},
+    style::{Color, Style},
+    text::{Line, Span},
+    widgets::{Block, Borders, Paragraph, Wrap},
+    Frame, Terminal,
+};
+
+use canvas::{
+    canvas::{
+        gui::render_canvas_default,
+        modes::AppMode,
+    },
+    DataProvider, FormEditor,
+    ValidationConfig, ValidationConfigBuilder, CharacterLimits, ValidationResult,
+};
+
+// Import CountMode from the validation module directly
+use canvas::validation::limits::CountMode;
+
+// Enhanced FormEditor that demonstrates validation functionality
+struct ValidationFormEditor<D: DataProvider> {
+    editor: FormEditor<D>,
+    has_unsaved_changes: bool,
+    debug_message: String,
+    command_buffer: String,
+    validation_enabled: bool,
+    field_switch_blocked: bool,
+    block_reason: Option<String>,
+}
+
+impl<D: DataProvider> ValidationFormEditor<D> {
+    fn new(data_provider: D) -> Self {
+        let mut editor = FormEditor::new(data_provider);
+        
+        // Enable validation by default
+        editor.set_validation_enabled(true);
+        
+        Self {
+            editor,
+            has_unsaved_changes: false,
+            debug_message: "🔍 Validation Demo - Try typing in different fields!".to_string(),
+            command_buffer: String::new(),
+            validation_enabled: true,
+            field_switch_blocked: false,
+            block_reason: None,
+        }
+    }
+
+    // === COMMAND BUFFER HANDLING ===
+    fn clear_command_buffer(&mut self) {
+        self.command_buffer.clear();
+    }
+
+    fn add_to_command_buffer(&mut self, ch: char) {
+        self.command_buffer.push(ch);
+    }
+
+    fn get_command_buffer(&self) -> &str {
+        &self.command_buffer
+    }
+
+    fn has_pending_command(&self) -> bool {
+        !self.command_buffer.is_empty()
+    }
+
+    // === VALIDATION CONTROL ===
+    fn toggle_validation(&mut self) {
+        self.validation_enabled = !self.validation_enabled;
+        self.editor.set_validation_enabled(self.validation_enabled);
+        
+        if self.validation_enabled {
+            self.debug_message = "✅ Validation ENABLED - Try exceeding limits!".to_string();
+        } else {
+            self.debug_message = "❌ Validation DISABLED - No limits enforced".to_string();
+        }
+    }
+
+    fn check_field_switch_allowed(&self) -> (bool, Option<String>) {
+        if !self.validation_enabled {
+            return (true, None);
+        }
+        
+        let can_switch = self.editor.can_switch_fields();
+        let reason = if !can_switch {
+            self.editor.field_switch_block_reason()
+        } else {
+            None
+        };
+        
+        (can_switch, reason)
+    }
+
+    fn get_validation_status(&self) -> String {
+        if !self.validation_enabled {
+            return "❌ DISABLED".to_string();
+        }
+
+        if self.field_switch_blocked {
+            return "🚫 SWITCH BLOCKED".to_string();
+        }
+
+        let summary = self.editor.validation_summary();
+        if summary.has_errors() {
+            format!("❌ {} ERRORS", summary.error_fields)
+        } else if summary.has_warnings() {
+            format!("⚠️  {} WARNINGS", summary.warning_fields)
+        } else if summary.validated_fields > 0 {
+            format!("✅ {} VALID", summary.valid_fields)
+        } else {
+            "🔍 READY".to_string()
+        }
+    }
+
+    fn validate_current_field(&mut self) {
+        let result = self.editor.validate_current_field();
+        match result {
+            ValidationResult::Valid => {
+                self.debug_message = "✅ Current field is valid!".to_string();
+            }
+            ValidationResult::Warning { message } => {
+                self.debug_message = format!("⚠️  Warning: {}", message);
+            }
+            ValidationResult::Error { message } => {
+                self.debug_message = format!("❌ Error: {}", message);
+            }
+        }
+    }
+
+    fn validate_all_fields(&mut self) {
+        let field_count = self.editor.data_provider().field_count();
+        for i in 0..field_count {
+            self.editor.validate_field(i);
+        }
+        
+        let summary = self.editor.validation_summary();
+        self.debug_message = format!(
+            "🔍 Validated all fields: {} valid, {} warnings, {} errors",
+            summary.valid_fields, summary.warning_fields, summary.error_fields
+        );
+    }
+
+    fn clear_validation_results(&mut self) {
+        self.editor.clear_validation_results();
+        self.debug_message = "🧹 Cleared all validation results".to_string();
+    }
+
+    // === ENHANCED MOVEMENT WITH VALIDATION ===
+    fn move_left(&mut self) {
+        self.editor.move_left();
+        self.field_switch_blocked = false;
+        self.block_reason = None;
+    }
+
+    fn move_right(&mut self) {
+        self.editor.move_right();
+        self.field_switch_blocked = false;
+        self.block_reason = None;
+    }
+
+    fn move_up(&mut self) {
+        match self.editor.move_up() {
+            Ok(()) => {
+                self.update_field_validation_status();
+                self.field_switch_blocked = false;
+                self.block_reason = None;
+            }
+            Err(e) => {
+                self.field_switch_blocked = true;
+                self.block_reason = Some(e.to_string());
+                self.debug_message = format!("🚫 Field switch blocked: {}", e);
+            }
+        }
+    }
+
+    fn move_down(&mut self) {
+        match self.editor.move_down() {
+            Ok(()) => {
+                self.update_field_validation_status();
+                self.field_switch_blocked = false;
+                self.block_reason = None;
+            }
+            Err(e) => {
+                self.field_switch_blocked = true;
+                self.block_reason = Some(e.to_string());
+                self.debug_message = format!("🚫 Field switch blocked: {}", e);
+            }
+        }
+    }
+
+    fn move_line_start(&mut self) {
+        self.editor.move_line_start();
+    }
+
+    fn move_line_end(&mut self) {
+        self.editor.move_line_end();
+    }
+
+    fn move_word_next(&mut self) {
+        self.editor.move_word_next();
+    }
+
+    fn move_word_prev(&mut self) {
+        self.editor.move_word_prev();
+    }
+
+    fn move_word_end(&mut self) {
+        self.editor.move_word_end();
+    }
+
+    fn move_first_line(&mut self) {
+        self.editor.move_first_line();
+    }
+
+    fn move_last_line(&mut self) {
+        self.editor.move_last_line();
+    }
+
+    fn update_field_validation_status(&mut self) {
+        if !self.validation_enabled {
+            return;
+        }
+
+        if let Some(result) = self.editor.current_field_validation() {
+            match result {
+                ValidationResult::Valid => {
+                    self.debug_message = format!("Field {}: ✅ Valid", self.editor.current_field() + 1);
+                }
+                ValidationResult::Warning { message } => {
+                    self.debug_message = format!("Field {}: ⚠️  {}", self.editor.current_field() + 1, message);
+                }
+                ValidationResult::Error { message } => {
+                    self.debug_message = format!("Field {}: ❌ {}", self.editor.current_field() + 1, message);
+                }
+            }
+        } else {
+            self.debug_message = format!("Field {}: 🔍 Not validated yet", self.editor.current_field() + 1);
+        }
+    }
+
+    // === MODE TRANSITIONS ===
+    fn enter_edit_mode(&mut self) {
+        self.editor.enter_edit_mode();
+        self.debug_message = "✏️  INSERT MODE - Type to test validation".to_string();
+    }
+
+    fn enter_append_mode(&mut self) {
+        self.editor.enter_append_mode();
+        self.debug_message = "✏️  INSERT (append) - Validation active".to_string();
+    }
+
+    fn exit_edit_mode(&mut self) {
+        self.editor.exit_edit_mode();
+        self.debug_message = "🔒 NORMAL MODE - Press 'v' to validate current field".to_string();
+        self.update_field_validation_status();
+    }
+
+    fn insert_char(&mut self, ch: char) -> anyhow::Result<()> {
+        let result = self.editor.insert_char(ch);
+        if result.is_ok() {
+            self.has_unsaved_changes = true;
+            // Show real-time validation feedback
+            if let Some(validation_result) = self.editor.current_field_validation() {
+                match validation_result {
+                    ValidationResult::Valid => {
+                        // Don't spam with valid messages, just show character count if applicable
+                        if let Some(limits) = self.get_current_field_limits() {
+                            if let Some(status) = limits.status_text(self.editor.current_text()) {
+                                self.debug_message = format!("✏️  {}", status);
+                            }
+                        }
+                    }
+                    ValidationResult::Warning { message } => {
+                        self.debug_message = format!("⚠️  {}", message);
+                    }
+                    ValidationResult::Error { message } => {
+                        self.debug_message = format!("❌ {}", message);
+                    }
+                }
+            }
+        }
+        Ok(result?)
+    }
+
+    fn get_current_field_limits(&self) -> Option<&CharacterLimits> {
+        let validation_state = self.editor.validation_state();
+        let config = validation_state.get_field_config(self.editor.current_field())?;
+        config.character_limits.as_ref()
+    }
+
+    // === DELETE OPERATIONS ===
+    fn delete_backward(&mut self) -> anyhow::Result<()> {
+        let result = self.editor.delete_backward();
+        if result.is_ok() {
+            self.has_unsaved_changes = true;
+            self.debug_message = "⌫ Deleted character".to_string();
+        }
+        Ok(result?)
+    }
+
+    fn delete_forward(&mut self) -> anyhow::Result<()> {
+        let result = self.editor.delete_forward();
+        if result.is_ok() {
+            self.has_unsaved_changes = true;
+            self.debug_message = "⌦ Deleted character".to_string();
+        }
+        Ok(result?)
+    }
+
+    // === DELEGATE TO ORIGINAL EDITOR ===
+    fn current_field(&self) -> usize {
+        self.editor.current_field()
+    }
+
+    fn cursor_position(&self) -> usize {
+        self.editor.cursor_position()
+    }
+
+    fn mode(&self) -> AppMode {
+        self.editor.mode()
+    }
+
+    fn current_text(&self) -> &str {
+        self.editor.current_text()
+    }
+
+    fn data_provider(&self) -> &D {
+        self.editor.data_provider()
+    }
+
+    fn ui_state(&self) -> &canvas::EditorState {
+        self.editor.ui_state()
+    }
+
+    fn set_mode(&mut self, mode: AppMode) {
+        self.editor.set_mode(mode);
+    }
+
+    fn next_field(&mut self) {
+        match self.editor.next_field() {
+            Ok(()) => {
+                self.update_field_validation_status();
+                self.field_switch_blocked = false;
+                self.block_reason = None;
+            }
+            Err(e) => {
+                self.field_switch_blocked = true;
+                self.block_reason = Some(e.to_string());
+                self.debug_message = format!("🚫 Cannot move to next field: {}", e);
+            }
+        }
+    }
+
+    fn prev_field(&mut self) {
+        match self.editor.prev_field() {
+            Ok(()) => {
+                self.update_field_validation_status();
+                self.field_switch_blocked = false;
+                self.block_reason = None;
+            }
+            Err(e) => {
+                self.field_switch_blocked = true;
+                self.block_reason = Some(e.to_string());
+                self.debug_message = format!("🚫 Cannot move to previous field: {}", e);
+            }
+        }
+    }
+
+    // === STATUS AND DEBUG ===
+    fn set_debug_message(&mut self, msg: String) {
+        self.debug_message = msg;
+    }
+
+    fn debug_message(&self) -> &str {
+        &self.debug_message
+    }
+
+    fn has_unsaved_changes(&self) -> bool {
+        self.has_unsaved_changes
+    }
+}
+
+// Demo form data with different validation rules
+struct ValidationDemoData {
+    fields: Vec<(String, String)>,
+}
+
+impl ValidationDemoData {
+    fn new() -> Self {
+        Self {
+            fields: vec![
+                ("👤 Name (max 20)".to_string(), "".to_string()),
+                ("📧 Email (max 50, warn@40)".to_string(), "".to_string()),
+                ("🔑 Password (5-20 chars)".to_string(), "".to_string()),
+                ("🔢 ID (min 3, max 10)".to_string(), "".to_string()),
+                ("📝 Comment (min 10, max 100)".to_string(), "".to_string()),
+                ("🏷️  Tag (max 30, bytes)".to_string(), "".to_string()),
+                ("🌍 Unicode (width, min 2)".to_string(), "".to_string()),
+            ],
+        }
+    }
+}
+
+impl DataProvider for ValidationDemoData {
+    fn field_count(&self) -> usize {
+        self.fields.len()
+    }
+
+    fn field_name(&self, index: usize) -> &str {
+        &self.fields[index].0
+    }
+
+    fn field_value(&self, index: usize) -> &str {
+        &self.fields[index].1
+    }
+
+    fn set_field_value(&mut self, index: usize, value: String) {
+        self.fields[index].1 = value;
+    }
+
+    fn supports_autocomplete(&self, _field_index: usize) -> bool {
+        false
+    }
+
+    fn display_value(&self, _index: usize) -> Option<&str> {
+        None
+    }
+
+    // 🎯 NEW: Validation configuration per field
+    fn validation_config(&self, field_index: usize) -> Option<ValidationConfig> {
+        match field_index {
+            0 => Some(ValidationConfig::with_max_length(20)), // Name: simple 20 char limit
+            1 => Some(
+                ValidationConfigBuilder::new()
+                    .with_character_limits(
+                        CharacterLimits::new(50).with_warning_threshold(40)
+                    )
+                    .build()
+            ), // Email: 50 chars with warning at 40
+            2 => Some(
+                ValidationConfigBuilder::new()
+                    .with_character_limits(CharacterLimits::new_range(5, 20))
+                    .build()
+            ), // Password: must be 5-20 characters (blocks field switching if 1-4 chars)
+            3 => Some(
+                ValidationConfigBuilder::new()
+                    .with_character_limits(CharacterLimits::new_range(3, 10))
+                    .build()
+            ), // ID: must be 3-10 characters (blocks field switching if 1-2 chars)
+            4 => Some(
+                ValidationConfigBuilder::new()
+                    .with_character_limits(CharacterLimits::new_range(10, 100))
+                    .build()
+            ), // Comment: must be 10-100 characters (blocks field switching if 1-9 chars)
+            5 => Some(
+                ValidationConfigBuilder::new()
+                    .with_character_limits(
+                        CharacterLimits::new(30).with_count_mode(CountMode::Bytes)
+                    )
+                    .build()
+            ), // Tag: 30 bytes (useful for UTF-8)
+            6 => Some(
+                ValidationConfigBuilder::new()
+                    .with_character_limits(
+                        CharacterLimits::new_range(2, 20).with_count_mode(CountMode::DisplayWidth)
+                    )
+                    .build()
+            ), // Unicode: 2-20 display width (useful for CJK characters, blocks if 1 char)
+            _ => None,
+        }
+    }
+}
+
+/// Handle key presses with validation-focused commands
+fn handle_key_press(
+    key: KeyCode,
+    modifiers: KeyModifiers,
+    editor: &mut ValidationFormEditor<ValidationDemoData>,
+) -> anyhow::Result<bool> {
+    let mode = editor.mode();
+
+    // Quit handling
+    if (key == KeyCode::Char('q') && modifiers.contains(KeyModifiers::CONTROL))
+        || (key == KeyCode::Char('c') && modifiers.contains(KeyModifiers::CONTROL))
+        || key == KeyCode::F(10)
+    {
+        return Ok(false);
+    }
+
+    match (mode, key, modifiers) {
+        // === MODE TRANSITIONS ===
+        (AppMode::ReadOnly, KeyCode::Char('i'), _) => {
+            editor.enter_edit_mode();
+            editor.clear_command_buffer();
+        }
+        (AppMode::ReadOnly, KeyCode::Char('a'), _) => {
+            editor.enter_append_mode();
+            editor.clear_command_buffer();
+        }
+        (AppMode::ReadOnly, KeyCode::Char('A'), _) => {
+            editor.move_line_end();
+            editor.enter_edit_mode();
+            editor.clear_command_buffer();
+        }
+
+        // Escape: Exit edit mode
+        (_, KeyCode::Esc, _) => {
+            if mode == AppMode::Edit {
+                editor.exit_edit_mode();
+            } else {
+                editor.clear_command_buffer();
+            }
+        }
+
+        // === VALIDATION COMMANDS ===
+        (AppMode::ReadOnly, KeyCode::Char('v'), _) => {
+            editor.validate_current_field();
+            editor.clear_command_buffer();
+        }
+        (AppMode::ReadOnly, KeyCode::Char('V'), _) => {
+            editor.validate_all_fields();
+            editor.clear_command_buffer();
+        }
+        (AppMode::ReadOnly, KeyCode::Char('c'), _) => {
+            editor.clear_validation_results();
+            editor.clear_command_buffer();
+        }
+        (AppMode::ReadOnly, KeyCode::F(1), _) => {
+            editor.toggle_validation();
+        }
+
+        // === MOVEMENT ===
+        (AppMode::ReadOnly, KeyCode::Char('h'), _) | (AppMode::ReadOnly, KeyCode::Left, _) => {
+            editor.move_left();
+            editor.clear_command_buffer();
+        }
+        (AppMode::ReadOnly, KeyCode::Char('l'), _) | (AppMode::ReadOnly, KeyCode::Right, _) => {
+            editor.move_right();
+            editor.clear_command_buffer();
+        }
+        (AppMode::ReadOnly, KeyCode::Char('j'), _) | (AppMode::ReadOnly, KeyCode::Down, _) => {
+            editor.move_down();
+            editor.clear_command_buffer();
+        }
+        (AppMode::ReadOnly, KeyCode::Char('k'), _) | (AppMode::ReadOnly, KeyCode::Up, _) => {
+            editor.move_up();
+            editor.clear_command_buffer();
+        }
+
+        // === EDIT MODE MOVEMENT ===
+        (AppMode::Edit, KeyCode::Left, _) => {
+            editor.move_left();
+        }
+        (AppMode::Edit, KeyCode::Right, _) => {
+            editor.move_right();
+        }
+        (AppMode::Edit, KeyCode::Up, _) => {
+            editor.move_up();
+        }
+        (AppMode::Edit, KeyCode::Down, _) => {
+            editor.move_down();
+        }
+
+        // === DELETE OPERATIONS ===
+        (AppMode::Edit, KeyCode::Backspace, _) => {
+            editor.delete_backward()?;
+        }
+        (AppMode::Edit, KeyCode::Delete, _) => {
+            editor.delete_forward()?;
+        }
+
+        // === TAB NAVIGATION ===
+        (_, KeyCode::Tab, _) => {
+            editor.next_field();
+        }
+        (_, KeyCode::BackTab, _) => {
+            editor.prev_field();
+        }
+
+        // === CHARACTER INPUT ===
+        (AppMode::Edit, KeyCode::Char(c), m) if !m.contains(KeyModifiers::CONTROL) => {
+            editor.insert_char(c)?;
+        }
+
+        // === DEBUG/INFO COMMANDS ===
+        (AppMode::ReadOnly, KeyCode::Char('?'), _) => {
+            let summary = editor.editor.validation_summary();
+            editor.set_debug_message(format!(
+                "Field {}/{}, Pos {}, Mode: {:?}, Validation: {} fields configured, {} validated",
+                editor.current_field() + 1,
+                editor.data_provider().field_count(),
+                editor.cursor_position(),
+                editor.mode(),
+                summary.total_fields,
+                summary.validated_fields
+            ));
+        }
+
+        _ => {
+            if editor.has_pending_command() {
+                editor.clear_command_buffer();
+                editor.set_debug_message("Invalid command sequence".to_string());
+            }
+        }
+    }
+
+    Ok(true)
+}
+
+fn run_app<B: Backend>(
+    terminal: &mut Terminal<B>,
+    mut editor: ValidationFormEditor<ValidationDemoData>,
+) -> io::Result<()> {
+    loop {
+        terminal.draw(|f| ui(f, &editor))?;
+
+        if let Event::Key(key) = event::read()? {
+            match handle_key_press(key.code, key.modifiers, &mut editor) {
+                Ok(should_continue) => {
+                    if !should_continue {
+                        break;
+                    }
+                }
+                Err(e) => {
+                    editor.set_debug_message(format!("Error: {}", e));
+                }
+            }
+        }
+    }
+
+    Ok(())
+}
+
+fn ui(f: &mut Frame, editor: &ValidationFormEditor<ValidationDemoData>) {
+    let chunks = Layout::default()
+        .direction(Direction::Vertical)
+        .constraints([Constraint::Min(8), Constraint::Length(12)])
+        .split(f.area());
+
+    render_enhanced_canvas(f, chunks[0], editor);
+    render_validation_status(f, chunks[1], editor);
+}
+
+fn render_enhanced_canvas(
+    f: &mut Frame,
+    area: Rect,
+    editor: &ValidationFormEditor<ValidationDemoData>,
+) {
+    render_canvas_default(f, area, &editor.editor);
+}
+
+fn render_validation_status(
+    f: &mut Frame,
+    area: Rect,
+    editor: &ValidationFormEditor<ValidationDemoData>,
+) {
+    let chunks = Layout::default()
+        .direction(Direction::Vertical)
+        .constraints([
+            Constraint::Length(3), // Status bar
+            Constraint::Length(4), // Validation summary
+            Constraint::Length(5), // Help
+        ])
+        .split(area);
+
+    // Status bar with validation information
+    let mode_text = match editor.mode() {
+        AppMode::Edit => "INSERT",
+        AppMode::ReadOnly => "NORMAL",
+        _ => "OTHER",
+    };
+
+    let validation_status = editor.get_validation_status();
+    let status_text = if editor.has_pending_command() {
+        format!("-- {} -- {} [{}] | Validation: {}", 
+                mode_text, editor.debug_message(), editor.get_command_buffer(), validation_status)
+    } else if editor.has_unsaved_changes() {
+        format!("-- {} -- [Modified] {} | Validation: {}", 
+                mode_text, editor.debug_message(), validation_status)
+    } else {
+        format!("-- {} -- {} | Validation: {}", 
+                mode_text, editor.debug_message(), validation_status)
+    };
+
+    let status = Paragraph::new(Line::from(Span::raw(status_text)))
+        .block(Block::default().borders(Borders::ALL).title("🔍 Validation Status"));
+
+    f.render_widget(status, chunks[0]);
+
+    // Validation summary with field switching info
+    let summary = editor.editor.validation_summary();
+    let summary_text = if editor.validation_enabled {
+        let switch_info = if editor.field_switch_blocked {
+            format!("\n🚫 Field switching blocked: {}", 
+                   editor.block_reason.as_deref().unwrap_or("Unknown reason"))
+        } else {
+            let (can_switch, reason) = editor.check_field_switch_allowed();
+            if !can_switch {
+                format!("\n⚠️  Field switching will be blocked: {}",
+                       reason.as_deref().unwrap_or("Unknown reason"))
+            } else {
+                "\n✅ Field switching allowed".to_string()
+            }
+        };
+        
+        format!(
+            "📊 Validation Summary: {} fields configured, {} validated{}\n\
+             ✅ Valid: {}  ⚠️  Warnings: {}  ❌ Errors: {}  📈 Progress: {:.0}%",
+            summary.total_fields,
+            summary.validated_fields,
+            switch_info,
+            summary.valid_fields,
+            summary.warning_fields,
+            summary.error_fields,
+            summary.completion_percentage() * 100.0
+        )
+    } else {
+        "❌ Validation is currently DISABLED\nPress F1 to enable validation".to_string()
+    };
+
+    let summary_style = if summary.has_errors() {
+        Style::default().fg(Color::Red)
+    } else if summary.has_warnings() {
+        Style::default().fg(Color::Yellow)
+    } else {
+        Style::default().fg(Color::Green)
+    };
+
+    let validation_summary = Paragraph::new(summary_text)
+        .block(Block::default().borders(Borders::ALL).title("📈 Validation Overview"))
+        .style(summary_style)
+        .wrap(Wrap { trim: true });
+
+    f.render_widget(validation_summary, chunks[1]);
+
+    // Enhanced help text
+    let help_text = match editor.mode() {
+        AppMode::ReadOnly => {
+            "🔍 VALIDATION DEMO: Different fields have different limits!\n\
+             Fields with MINIMUM requirements will block field switching if too short!\n\
+             Movement: hjkl/arrows=move, Tab/Shift+Tab=fields\n\
+             Edit: i/a/A=insert modes, Esc=normal\n\
+             Validation: v=validate current, V=validate all, c=clear results, F1=toggle\n\
+             ?=info, Ctrl+C/Ctrl+Q=quit"
+        }
+        AppMode::Edit => {
+            "✏️  INSERT MODE - Type to test validation limits!\n\
+             Some fields have MINIMUM character requirements!\n\
+             Try typing 1-2 chars in Password/ID/Comment fields, then try to switch!\n\
+             arrows=move, Backspace/Del=delete, Esc=normal, Tab=next field\n\
+             Field switching may be BLOCKED if minimum requirements not met!"
+        }
+        _ => "🔍 Validation Demo Active!"
+    };
+
+    let help = Paragraph::new(help_text)
+        .block(Block::default().borders(Borders::ALL).title("🚀 Validation Commands"))
+        .style(Style::default().fg(Color::Gray))
+        .wrap(Wrap { trim: true });
+
+    f.render_widget(help, chunks[2]);
+}
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    // Print feature status
+    println!("🔍 Canvas Validation Demo");
+    println!("✅ validation feature: ENABLED");
+    println!("🚀 Field validation: ACTIVE");
+    println!("🚫 Field switching validation: ACTIVE");
+    println!("📊 Try typing in fields with minimum requirements!");
+    println!("   - Password (min 5): Type 1-4 chars, then try to switch fields");
+    println!("   - ID (min 3): Type 1-2 chars, then try to switch fields");
+    println!("   - Comment (min 10): Type 1-9 chars, then try to switch fields");
+    println!("   - Unicode (min 2): Type 1 char, then try to switch fields");
+    println!();
+
+    enable_raw_mode()?;
+    let mut stdout = io::stdout();
+    execute!(stdout, EnterAlternateScreen, EnableMouseCapture)?;
+    let backend = CrosstermBackend::new(stdout);
+    let mut terminal = Terminal::new(backend)?;
+
+    let data = ValidationDemoData::new();
+    let editor = ValidationFormEditor::new(data);
+
+    let res = run_app(&mut terminal, editor);
+
+    disable_raw_mode()?;
+    execute!(
+        terminal.backend_mut(),
+        LeaveAlternateScreen,
+        DisableMouseCapture
+    )?;
+    terminal.show_cursor()?;
+
+    if let Err(err) = res {
+        println!("{:?}", err);
+    }
+
+    println!("🔍 Validation demo completed!");
+    Ok(())
+}

canvas/src/editor.rs

@@ -326,6 +326,20 @@ impl<D: DataProvider> FormEditor<D> {
     pub fn validation_summary(&self) -> crate::validation::ValidationSummary {
         self.ui_state.validation.summary()
     }
+    
+    /// Check if field switching is allowed from current field
+    #[cfg(feature = "validation")]
+    pub fn can_switch_fields(&self) -> bool {
+        let current_text = self.current_text();
+        self.ui_state.validation.allows_field_switch(self.ui_state.current_field, current_text)
+    }
+    
+    /// Get reason why field switching is blocked (if any)
+    #[cfg(feature = "validation")]
+    pub fn field_switch_block_reason(&self) -> Option<String> {
+        let current_text = self.current_text();
+        self.ui_state.validation.field_switch_block_reason(self.ui_state.current_field, current_text)
+    }
 
     // ===================================================================
     // ASYNC OPERATIONS: Only autocomplete needs async
@@ -409,10 +423,22 @@ impl<D: DataProvider> FormEditor<D> {
     // ===================================================================
 
     /// Move to previous field (vim k / up arrow)
-    pub fn move_up(&mut self) {
+    pub fn move_up(&mut self) -> Result<()> {
         let field_count = self.data_provider.field_count();
         if field_count == 0 {
-            return;
+            return Ok(());
+        }
+
+        // Check if field switching is allowed (minimum character enforcement)
+        #[cfg(feature = "validation")]
+        {
+            let current_text = self.current_text();
+            if !self.ui_state.validation.allows_field_switch(self.ui_state.current_field, current_text) {
+                if let Some(reason) = self.ui_state.validation.field_switch_block_reason(self.ui_state.current_field, current_text) {
+                    tracing::debug!("Field switch blocked: {}", reason);
+                    return Err(anyhow::anyhow!("Cannot switch fields: {}", reason));
+                }
+            }
         }
 
         // Validate current field before moving
@@ -430,13 +456,26 @@ impl<D: DataProvider> FormEditor<D> {
 
         self.ui_state.move_to_field(new_field, field_count);
         self.clamp_cursor_to_current_field();
+        Ok(())
     }
 
     /// Move to next field (vim j / down arrow)
-    pub fn move_down(&mut self) {
+    pub fn move_down(&mut self) -> Result<()> {
         let field_count = self.data_provider.field_count();
         if field_count == 0 {
-            return;
+            return Ok(());
+        }
+
+        // Check if field switching is allowed (minimum character enforcement)
+        #[cfg(feature = "validation")]
+        {
+            let current_text = self.current_text();
+            if !self.ui_state.validation.allows_field_switch(self.ui_state.current_field, current_text) {
+                if let Some(reason) = self.ui_state.validation.field_switch_block_reason(self.ui_state.current_field, current_text) {
+                    tracing::debug!("Field switch blocked: {}", reason);
+                    return Err(anyhow::anyhow!("Cannot switch fields: {}", reason));
+                }
+            }
         }
 
         // Validate current field before moving
@@ -454,6 +493,7 @@ impl<D: DataProvider> FormEditor<D> {
 
         self.ui_state.move_to_field(new_field, field_count);
         self.clamp_cursor_to_current_field();
+        Ok(())
     }
 
     /// Move to first field (vim gg)
@@ -480,13 +520,13 @@ impl<D: DataProvider> FormEditor<D> {
     }
 
     /// Move to previous field (alternative to move_up)
-    pub fn prev_field(&mut self) {
-        self.move_up();
+    pub fn prev_field(&mut self) -> Result<()> {
+        self.move_up()
     }
 
     /// Move to next field (alternative to move_down)
-    pub fn next_field(&mut self) {
-        self.move_down();
+    pub fn next_field(&mut self) -> Result<()> {
+        self.move_down()
     }
 
     /// Move to start of current field (vim 0)
@@ -649,15 +689,16 @@ impl<D: DataProvider> FormEditor<D> {
     }
 
     /// Exit edit mode to read-only mode (vim Escape)
-    pub fn exit_edit_mode(&mut self) {
+    pub fn exit_edit_mode(&mut self) -> Result<()> {
         // Validate current field content when exiting edit mode
         #[cfg(feature = "validation")]
         {
-            let current_text = self.current_text().to_string(); // Convert to String to avoid borrow conflicts
-            let _validation_result = self.ui_state.validation.validate_field_content(
-                self.ui_state.current_field,
-                &current_text,
-            );
+            let current_text = self.current_text();
+            if !self.ui_state.validation.allows_field_switch(self.ui_state.current_field, current_text) {
+                if let Some(reason) = self.ui_state.validation.field_switch_block_reason(self.ui_state.current_field, current_text) {
+                    return Err(anyhow::anyhow!("Cannot exit edit mode: {}", reason));
+                }
+            }
         }
         
         // Adjust cursor position when transitioning from edit to normal mode
@@ -674,6 +715,8 @@ impl<D: DataProvider> FormEditor<D> {
         self.set_mode(AppMode::ReadOnly);
         // Deactivate autocomplete when exiting edit mode
         self.ui_state.deactivate_autocomplete();
+
+        Ok(())
     }
 
     /// Enter edit mode from read-only mode (vim i/a/o)

canvas/src/validation/config.rs

@@ -1,3 +1,4 @@
+// src/validation/config.rs
 //! Validation configuration types and builders
 
 use crate::validation::CharacterLimits;
@@ -158,6 +159,32 @@ impl ValidationConfig {
         // || self.custom_formatting.is_some()
         // || self.external_validation.is_some()
     }
+    pub fn allows_field_switch(&self, text: &str) -> bool {
+        // Character limits validation
+        if let Some(ref limits) = self.character_limits {
+            if !limits.allows_field_switch(text) {
+                return false;
+            }
+        }
+        
+        // Future: Add other validation types here
+        
+        true
+    }
+    
+    /// Get reason why field switching is blocked (if any)
+    pub fn field_switch_block_reason(&self, text: &str) -> Option<String> {
+        // Character limits validation
+        if let Some(ref limits) = self.character_limits {
+            if let Some(reason) = limits.field_switch_block_reason(text) {
+                return Some(reason);
+            }
+        }
+        
+        // Future: Add other validation types here
+        
+        None
+    }
 }
 
 #[cfg(test)]

canvas/src/validation/limits.rs

@@ -1,3 +1,4 @@
+// src/validation/limits.rs
 //! Character limits validation implementation
 
 use crate::validation::ValidationResult;
@@ -250,6 +251,29 @@ impl CharacterLimits {
             },
         }
     }
+    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 {} characters (currently: {})",
+                    min, count
+                ));
+            }
+        }
+        None
+    }
 }
 
 impl Default for CharacterLimits {
@@ -362,4 +386,39 @@ mod tests {
         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());
+    }
 }

canvas/src/validation/state.rs

@@ -1,3 +1,4 @@
+// src/validation/state.rs
 //! Validation state management
 
 use crate::validation::{ValidationConfig, ValidationResult};
@@ -174,7 +175,31 @@ impl ValidationState {
         self.field_configs.len()
     }
     
-    /// Get validation summary
+    /// Check if field switching is allowed for a specific field
+    pub fn allows_field_switch(&self, field_index: usize, text: &str) -> bool {
+        if !self.enabled {
+            return true;
+        }
+        
+        if let Some(config) = self.field_configs.get(&field_index) {
+            config.allows_field_switch(text)
+        } else {
+            true // No validation configured, allow switching
+        }
+    }
+    
+    /// Get reason why field switching is blocked (if any)
+    pub fn field_switch_block_reason(&self, field_index: usize, text: &str) -> Option<String> {
+        if !self.enabled {
+            return None;
+        }
+        
+        if let Some(config) = self.field_configs.get(&field_index) {
+            config.field_switch_block_reason(text)
+        } else {
+            None // No validation configured
+        }
+    }
     pub fn summary(&self) -> ValidationSummary {
         let total_validated = self.validated_fields.len();
         let errors = self.fields_with_errors().count();