// src/table_script/handlers/post_table_script.rs
// TODO MAKE THE SCRIPTS PUSH ONLY TO THE EMPTY FILES

use tonic::Status;
use sqlx::{PgPool, Error as SqlxError};
use common::proto::multieko2::table_script::{PostTableScriptRequest, TableScriptResponse};
use serde_json::Value;
use steel_decimal::SteelDecimal;

use crate::table_script::handlers::dependency_analyzer::DependencyAnalyzer;

const SYSTEM_COLUMNS: &[&str] = &["id", "deleted", "created_at"];

/// Validates the target column and ensures it is not a system column.
/// Returns the column type if valid.
fn validate_target_column(
    table_name: &str,
    target: &str,
    table_columns: &Value,
) -> Result<String, String> {
    if SYSTEM_COLUMNS.contains(&target) {
        return Err(format!("Cannot override system column: {}", target));
    }

    // Parse the columns JSON into a vector of strings
    let columns: Vec<String> = serde_json::from_value(table_columns.clone())
        .map_err(|e| format!("Invalid column data: {}", e))?;

    // Extract column names and types
    let column_info: Vec<(&str, &str)> = columns
        .iter()
        .filter_map(|c| {
            let mut parts = c.split_whitespace();
            let name = parts.next()?.trim_matches('"');
            let data_type = parts.next()?;
            Some((name, data_type))
        })
        .collect();

    // Find the target column and return its type
    column_info
        .iter()
        .find(|(name, _)| *name == target)
        .map(|(_, dt)| dt.to_string())
        .ok_or_else(|| format!("Target column '{}' not defined in table '{}'", target, table_name))
}

/// Handles the creation of a new table script with dependency validation.
pub async fn post_table_script(
    db_pool: &PgPool,
    request: PostTableScriptRequest,
) -> Result<TableScriptResponse, Status> {
    // Start a transaction for ALL operations - critical for atomicity
    let mut tx = db_pool.begin().await
        .map_err(|e| Status::internal(format!("Failed to start transaction: {}", e)))?;

    // Fetch the table definition
    let table_def = sqlx::query!(
        r#"SELECT id, table_name, columns, schema_id
         FROM table_definitions WHERE id = $1"#,
        request.table_definition_id
    )
    .fetch_optional(&mut *tx)
    .await
    .map_err(|e| Status::internal(format!("Failed to fetch table definition: {}", e)))?
    .ok_or_else(|| Status::not_found("Table definition not found"))?;

    // Validate the target column and get its type
    let column_type = validate_target_column(
        &table_def.table_name,
        &request.target_column,
        &table_def.columns,
    )
    .map_err(|e| Status::invalid_argument(e))?;

    // Create dependency analyzer for this schema
    let analyzer = DependencyAnalyzer::new(table_def.schema_id, db_pool.clone());

    // Analyze script dependencies
    let dependencies = analyzer
        .analyze_script_dependencies(&request.script)
        .map_err(|e| Status::from(e))?;

    // Check for circular dependencies BEFORE making any changes
    // Pass the transaction to ensure we see any existing dependencies
    analyzer
        .check_for_cycles(&mut tx, table_def.id, &dependencies)
        .await
        .map_err(|e| Status::from(e))?;

    // Transform the script using steel_decimal
    let steel_decimal = SteelDecimal::new();
    let parsed_script = steel_decimal.transform(&request.script);

    // Insert or update the script
    let script_record = sqlx::query!(
        r#"INSERT INTO table_scripts
        (table_definitions_id, target_table, target_column,
         target_column_type, script, description, schema_id)
        VALUES ($1, $2, $3, $4, $5, $6, $7)
        ON CONFLICT (table_definitions_id, target_column)
        DO UPDATE SET
            script = EXCLUDED.script,
            description = EXCLUDED.description,
            target_column_type = EXCLUDED.target_column_type
        RETURNING id"#,
        request.table_definition_id,
        table_def.table_name,
        request.target_column,
        column_type,
        parsed_script,
        request.description,
        table_def.schema_id
    )
    .fetch_one(&mut *tx)
    .await
    .map_err(|e| {
        match e {
            SqlxError::Database(db_err)
                if db_err.constraint() == Some("table_scripts_table_definitions_id_target_column_key") => {
                Status::already_exists("Script already exists for this column")
            }
            _ => Status::internal(format!("Failed to insert script: {}", e)),
        }
    })?;

    // Save the dependencies within the same transaction
    analyzer
        .save_dependencies(&mut tx, script_record.id, table_def.id, &dependencies)
        .await
        .map_err(|e| Status::from(e))?;

    // Only now commit the entire transaction - script + dependencies together
    tx.commit().await
        .map_err(|e| Status::internal(format!("Failed to commit transaction: {}", e)))?;

    // Generate warnings for potential issues
    let warnings = generate_warnings(&dependencies, &table_def.table_name);

    Ok(TableScriptResponse {
        id: script_record.id,
        warnings,
    })
}

/// Generate helpful warnings for script dependencies
fn generate_warnings(dependencies: &[crate::table_script::handlers::dependency_analyzer::Dependency], table_name: &str) -> String {
    let mut warnings = Vec::new();

    // Check for self-references
    if dependencies.iter().any(|d| d.target_table == table_name) {
        warnings.push("Warning: Script references its own table, which may cause issues during initial population.".to_string());
    }

    // Check for complex SQL queries
    let sql_deps_count = dependencies.iter()
        .filter(|d| matches!(d.dependency_type, crate::table_script::handlers::dependency_analyzer::DependencyType::SqlQuery { .. }))
        .count();

    if sql_deps_count > 0 {
        warnings.push(format!(
            "Warning: Script contains {} raw SQL quer{}, ensure they are read-only and reference valid tables.",
            sql_deps_count,
            if sql_deps_count == 1 { "y" } else { "ies" }
        ));
    }

    // Check for many dependencies
    if dependencies.len() > 5 {
        warnings.push(format!(
            "Warning: Script depends on {} tables, which may affect processing performance.",
            dependencies.len()
        ));
    }

    // Count structured access dependencies
    let structured_deps_count = dependencies.iter()
        .filter(|d| matches!(
            d.dependency_type,
            crate::table_script::handlers::dependency_analyzer::DependencyType::ColumnAccess { .. } |
            crate::table_script::handlers::dependency_analyzer::DependencyType::IndexedAccess { .. }
        ))
        .count();

    if structured_deps_count > 0 {
        warnings.push(format!(
            "Info: Script uses {} linked table{} via steel_get_column functions.",
            structured_deps_count,
            if structured_deps_count == 1 { "" } else { "s" }
        ));
    }

    warnings.join(" ")
}