<?php

namespace App\Services;

use DateTimeImmutable;
use Illuminate\Support\Facades\DB; // <-- Added DB facade for schema introspection

class HfsqlDataConverter
{
    // Cache for PostgreSQL column types (key: tableName, value: [columnName => dataType])
    protected $pgSchemaCache = [];

    /**
     * Converts a single HFSQL record array into a numerically indexed array
     * ready for fputcsv, ensuring order and PostgreSQL type compliance.
     * * @param string $tableName The target PostgreSQL table name.
     * @param array $hfsqlRecord The associative HFSQL record array.
     * @param array $pgColumnOrder The list of column names in the correct order for COPY.
     * @return array The numerically indexed array of converted values.
     */
    public function convertToPostgres(string $tableName, array $hfsqlRecord, array $pgColumnOrder): array
    {
        $postgresRecordValues = [];
        // 1. Get the PostgreSQL schema for the table (cached)
        $pgSchemaTypes = $this->getPostgresSchema($tableName);

        // Ensure keys are lowercase for safe lookup
        $hfsqlRecord = array_change_key_case($hfsqlRecord, CASE_LOWER);

        foreach ($pgColumnOrder as $pgColumn) {
            // Buscar el tipo usando lowercase para la comparación
            $pgColumnLower = strtolower($pgColumn);

            // Get the target Postgres type (e.g., 'timestamp without time zone', 'numeric')
            // Default to 'text' if the column is not found in the schema (should not happen normally)
            $pgType = $pgSchemaTypes[$pgColumnLower] ?? 'text';

            // The value is read by column name (lowercase), which is safer than assuming associative order
            $value = $hfsqlRecord[$pgColumnLower] ?? null;

            // 2. STAGE 1: Sanitization
            if (is_string($value)) {
                $value = trim($value);
                $value = $this->sanitizeEncoding($value);
            }

            // 3. STAGE 2: NULL and EMPTY string handling
            // For Postgres COPY, an unquoted empty string signals NULL for any type.
            if (is_null($value) || $value === '') {
                // If it's NULL or an empty string, return an empty string for COPY.
                $convertedValue = '';
            } else {
                // 4. STAGE 3: Type-specific conversion based on the actual PG schema type
                $convertedValue = $this->convertValue($value, $pgType);
            }

            $postgresRecordValues[] = $convertedValue;
        }

        return $postgresRecordValues;
    }

    /**
     * Dynamically fetches the PostgreSQL column types for the target table
     * and caches the result.
     * * @param string $tableName The table name.
     * @return array [columnName => dataType] map (keys in lowercase for comparison).
     */
    protected function getPostgresSchema(string $tableName): array
    {
        if (isset($this->pgSchemaCache[$tableName])) {
            return $this->pgSchemaCache[$tableName];
        }

        // Query information_schema to get column names and data types in ordinal position
        // Buscar por el nombre exacto de la tabla (sin convertir a lowercase)
        $results = DB::select("
            SELECT column_name, data_type
            FROM information_schema.columns
            WHERE table_name = ?
            ORDER BY ordinal_position",
            [$tableName] // Mantener el case original
        );

        $schemaMap = [];
        foreach ($results as $column) {
            // Store the type with lowercase key for safe comparison
            // pero mantener el valor del tipo en lowercase (e.g., 'timestamp without time zone')
            $schemaMap[strtolower($column->column_name)] = strtolower($column->data_type);
        }

        return $this->pgSchemaCache[$tableName] = $schemaMap;
    }

    /**
     * Central logic to convert a non-null/non-empty value based on destination type.
     * The $pgType is the actual type string from information_schema (e.g., 'numeric', 'timestamp without time zone').
     */
    protected function convertValue($value, string $pgType): string
    {
        // Value is guaranteed to be non-null and non-empty at this point.

        // Normalize the PostgreSQL type string for cleaner switch logic
        // Example: 'timestamp without time zone' becomes 'timestamp'
        $type = explode(' ', $pgType)[0];

        switch ($type) {
            case 'timestamp': // Includes 'timestamp with/without time zone'
                // Output format: YYYY-MM-DD HH:MI:SS (Postgres standard)
                return $this->convertDateTime($value, 'Y-m-d H:i:s');

            case 'date':
                // Output format: YYYY-MM-DD
                return $this->convertDateTime($value, 'Y-m-d');

            case 'numeric':
            case 'double':
            case 'real':
            case 'money':
                // Cleans up numeric formats (e.g., handles "1,234.56" or "1.234,56").
                // This ensures the decimal point is consistent (dot) and removes thousand separators.
                $cleanValue = (string) $value;
                // Remove non-digit, non-decimal-point, non-minus signs
                $cleanValue = preg_replace('/[^0-9\.\-]/', '', $cleanValue);

                return is_numeric($cleanValue) ? (string) (float) $cleanValue : '';

            case 'integer':
            case 'smallint':
            case 'bigint':
                // Output format: integer (no decimal point)
                $cleanValue = (string) $value;
                // Remove non-digit, non-minus, non-plus signs
                $cleanValue = preg_replace('/[^0-9\-\+]/', '', $cleanValue);

                return is_numeric($cleanValue) ? (string) (int) $cleanValue : '';

            case 'boolean':
                $cleanValue = strtolower((string) $value);
                // Postgres BOOLEAN accepts 't', 'f', 'true', 'false', 'y', 'n', '1', '0'
                if (in_array($cleanValue, ['true', 't', 'y', '1', 'oui'])) {
                    return 't';
                }
                return 'f';

            case 'text':
            case 'character':
            case 'varchar':
            default:
                // Ensure text is cast to string and returned.
                return (string) $value;
        }
    }

    /**
     * Converts various date/time inputs into a strict Postgres format.
     */
    protected function convertDateTime($value, string $format): string
    {
        // Try parsing the value robustly
        try {
            // Use DateTimeImmutable for parsing, which is safer than strtotime
            if ($value instanceof DateTimeImmutable) {
                $date = $value;
            } elseif (is_numeric($value) && $value > 0) {
                // Assume timestamp if numeric
                $date = (new DateTimeImmutable())->setTimestamp((int) $value);
            } else {
                // Parse string value, handles many formats including YYYYMMDD
                $date = new DateTimeImmutable((string) $value);
            }

            return $date->format($format);

        } catch (\Exception $e) {
            // If parsing fails, return an empty string (which becomes NULL in COPY)
            return '';
        }
    }

    /**
     * Sanitizes and converts string encoding from Windows-1252 to UTF-8.
     * This is critical for compatibility between HFSQL and Postgres.
     */
    protected function sanitizeEncoding(string $value): string
    {
        // Assuming the most common source encoding for HFSQL on Windows is CP1252
        $fromEncoding = 'Windows-1252';

        if (mb_check_encoding($value, 'UTF-8')) {
            return $value;
        }

        // Use @iconv to suppress warnings if the conversion is incomplete
        $cleaned = @iconv($fromEncoding, 'UTF-8//IGNORE', $value);

        return ($cleaned !== false) ? $cleaned : $value;
    }
}