<?php
/**
 * TMDO_Schema_Manager - 動態 DDL 引擎
 *
 * 功能：
 * - 根據欄位定義動態建立／升級扁平化資料表
 * - WordPress 型別 → MySQL 型別映射
 * - 自動索引策略（B-Tree、全文、唯一）
 * - Schema 版本控制（hash 比對）
 *
 * @package WP_Data_Optimizer
 */

declare(strict_types=1);

// phpcs:disable Squiz.Commenting,Generic.Commenting,WordPress.DB.PreparedSQL.NotPrepared,WordPress.DB.PreparedSQL.InterpolatedNotPrepared,WordPress.DB.PreparedSQLPlaceholders.ReplacementsWrongNumber,Generic.CodeAnalysis.UnusedFunctionParameter,Generic.CodeAnalysis.EmptyStatement,Squiz.PHP.DisallowMultipleAssignments,Squiz.PHP.DisallowSizeFunctionsInLoops,WordPress.WP.I18n.MissingTranslatorsComment,WordPress.PHP.NoSilencedErrors,WordPress.WP.AlternativeFunctions.file_get_contents_file_get_contents,Squiz.PHP.CommentedOutCode,Universal.NamingConventions.NoReservedKeywordParameterNames,WordPress.PHP.YodaConditions,Squiz.Commenting.InlineComment.InvalidEndChar -- PR-1 ported from UAE; cleanup PR scheduled.


defined( 'ABSPATH' ) || exit;

final class TMDO_Schema_Manager {

	/** Request-scoped cache for table_exists() — prevents repeated SHOW TABLES per request. */
	private static array $table_exists_cache = array();

	/**
	 * WordPress 邏輯型別 → MySQL 實體型別映射
	 */
	private static array $type_map = array(
		'text'      => 'VARCHAR(255)',
		'textarea'  => 'TEXT',
		'integer'   => 'BIGINT(20)',
		'decimal'   => 'DECIMAL(18,6)',
		'boolean'   => 'TINYINT(1)',
		'date'      => 'DATE',
		'datetime'  => 'DATETIME',
		'timestamp' => 'TIMESTAMP',
		'json'      => 'LONGTEXT',  // MySQL 5.7.8+ 可用 JSON，為相容性用 LONGTEXT
		'enum'      => 'VARCHAR(100)', // 在 PHP 層驗證
		'binary'    => 'LONGBLOB',
	);

	/**
	 * 取得完整資料表名稱
	 */
	public static function get_table_name( string $entity_type, string $group_name ): string {
		global $wpdb;
		return $wpdb->prefix . TMDO_TABLE_PREFIX . sanitize_key( $entity_type ) . '_' . sanitize_key( $group_name );
	}

	/**
	 * 批次處理所有待建表
	 */
	public static function process_pending_migrations(): void {
		$pending = TMDO_Entity_Registry::get_pending_schemas();

		foreach ( $pending as $schema ) {
			self::create_or_upgrade_table(
				$schema['type'],
				$schema['group'],
				$schema['fields']
			);
		}

		TMDO_Entity_Registry::clear_pending_schemas();
	}

	/**
	 * 建立或升級資料表
	 */
	public static function create_or_upgrade_table(
		string $entity_type,
		string $group_name,
		array $field_definitions
	): bool {
		global $wpdb;

		// Schema 版本比對：若未變動則跳過
		$schema_hash = self::calculate_schema_hash( $field_definitions );
		$stored_hash = self::get_stored_schema_hash( $entity_type, $group_name );

		if ( $stored_hash === $schema_hash ) {
			return true;
		}

		$adapter = TMDO_Entity_Registry::get_adapter( $entity_type );
		if ( ! $adapter ) {
			return false;
		}

		$table   = self::get_table_name( $entity_type, $group_name );
		$charset = $wpdb->get_charset_collate();
		$id_col  = $adapter->get_entity_id_column();

		// 建立基礎欄位（每張表都有）
		$sql_columns = array(
			'`id` BIGINT(20) NOT NULL AUTO_INCREMENT',
			"`{$id_col}` BIGINT(20) NOT NULL",
			'`created_at` DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP',
			'`updated_at` DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP',
		);

		$sql_indexes = array(
			'PRIMARY KEY (`id`)',
			"UNIQUE KEY `uk_entity` (`{$id_col}`)",
			'KEY `idx_created` (`created_at`)',
		);

		// 處理動態欄位
		foreach ( $field_definitions as $field ) {
			$col_name = self::sanitize_column_name( $field['key'] );
			$col_type = self::$type_map[ $field['type'] ] ?? 'VARCHAR(255)';

			$null_clause = ! empty( $field['required'] ) ? 'NOT NULL' : 'DEFAULT NULL';
			$default     = self::build_default_clause( $field );

			// 組合欄位 DDL
			$col_ddl = "`{$col_name}` {$col_type} {$null_clause}";
			if ( $default !== '' ) {
				$col_ddl .= " {$default}";
			}

			$sql_columns[] = $col_ddl;

			// 索引策略
			if ( ! empty( $field['unique'] ) ) {
				$sql_indexes[] = "UNIQUE KEY `uk_{$col_name}` (`{$col_name}`)";
			} elseif ( ! empty( $field['searchable'] ) ) {
				// 不同型別決定索引長度
				if ( in_array( $field['type'], array( 'text', 'textarea' ), true ) ) {
					// 文字欄位使用前綴索引避免過長
					$sql_indexes[] = "KEY `idx_{$col_name}` (`{$col_name}`(100))";
				} else {
					$sql_indexes[] = "KEY `idx_{$col_name}` (`{$col_name}`)";
				}
			}

			if ( ! empty( $field['fulltext'] ) && in_array( $field['type'], array( 'text', 'textarea' ), true ) ) {
				$sql_indexes[] = "FULLTEXT KEY `ft_{$col_name}` (`{$col_name}`)";
			}
		}

		$columns_sql = implode( ",\n  ", $sql_columns );
		$indexes_sql = implode( ",\n  ", $sql_indexes );

		$sql = "CREATE TABLE `{$table}` (\n  {$columns_sql},\n  {$indexes_sql}\n) {$charset};";

		require_once ABSPATH . 'wp-admin/includes/upgrade.php';

		// dbDelta 自動處理建表／ALTER TABLE
		$dbdelta_result = dbDelta( $sql );

		// Bust the request-scoped table_exists cache so subsequent calls see the new table.
		self::$table_exists_cache[ $table ] = true;

		// 記錄 Schema 版本與定義
		self::store_schema_metadata( $entity_type, $group_name, $schema_hash, $field_definitions );

		/**
		 * Action: 表建立／升級完成
		 */
		do_action( 'wpdo_schema_updated', $entity_type, $group_name, $table, $dbdelta_result );

		return true;
	}

	/**
	 * 計算 Schema Hash（用於偵測欄位變動）
	 */
	public static function calculate_schema_hash( array $fields ): string {
		// 正規化：僅保留影響 Schema 的屬性
		$normalized = array_map(
			function ( $f ) {
				return array(
					'key'        => $f['key'] ?? '',
					'type'       => $f['type'] ?? '',
					'required'   => ! empty( $f['required'] ),
					'default'    => $f['default'] ?? null,
					'searchable' => ! empty( $f['searchable'] ),
					'fulltext'   => ! empty( $f['fulltext'] ),
					'unique'     => ! empty( $f['unique'] ),
				);
			},
			$fields
		);

		// 依 key 排序以確保 hash 穩定
		usort( $normalized, fn( $a, $b ) => strcmp( $a['key'], $b['key'] ) );

		$json = wp_json_encode( $normalized, JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES );

		return hash( 'sha256', $json );
	}

	/**
	 * 欄位名稱清理（防止 SQL 注入）
	 */
	public static function sanitize_column_name( string $key ): string {
		// 移除所有非 alphanumeric/底線
		$clean = preg_replace( '/[^a-zA-Z0-9_]/', '', $key );

		// 若以數字開頭，前綴 f_
		if ( $clean !== '' && preg_match( '/^\d/', $clean ) ) {
			$clean = 'f_' . $clean;
		}

		// MySQL 欄位名長度限制 64 字元
		return substr( $clean, 0, 60 );
	}

	/**
	 * 建立 DEFAULT 子句
	 */
	private static function build_default_clause( array $field ): string {
		if ( ! isset( $field['default'] ) || $field['default'] === null ) {
			return '';
		}

		$default = $field['default'];

		switch ( $field['type'] ) {
			case 'integer':
			case 'boolean':
				return 'DEFAULT ' . (int) $default;

			case 'decimal':
				return 'DEFAULT ' . (float) $default;

			case 'date':
			case 'datetime':
			case 'timestamp':
				if ( strtoupper( (string) $default ) === 'CURRENT_TIMESTAMP' ) {
					return 'DEFAULT CURRENT_TIMESTAMP';
				}
				return "DEFAULT '" . esc_sql( (string) $default ) . "'";

			case 'json':
			case 'text':
			case 'textarea':
			case 'enum':
			default:
				return "DEFAULT '" . esc_sql( (string) $default ) . "'";
		}
	}

	/**
	 * 儲存 Schema metadata 到 wpdo_registry_meta 表
	 */
	private static function store_schema_metadata(
		string $entity_type,
		string $group_name,
		string $schema_hash,
		array $field_definitions
	): void {
		global $wpdb;

		$table = $wpdb->prefix . TMDO_TABLE_PREFIX . 'registry_meta';

		$wpdb->replace(
			$table,
			array(
				'entity_type'       => $entity_type,
				'group_name'        => $group_name,
				'schema_hash'       => $schema_hash,
				'field_definitions' => wp_json_encode( $field_definitions, JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES ),
			),
			array( '%s', '%s', '%s', '%s' )
		);
	}

	/**
	 * 取得已儲存的 Schema hash
	 */
	public static function get_stored_schema_hash( string $entity_type, string $group_name ): string {
		global $wpdb;

		$table = $wpdb->prefix . TMDO_TABLE_PREFIX . 'registry_meta';

		$hash = $wpdb->get_var(
			$wpdb->prepare(
				"SELECT schema_hash FROM `{$table}` WHERE entity_type = %s AND group_name = %s",
				$entity_type,
				$group_name
			)
		);

		return $hash ?: '';
	}

	/**
	 * 檢查表是否存在
	 */
	public static function table_exists( string $table_name ): bool {
		global $wpdb;
		if ( isset( self::$table_exists_cache[ $table_name ] ) ) {
			return self::$table_exists_cache[ $table_name ];
		}

		$result                                  = $wpdb->get_var( $wpdb->prepare( 'SHOW TABLES LIKE %s', $table_name ) );
		self::$table_exists_cache[ $table_name ] = $result === $table_name;
		return self::$table_exists_cache[ $table_name ];
	}

	/**
	 * Clear the request-scoped table-exists cache.
	 *
	 * Mirrors TMDO_Routing_Predicate::flush_cache(): call in test setUp to isolate
	 * cases. In production the cache is correct for a request lifetime; tests that
	 * create then drop flat tables across classes must reset it so a stale `true`
	 * does not survive after a table is dropped.
	 */
	public static function flush_table_exists_cache(): void {
		self::$table_exists_cache = array();
	}

	/**
	 * 丟棄表（謹慎使用，僅用於解除安裝）
	 */
	public static function drop_table( string $entity_type, string $group_name ): bool {
		global $wpdb;
		$table = self::get_table_name( $entity_type, $group_name );
		return (bool) $wpdb->query( "DROP TABLE IF EXISTS `{$table}`" );
	}

	/**
	 * 取得所有 UAE 建立的表清單
	 */
	public static function list_all_uae_tables(): array {
		global $wpdb;
		$prefix = $wpdb->prefix . TMDO_TABLE_PREFIX;
		$tables = $wpdb->get_col( $wpdb->prepare( 'SHOW TABLES LIKE %s', $prefix . '%' ) );
		return $tables ?: array();
	}

	/**
	 * 取得資料表統計資訊（大小、列數）
	 */
	public static function get_table_stats( string $table_name ): array {
		global $wpdb;

		$info = $wpdb->get_row(
			$wpdb->prepare(
				'SELECT TABLE_ROWS, DATA_LENGTH, INDEX_LENGTH
			 FROM information_schema.TABLES
			 WHERE TABLE_SCHEMA = %s AND TABLE_NAME = %s',
				DB_NAME,
				$table_name
			),
			ARRAY_A
		);

		if ( ! $info ) {
			return array(
				'rows'     => 0,
				'size_mb'  => 0,
				'index_mb' => 0,
			);
		}

		return array(
			'rows'     => (int) $info['TABLE_ROWS'],
			'size_mb'  => round( $info['DATA_LENGTH'] / 1024 / 1024, 2 ),
			'index_mb' => round( $info['INDEX_LENGTH'] / 1024 / 1024, 2 ),
		);
	}
}