<?php
/**
 * Database abstraction layer for WP Data Optimizer.
 *
 * @package WP_Data_Optimizer
 */

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * TMDO_DB — Database abstraction layer for MySQL / SQLite dual support.
 *
 * Provides unified transaction interface, SQL dialect helpers, and
 * table name resolution. Absorbs and extends the FCB_DB pattern.
 */
class TMDO_DB {

	/**
	 * Check if the current database engine is SQLite.
	 */
	public static function is_sqlite(): bool {
		return TMDO_IS_SQLITE;
	}

	/**
	 * Check if the current database engine is MySQL.
	 */
	public static function is_mysql(): bool {
		return TMDO_IS_MYSQL;
	}

	/**
	 * Begin a database transaction.
	 *
	 * SQLite: BEGIN IMMEDIATE (write-lock, prevents concurrent writes).
	 * MySQL:  START TRANSACTION (row-level locking via InnoDB).
	 */
	public static function begin(): void {
		global $wpdb;
		$wpdb->query( self::is_sqlite() ? 'BEGIN IMMEDIATE' : 'START TRANSACTION' ); // phpcs:ignore WordPress.DB.PreparedSQL.NotPrepared -- Static SQL literals; no user input.
	}

	/**
	 * Commit the current transaction.
	 */
	public static function commit(): void {
		global $wpdb;
		$wpdb->query( 'COMMIT' );
	}

	/**
	 * Roll back the current transaction.
	 */
	public static function rollback(): void {
		global $wpdb;
		$wpdb->query( 'ROLLBACK' );
	}

	/**
	 * Get the current WordPress local time as a MySQL datetime string.
	 */
	public static function now(): string {
		return current_time( 'mysql' );
	}

	/**
	 * Get the full table name with wpdb prefix.
	 *
	 * @param string $name Table name without prefix (e.g. 'wpdo_warm').
	 * @return string Fully-prefixed, sanitized table name.
	 */
	public static function table( string $name ): string {
		global $wpdb;
		return $wpdb->prefix . sanitize_key( $name );
	}

	/**
	 * Execute an INSERT IGNORE statement (MySQL) or INSERT OR IGNORE (SQLite).
	 *
	 * @param string $table  Full table name.
	 * @param array  $data   Column => value pairs.
	 * @param array  $format Optional wpdb format array ('%s', '%d', etc.).
	 * @return int|false      Number of rows affected, or false on error.
	 */
	public static function insert_ignore( string $table, array $data, array $format = array() ): int|false {
		global $wpdb;

		$columns     = array_keys( $data );
		$values      = array_values( $data );
		$col_list    = implode( ', ', array_map( fn( $c ) => '`' . sanitize_key( $c ) . '`', $columns ) );
		$placeholder = implode( ', ', $format ?: array_fill( 0, count( $values ), '%s' ) );

		$keyword = self::is_sqlite() ? 'INSERT OR IGNORE' : 'INSERT IGNORE';

		$sql = "{$keyword} INTO `{$table}` ({$col_list}) VALUES ({$placeholder})";

		return $wpdb->query( $wpdb->prepare( $sql, ...$values ) ); // phpcs:ignore WordPress.DB.PreparedSQL.NotPrepared
	}

	/**
	 * Build a JSON_EXTRACT expression compatible with both MySQL and SQLite.
	 *
	 * Both MySQL 5.7+ and SQLite 3.38+ support json_extract().
	 *
	 * @param string $column Column name containing JSON data.
	 * @param string $path   JSON path (e.g. '$.social_links').
	 * @return string         SQL expression.
	 */
	public static function json_extract( string $column, string $path ): string {
		$column = sanitize_key( $column );
		// JSON path must start with '$' and contain only word chars, dots, brackets, and digits.
		if ( ! preg_match( '/^\$[\w.\[\]0-9]*$/', $path ) ) {
			$path = '$';
		}
		return "json_extract(`{$column}`, '{$path}')";
	}

	/**
	 * Build an UPSERT statement.
	 *
	 * MySQL:  INSERT ... ON DUPLICATE KEY UPDATE ...
	 * SQLite: INSERT ... ON CONFLICT(...) DO UPDATE SET ...
	 *
	 * @param string          $table          Full table name.
	 * @param array           $data           Column => value pairs to insert.
	 * @param array           $update_columns Columns to update on conflict.
	 * @param string|string[] $conflict_key   Column name (string) or columns (array)
	 *                                        for ON CONFLICT (SQLite). On MySQL it
	 *                                        is informational only — ON DUPLICATE
	 *                                        KEY UPDATE matches any unique key.
	 * @param array           $format         Optional wpdb format array.
	 * @return int|false
	 */
	public static function upsert( string $table, array $data, array $update_columns, string|array $conflict_key = 'post_id', array $format = array() ): int|false {
		global $wpdb;

		$columns = array_keys( $data );
		$values  = array_values( $data );
		// Normalise composite vs single conflict key.
		$conflict_keys = is_array( $conflict_key ) ? $conflict_key : array( $conflict_key );
		$conflict_keys = array_map( 'sanitize_key', $conflict_keys );
		$conflict_list = implode(
			', ',
			array_map( static fn( $k ) => '`' . $k . '`', $conflict_keys )
		);

		$col_list = implode( ', ', array_map( fn( $c ) => '`' . sanitize_key( $c ) . '`', $columns ) );

		// Build per-value placeholders, using NULL literal for null values.
		$prepare_values = array();
		$placeholders   = array();
		$fmt            = $format ?: array_fill( 0, count( $values ), '%s' );
		foreach ( $values as $i => $v ) {
			if ( null === $v ) {
				$placeholders[] = 'NULL';
			} else {
				$placeholders[]   = $fmt[ $i ] ?? '%s';
				$prepare_values[] = $v;
			}
		}
		$placeholder = implode( ', ', $placeholders );

		// ON DUPLICATE KEY UPDATE: null columns use NULL literal, others use VALUES().
		$null_cols = array();
		foreach ( $update_columns as $c ) {
			$col_index = array_search( $c, $columns, true );
			if ( false !== $col_index && null === $values[ $col_index ] ) {
				$null_cols[] = $c;
			}
		}

		if ( self::is_mysql() ) {
			$updates = implode(
				', ',
				array_map(
					function ( $c ) use ( $null_cols ) {
						$safe = sanitize_key( $c );
						return in_array( $c, $null_cols, true )
							? "`{$safe}` = NULL"
							: "`{$safe}` = VALUES(`{$safe}`)";
					},
					$update_columns
				)
			);
			$sql     = "INSERT INTO `{$table}` ({$col_list}) VALUES ({$placeholder}) ON DUPLICATE KEY UPDATE {$updates}";
		} else {
			$updates = implode(
				', ',
				array_map(
					function ( $c ) use ( $null_cols ) {
						$safe = sanitize_key( $c );
						return in_array( $c, $null_cols, true )
							? "`{$safe}` = NULL"
							: "`{$safe}` = excluded.`{$safe}`";
					},
					$update_columns
				)
			);
			$sql     = "INSERT INTO `{$table}` ({$col_list}) VALUES ({$placeholder}) ON CONFLICT({$conflict_list}) DO UPDATE SET {$updates}";
		}

		if ( empty( $prepare_values ) ) {
			return $wpdb->query( $sql ); // phpcs:ignore WordPress.DB.PreparedSQL.NotPrepared
		}

		return $wpdb->query( $wpdb->prepare( $sql, ...$prepare_values ) ); // phpcs:ignore WordPress.DB.PreparedSQL.NotPrepared
	}
}