<?php
/**
 * Check PDO statement for errors
 * Logs full error server-side, returns generic message to client
 *
 * @param PDOStatement $sth      - The executed PDO statement
 * @param array        &$answer  - Response array passed by reference
 * @param array        $options  - Optional settings:
 *                                  'message'     => Custom client-facing error message
 *                                  'log'         => Custom server log label
 *                                  'code'        => HTTP response code (default: 500)
 *                                  'before_exit' => Callback function before exit
 *
 * @example
 * // Simple — use all defaults
 * db_check($sth, $answer);
 *
 * @example
 * // Custom client message
 * db_check($sth, $answer, [
 *     'message' => "Contact not found."
 * ]);
 *
 * @example
 * // Custom log label + message
 * db_check($sth, $answer, [
 *     'log'     => "Failed to fetch contact",
 *     'message' => "Could not load contact. Please try again."
 * ]);
 *
 * @example
 * // Custom HTTP status code
 * db_check($sth, $answer, [
 *     'code'    => 403,
 *     'message' => "Access denied."
 * ]);
 *
 * @example
 * // Cleanup callback before exit
 * db_check($sth, $answer, [
 *     'message'     => "Upload failed.",
 *     'before_exit' => function() use ($tmp_file) {
 *         if(file_exists($tmp_file)) unlink($tmp_file);
 *     }
 * ]);
 */


function db_check($sth, &$answer, $options = []) {
    if ($sth->errorInfo()[0] != "00000" && !empty($sth->errorInfo()[0])) {
        
        $trace = debug_backtrace()[0];
        
        $log_message = $options['log'] ?? "DB Error";
        error_log($log_message . " in " . $trace['file'] . " line " . $trace['line'] . ": " . $sth->errorInfo()[2]);
        
        // production version
        $answer["message"] = $options['message'] ?? "A server error occurred. Please try again.";
        
        http_response_code($options['code'] ?? 500);
        
        if(isset($options['before_exit'])) {
            call_user_func($options['before_exit']);
        }
        
        exit(json_encode($answer));
    }
}


// Run a callback after the surrounding dbTransaction() commits. If no managed
// transaction is active, run immediately. Used for non-authoritative side effects
// such as live dashboard notifications.
function db_after_commit(callable $callback): void {
    if (!isset($GLOBALS['_db_after_commit_stack']) || empty($GLOBALS['_db_after_commit_stack'])) {
        $callback();
        return;
    }

    $idx = count($GLOBALS['_db_after_commit_stack']) - 1;
    $GLOBALS['_db_after_commit_stack'][$idx][] = $callback;
}

// transaction wrapper with retry logic for deadlocks
function dbTransaction($pdo, $callback, $maxRetries = 3) {
    for ($attempt = 0; $attempt < $maxRetries; $attempt++) {
        $GLOBALS['_db_after_commit_stack'][] = [];

        try {
            $pdo->beginTransaction();
            $result = $callback($pdo);
            $pdo->commit();

            $callbacks = array_pop($GLOBALS['_db_after_commit_stack']);
            foreach ($callbacks as $after_commit) {
                try {
                    $after_commit();
                } catch (Throwable $e) {
                    error_log("[AFTER COMMIT ERROR] " . $e->getMessage() . " | " . $e->getFile() . ":" . $e->getLine());
                }
            }

            return $result;

        } catch (PDOException $e) {
            if ($pdo->inTransaction()) $pdo->rollBack();
            array_pop($GLOBALS['_db_after_commit_stack']);

            if ($e->getCode() == '40001' && $attempt < $maxRetries - 1) {
                usleep(600000 * ($attempt + 1));
                continue;
            }

            error_log("[DB ERROR] " . $e->getMessage() . " | " . $e->getFile() . ":" . $e->getLine());
            throw $e;

        } catch (Exception $e) {
            if ($pdo->inTransaction()) $pdo->rollBack();
            array_pop($GLOBALS['_db_after_commit_stack']);
            error_log("[ERROR] " . $e->getMessage() . " | " . $e->getFile() . ":" . $e->getLine());
            throw $e;
        }
    }
}

?>