<?php


namespace Vizyt\Support;

defined( 'ABSPATH' ) || exit;
// phpcs:disable WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- transaction statements (START TRANSACTION, SAVEPOINT, COMMIT, ROLLBACK) and server variables have no WordPress API and must never be cached.

/**
 * Run several writes as one unit (InnoDB).
 *
 * Outside a transaction it opens one (START TRANSACTION … COMMIT/ROLLBACK).
 * When a transaction is already open — a nested Tx::run(), autocommit is off
 * as in the WordPress test suite, or (on MariaDB, through @@in_transaction)
 * somebody else's START TRANSACTION — it uses a savepoint instead, so it
 * never commits somebody else's transaction. On MySQL an explicit outer
 * START TRANSACTION with autocommit on cannot be detected; callers that open
 * their own transaction must not rely on Tx to stay out of it.
 *
 * Contract for callbacks: $wpdb does not throw, so the callback must check
 * every write and return false (or throw) when one fails — only then is
 * everything rolled back. Any other return value is committed.
 *
 * Every transaction statement is checked: when START TRANSACTION / SAVEPOINT
 * fails the callback is not run; when COMMIT / RELEASE SAVEPOINT fails a
 * rollback is attempted and run() returns false.
 *
 * Atomicity needs InnoDB. On MyISAM tables the statements succeed but nothing
 * is undone; Vizyt\Admin\EngineNotice warns the admin about such tables.
 */
final class Tx {

    private static int $depth = 0;

    /** Whether the server knows @@in_transaction (null = not asked yet). */
    private static ?bool $has_in_transaction = null;

    /**
     * @param callable $fn Does the writes. Return false (or throw) to roll back.
     * @return mixed $fn's result, or false after a rollback or a failed transaction statement.
     */
    public static function run( callable $fn ) {
        global $wpdb;

        $outer = 0 === self::$depth && '1' === (string) $wpdb->get_var( 'SELECT @@autocommit' ) && ! self::in_transaction();
        $point = 'vizyt_tx_' . self::$depth;

        if ( false === ( $outer ? $wpdb->query( 'START TRANSACTION' ) : $wpdb->query( "SAVEPOINT {$point}" ) ) ) { // phpcs:ignore WordPress.DB.PreparedSQL.InterpolatedNotPrepared, PluginCheck.Security.DirectDB.UnescapedDBParameter -- $point is 'vizyt_tx_' plus the nesting depth (an int), never input.
            return false;
        }

        self::$depth++;

        try {
            $result = $fn();
        } catch ( \Throwable $e ) {
            self::$depth--;
            self::rollback( $outer, $point );
            throw $e;
        }

        self::$depth--;

        if ( false === $result ) {
            self::rollback( $outer, $point );
            return false;
        }

        if ( false === ( $outer ? $wpdb->query( 'COMMIT' ) : $wpdb->query( "RELEASE SAVEPOINT {$point}" ) ) ) { // phpcs:ignore WordPress.DB.PreparedSQL.InterpolatedNotPrepared, PluginCheck.Security.DirectDB.UnescapedDBParameter -- $point is 'vizyt_tx_' plus the nesting depth (an int), never input.
            self::rollback( $outer, $point );
            return false;
        }

        return $result;
    }

    private static function rollback( bool $outer, string $point ): void {
        global $wpdb;

        if ( false === ( $outer ? $wpdb->query( 'ROLLBACK' ) : $wpdb->query( "ROLLBACK TO SAVEPOINT {$point}" ) ) ) { // phpcs:ignore WordPress.DB.PreparedSQL.InterpolatedNotPrepared, PluginCheck.Security.DirectDB.UnescapedDBParameter -- $point is 'vizyt_tx_' plus the nesting depth (an int), never input.
            error_log( 'Vizyt: rollback failed: ' . $wpdb->last_error ); // phpcs:ignore WordPress.PHP.DevelopmentFunctions.error_log_error_log -- a failed rollback leaves data half-written; the site owner's log is the only place to report it.
        }
    }

    /**
     * MariaDB: is a transaction open on this connection? Always false where
     * the server has no @@in_transaction (MySQL).
     */
    private static function in_transaction(): bool {
        global $wpdb;

        if ( false === self::$has_in_transaction ) {
            return false;
        }

        $suppress = $wpdb->suppress_errors( true );
        $value    = $wpdb->get_var( 'SELECT @@in_transaction' );
        $wpdb->suppress_errors( $suppress );

        self::$has_in_transaction = null !== $value;

        return '1' === (string) $value;
    }
}