<?php
declare(strict_types=1);

class TaskCertDb
{
    public static function conn(): mysqli
    {
        if (!isset($GLOBALS['mysql_con']) || !($GLOBALS['mysql_con'] instanceof mysqli)) {
            throw new RuntimeException('task_cert: Missing mysqli connection in $GLOBALS["mysql_con"].');
        }

        return $GLOBALS['mysql_con'];
    }

    public static function beginTransaction(): void
    {
        mysqli_begin_transaction(self::conn());
    }

    public static function commit(): void
    {
        mysqli_commit(self::conn());
    }

    public static function rollback(): void
    {
        mysqli_rollback(self::conn());
    }

    public static function fetchAll(string $sql, string $types = '', array $params = []): array
    {
        if ($types === '' && $params === []) {
            $result = mysqli_query(self::conn(), $sql);
            if ($result === false) {
                throw new RuntimeException('task_cert query failed: ' . mysqli_error(self::conn()));
            }

            if ($result instanceof mysqli_result) {
                $rows = mysqli_fetch_all($result, MYSQLI_ASSOC);
                mysqli_free_result($result);
                return $rows;
            }

            return [];
        }

        $stmt = self::prepareAndBind($sql, $types, $params);
        mysqli_stmt_execute($stmt);
        $result = mysqli_stmt_get_result($stmt);

        if ($result === false) {
            $error = mysqli_stmt_error($stmt);
            mysqli_stmt_close($stmt);
            throw new RuntimeException('task_cert fetchAll failed: ' . $error);
        }

        $rows = mysqli_fetch_all($result, MYSQLI_ASSOC);
        mysqli_free_result($result);
        mysqli_stmt_close($stmt);

        return $rows;
    }

    public static function fetchOne(string $sql, string $types = '', array $params = []): ?array
    {
        $rows = self::fetchAll($sql, $types, $params);
        if ($rows === []) {
            return null;
        }

        return $rows[0];
    }

    public static function scalar(string $sql, string $types = '', array $params = [])
    {
        $row = self::fetchOne($sql, $types, $params);
        if ($row === null) {
            return null;
        }

        foreach ($row as $value) {
            return $value;
        }

        return null;
    }

    public static function execute(string $sql, string $types = '', array $params = []): int
    {
        if ($types === '' && $params === []) {
            $ok = mysqli_query(self::conn(), $sql);
            if ($ok === false) {
                throw new RuntimeException('task_cert execute failed: ' . mysqli_error(self::conn()));
            }

            return mysqli_affected_rows(self::conn());
        }

        $stmt = self::prepareAndBind($sql, $types, $params);
        mysqli_stmt_execute($stmt);
        $affected = mysqli_stmt_affected_rows($stmt);
        $error = mysqli_stmt_error($stmt);
        mysqli_stmt_close($stmt);

        if ($error !== '') {
            throw new RuntimeException('task_cert execute failed: ' . $error);
        }

        return $affected;
    }

    public static function insert(string $sql, string $types, array $params): int
    {
        $stmt = self::prepareAndBind($sql, $types, $params);
        mysqli_stmt_execute($stmt);
        $error = mysqli_stmt_error($stmt);
        mysqli_stmt_close($stmt);

        if ($error !== '') {
            throw new RuntimeException('task_cert insert failed: ' . $error);
        }

        return (int) mysqli_insert_id(self::conn());
    }

    private static function prepareAndBind(string $sql, string $types, array $params): mysqli_stmt
    {
        $stmt = mysqli_prepare(self::conn(), $sql);
        if (!$stmt) {
            throw new RuntimeException('task_cert prepare failed: ' . mysqli_error(self::conn()));
        }

        self::bindParams($stmt, $types, $params);

        return $stmt;
    }

    private static function bindParams(mysqli_stmt $stmt, string $types, array $params): void
    {
        if ($types === '') {
            return;
        }

        $params = array_values($params);
        if (strlen($types) !== count($params)) {
            throw new InvalidArgumentException('task_cert bind mismatch: number of types != number of params');
        }

        $bindValues = [$types];
        foreach ($params as $index => $value) {
            $bindValues[] = &$params[$index];
        }

        $ok = call_user_func_array([$stmt, 'bind_param'], $bindValues);
        if ($ok === false) {
            throw new RuntimeException('task_cert bind_param failed: ' . mysqli_stmt_error($stmt));
        }
    }
}