<?php
declare(strict_types=1);

require_once __DIR__ . '/db/config.php';

if (PHP_SAPI !== 'cli') {
    header('Content-Type: text/plain; charset=utf-8');
    header('X-Robots-Tag: noindex, nofollow');
}

@set_time_limit(0);

function migrationOutput(string $message = ''): void
{
    echo $message . PHP_EOL;
}

function canRunMigrations(): bool
{
    if (PHP_SAPI === 'cli') {
        return true;
    }

    if (session_status() === PHP_SESSION_NONE) {
        @session_start();
    }

    if (($_SESSION['user_role_name'] ?? '') === 'Administrator') {
        return true;
    }

    $remoteAddress = $_SERVER['REMOTE_ADDR'] ?? '';
    return in_array($remoteAddress, ['127.0.0.1', '::1'], true);
}

function ensureMigrationsTable(PDO $pdo): void
{
    $pdo->exec(<<<SQL
CREATE TABLE IF NOT EXISTS migrations (
    id INT AUTO_INCREMENT PRIMARY KEY,
    migration VARCHAR(255) NOT NULL,
    executed_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4
SQL);
}

function getExecutedMigrations(PDO $pdo): array
{
    $stmt = $pdo->query('SELECT migration FROM migrations');
    $rows = $stmt->fetchAll(PDO::FETCH_COLUMN) ?: [];
    return array_fill_keys($rows, true);
}

function getMigrationFiles(): array
{
    $sqlFiles = glob(__DIR__ . '/db/migrations/*.sql') ?: [];
    $phpFiles = glob(__DIR__ . '/db/migrations/*.php') ?: [];
    $files = array_merge($sqlFiles, $phpFiles);

    usort($files, static function (string $left, string $right): int {
        return strnatcasecmp(basename($left), basename($right));
    });

    return $files;
}

function splitSqlStatements(string $sql): array
{
    $sql = preg_replace('/^\xEF\xBB\xBF/', '', $sql) ?? $sql;
    $sql = preg_replace('/\/\*.*?\*\//s', '', $sql) ?? $sql;

    $lines = preg_split('/\R/', $sql) ?: [];
    $filteredLines = [];

    foreach ($lines as $line) {
        $trimmed = ltrim($line);
        if ($trimmed === '' || str_starts_with($trimmed, '--') || str_starts_with($trimmed, '#')) {
            continue;
        }
        $filteredLines[] = $line;
    }

    $cleanSql = implode("\n", $filteredLines);
    $statements = [];
    $buffer = '';
    $inSingleQuote = false;
    $inDoubleQuote = false;
    $length = strlen($cleanSql);

    for ($index = 0; $index < $length; $index++) {
        $char = $cleanSql[$index];
        $previous = $index > 0 ? $cleanSql[$index - 1] : '';

        if ($char === "'" && !$inDoubleQuote && $previous !== '\\') {
            $inSingleQuote = !$inSingleQuote;
        } elseif ($char === '"' && !$inSingleQuote && $previous !== '\\') {
            $inDoubleQuote = !$inDoubleQuote;
        }

        if ($char === ';' && !$inSingleQuote && !$inDoubleQuote) {
            $statement = trim($buffer);
            if ($statement !== '') {
                $statements[] = $statement;
            }
            $buffer = '';
            continue;
        }

        $buffer .= $char;
    }

    $tail = trim($buffer);
    if ($tail !== '') {
        $statements[] = $tail;
    }

    return $statements;
}

function isIgnorableMigrationError(PDOException $exception): bool
{
    $driverCode = isset($exception->errorInfo[1]) ? (int) $exception->errorInfo[1] : null;
    $message = strtolower($exception->getMessage());
    $ignorableCodes = [1050, 1060, 1061, 1062, 1091, 1826];
    $ignorableSnippets = [
        'already exists',
        'duplicate column name',
        'duplicate key name',
        'duplicate entry',
        'duplicate foreign key constraint name',
        'check that column/key exists',
    ];

    if ($driverCode !== null && in_array($driverCode, $ignorableCodes, true)) {
        return true;
    }

    foreach ($ignorableSnippets as $snippet) {
        if (str_contains($message, $snippet)) {
            return true;
        }
    }

    return false;
}

function executeSqlMigration(PDO $pdo, string $filePath): void
{
    $sql = file_get_contents($filePath);
    if ($sql === false) {
        throw new RuntimeException('Unable to read SQL migration: ' . basename($filePath));
    }

    $statements = splitSqlStatements($sql);
    if ($statements === []) {
        migrationOutput('  - no executable SQL statements found');
        return;
    }

    foreach ($statements as $number => $statement) {
        try {
            $pdo->exec($statement);
        } catch (PDOException $exception) {
            if (isIgnorableMigrationError($exception)) {
                migrationOutput('  - skipped statement ' . ($number + 1) . ': ' . $exception->getMessage());
                continue;
            }

            throw new RuntimeException(
                'SQL migration failed in ' . basename($filePath) . ' at statement ' . ($number + 1) . ': ' . $exception->getMessage(),
                0,
                $exception
            );
        }
    }
}

function executePhpMigration(string $filePath): void
{
    ob_start();

    try {
        $result = include $filePath;
    } catch (Throwable $throwable) {
        ob_end_clean();
        throw new RuntimeException('PHP migration failed in ' . basename($filePath) . ': ' . $throwable->getMessage(), 0, $throwable);
    }

    $output = trim((string) ob_get_clean());

    if ($result === false) {
        throw new RuntimeException('PHP migration returned false: ' . basename($filePath));
    }

    if ($output !== '') {
        foreach (preg_split('/\R/', $output) ?: [] as $line) {
            migrationOutput('  ' . $line);
        }
    }
}

function recordMigration(PDO $pdo, string $migrationName): void
{
    $stmt = $pdo->prepare('INSERT INTO migrations (migration) VALUES (:migration)');
    $stmt->execute(['migration' => $migrationName]);
}

function runAllMigrations(): int
{
    if (!canRunMigrations()) {
        if (PHP_SAPI !== 'cli') {
            http_response_code(403);
        }

        migrationOutput('Forbidden: run migrate.php from CLI, localhost, or while logged in as an Administrator.');
        return 1;
    }

    try {
        $pdo = db();
        ensureMigrationsTable($pdo);
        $executed = getExecutedMigrations($pdo);
        $files = getMigrationFiles();

        if ($files === []) {
            migrationOutput('No migration files found in db/migrations.');
            return 0;
        }

        $applied = 0;
        $skipped = 0;

        migrationOutput('Starting migration run...');

        foreach ($files as $filePath) {
            $migrationName = basename($filePath);

            if (isset($executed[$migrationName])) {
                migrationOutput('SKIP ' . $migrationName);
                $skipped++;
                continue;
            }

            migrationOutput('RUN  ' . $migrationName);
            $extension = strtolower((string) pathinfo($filePath, PATHINFO_EXTENSION));

            if ($extension === 'sql') {
                executeSqlMigration($pdo, $filePath);
            } elseif ($extension === 'php') {
                executePhpMigration($filePath);
            } else {
                throw new RuntimeException('Unsupported migration type: ' . $migrationName);
            }

            recordMigration($pdo, $migrationName);
            $executed[$migrationName] = true;
            $applied++;
            migrationOutput('OK   ' . $migrationName);
        }

        migrationOutput('Done. Applied ' . $applied . ' migration(s), skipped ' . $skipped . ' already executed.');
        return 0;
    } catch (Throwable $throwable) {
        if (PHP_SAPI !== 'cli') {
            http_response_code(500);
        }

        migrationOutput('ERROR: ' . $throwable->getMessage());
        return 1;
    }
}

exit(runAllMigrations());