<?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 schemaDebugOutput(string $message = ''): void
{
    echo $message . PHP_EOL;
}

function configureSchemaDebugSession(): void
{
    if (PHP_SAPI === 'cli') {
        return;
    }

    $sessionsDir = __DIR__ . '/sessions';
    if (!is_dir($sessionsDir)) {
        @mkdir($sessionsDir, 0777, true);
    }

    if (is_writable($sessionsDir)) {
        session_save_path("0;0660;" . $sessionsDir);
    }

    if (
        (isset($_SERVER['HTTPS']) && $_SERVER['HTTPS'] === 'on')
        || (isset($_SERVER['HTTP_X_FORWARDED_PROTO']) && $_SERVER['HTTP_X_FORWARDED_PROTO'] === 'https')
    ) {
        session_set_cookie_params([
            'lifetime' => 0,
            'path' => '/',
            'secure' => true,
            'httponly' => true,
            'samesite' => 'None',
        ]);
    }
}

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

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

    $roleName = (string) ($_SESSION['user_role_name'] ?? '');
    if (strcasecmp($roleName, 'Administrator') === 0 || (int) ($_SESSION['user_id'] ?? 0) === 1) {
        return true;
    }

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

function getSchemaSourceFile(): string
{
    $complete = __DIR__ . '/complete_schema.sql';
    if (is_file($complete)) {
        return $complete;
    }

    return __DIR__ . '/db/schema.sql';
}

function parseExpectedSchema(string $filePath): array
{
    if (!is_file($filePath)) {
        throw new RuntimeException('Schema file not found: ' . basename($filePath));
    }

    $sql = file_get_contents($filePath);
    if ($sql === false) {
        throw new RuntimeException('Unable to read schema file: ' . basename($filePath));
    }

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

    foreach ($lines as $line) {
        if (preg_match('/^\s*CREATE\s+TABLE(?:\s+IF\s+NOT\s+EXISTS)?\s+`?([a-zA-Z0-9_]+)`?/i', $line, $matches)) {
            $currentTable = strtolower((string) $matches[1]);
            $schema[$currentTable] = [];
            continue;
        }

        if ($currentTable === null) {
            continue;
        }

        if (preg_match('/^\s*\)\s*(ENGINE|DEFAULT|COMMENT|CHARSET|COLLATE|ROW_FORMAT|AUTO_INCREMENT|PARTITION|;)/i', $line)) {
            $currentTable = null;
            continue;
        }

        if (preg_match('/^\s*`([^`]+)`\s+/u', $line, $matches)) {
            $schema[$currentTable][] = (string) $matches[1];
        }
    }

    foreach ($schema as $tableName => $columns) {
        $columns = array_values(array_unique($columns));
        natcasesort($columns);
        $schema[$tableName] = array_values($columns);
    }

    ksort($schema, SORT_NATURAL | SORT_FLAG_CASE);
    return $schema;
}

function fetchActualSchema(PDO $pdo): array
{
    $stmt = $pdo->query(
        "SELECT TABLE_NAME, COLUMN_NAME\n"
        . "FROM information_schema.COLUMNS\n"
        . "WHERE TABLE_SCHEMA = DATABASE()\n"
        . "ORDER BY TABLE_NAME ASC, ORDINAL_POSITION ASC"
    );

    $rows = $stmt ? $stmt->fetchAll(PDO::FETCH_ASSOC) : [];
    $schema = [];

    foreach ($rows as $row) {
        $tableName = strtolower((string) ($row['TABLE_NAME'] ?? ''));
        $columnName = (string) ($row['COLUMN_NAME'] ?? '');
        if ($tableName === '' || $columnName === '') {
            continue;
        }

        $schema[$tableName] ??= [];
        $schema[$tableName][] = $columnName;
    }

    foreach ($schema as $tableName => $columns) {
        $columns = array_values(array_unique($columns));
        natcasesort($columns);
        $schema[$tableName] = array_values($columns);
    }

    ksort($schema, SORT_NATURAL | SORT_FLAG_CASE);
    return $schema;
}

function tailRuntimeDebugLog(int $maxLines = 10): array
{
    $logFile = __DIR__ . '/runtime_debug.log';
    if (!is_file($logFile)) {
        return [];
    }

    $lines = file($logFile, FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);
    if (!is_array($lines) || $lines === []) {
        return [];
    }

    return array_slice($lines, -$maxLines);
}

if (!canViewSchemaDebug()) {
    http_response_code(403);
    schemaDebugOutput('Forbidden');
    exit;
}

try {
    $pdo = db();
    $schemaFile = getSchemaSourceFile();
    $expectedSchema = parseExpectedSchema($schemaFile);
    $actualSchema = fetchActualSchema($pdo);

    $expectedTables = array_keys($expectedSchema);
    $actualTables = array_keys($actualSchema);
    $missingTables = array_values(array_diff($expectedTables, $actualTables));
    $unexpectedTables = array_values(array_diff($actualTables, $expectedTables));
    natcasesort($missingTables);
    natcasesort($unexpectedTables);
    $missingTables = array_values($missingTables);
    $unexpectedTables = array_values($unexpectedTables);

    $tablesWithMissingColumns = [];
    foreach ($expectedSchema as $tableName => $expectedColumns) {
        if (!isset($actualSchema[$tableName])) {
            continue;
        }

        $missingColumns = array_values(array_diff($expectedColumns, $actualSchema[$tableName]));
        if ($missingColumns !== []) {
            natcasesort($missingColumns);
            $tablesWithMissingColumns[$tableName] = array_values($missingColumns);
        }
    }

    schemaDebugOutput('Schema Debug Report');
    schemaDebugOutput('===================');
    schemaDebugOutput('Database: ' . DB_NAME);
    schemaDebugOutput('Schema source: ' . basename($schemaFile));
    schemaDebugOutput('Expected tables: ' . count($expectedTables));
    schemaDebugOutput('Actual tables: ' . count($actualTables));
    schemaDebugOutput('Missing tables: ' . count($missingTables));
    schemaDebugOutput('Tables with missing columns: ' . count($tablesWithMissingColumns));
    schemaDebugOutput('Unexpected tables: ' . count($unexpectedTables));

    if ($missingTables === [] && $tablesWithMissingColumns === []) {
        schemaDebugOutput('');
        schemaDebugOutput('OK: current database matches the schema snapshot for table and column presence.');
    }

    if ($missingTables !== []) {
        schemaDebugOutput('');
        schemaDebugOutput('Missing tables:');
        foreach ($missingTables as $tableName) {
            schemaDebugOutput('- ' . $tableName);
        }
    }

    if ($tablesWithMissingColumns !== []) {
        schemaDebugOutput('');
        schemaDebugOutput('Missing columns by table:');
        foreach ($tablesWithMissingColumns as $tableName => $columns) {
            schemaDebugOutput('- ' . $tableName . ': ' . implode(', ', $columns));
        }
    }

    if ($unexpectedTables !== []) {
        schemaDebugOutput('');
        schemaDebugOutput('Unexpected tables (present in DB but not in schema snapshot):');
        foreach ($unexpectedTables as $tableName) {
            schemaDebugOutput('- ' . $tableName);
        }
    }

    $recentErrors = tailRuntimeDebugLog();
    if ($recentErrors !== []) {
        schemaDebugOutput('');
        schemaDebugOutput('Recent runtime_debug.log entries:');
        foreach ($recentErrors as $line) {
            schemaDebugOutput('- ' . $line);
        }
    }
} catch (Throwable $throwable) {
    http_response_code(500);
    schemaDebugOutput('Schema debug failed: ' . $throwable->getMessage());
    exit(1);
}