<?php

class Database
{
    private static ?PDO $pdo = null;

    public static function connect(): PDO
    {
        if (self::$pdo === null) {
            $dir = dirname(DB_PATH);
            if (!is_dir($dir)) {
                mkdir($dir, 0755, true);
            }

            self::$pdo = new PDO('sqlite:' . DB_PATH, null, null, [
                PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
                PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
            ]);

            self::$pdo->exec('PRAGMA journal_mode = WAL');
            self::$pdo->exec('PRAGMA foreign_keys = ON');

            self::migrate();
        }

        return self::$pdo;
    }

    private static function migrate(): void
    {
        self::$pdo->exec('
            CREATE TABLE IF NOT EXISTS settings (
                key TEXT PRIMARY KEY,
                value TEXT NOT NULL
            )
        ');

        self::$pdo->exec('
            CREATE TABLE IF NOT EXISTS buckets (
                id INTEGER PRIMARY KEY AUTOINCREMENT,
                name TEXT NOT NULL,
                position INTEGER NOT NULL DEFAULT 0,
                created_at TEXT NOT NULL DEFAULT CURRENT_TIMESTAMP
            )
        ');

        self::$pdo->exec('
            CREATE TABLE IF NOT EXISTS cards (
                id INTEGER PRIMARY KEY AUTOINCREMENT,
                title TEXT NOT NULL,
                body TEXT NOT NULL DEFAULT "",
                color TEXT NOT NULL DEFAULT "#ffffff",
                bucket_id INTEGER DEFAULT NULL,
                position INTEGER NOT NULL DEFAULT 0,
                created_at TEXT NOT NULL DEFAULT CURRENT_TIMESTAMP,
                updated_at TEXT NOT NULL DEFAULT CURRENT_TIMESTAMP,
                FOREIGN KEY (bucket_id) REFERENCES buckets(id) ON DELETE SET NULL
            )
        ');

        // Migrations for existing installs
        $cols = self::$pdo->query('PRAGMA table_info(cards)')->fetchAll();
        $colNames = array_column($cols, 'name');

        if (!in_array('bucket_id', $colNames)) {
            self::$pdo->exec('ALTER TABLE cards ADD COLUMN bucket_id INTEGER DEFAULT NULL REFERENCES buckets(id) ON DELETE SET NULL');
        }
        if (!in_array('parent_id', $colNames)) {
            self::$pdo->exec('ALTER TABLE cards ADD COLUMN parent_id INTEGER DEFAULT NULL REFERENCES cards(id) ON DELETE SET NULL');
        }

        if (!in_array('tags', $colNames)) {
            self::$pdo->exec("ALTER TABLE cards ADD COLUMN tags TEXT NOT NULL DEFAULT ''");
            // Backfill tags from existing card bodies
            $all = self::$pdo->query('SELECT id, body FROM cards')->fetchAll();
            foreach ($all as $row) {
                preg_match_all('/(?<=\s|^)#([a-zA-Z0-9_\/-][a-zA-Z0-9_\/-]*[a-zA-Z0-9_-]|[a-zA-Z0-9_-]+)/m', $row['body'], $matches);
                if (!empty($matches[1])) {
                    $tags = implode(',', array_unique(array_map('strtolower', $matches[1])));
                    self::$pdo->prepare('UPDATE cards SET tags = :tags WHERE id = :id')
                        ->execute(['tags' => $tags, 'id' => $row['id']]);
                }
            }
        }

        if (!in_array('due_date', $colNames)) {
            self::$pdo->exec('ALTER TABLE cards ADD COLUMN due_date TEXT DEFAULT NULL');
        }

        // CalDAV columns
        if (!in_array('caldav_uid', $colNames)) {
            self::$pdo->exec('ALTER TABLE cards ADD COLUMN caldav_uid TEXT DEFAULT NULL');
            self::$pdo->exec('ALTER TABLE cards ADD COLUMN caldav_etag TEXT DEFAULT NULL');
            self::$pdo->exec('ALTER TABLE cards ADD COLUMN caldav_href TEXT DEFAULT NULL');
            self::$pdo->exec('ALTER TABLE cards ADD COLUMN caldav_synced_at TEXT DEFAULT NULL');
            self::$pdo->exec('ALTER TABLE cards ADD COLUMN caldav_rrule TEXT DEFAULT NULL');
        }
        if (!in_array('caldav_rrule', $colNames) && in_array('caldav_uid', $colNames)) {
            self::$pdo->exec('ALTER TABLE cards ADD COLUMN caldav_rrule TEXT DEFAULT NULL');
        }

        // CalDAV support tables
        self::$pdo->exec('
            CREATE TABLE IF NOT EXISTS caldav_sync_log (
                id INTEGER PRIMARY KEY AUTOINCREMENT,
                direction TEXT NOT NULL,
                card_id INTEGER,
                caldav_uid TEXT,
                action TEXT NOT NULL,
                status TEXT NOT NULL,
                detail TEXT DEFAULT "",
                created_at TEXT NOT NULL DEFAULT CURRENT_TIMESTAMP
            )
        ');
        self::$pdo->exec('
            CREATE TABLE IF NOT EXISTS caldav_tombstones (
                caldav_uid TEXT PRIMARY KEY,
                card_id INTEGER,
                deleted_at TEXT NOT NULL DEFAULT CURRENT_TIMESTAMP
            )
        ');

        // Bucket color migration
        $bcols = self::$pdo->query('PRAGMA table_info(buckets)')->fetchAll();
        $bcolNames = array_column($bcols, 'name');
        if (!in_array('color', $bcolNames)) {
            self::$pdo->exec("ALTER TABLE buckets ADD COLUMN color TEXT NOT NULL DEFAULT '#64748b'");
        }
    }
}