import { Request, Response, NextFunction } from 'express';
import { Pool } from 'pg';

// Helper utility to parse cookies manually without adding extra npm packages
function parseCookieString(cookieHeader: string | undefined, name: string): string | null {
    if (!cookieHeader) return null;
    const match = cookieHeader.match(new RegExp('(^| )' + name + '=([^;]+)'));
    return match ? match[2] : null;
}

export function createAuthMiddleware(db: Pool) {
    return async (req: Request, res: Response, next: NextFunction): Promise<void> => {
        try {
            const cookieHeader = req.headers.cookie;
            const token = parseCookieString(cookieHeader, 'session_token');

            if (!token) {
                res.status(401).json({ success: false, error: 'Unauthorized. Session cookie missing.' });
                return;
            }

            // Query the database to find an active session matching the token
            const query = `
        SELECT user_id, expires_at 
        FROM sessions 
        WHERE id = $1;
      `;
            const result = await db.query(query, [token]);

            if (result.rows.length === 0) {
                res.status(401).json({ success: false, error: 'Unauthorized. Invalid session token.' });
                return;
            }

            const session = result.rows[0];
            const now = new Date();

            // Validate expiration constraint
            if (new Date(session.expires_at) < now) {
                res.status(401).json({ success: false, error: 'Unauthorized. Session expired.' });
                return;
            }

            // Inject the authenticated identity directly into the Request object for use in down-stream router handlers
            (req as any).userId = session.user_id;

            next(); // Execution matches, pass cleanly to route target
        } catch (error) {
            console.error('Auth middleware failure:', error);
            res.status(500).json({ success: false, error: 'Internal Server Error' });
        }
    };
}