import express from 'express';
import * as userCtrl from '../controllers/userController.js';

const router = express.Router();

const USERNAME_MIN = 3;
const USERNAME_MAX = 30;
const DISPLAY_NAME_MAX = 100;
const DEFAULT_LIMIT = 50;
const MAX_LIMIT = 200;

function isValidUsername(username) {
    if (typeof username !== 'string') {
        return false;
    }
    if (username.length < USERNAME_MIN || username.length > USERNAME_MAX) {
        return false;
    }
    const allowed = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_';
    for (let i = 0; i < username.length; i++) {
        if (allowed.indexOf(username[i]) === -1) {
            return false;
        }
    }
    return true;
}

function isValidDisplayName(displayName) {
    if (displayName === undefined || displayName === null) {
        return true;
    }
    if (typeof displayName !== 'string') {
        return false;
    }
    return displayName.length <= DISPLAY_NAME_MAX;
}

// Search users (must be before /:id)
router.get('/search', async function(req, res) {
    const q = req.query.q;
    if (typeof q !== 'string' || q.length < 1) {
        return res.status(400).json({ error: 'invalid_query' });
    }
    const results = await userCtrl.searchUsers({ q: q, fields: ['username', 'displayName'] });
    res.json(results);
});

// List users with pagination
router.get('/', async function(req, res) {
    let limit = parseInt(req.query.limit, 10);
    let offset = parseInt(req.query.offset, 10);

    if (isNaN(limit) || limit < 1) {
        limit = DEFAULT_LIMIT;
    }
    if (limit > MAX_LIMIT) {
        limit = MAX_LIMIT;
    }
    if (isNaN(offset) || offset < 0) {
        offset = 0;
    }

    const users = await userCtrl.listUsers({ limit: limit, offset: offset });
    res.json(users);
});

// Get user by id
router.get('/:id', async function(req, res) {
    const user = await userCtrl.getUserById(req.params.id);
    if (!user) {
        return res.status(404).json({ error: 'not_found' });
    }
    res.json(user);
});

// Create user
router.post('/', async function(req, res) {
    const username = req.body.username;
    const displayName = req.body.displayName;

    if (!isValidUsername(username)) {
        return res.status(400).json({ error: 'invalid_username' });
    }
    if (!isValidDisplayName(displayName)) {
        return res.status(400).json({ error: 'invalid_display_name' });
    }

    const user = await userCtrl.createUser({ username: username, displayName: displayName });
    res.status(201).json(user);
});

// Update user
router.put('/:id', async function(req, res) {
    const username = req.body.username;
    const displayName = req.body.displayName;

    if (username !== undefined && !isValidUsername(username)) {
        return res.status(400).json({ error: 'invalid_username' });
    }
    if (!isValidDisplayName(displayName)) {
        return res.status(400).json({ error: 'invalid_display_name' });
    }

    const updates = {};
    if (username !== undefined) {
        updates.username = username;
    }
    if (displayName !== undefined) {
        updates.displayName = displayName;
    }

    const user = await userCtrl.updateUser(req.params.id, updates);
    if (!user) {
        return res.status(404).json({ error: 'not_found' });
    }
    res.json(user);
});

// Delete user
router.delete('/:id', async function(req, res) {
    const ok = await userCtrl.deleteUser(req.params.id);
    if (!ok) {
        return res.status(404).json({ error: 'not_found' });
    }
    res.status(204).send();
});

// Login - get token by username
router.post('/login', async function(req, res) {
    const username = req.body.username;

    if (!isValidUsername(username)) {
        return res.status(400).json({ error: 'invalid_username' });
    }

    const user = await userCtrl.getUserByUsername(username);
    if (!user) {
        return res.status(404).json({ error: 'user_not_found' });
    }

    res.json({ token: user.token, userId: user._id });
});

export default router;