require("dotenv").config();
const express = require('express');
const app = express();
const sqlite3 = require('sqlite3').verbose();
const db = new sqlite3.Database('url.db');
db.on('open', () => {
	db.run('CREATE TABLE IF NOT EXISTS urls (shortUrl TEXT, url TEXT, visits INTEGER DEFAULT 0)');
	db.run('CREATE TABLE IF NOT EXISTS refs (shortUrl TEXT, referrer TEXT UNIQUE, visits INTEGER DEFAULT 0)');
})

app.use(express.json());
app.use(express.urlencoded({ extended: true }));

app.get("/", (req, res) => {
	res.status(404).json({ error: 'Not found' });
});

// Add your routes and middleware here
app.get('/:shortUrl', (req, res) => { // Shortened URL
	const shortUrl = req.params.shortUrl;
	db.get('SELECT url FROM urls WHERE shortUrl = ?', [shortUrl], (err, row) => {
		if (err) {
			console.error(err);
			return res.status(500).json({ error: 'Internal server error', fullError: err.stack });
		}
		if (row) {
			res.redirect(row.url);
			// If the UA isn't a bot, increment the view count
			if (!req.headers['user-agent'].includes('bot')) {
				db.run('UPDATE urls SET visits = visits + 1 WHERE shortUrl = ?', [shortUrl]);
				// If req.params.ref exists, increment the referrer count, if the row doesn't exist, insert it
				if (req.query.ref) {
					db.run('INSERT OR IGNORE INTO refs (shortUrl, referrer) VALUES (?, ?)', [shortUrl, req.query.ref]);
					db.run('UPDATE refs SET visits = visits + 1 WHERE shortUrl = ? AND referrer = ?', [shortUrl, req.query.ref]);
				}
			}
		}
		else {
			res.status(404).json({ error: 'Short URL not found' });
		}
	});
});

app.get('/stats/:shortUrl', (req, res) => { // Stats
	if (req.query.passcode !== passcode) {
		return res.status(403).json({ error: 'Invalid passcode' });
	}

	const shortUrl = req.params.shortUrl;

	if (shortUrl === 'all') {
		// Get all URLs and refs. nest refs inside urls
		db.all('SELECT * FROM urls', (err, rows) => {
			if (err) {
				console.error(err);
				return res.status(500).json({ error: 'Internal server error', fullError: err.stack });
			}
			rows.forEach((row, i) => {
				db.all('SELECT * FROM refs WHERE shortUrl = ?', [row.shortUrl], (err, refs) => {
					if (err) {
						console.error(err);
						return res.status(500).json({ error: 'Internal server error', fullError: err.stack });
					}
					rows[i].refs = refs;
					if (i === rows.length - 1) {
						res.json(rows);
					}
				});
			});
		});
	} else {

		db.get('SELECT * FROM urls WHERE shortUrl = ?', [shortUrl], (err, row) => {
			if (err) {
				console.error(err);
				return res.status(500).json({ error: 'Internal server error', fullError: err.stack });
			}
			if (row) {
				db.all('SELECT * FROM refs WHERE shortUrl = ?', [shortUrl], (err, rows) => {
					if (err) {
						console.error(err);
						return res.status(500).json({ error: 'Internal server error', fullError: err.stack });
					}
					res.json({ url: row.url, shortUrl: row.shortUrl, visits: row.visits, refs: rows });
				});
			}
			else {
				res.status(404).json({ error: 'Short URL not found' });
			}
		});
	}
});

app.post('/shorten', (req, res) => { // Shorten URL
	// Check that { url} exists
	if (!req.body.url) {
		return res.status(400).json({ error: 'Please provide a URL' });
	}
	if (req.body.passcode !== passcode) {
		return res.status(403).json({ error: 'Invalid passcode' });
	}
	// Generate a 8 character long string, only if { shortUrl } doesnt exist in body
	const shortUrl = req.body.shortUrl || Math.random().toString(36).substr(2, 8);
	// Check if shortUrl is already in use
	db.get('SELECT shortUrl FROM urls WHERE shortUrl = ?', [shortUrl], (err, row) => {
		if (err) {
			console.error(err);
			return res.status(500).json({ error: 'Internal server error', fullError: err.stack });
		}
		if (row) {
			return res.status(400).json({ error: 'Short URL already in use' });
		}
		// Insert the URL into the database
		db.run('INSERT INTO urls (shortUrl, url) VALUES (?, ?)', [shortUrl, req.body.url], (err) => {
			if (err) {
				console.error(err);
				return res.status(500).json({ error: 'Internal server error', fullError: err.stack });
			}
			res.json({ shortUrl });
		});
	});
});

port = process.env.SERVER_PORT || 3000;
passcode = process.env.API_KEY;

app.listen(port, () => {
	console.log(`Server is running on port ${port}`);
	console.log(`API Passcode is ${passcode}`);
});