const express = require('express')
const sqlite3 = require('sqlite3')
const cors = require('cors')
const app = express()
const db = new sqlite3.Database(':memory:');

const getCurrentUnixTimestamp = () => Math.floor(Date.now() / 1000);

db.serialize(() => {
    db.run(`CREATE TABLE cache (
        id TEXT PRIMARY KEY,
        response TEXT,
        time TEXT
    )`);
});
app.use(cors());
app.get('/', async (req, res) => {
    const url = req.query.url;

    if (!url) {
        res.status(400).contentType("text/plain").send("nop");
        return;
    }

    db.get(`SELECT * FROM cache WHERE id = ?`, [url], async (err, row) => {
        if (err) {
            console.error(err);
            res.status(500).send("damn");
            return;
        }

        if (row) {
            const currentTime = getCurrentUnixTimestamp();
            const twoHoursInSeconds = 7200;

            if (currentTime - row.time > twoHoursInSeconds) {
                db.run(`DELETE FROM cache WHERE id = ?`, [url], async (err) => {
                    if (err) {
                        console.error(err);
                        res.status(500).send("damn");
                        return;
                    }
                    
                    const resp = await getinfosl(url)
                    const insertStmt = db.prepare(`INSERT INTO cache (id, response, time) VALUES (?, ?, ?)`);
                    const currentTime = getCurrentUnixTimestamp();
        
                    insertStmt.run(url, resp, currentTime, (err) => {
                        if (err) {
                            console.error(err);
                            res.status(500).send("damn");
                            return;
                        }
                        res.contentType("application/json");
                        res.header("cache", "stale - invalidated");
                        res.send(resp)
                        console.log("old response (entry readded)");
                    });
        
                    insertStmt.finalize();
                });
            } else {
                res.header("cache", "fresh");
                res.contentType("application/json");
                res.send(row.response);
            }
        } else {
            const insertStmt = db.prepare(`INSERT INTO cache (id, response, time) VALUES (?, ?, ?)`);
            const currentTime = getCurrentUnixTimestamp();
            const resp = await getinfosl(url)
            insertStmt.run(url, resp, currentTime, (err) => {
                if (err) {
                    console.error(err);
                    res.status(500).send("damn");
                    return;
                }
                res.contentType("application/json");
                res.header("cache", "wasnt");
                res.send(resp)

                console.log("New entry added");
            });

            insertStmt.finalize();
        }
    });
});


async function getinfosl(url) {
    const response = await fetch(`https://api.song.link/v1-alpha.1/links?url=${url}`);
    const meow = await response.text();
    return meow;
}

app.listen(3000, async () => {
    console.log("running")
})