const Router = require('./router')
const aesjs = require('aes-js');

addEventListener('fetch', event => {
    event.respondWith(handleRequest(event.request))
})

const AESKEY = [106, 111, 54, 97, 101, 121, 54, 104, 97, 105, 100, 50, 84, 101, 105, 104]

async function url_gen(md5_origin, format, id, media_version) {
    const cipher = new aesjs.ModeOfOperation.ecb(AESKEY)

    result = [md5_origin, format, id, media_version].join('\xa4')

    buf = new ArrayBuffer(result.length);
    result_hash = new Uint8Array(buf);
    for (i = 0; i < result.length; i++) {
        result_hash[i] = result.charCodeAt(i);
    }
    result_hash = await crypto.subtle.digest('MD5', result_hash)
    result_hash = Array.from(new Uint8Array(result_hash))
    result_hash = result_hash.reduce(function(previous, current) {
        return previous + "0".concat(current.toString(16)).substr(-2, 2);
    }, ''),

    result = result_hash + '\xa4' + result + '\xa4'

    // padding
    result += '\x00'.repeat(result.length % 16 ? 16 - result.length % 16 : 0)

    // converting to array for encryption / hex string
    result = Array.from(result).map(function(item) {
        return item.charCodeAt(0);
    })
    // encryption / hex string
    result = (result = cipher.encrypt(result)).reduce(function(previous, current) {
        return previous + "0".concat(current.toString(16)).substr(-2, 2);
    }, '')

    // cdn template with first character of md5 string + hash
    return `https://e-cdns-proxy-${md5_origin[0]}.dzcdn.net/api/1/${result}`
}

async function track(request) {
    const id = request.url.split('/')[4]

    if (id === "") {
        return new Response("Track ID needs to be specified", {status: 400, headers: {'content-type': "text/plain"}})
    }

    access_token = await KV.get("access_token")
    if (access_token === null) {
        const response = await fetch("https://connect.deezer.com/oauth/access_token.php?grant_type=client_credentials&client_id=447462&client_secret=a83bf7f38ad2f137e444727cfc3775cf&output=json")
        const json = await response.json()
        if (json.error !== undefined) {
            return new Response("Couldn't get access token from Deezer", {status: 500, headers: {'content-type': "text/plain"}})
        }

        access_token = json.access_token
        await KV.put("access_token", access_token, {expirationTtl: Number(json.expires)})
    }
    
    const response = await fetch(`https://api.deezer.com/track/${id}?access_token=${access_token}`)
    const json = await response.json()
    if (json.error !== undefined) {
        return new Response(JSON.stringify(json.error), {status: 403, headers: {'content-type': "application/json"}})
    }

    const md5_origin = json.md5_origin
    const format = "3"
    const media_version = json.media_version

    const url = await url_gen(md5_origin, format, id, media_version)

    return new Response(null, {status: 302, headers: {'location': url}})
}

async function handleRequest(request) {
    const r = new Router()
    // Replace with the appropriate paths and handlers
    r.get('/track/.*', () => track(request))

    r.get('/', () => new Response('Hello worker!')) // return a default message for the root route

    const resp = await r.route(request)
    return resp
}