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://cdns-proxy-${md5_origin[0]}.dzcdn.net/api/1/${result}`
}

const format_string_to_num = {
    '64': '10',
    '128': '1',
    '320': '3',
    'flac': '9',
    'misc': '0',
}

async function handler(type, request) {
    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 url = new URL(request.url)
    const id = url.pathname.split('/')[2]

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

    format = url.searchParams.get('f')
    if (format === null) {
        format = '320'
    } else {
        format = format.toLowerCase()
        if (format_string_to_num[format] === undefined) {
            index = Object.values(format_string_to_num).indexOf(format)
            if (index === -1) {
                return new Response('Invalid format', {status: 400, headers: {'content-type': 'text/plain'}})
            }
            format = Object.keys(format_string_to_num)[index]
        }
    }

    switch (type) {
        case 'track':
            return await track(id, format, access_token)
        case 'album':
        case 'playlist':
            return await m3u8(type, id, format, access_token)
    }
}

async function track(id, format, access_token) {
    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"}})
    }

    result = await track_url(json, format)
    if (typeof result === 'object') {
        return result
    }
    return new Response(null, {status: 302, headers: {'location': result}})

}

async function track_url(json, format) {
    const id = json.id
    const md5_origin = json.md5_origin
    const media_version = json.media_version

    if (id < 0) {
        format = 'misc'
    }

    if (json['filesize_' + format] === '0') {
        return new Response('Format unavailable', {status: 403, headers: {'content-type': 'text/plain'}})
    }

    format = format_string_to_num[format]

    return await url_gen(md5_origin, format, id, media_version)
}

async function m3u8(type, id, format, access_token) {
    const response = await fetch(`https://api.deezer.com/${type}/${id}?access_token=${access_token}&limit=-1`)
    const json = await response.json()
    if (json.error !== undefined) {
        return new Response(JSON.stringify(json.error), {status: 403, headers: {'content-type': "application/json"}})
    }

    var list = '#EXTM3U\n'

    for (const track of json.tracks.data) {
        const result = await track_url(track, format)
        if (typeof result === 'object') {
            return result
        }
        list += `#EXTINF:${track.duration},${track.title}\n${result}\n`
    }

    return new Response(list, {status: 200, headers: {'content-type': 'audio/mpegurl'}})
}

async function handleRequest(request) {
    const r = new Router()
    r.get('/track/.*', () => handler('track', request))
    r.get('/album/.*', () => handler('album', request))
    r.get('/playlist/.*', () => handler('playlist', request))

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