const Router = require('./router')
const aesjs = require('aes-js');
const ID3Writer = require('browser-id3-writer');

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]

function str2bin(str) {
    return Array.from(str).map(function (item) {
        return item.charCodeAt(0);
    })
}

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

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

    let result_md5 = await crypto.subtle.digest('MD5', new Uint8Array(str2bin(result)))

    result_md5 = aesjs.utils.hex.fromBytes(new Uint8Array(result_md5))

    result = result_md5 + '\xa4' + result + '\xa4'

    // zero-padding
    if (result.length % 16) {
        result += '\x00'.repeat(16 - result.length % 16)
    }

    result = aesjs.utils.hex.fromBytes(cipher.encrypt(str2bin(result)))

    // 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]
        }
    }
    
    var tagging = url.searchParams.get('t')
    tagging = (tagging === 'true' || tagging === '1') && format !== 'flac'

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

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

    if (!tagging) {
        return new Response(null, {status: 302, headers: {'location': result}})
    } else {
        const track = await fetch(result)
        if (track.status !== 200) {
            return new Response("Couldn't get track stream", {status: 403, headers: {'content-type': 'text/plain'}})
        }

        const id3 = new ID3Writer(Buffer.alloc(0));
        id3.padding = 0
        id3.setFrame('TIT2', json.title)
            .setFrame('TALB', json.album.title)
            .setFrame('TPE2', json.artist.name)

        if (json.contributors !== undefined) {
            contr_list = [];
            for (const c of json.contributors) {
                contr_list.push(c.name)
            }

            id3.setFrame('TPE1', contr_list)
        }

        if (json.track_position !== undefined) {
            id3.setFrame('TRCK', json.track_position)
        }

        if (json.disk_number !== undefined) {
            id3.setFrame('TPOS', json.disk_number)
        }

        if (json.isrc !== "") {
            id3.setFrame('TSRC', json.isrc)
        }

        if (json.bpm !== undefined) {
            id3.setFrame('TBPM', json.bpm)
        }

        if (json.release_date !== undefined) {
            const split = json.release_date.split('-')
            id3.setFrame('TYER', split[0])
            id3.setFrame('TDAT', split[2]+split[1])
        }

        if (json.md5_image !== "") {
            const url = `https://cdns-images.dzcdn.net/images/cover/${json.md5_image}/1000x1000-000000-80-0-0.jpg`
            const cover = await fetch(url)
            const coverBuffer = await cover.arrayBuffer()

            id3.setFrame('APIC', {
                type: 3,
                data: coverBuffer,
                description: 'cover'
            });
        }

        id3.addTag();

        let { readable, writable } = new TransformStream()
        const writer = writable.getWriter()

        writer.write(id3.arrayBuffer)
        writer.releaseLock()
        track.body.pipeTo(writable)

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

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) {   // user-uploaded track
        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, tagging) {
    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) {
        let result
        if (!tagging) {
            result = await track_url(track, format)
            if (typeof result === 'object') {
                return result
            }
        } else {
            if (track.id < 0) {   // user-uploaded track
                format = 'misc'
            }
            result = `https://dz.uhwot.workers.dev/track/${track.id}?f=${format}&t=1`
        }
        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
}