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

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

const trackCDNKey = [106, 111, 54, 97, 101, 121, 54, 104, 97, 105, 100, 50, 84, 101, 105, 104]
const bfSecret = [103, 52, 101, 108, 53, 56, 119, 99, 48, 122, 118, 102, 57, 110, 97, 49]

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

function bin2str(bin) {
    return String.fromCharCode.apply(String, bin);
}

async function bf_key(id) {
    let id_md5 = await crypto.subtle.digest('MD5', new Uint8Array(str2bin(id)))
    id_md5 = aesjs.utils.hex.fromBytes(new Uint8Array(id_md5))

    key = []
    for (let i = 0; i < 16; i++) {
        key.push(id_md5[i].charCodeAt(0) ^ id_md5[i + 16].charCodeAt(0) ^ bfSecret[i])
    }
    return bin2str(key)
}

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

    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-${md5_origin[0]}.dzcdn.net/mobile/1/${result}`
}

const format_string_to_num = {
    '64': '10',
    '128': '1',
    '320': '3',
    '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'

    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
    }

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

    let id3
    if (tagging) {
        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()

    if (id3) {
        writer.write(id3.arrayBuffer)
    }

    const bfKey = await bf_key(id)
    const length = Number(track.headers.get('Content-Length'))
    
    pipeDecryptedStream(writer, track.body, length, bfKey, id3)

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

async function pipeDecryptedStream(writer, body, length, bfKey) {
    const cipher = new Blowfish(bfKey, Blowfish.MODE.CBC, Blowfish.PADDING.NULL)
    cipher.setIv('\x00\x01\x02\x03\x04\x05\x06\x07')

    const reader = body.getReader({ mode: 'byob' })
    let byteCount = 0
    let end = false
    while (!end) {
        end = byteCount + 2048 > length
        let chunk
        if (!end) {
            chunk = new Int8Array(2048)
        } else {
            chunk = new Int8Array(length - byteCount)
        }

        // if read chunk isn't 2048 bytes, read until it is
        // cause of retarded readable streams not having an option to specify min bytes
        let tempLength = 0
        while (tempLength !== chunk.length) {
            let read = (await reader.read(new Int8Array(chunk.length - tempLength))).value
            chunk.set(read, tempLength)
            tempLength += read.length
        }

        if (byteCount % 6144 === 0 && !end) {
            // encrypted chunk
            chunk = cipher.decode(chunk, Blowfish.TYPE.UINT8_ARRAY)
        }

        writer.write(chunk)
        byteCount += 2048
    }
}

async function track_url(json, format) {
    // needed if track has fallback, like https://www.deezer.com/track/1398759152
    if (json.alternative) {
        json = json.alternative
    }

    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) {
        if (track.id < 0) {   // user-uploaded track
            format = 'misc'
        }
        let result = `https://dz.uhwot.workers.dev/track/${track.id}?f=${format}&t=${Number(tagging)}`
        list += `#EXTINF:${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
}