const crypto = require('crypto');
const getParams = (ep) => {
    const a1 = 'xkt3a41psizxrh9l';
    const a = [
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63, 52, 53, 54, 55, 56, 57, 58, 59,
        60, 61, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1, -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43,
        44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1,
    ];
    let o = ep.length;
    let r = 0;
    let n, e;
    const a2 = [];
    while (r < o) {
        e = a[255 & ep[r].charCodeAt()];
        r += 1;
        while (r < o && -1 === e) {
            e = a[255 & ep[r].charCodeAt()];
            r += 1;
        }

        if (-1 === e) {
            break;
        }
        n = a[255 & ep[r].charCodeAt()];
        r += 1;
        while (r < o && -1 === n) {
            n = a[255 & ep[r].charCodeAt()];
            r += 1;
        }
        if (-1 === n) {
            break;
        }
        a2.push((e << 2) | ((48 & n) >> 4));
        e = 255 & ep[r].charCodeAt();
        r += 1;
        if (61 === e) {
            break;
        }
        e = a[e];
        while (r < o && -1 === e) {
            e = 255 & ep[r].charCodeAt();
            if (61 === e) {
                break;
            }
            e = a[e];
        }
        if (-1 === e) {
            break;
        }
        a2.push(((15 & n) << 4) | ((60 & e) >> 2));
        n = 255 & ep[r].charCodeAt();
        r += 1;
        if (61 === n) {
            break;
        }
        n = a[n];
        while (r < o && -1 === n) {
            n = 255 & ep[r].charCodeAt();
            if (61 === n) {
                break;
            }
            n = a[n];
        }
        if (-1 === n) {
            break;
        }
        a2.push(((3 & e) << 6) | n);
    }

    const r1 = Array.from(Array(256), (v, i) => i);

    let i = '';
    o = 0;
    for (let a = 0; a < 256; a++) {
        o = (o + r1[a] + a1[a % a1.length].charCodeAt()) % 256;
        [r1[a], r1[o]] = [r1[o], r1[a]];
    }

    let a3 = 0;
    o = 0;
    for (const u of a2) {
        a3 = (a3 + 1) % 256;
        o = (o + r1[a3]) % 256;
        [r1[a3], r1[o]] = [r1[o], r1[a3]];
        i += String.fromCharCode(u ^ r1[(r1[a3] + r1[o]) % 256]);
    }
    i = i.split('-');
    return {
        sign: i[1],
        buy_key: i[0],
        token: i[2],
        timestamp: i[3],
    };
};

const getPath = (seed, fileId) => {
    let t = String.raw`abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ/\:._-1234567890`;
    let cgStr = '';
    const l = t.length;
    let o;
    const idKey = fileId.split('*');
    for (let i = 0; i < l; i++) {
        seed = (211 * seed + 30031) % 65536;
        o = parseInt((seed * t.length) / 65536);
        cgStr += t[o];
        t = t.split(t[o]).join('');
    }

    const url = idKey.map((id) => cgStr[id]).join('');
    return url;
};

const getUrl = (r) => {
    const params = getParams(r.ep);
    params.duration = r.duration;
    const paramsArray = Object.keys(params)
        .filter((key) => params[key])
        .map((key) => `${key}=${params[key]}`);
    const url = `https://audiopay.cos.xmcdn.com/download/${r.apiVersion}/${getPath(r.seed, r.fileId)}?${paramsArray.join('&')}`;
    return url;
};

const getRandom16 = (len) =>
    crypto
        .randomBytes(Math.ceil(len / 2))
        .toString('hex')
        .slice(0, len);

module.exports = {
    getUrl,
    getRandom16,
};