namespace CRD.Utils.DRM;

using System;
using System.Collections.Generic;
using System.Linq;

class PSSHBox{
    static readonly byte[] PSSH_HEADER = new byte[]{ 0x70, 0x73, 0x73, 0x68 };

    public List<byte[]> KIDs{ get; set; } = new List<byte[]>();
    public byte[] Data{ get; set; }

    PSSHBox(List<byte[]> kids, byte[] data){
        KIDs = kids;
        Data = data;
    }

    public static PSSHBox FromByteArray(byte[] psshbox){
        using var stream = new System.IO.MemoryStream(psshbox);

        stream.Seek(4, System.IO.SeekOrigin.Current);
        byte[] header = new byte[4];
        stream.Read(header, 0, 4);

        if (!header.SequenceEqual(PSSH_HEADER))
            throw new Exception("Not a pssh box");

        stream.Seek(20, System.IO.SeekOrigin.Current);
        byte[] kidCountBytes = new byte[4];
        stream.Read(kidCountBytes, 0, 4);

        if (BitConverter.IsLittleEndian)
            Array.Reverse(kidCountBytes);
        uint kidCount = BitConverter.ToUInt32(kidCountBytes);

        List<byte[]> kids = new List<byte[]>();
        for (int i = 0; i < kidCount; i++){
            byte[] kid = new byte[16];
            stream.Read(kid);
            kids.Add(kid);
        }

        byte[] dataLengthBytes = new byte[4];
        stream.Read(dataLengthBytes);

        if (BitConverter.IsLittleEndian)
            Array.Reverse(dataLengthBytes);
        uint dataLength = BitConverter.ToUInt32(dataLengthBytes);

        if (dataLength == 0)
            return new PSSHBox(kids, null);

        byte[] data = new byte[dataLength];
        stream.Read(data);

        return new PSSHBox(kids, data);
    }
}