using System.IO;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using Wabbajack.Common;
using Wabbajack.Compression.BSA.Interfaces;
using Wabbajack.DTOs.BSA.ArchiveStates;
using Wabbajack.DTOs.BSA.FileStates;

namespace Wabbajack.Compression.BSA.TES3Archive
{
    public class Builder : IBuilder
    {
        private readonly (TES3File state, Stream data)[] _files;
        private readonly TES3State _state;

        public Builder(TES3State state)
        {
            _state = state;
            _files = new (TES3File state, Stream data)[_state.FileCount];
        }

        public async ValueTask AddFile(AFile state, Stream src, CancellationToken token)
        {
            var tesState = (TES3File)state;
            _files[state.Index] = (tesState, src);
        }

        public async ValueTask Build(Stream file, CancellationToken token)
        {
            await using var bw = new BinaryWriter(file, Encoding.Default, true);

            bw.Write(_state.VersionNumber);
            bw.Write(_state.HashOffset);
            bw.Write(_state.FileCount);

            foreach (var (state, _) in _files)
            {
                bw.Write(state.Size);
                bw.Write(state.Offset);
            }

            foreach (var (state, _) in _files) bw.Write(state.NameOffset);

            var orgPos = bw.BaseStream.Position;

            foreach (var (state, _) in _files)
            {
                if (bw.BaseStream.Position != orgPos + state.NameOffset)
                    throw new BSAException("Offsets don't match when writing TES3 BSA");
                bw.Write(Encoding.ASCII.GetBytes((string)state.Path));
                bw.Write((byte)0);
            }

            bw.BaseStream.Position = _state.HashOffset + 12;
            foreach (var (state, _) in _files)
            {
                bw.Write(state.Hash1);
                bw.Write(state.Hash2);
            }

            if (bw.BaseStream.Position != _state.DataOffset)
                throw new InvalidDataException("Data offset doesn't match when writing TES3 BSA");

            foreach (var (state, data) in _files)
            {
                bw.BaseStream.Position = _state.DataOffset + state.Offset;
                await data.CopyToWithStatusAsync(data.Length, bw.BaseStream, token);
                await data.DisposeAsync();
            }
        }
    }
}