using System;
using System.Buffers.Binary;
using System.IO;
using System.Linq;
using SharpCompress.Common.Zip.Headers;
using SharpCompress.Compressors;
using SharpCompress.Compressors.BZip2;
using SharpCompress.Compressors.Deflate;
using SharpCompress.Compressors.Deflate64;
using SharpCompress.Compressors.LZMA;
using SharpCompress.Compressors.PPMd;
using SharpCompress.IO;

namespace SharpCompress.Common.Zip
{
    internal abstract class ZipFilePart : FilePart
    {
        internal ZipFilePart(ZipFileEntry header, Stream stream) : base(header.ArchiveEncoding)
        {
            Header = header;
            header.Part = this;
            BaseStream = stream;
        }

        internal Stream BaseStream { get; }
        internal ZipFileEntry Header { get; set; }

        internal override string FilePartName => Header.Name;

        internal override Stream GetCompressedStream()
        {
            if (!Header.HasData)
            {
                return Stream.Null;
            }
            Stream decompressionStream = CreateDecompressionStream(
                GetCryptoStream(CreateBaseStream()),
                Header.CompressionMethod
            );
            if (LeaveStreamOpen)
            {
                return NonDisposingStream.Create(decompressionStream);
            }
            return decompressionStream;
        }

        internal override Stream GetRawStream()
        {
            if (!Header.HasData)
            {
                return Stream.Null;
            }
            return CreateBaseStream();
        }

        protected abstract Stream CreateBaseStream();

        protected bool LeaveStreamOpen =>
            FlagUtility.HasFlag(Header.Flags, HeaderFlags.UsePostDataDescriptor) || Header.IsZip64;

        protected Stream CreateDecompressionStream(Stream stream, ZipCompressionMethod method)
        {
            switch (method)
            {
                case ZipCompressionMethod.None:
                {
                    return stream;
                }
                case ZipCompressionMethod.Deflate:
                {
                    return new DeflateStream(stream, CompressionMode.Decompress);
                }
                case ZipCompressionMethod.Deflate64:
                {
                    return new Deflate64Stream(stream, CompressionMode.Decompress);
                }
                case ZipCompressionMethod.BZip2:
                {
                    return new BZip2Stream(stream, CompressionMode.Decompress, false);
                }
                case ZipCompressionMethod.LZMA:
                {
                    if (FlagUtility.HasFlag(Header.Flags, HeaderFlags.Encrypted))
                    {
                        throw new NotSupportedException("LZMA with pkware encryption.");
                    }
                    var reader = new BinaryReader(stream);
                    reader.ReadUInt16(); //LZMA version
                    var props = new byte[reader.ReadUInt16()];
                    reader.Read(props, 0, props.Length);
                    return new LzmaStream(
                        props,
                        stream,
                        Header.CompressedSize > 0 ? Header.CompressedSize - 4 - props.Length : -1,
                        FlagUtility.HasFlag(Header.Flags, HeaderFlags.Bit1)
                            ? -1
                            : (long)Header.UncompressedSize
                    );
                }
                case ZipCompressionMethod.PPMd:
                {
                    Span<byte> props = stackalloc byte[2];
                    stream.ReadFully(props);
                    return new PpmdStream(new PpmdProperties(props), stream, false);
                }
                case ZipCompressionMethod.WinzipAes:
                {
                    ExtraData? data = Header.Extra.SingleOrDefault(
                        x => x.Type == ExtraDataType.WinZipAes
                    );
                    if (data is null)
                    {
                        throw new InvalidFormatException("No Winzip AES extra data found.");
                    }
                    if (data.Length != 7)
                    {
                        throw new InvalidFormatException("Winzip data length is not 7.");
                    }
                    ushort compressedMethod = BinaryPrimitives.ReadUInt16LittleEndian(
                        data.DataBytes
                    );

                    if (compressedMethod != 0x01 && compressedMethod != 0x02)
                    {
                        throw new InvalidFormatException(
                            "Unexpected vendor version number for WinZip AES metadata"
                        );
                    }

                    ushort vendorId = BinaryPrimitives.ReadUInt16LittleEndian(
                        data.DataBytes.AsSpan(2)
                    );
                    if (vendorId != 0x4541)
                    {
                        throw new InvalidFormatException(
                            "Unexpected vendor ID for WinZip AES metadata"
                        );
                    }
                    return CreateDecompressionStream(
                        stream,
                        (ZipCompressionMethod)
                            BinaryPrimitives.ReadUInt16LittleEndian(data.DataBytes.AsSpan(5))
                    );
                }
                default:
                {
                    throw new NotSupportedException(
                        "CompressionMethod: " + Header.CompressionMethod
                    );
                }
            }
        }

        protected Stream GetCryptoStream(Stream plainStream)
        {
            bool isFileEncrypted = FlagUtility.HasFlag(Header.Flags, HeaderFlags.Encrypted);

            if (Header.CompressedSize == 0 && isFileEncrypted)
            {
                throw new NotSupportedException("Cannot encrypt file with unknown size at start.");
            }

            if (
                (
                    Header.CompressedSize == 0
                    && FlagUtility.HasFlag(Header.Flags, HeaderFlags.UsePostDataDescriptor)
                ) || Header.IsZip64
            )
            {
                plainStream = NonDisposingStream.Create(plainStream); //make sure AES doesn't close
            }
            else
            {
                plainStream = new ReadOnlySubStream(plainStream, Header.CompressedSize); //make sure AES doesn't close
            }

            if (isFileEncrypted)
            {
                switch (Header.CompressionMethod)
                {
                    case ZipCompressionMethod.None:
                    case ZipCompressionMethod.Deflate:
                    case ZipCompressionMethod.Deflate64:
                    case ZipCompressionMethod.BZip2:
                    case ZipCompressionMethod.LZMA:
                    case ZipCompressionMethod.PPMd:
                    {
                        return new PkwareTraditionalCryptoStream(
                            plainStream,
                            Header.ComposeEncryptionData(plainStream),
                            CryptoMode.Decrypt
                        );
                    }

                    case ZipCompressionMethod.WinzipAes:
                    {
                        if (Header.WinzipAesEncryptionData != null)
                        {
                            return new WinzipAesCryptoStream(
                                plainStream,
                                Header.WinzipAesEncryptionData,
                                Header.CompressedSize - 10
                            );
                        }
                        return plainStream;
                    }

                    default:
                    {
                        throw new InvalidOperationException("Header.CompressionMethod is invalid");
                    }
                }
            }
            return plainStream;
        }
    }
}