using System.IO.Compression;

namespace LibGit.Extensions;

public static class StreamExtensions
{
    private const bool _debug = false;

    public static long Remaining(this Stream stream)
    {
        //if (_debug) Console.WriteLine($"stream pos: {stream.Position}, stream len: {stream.Length}, stream rem: {stream.Length - stream.Position}");
        return stream.Length - stream.Position;
    }

    public static int Peek(this Stream stream)
    {
        if (!stream.CanRead)
            throw new InvalidOperationException("Can't peek a non-readable stream");
        if (!stream.CanSeek)
            throw new InvalidOperationException("Can't peek a non-seekable stream");

        int peek = stream.ReadByte();
        if (peek != -1)
            stream.Seek(-1, SeekOrigin.Current);

        return peek;
    }

    public static IEnumerable<byte> Peek(this Stream stream, long count)
    {
        if (!stream.CanRead)
            throw new InvalidOperationException("Can't peek a non-readable stream");
        if (!stream.CanSeek)
            throw new InvalidOperationException("Can't peek a non-seekable stream");
        long i;
        for (i = 0; i < count; i++)
        {
            int peek = stream.ReadByte();
            if (peek == -1)
            {
                if(_debug) Console.WriteLine($"Can't peek {count} bytes, only {i} bytes remaining");
                stream.Seek(-i, SeekOrigin.Current);
                yield break;
            }

            yield return (byte)peek;
        }
        stream.Seek(-i, SeekOrigin.Current);
    }

    public static IEnumerable<byte> ReadBytes(this Stream stream, long count)
    {
        if (!stream.CanRead)
            throw new InvalidOperationException("Can't read a non-readable stream");
        if (!stream.CanSeek)
            throw new InvalidOperationException("Can't read a non-seekable stream");

        for (long i = 0; i < count; i++)
        {
            int read = stream.ReadByte();
            if (read == -1)
                yield break;
            yield return (byte)read;
        }
    }

    public static bool StartsWith(this Stream stream, IEnumerable<byte> sequence)
    {
        if (!stream.CanRead)
            throw new InvalidOperationException("Can't read a non-readable stream");
        if (!stream.CanSeek)
            throw new InvalidOperationException("Can't read a non-seekable stream");

        if (_debug)
        {
            Console.WriteLine($"Expected: {sequence.AsHexString()} ({sequence.AsString()})");
            Console.WriteLine($"Actual:   {stream.Peek(sequence.Count()).AsHexString()} ({stream.Peek(sequence.Count()).AsString()})");
        }
        
        int readCount = 0;
        foreach (int b in sequence)
        {
            int read = stream.ReadByte();
            readCount++;
            if (read == -1)
            {
                stream.Seek(-readCount, SeekOrigin.Current);
                return false;
            }
            
            if (read != b)
            {
                if (_debug)
                {
                    Console.ForegroundColor = ConsoleColor.Red;
                    Console.WriteLine("^^".PadLeft(readCount * 3 + 9));
                    Console.ResetColor();
                }

                stream.Seek(-readCount, SeekOrigin.Current);
                return false;
            }
        }
        stream.Seek(-readCount, SeekOrigin.Current);
        
        return true;
    }

    public static bool StartsWith(this Stream stream, string ascii_seq)
    {
        return stream.StartsWith(ascii_seq.Select(x => (byte)x));
    }

    public static Stream Skip(this Stream stream, long count = 1)
    {
        if (!stream.CanSeek)
            throw new InvalidOperationException("Can't skip a non-seekable stream");
        stream.Seek(count, SeekOrigin.Current);
        return stream;
    }

    public static IEnumerable<byte> ReadNullTerminatedField(this Stream stream, IEnumerable<byte>? binaryPrefix = null, string? asciiPrefix = null) => ReadTerminatedField(stream: stream, terminator: 0x00, binaryPrefix: binaryPrefix, asciiPrefix: asciiPrefix);
    public static IEnumerable<byte> ReadSpaceTerminatedField(this Stream stream, IEnumerable<byte>? binaryPrefix = null, string? asciiPrefix = null) => ReadTerminatedField(stream: stream, terminator: 0x20, binaryPrefix: binaryPrefix, asciiPrefix: asciiPrefix);
    public static IEnumerable<byte> ReadTerminatedField(this Stream stream, byte terminator, IEnumerable<byte>? binaryPrefix = null, string? asciiPrefix = null)
    {
        if (!stream.CanRead)
            throw new InvalidOperationException("Can't read a non-readable stream");
        if (binaryPrefix != null)
            if (!stream.StartsWith(binaryPrefix))
                throw new InvalidDataException($"Binary prefix {stream.Peek(binaryPrefix.Count()).AsHexString()} does not match expected value of {binaryPrefix.AsHexString()}!");
            else stream.Skip(binaryPrefix.Count());
        else if (asciiPrefix != null)
            if (!stream.StartsWith(asciiPrefix))
                throw new InvalidDataException($"Text prefix {stream.Peek(asciiPrefix.Length).AsHexString()} ({stream.Peek(asciiPrefix.Length).AsString()}) does not match expected value of {asciiPrefix.AsBytes().AsHexString()} ({asciiPrefix})!");
            else stream.Skip(asciiPrefix.Length);

        var read = 0;
        while (stream.Peek() != terminator)
        {
            if (_debug) Console.WriteLine($"ReadTerminatedField -- pos: {stream.Position}/+{stream.Remaining()}/{stream.Length} | next: {(char)stream.Peek()} | Length: {read}");
            if (stream.Peek() == -1)
            {
                Console.WriteLine($"Warning: Reached end of stream while reading null-terminated field");
                yield break;
            }

            read++;
            yield return (byte)stream.ReadByte();
        }

        if (stream.Peek() == terminator) stream.Skip();
    }
    
    public static IEnumerable<byte> ReadToEnd(this Stream stream)
    {
        if (!stream.CanRead)
            throw new InvalidOperationException("Can't read a non-readable stream");

        while (stream.Peek() != -1)
            yield return (byte)stream.ReadByte();
    }
    
    public static int ReadInt32BE(this Stream stream)
    {
        if (!stream.CanRead)
            throw new InvalidOperationException("Can't read a non-readable stream");

        var bytes = stream.ReadBytes(4).ToArray();
        
        if (BitConverter.IsLittleEndian)
            Array.Reverse(bytes);
        
        Console.WriteLine("ReadInt32BE: " + bytes.AsHexString() + " => " + BitConverter.ToInt32(bytes));
        return BitConverter.ToInt32(bytes);
    }
    
    //read variable length number
    public static int ReadVLQ(this Stream stream)
    {
        if (!stream.CanRead)
            throw new InvalidOperationException("Can't read a non-readable stream");

        int result = 0;
        int shift = 0;
        byte b;
        do
        {
            b = (byte)stream.ReadByte();
            result |= (b & 0b0111_1111) << shift;
            shift += 7;
        } while ((b & 0b1000_0000) != 0);

        return result;
    }
    public static int ReadVLQBigEndian(this Stream stream)
    {
        if (!stream.CanRead)
            throw new InvalidOperationException("Can't read a non-readable stream");

        int result = 0;
        int shift = 0;
        byte b;
        do
        {
            b = (byte)stream.ReadByte();
            result = (result << 7) | (b & 0b0111_1111);
        } while ((b & 0b1000_0000) != 0);

        return result;
    }
}