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

namespace Packer{
    class Program{

        static readonly List<Extensions> extensions = new List<Extensions>(
            new Extensions[] {
                new Extensions { Source = ".mmm", Destination = ".mad" },
                new Extensions { Source = ".mtm", Destination = ".mtd" },
                new Extensions { Source = ".pmm", Destination = ".pmg" },
                new Extensions { Source = ".pom", Destination = ".pog" },
                new Extensions { Source = ".ptm", Destination = ".ptg" }
            });


        static byte[] Decompress(byte[] source) {
            int offset = 0;

            List<byte> outBuffer = new List<byte>();



            while (source[offset] != 0) {
                byte blockType = source[offset];


            }



            while (source[offset] != 0) {
                byte blockType = source[offset];

                if (blockType < 0x40) {
                    outBuffer.AddRange(source.AsSpan(offset + 1, blockType).ToArray());
                    offset += 1 + blockType;
                } else if (blockType < 0x50) {
                    var count = (blockType - 0x40) + 3;

                    byte v0 = outBuffer[outBuffer.Count - 2];
                    byte v1 = outBuffer[outBuffer.Count - 1];

                    //byte v0 = source[offset - 2];
                    //byte v1 = source[offset - 1];

                    v0 = (byte)(v1 - v0);
                    do {
                        v1 += v0;
                        outBuffer.Add(v1);
                        --count;
                    }
                    while (count != 0);

                    offset += 1;

                } else if (blockType < 0x60) {
                    var count = (blockType - 0x50) + 2;

                    short v0 = (short)(outBuffer[outBuffer.Count - 4] | ((short)outBuffer[outBuffer.Count - 3] << 8));
                    short v1 = (short)(outBuffer[outBuffer.Count - 2] | ((short)outBuffer[outBuffer.Count - 1] << 8));

                    //short v0 = (short)(source[offset - 4] | ((short)source[offset - 3] << 8));
                    //short v1 = (short)(source[offset - 2] | ((short)source[offset - 1] << 8));

                    v0 = (short)(v1 - v0);
                    do {
                        v1 += v0;
                        outBuffer.Add((byte)(v1 & 0xff));
                        outBuffer.Add((byte)((v1 >> 8) & 0xff));
                        --count;
                    }
                    while (count != 0);

                    offset += 1;
                } else if (blockType < 0x70) { //Copy last written byte (base 3)
                    var b = outBuffer[outBuffer.Count - 1];
                    var copyCount = (blockType - 0x60) + 3;
                    for (int i = 0; i < copyCount; ++i) {
                        outBuffer.Add(b);
                    }
                    offset += 1;
                } else if (blockType < 0x80) {
                    var b0 = outBuffer[outBuffer.Count - 2];
                    var b1 = outBuffer[outBuffer.Count - 1];

                    var copyCount = (blockType - 0x70) + 2;
                    for (int i = 0; i < copyCount; ++i) {
                        outBuffer.Add(b0);
                        outBuffer.Add(b1);
                    }
                    offset += 1;
                } else if (blockType < 0xC0) { //Copy 3 bytes
                    var backOffset = (blockType - 0x80) + 3;
                    var readOffset = (outBuffer.Count) - backOffset;
                    outBuffer.Add(outBuffer[readOffset + 0]);
                    outBuffer.Add(outBuffer[readOffset + 1]);
                    outBuffer.Add(outBuffer[readOffset + 2]);
                    offset += 1;
                } else if (blockType < 0xE0) {

                    var copyCount = ((blockType - 0xC0) >> 2) + 4;
                    var backOffset = ((blockType - 0xC0) & 3) << 8;

                    backOffset += (source[offset + 1] + 3);

                    var readStart = (outBuffer.Count) - backOffset;


                    var block = outBuffer.ToArray().AsSpan(readStart, Math.Min(copyCount, backOffset));

                    for(int i = 0; i < copyCount; ++i) {
                        outBuffer.Add(block[i % block.Length]);
                    }
                  
                    offset += 2;
                } else {
                    var backOffset = ((blockType - 0xE0) * 256) + (source[offset + 1] + 3);
                    var bytesCount = source[offset + 2] + 5;
                    var readStart = (outBuffer.Count) - backOffset;
                    for (int i = 0; i < bytesCount; ++i) {
                        outBuffer.Add(outBuffer[readStart + (i % backOffset)]);
                    }
                    offset += 3;
                }
            }
            return outBuffer.ToArray();
        }

        static void DecompressFile(string input, string output) {
            var bytes = File.ReadAllBytes(input);
            var decompressed = Decompress(bytes);
            File.WriteAllBytes(output, decompressed);
        }

        struct Extensions {
            public string Source;
            public string Destination;
        }

        static void DecompressDirectory(string directory) {
            var files = Directory.GetFiles(directory);
            files = files.Where(v => extensions.Any( g=> g.Source == Path.GetExtension(v).ToLower())).ToArray();

            foreach(var file in files) {
                var referenceFilePath = Path.GetDirectoryName(file);
                referenceFilePath = Path.Combine(referenceFilePath, "Decompressed",
                    Path.GetFileNameWithoutExtension(file) + extensions.First(v => v.Source == Path.GetExtension(file).ToLower()).Destination);

                if (!File.Exists(referenceFilePath)) {
                    continue;
                }

                var compressedData = File.ReadAllBytes(file);
                var referenceData = File.ReadAllBytes(referenceFilePath);

                var decompressedData = Decompress(compressedData);

            

                var equal = decompressedData.SequenceEqual(referenceData);
                if (!equal) {
                    throw new Exception("Invalid bytes :(");
                }

            }

            Console.WriteLine();
        }

        static void Main(string[] args) {
            string input = @"C:\Users\l-pro\Downloads\!HOW\COLD1.PMM";
            string output = @"C:\Users\l-pro\Downloads\!HOW\COLD1.PMM_UNK";

            DecompressFile(input, output);

            DecompressDirectory(@"C:\Users\l-pro\Downloads\!HOW\Test");

            Console.WriteLine("Done");
        }
    }
}