using System.Collections.Generic;
using System;
using System.Runtime.InteropServices;

public class PmgFile {

    [Serializable]
    [StructLayout(LayoutKind.Sequential, Pack = 1)]
    public class PmgBlock {
        [Serializable]
        [StructLayout(LayoutKind.Sequential, Pack = 1)]
        public struct Vertex {
            public short height;                // height sample
            public short lighting;             // <= 255
        }

        [Serializable]
        [StructLayout(LayoutKind.Sequential, Pack = 1)]
        public struct Tile {

            [Flags]
            public enum Transform : byte {
                FlipX = 1,
                Rotate90 = 2,
                Rotate180 = 4
            }

            public enum Slip : byte {
                Full = 0,
                Bottom = 1,
                Left = 2,
                Top = 3,
                Right = 4,
                BottomRight = 5,
                BottomLeft = 6,
                TopLeft = 7,
                TopRight = 8
            }

            public short Field0;          // always 0 -> obsolete xOffset?
            public short Field1;          // always 0 -> obsolete yOffset?
            public short Field2;          // always 0 -> obsolete zOffset?

            public char Type;
            public Slip slip;
            public short Field3;
            public Transform RotationFlip;
            public int TextureIndex;
            public char Field4;
        }

        public short xOffset;                   // -16384 ~ 16384
        public short yOffset;                   // unreliable?
        public short zOffset;                  // -16384 ~ 16384
        public short Field0;

        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 25)]
        public Vertex[] vertices;

        public int Field1;

        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 16)]
        public Tile[] tiles;
    }

    public PmgBlock[] Blocks;

    public static PmgFile Parse(byte[] data) {
        PmgFile result = new PmgFile();
        var blockSize = Marshal.SizeOf(typeof(PmgBlock));
        int blockCount = data.Length / blockSize;

        var handle = GCHandle.Alloc(data, GCHandleType.Pinned);
        var ptr = handle.AddrOfPinnedObject();

        List<PmgBlock> blocks = new List<PmgBlock>();
        for (int Block = 0; Block < blockCount; Block++) {
            blocks.Add(Marshal.PtrToStructure<PmgBlock>(ptr));
            ptr += blockSize;
        }
        handle.Free();
        result.Blocks = blocks.ToArray();
        return result;
    }
}