//! \file       ImageZBM.cs
//! \date       Sun Jan 10 00:41:42 2016
//! \brief      BlueGale image format.
//
// Copyright (C) 2016 by morkt
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to
// deal in the Software without restriction, including without limitation the
// rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
// sell copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
// IN THE SOFTWARE.
//

using GameRes.Utility;
using System;
using System.ComponentModel.Composition;
using System.IO;

namespace GameRes.Formats.BlueGale
{
    internal class ZbmMetaData : ImageMetaData
    {
        public  int UnpackedSize;
        public  int DataOffset;
    }

    [Export(typeof(ImageFormat))]
    public class ZbmFormat : ImageFormat
    {
        public override string         Tag { get { return "ZBM/BLUEGALE"; } }
        public override string Description { get { return "BlueGale compressed image format"; } }
        public override uint     Signature { get { return 0x5F706D61; } } // 'amp_'

        public ZbmFormat ()
        {
            Extensions = new string[] { "zbm" };
        }

        public override ImageMetaData ReadMetaData (Stream stream)
        {
            stream.Position = 4;
            using (var reader = new ArcView.Reader (stream))
            {
                int version = reader.ReadInt16();
                if (version != 1)
                    return null;
                int unpacked_size = reader.ReadInt32();
                int data_offset = reader.ReadInt32();
                if (unpacked_size < 0x36 || data_offset < stream.Position)
                    return null;
                var header = new byte[0x20];
                stream.Position = data_offset;
                Unpack (stream, header);
                Decrypt (header);
                if ('B' != header[0] || 'M' != header[1])
                    return null;
                return new ZbmMetaData
                {
                    Width = LittleEndian.ToUInt32 (header, 0x12),
                    Height = LittleEndian.ToUInt32 (header, 0x16),
                    BPP = LittleEndian.ToInt16 (header, 0x1C),
                    UnpackedSize = unpacked_size,
                    DataOffset = data_offset,
                };
            }
        }

        public override ImageData Read (Stream stream, ImageMetaData info)
        {
            var meta = (ZbmMetaData)info;
            var data = new byte[meta.UnpackedSize];
            stream.Position = meta.DataOffset;
            Unpack (stream, data);
            Decrypt (data);
            using (var bmp = new MemoryStream (data))
                return Bmp.Read (bmp, info);
        }

        public override void Write (Stream file, ImageData image)
        {
            throw new System.NotImplementedException ("ZbmFormat.Write not implemented");
        }

        internal static void Unpack (Stream input, byte[] output, int dst = 0)
        {
            using (var bits = new MsbBitStream (input, true))
            {
                bits.GetNextBit();
                while (dst < output.Length)
                {
                    int count = bits.GetBits (8);
                    if (-1 == count)
                        break;
                    if (count > 0x7F)
                    {
                        int offset = bits.GetBits (10);
                        if (-1 == offset)
                            throw new EndOfStreamException();
                        count = Math.Min (count & 0x7F, output.Length-dst);
                        Binary.CopyOverlapped (output, dst-offset, dst, count);
                        dst += count;
                    }
                    else
                    {
                        if (0 == count)
                            break;
                        for (int i = 0 ; i < count && dst < output.Length; i++)
                        {
                            int v = bits.GetBits (8);
                            if (-1 == v)
                                throw new EndOfStreamException();
                            output[dst++] = (byte)v;
                        }
                    }
                }
            }
        }

        static void Decrypt (byte[] data)
        {
            if (('B'^0xFF) == data[0] && ('M'^0xFF) == data[1])
            {
                int encrypted = Math.Min (100, data.Length);
                for (int i = 0; i < encrypted; ++i)
                    data[i] ^= 0xFF;
            }
        }
    }
}