//! \file       ArcRIO.cs
//! \date       Thu Nov 03 13:21:56 2016
//! \brief      rUGP engine resource archive.
//
// 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 System;
using System.Collections;
using System.Collections.Generic;
using System.ComponentModel.Composition;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Text;

namespace GameRes.Formats.Rugp
{
    [Export(typeof(ArchiveFormat))]
    public class RioOpener : ArchiveFormat
    {
        public override string         Tag { get { return "RIO"; } }
        public override string Description { get { return "rUGP engine resource archive"; } }
        public override uint     Signature { get { return 0; } }
        public override bool  IsHierarchic { get { return false; } }
        public override bool      CanWrite { get { return false; } }
        
        public RioOpener ()
        {
            Signatures = new uint[] { CRioArchive.RioSignature, 0 };
        }

        static readonly Dictionary<string, string> SupportedClasses = new Dictionary<string, string> {
            { "CRip007",    "image" },
            { "CRip",       "image" },
            { "CS5i",       "image" },
            { "CIcon",      "image" },
            { "CRsa",       "script" },
            { "CVmFunc",    "script" },
            { "CrelicHicompAudio", "audio" },
        };

        public override ArcFile TryOpen (ArcView file)
        {
            using (var reader = RioReader.Create (file))
            {
                if (null == reader)
                    return null;
                reader.DeserializeRelic();
                var nodes = reader.Arc.LoadArray.OfType<COceanNode>();
                var types = nodes.Select (n => n.ClassName).Distinct();
                var dir = nodes.Where (n => SupportedClasses.ContainsKey (n.ClassName))
                    .Select (n => new Entry {
                        Name    = n.Name,
                        Type    = SupportedClasses[n.ClassName],
                        Offset  = n.Offset,
                        Size    = n.Size
                    });
                if (!dir.Any())
                    return null;
                return new ArcFile (file, this, dir.ToList());
            }
        }
    }

    internal sealed class RioReader : IDisposable
    {
        IBinaryStream   m_input;
        IBinaryStream   m_toc;
        CRioArchive     m_arc;
        bool            m_read_toc;
        CrelicUnitedGameProject     m_relic;

        const uint IciKey = 0xB29D5A0C;

        public CRioArchive Arc { get { return m_arc; } }

        public CrelicUnitedGameProject DeserializeRelic ()
        {
            if (!m_read_toc)
            {
                m_read_toc = true;
                m_relic = m_arc.DeserializeRoot() as CrelicUnitedGameProject;
                if (m_toc != m_input)
                {
                    m_toc.Dispose();
                    m_toc = m_input;
                    m_arc.SetSource (m_input);
                }
            }
            return m_relic;
        }

        static public RioReader Create (ArcView file)
        {
            if (CRioArchive.RioSignature == file.View.ReadUInt32 (0))
                return new RioReader (file);

            if (file.Name.EndsWith (".ici", StringComparison.InvariantCultureIgnoreCase))
                return null;
            var ici_name = file.Name + ".ici";
            if (!VFS.FileExists (ici_name))
            {
                ici_name = Path.ChangeExtension (file.Name, ".ici");
                if (!VFS.FileExists (ici_name))
                    return null;
            }
            byte[] ici_data;
            using (var ici = VFS.OpenBinaryStream (ici_name))
                ici_data = ReadIci (ici, IciKey);

            CObjectArcMan arc_man;
            using (var ici = new BinMemoryStream (ici_data))
            {
                var rio = new CRioArchive (ici);
                arc_man = rio.DeserializeRoot() as CObjectArcMan;
                if (null == arc_man)
                    return null;
            }
            var base_name = Path.GetFileName (file.Name);
            var arc_object = arc_man.ArcList.FirstOrDefault();
            if (null == arc_object || !base_name.Equals (arc_object.RioName, StringComparison.InvariantCultureIgnoreCase))
                return null;
            return new RioReader (arc_man, file);
        }

        private RioReader (ArcView file)
        {
            m_input = file.CreateStream();
            m_toc = m_input;
            m_arc = new CRioArchive (m_input);
        }

        private RioReader (CObjectArcMan arc_man, ArcView file)
        {
            long toc_offset = arc_man.TocOffset;
            uint signature = file.View.ReadUInt32 (toc_offset);
            int shift = 0;
            if (signature != CRioArchive.EncryptedSignature)
            {
                toc_offset *= 2;
                signature = file.View.ReadUInt32 (toc_offset);
                if (signature != CRioArchive.EncryptedSignature)
                    throw new InvalidFormatException ("CPmArchive signature not found");
                shift = 1;
            }
            m_input = file.CreateStream();
            m_toc = file.CreateStream (toc_offset, (uint)arc_man.TocSize);
            m_arc = new CRioArchive (m_toc, shift, true);
        }

        public CObject ReadObject (COceanNode node)
        {
            return m_arc.ReadObject (node);
        }

        static byte[] ReadIci (IBinaryStream ici, uint key)
        {
            var rio = new CRioArchive (ici);
            var ici_data = rio.ReadEncrypted (key);
            return DecryptIci (ici_data);
        }

        static byte[] DecryptIci (byte[] input)
        {
            var output = new byte[input.Length];
            int src = 0;
            int dst = 0;
            int tail_size;
            int chunk_count = Math.DivRem (input.Length, 6, out tail_size);
            for (int n = chunk_count; n > 0; --n)
            {
                output[dst++] = input[src];
                output[dst++] = input[src + chunk_count];
                output[dst++] = input[src + chunk_count * 2];
                output[dst++] = input[src + chunk_count * 3];
                output[dst++] = input[src + chunk_count * 4];
                output[dst++] = input[src + chunk_count * 5];
                ++src;
            }
            if (tail_size > 0)
                Buffer.BlockCopy (input, input.Length - tail_size, output, dst, tail_size);

            byte acc = 0;
            for (int i = 0; i < output.Length; ++i)
            {
                output[i] -= acc;
                acc += output[i];
                output[i] ^= 0xA5;
            }

            src = 0;
            dst = 0;
            chunk_count = Math.DivRem (input.Length, 5, out tail_size);
            for (int n = chunk_count; n > 0; --n)
            {
                input[dst++] = output[src];
                input[dst++] = output[src + chunk_count];
                input[dst++] = output[src + chunk_count * 2];
                input[dst++] = output[src + chunk_count * 3];
                input[dst++] = output[src + chunk_count * 4];
                ++src;
            }
            if (tail_size > 0)
                Buffer.BlockCopy (output, output.Length - tail_size, input, dst, tail_size);

            acc = 0;
            for (int i = input.Length-1; i >= 0; --i)
            {
                input[i] -= acc;
                acc += input[i];
            }

            src = 0;
            dst = 0;
            chunk_count = Math.DivRem (input.Length, 3, out tail_size);
            for (int n = chunk_count; n > 0; --n)
            {
                output[dst++] = (byte)(input[src] ^ 0x18);
                output[dst++] = (byte)(input[src + chunk_count] ^ 0x3F);
                output[dst++] = (byte)(input[src + chunk_count * 2] ^ 0xE2);
                ++src;
            }
            if (tail_size > 0)
                Buffer.BlockCopy (input, input.Length - tail_size, output, dst, tail_size);

            return output;
        }

        #region IDisposable Members
        bool _disposed = false;
        public void Dispose ()
        {
            if (!_disposed)
            {
                m_input.Dispose();
                if (m_toc != m_input)
                    m_toc.Dispose();
                _disposed = true;
            }
        }
        #endregion
    }

    internal class CRioArchive
    {
        IBinaryStream   m_input;
        int             m_field_4C;
        string          m_field_50;
        int             m_field_54;
        bool            m_field_60;
        int             m_shift;
        int             m_objectSchema = -1;

        Dictionary<int, COceanNode> m_OceanMap = new Dictionary<int, COceanNode>();
        ArrayList                   m_LoadArray = new ArrayList();

        public IBinaryStream Input { get { return m_input; } }
        public ArrayList LoadArray { get { return m_LoadArray; } }
        public  bool   IsEncrypted { get { return 0 != (m_field_4C & 4); } }
        private bool    m_field_5C { get { return IsEncrypted; } }

        public const uint EncryptedSignature    = 0x1EDB927C;
        public const uint ObjectSignature       = 0x29F6CBA4;
        public const uint RioSignature          = 0x596E32CD;
        public const uint IciSignature          = 0x673CE92A;

        public CRioArchive (IBinaryStream input)
        {
            m_input = input;
        }

        public CRioArchive (IBinaryStream input, int shift, bool encrypted) : this (input)
        {
            m_shift = shift;
            if (encrypted)
                m_field_4C |= 4;
        }

        public IBinaryStream SetSource (IBinaryStream source)
        {
            var prev = m_input;
            m_input = source;
            return prev;
        }

        public int GetObjectSchema ()
        {
            int schema = m_objectSchema;
            m_objectSchema = -1;
            return schema;
        }

        public CObject DeserializeRoot ()
        {
            PopulateLoadArray();
            uint signature;
            var arc_class = LoadRioTypeCore (out signature);
            var obj = CreateObject (arc_class);
            MapObjectEntry (obj);
            if (RioSignature == signature)
                obj.Flags |= 0x80;
            else if (EncryptedSignature == signature)
                obj.Flags |= 0x180;
            DeserializeClassList (obj);
            obj.Deserialize (this);
            return obj;
        }

        public CObject ReadObject (COceanNode node)
        {
            var obj = CreateObject (node.Name);
            PopulateLoadArray();
            m_input.Position = ((long)node.Offset << m_shift);
            int f1 = ReadByte() & 3;
            int f2 = ReadByte();
            int f3 = ReadByte();
            int f4 = 0;
            switch (f2 >> 6)
            {
            case 0: f4 = f3 >> 6; break;
            case 1: f4 = f3 >> 2; break;
            case 2: f4 = (f3 & 0xFE) << 1 | (ReadByte() & 0xC0) << 1; break;
            case 3: f4 = (f3 & 0xFE) << 1 | (ReadByte() & 0xFE) << 6; break;
            }
            obj.Flags = node.Flags;
            MapObjectEntry (obj);
            if (2 == f1)
            {
                int flags = ReadUInt16();
                m_field_4C = (m_field_4C & 0xFFFF) | flags << 16;
            }
            else if (3 == f1)
            {
                int schema = ReadUInt16();
                int flags = ReadUInt16();
                m_field_4C = (m_field_4C & 0xFFFF) | flags << 16;
            }
            obj.Deserialize (this);
            return obj;
        }

        CObject CreateObject (string class_name)
        {
            if (!s_classTable.ContainsKey (class_name))
                throw new InvalidFormatException (string.Format ("[RIO] Unknown class '{0}'", class_name));
            return s_classTable[class_name].CreateObject();
        }

        void PopulateLoadArray ()
        {
            m_LoadArray.Clear();
            m_LoadArray.Add (null);
            m_LoadArray.Add (this);
        }

        static readonly ISet<uint> CoreSignatures = new HashSet<uint> {
            IciSignature, EncryptedSignature, RioSignature, ObjectSignature
        };

        public string LoadRioTypeCore (out uint signature)
        {
            signature = m_input.ReadUInt32();
            if (!CoreSignatures.Contains (signature))
                throw new InvalidFormatException ("[RIO] invalid signature");
            int version = ReadUInt16();
            if (version < 0x10 || version > 0x3FFF)
                throw new InvalidFormatException ("[RIO] invalid version");
            if (version >= 0x11)
            {
                m_field_4C &= 0xFFFF;
                m_field_4C |= ReadUInt16() << 16;
            }
            if (EncryptedSignature == signature)
                m_field_4C |= 0xC;

            return ReadClass();
        }

        int m_depth = 0;
        const int MaxRecursionDepth = 40; // arbitrary

        void DeserializeClassList (CObject root)
        {
            if (IsEncrypted && 0 != (root.Flags & 0x200))
                return;
            try
            {
                if (++m_depth > MaxRecursionDepth)
                    throw new InvalidFormatException ("[RIO] deserialization recursion limit exceeded");
                int count = ReadCount();
                for (int i = 0; i < count; ++i)
                {
                    if (IsEncrypted)
                    {
                        var node = CreateOceanEntry1 ("unrefix");
                        DeserializeNode (node, node != null);
                        if (node != null)
                            node.Parent = root;
                    }
                    else
                    {
                        m_field_50 = ReadString();
                        m_field_54 = 0;
                        var node = CreateOceanEntry2 (m_field_50);
                        if (node != null)
                        {
                            MapObjectEntry (node);
                            DeserializeNode (node);
                            node.Parent = root;
                        }
                        else
                        {
                            node = FindObject (m_field_50) as COceanNode;
                            MapObjectEntry (node);
                            DeserializeNode (node, false);
                        }
                    }
                }
            }
            finally
            {
                --m_depth;
            }
        }

        void DeserializeNode (COceanNode node, bool store_to_map = true)
        {
            int flags = ReadUInt16(); // this.field_1E
            string class_ref;
            switch (flags & 7)
            {
            case 0:
                if (0 != (flags & 0x8000))
                    ReadByte();
                else
                    ReadUInt16();
                class_ref = ReadClass();
                break;

            case 1:
                ReadInt32();
                class_ref = ReadCType();
                break;

            default:
                    throw new InvalidFormatException();
            }
            node.ClassName = class_ref;
            if (node != null)
            {
                if (store_to_map)
                    node.Flags = flags;
                if (0 != (flags & 8))
                {
                    if (!store_to_map)
                        node.Flags |= 8;
                    int id1 = ReadInt32(); // this.field_20
                    int id2 = ReadInt32(); // this.field_24
                    if (IsEncrypted && store_to_map)
                    {
                        node.Flags |= 0x100;
                        if (!m_OceanMap.ContainsKey (id1))
                            m_OceanMap[id1] = node;
                    }
                    if (node != null)
                    {
                        node.Offset = (uint)id1;
                        node.Size   = (uint)id2;
                    }
                }
            }
            else
            {
                if (0 == (flags & 8))
                    throw new InvalidFormatException();
                int id = ReadInt32();
                ReadInt32();
                if (!m_OceanMap.TryGetValue (id, out node))
                    throw new InvalidFormatException();
            }
            DeserializeClassList (node);
        }

        string ReadCType ()
        {
            int c = ReadUInt16();
            switch (c)
            {
            case 0x1E57:
                return ReadClass();
            case 0x2D6B:
                return ReadBasicType();
            case 0x2F1A:
                return ReadBasicType();
            case 0x369E:
                if (m_field_54 > 0x13)
                    return ReadMsgClass();
                else
                    return ReadMessage();
            default:
                throw new InvalidFormatException();
            }
        }

        string ReadMessage ()
        {
            int id = ReadUInt16();
            int cLen = ReadUInt16();
            if (id != -1 || cLen >= 0x400)
                throw new InvalidFormatException();
            var buffer = new byte[cLen];
            if (cLen != Read (buffer, 0, cLen))
                return null;
            var name = Encodings.cp932.GetString (buffer, 2, cLen-2);
            return GetRtcFromMessageName (name);
        }

        string ReadBasicType ()
        {
            ReadUInt16();
            int cLen = ReadUInt16();
            if (cLen >= 0x40 || cLen != Read (m_name_buf, 0, cLen))
                throw new InvalidFormatException();
            var name = Encodings.cp932.GetString (m_name_buf, 0, cLen);
            if (!s_basicTypeList.ContainsKey (name))
                throw new InvalidFormatException (string.Format ("[RIO] Unknown basic type '{0}'", name));
            return s_basicTypeList[name];
        }

        string ReadMsgClass ()
        {
            int wTag = ReadUInt16();
            int obTag;
            if (0x7FFF == wTag)
                obTag = ReadInt32();
            else
                obTag = ((wTag & wClassTag) << 16) | (wTag & ~wClassTag);

            if (0 == (obTag & dwBigClassTag))
                throw new InvalidFormatException ("[RIO] invalid message class");
            if (0xFFFF == wTag)
            {
                throw new NotImplementedException();
            }
            else
            {
                throw new NotImplementedException();
            }
        }

        string GetRtcFromMessageName (string name)
        {
            throw new NotImplementedException();
        }

        void MapObjectEntry (CObject node) // CArchive::MapObject
        {
            m_LoadArray.Add (node);
        }

        CObject FindObject (string name)
        {
            throw new NotImplementedException();
        }

        COceanNode CreateOceanEntry1 (string name)
        {
            return new COceanNode (name);
        }

        COceanNode CreateOceanEntry2 (string name)
        {
            return new COceanNode (name);
        }

        COceanNode CreateAnonymousRio (string name)
        {
            throw new NotImplementedException();
        }

        const int wClassTag     = 0x8000;           // 0x8000 indicates class tag (OR'd)
        const int dwBigClassTag = (int)-0x80000000; // 0x8000000 indicates big class tag (OR'd)

        public CObject ReadRioReference (string base_ref)
        {
            if (!m_field_60)
            {
                m_field_60 = true;
                if (m_field_5C)
                {
                    int count = ReadShortCount();
                    for (int i = 0; i < count; ++i)
                        MapObjectEntry (null); // new CObject()
                }
            }
            int tag;
            var class_ref = ReadClass (out tag);
            if (null == class_ref)
            {
                if (tag >= m_LoadArray.Count)
                    throw new InvalidFormatException ("Bad class");
                return m_LoadArray[tag] as CObject;
            }

            COceanNode obj;
            int flags = ReadUInt16();
            if (0 != (flags & 0x40))
            {
                obj = CreateAnonymousRio (class_ref);
                MapObjectEntry (obj);
                return obj;
            }
            int id1 = 0, id2 = 0;
            string name = null;
            if (IsEncrypted)
            {
                id1 = ReadInt32();
                id2 = ReadInt32();
            }
            else
            {
                name = ReadString();
            }
            var rio = ReadRioReference ("CRio");
            if (null == rio)
                throw new InvalidFormatException();
            if (0 != (flags & 7))
                ReadInt32();
            else if (0 != (flags & 0x8000))
                ReadByte();
            else
                ReadUInt16();
            if (IsEncrypted)
            {
                obj = ReadEncryptedObject (rio, class_ref, flags, id1, id2);
                obj.Name = base_ref;
            }
            else
            {
                throw new NotImplementedException();
            }
            MapObjectEntry (obj);
            return obj;
        }

        string ReadClass ()
        {
            int tag;
            return ReadClass (out tag);
        }

        string ReadClass (out int obTag)
        {
            int wTag = ReadUInt16();
            if (0x7FFF == wTag)
            {
                obTag = ReadInt32();
            }
            else
            {
                obTag = ((wTag & wClassTag) << 16) | (wTag & ~wClassTag);
            }
            if (0 == (obTag & dwBigClassTag))
            {
                return null;
            }

            string class_ref;
            if (0xFFFF == wTag)
            {
                uint schema = 0;
                if ((m_field_4C & 8) != 0)
                    class_ref = LoadScrambledClass (out schema);
                else
                    class_ref = LoadRuntimeClass (out schema);
                if (null == class_ref)
                    throw new InvalidFormatException();
//                m_objectSchema = (int)schema;

                m_LoadArray.Add (class_ref);
            }
            else
            {
                obTag &= 0x7FFFFFFF;
                if (0 == obTag || obTag >= m_LoadArray.Count)
                    throw new InvalidFormatException ("Bad class");
                class_ref = (string)m_LoadArray[obTag];
            }
            return class_ref;
        }

        byte[] m_name_buf = new byte[0x100];

        // loads a runtime class description
        string LoadRuntimeClass (out uint schema)
        {
            schema = ReadUInt16();
            int nLen = ReadUInt16();

            // load the class name
            if (nLen >= 0x40 || Read (m_name_buf, 0, nLen) != nLen)
                return null;
            return Encoding.ASCII.GetString (m_name_buf, 0, nLen);
        }

        string LoadScrambledClass (out uint schema)
        {
            schema = ReadUInt16();
            int length = ReadByte();
            if (0xFF == length)
            {
                length = ReadUInt16();
            }
            if (length >= 0x100 || Read (m_name_buf, 0, length) != length)
                return null;

            return DecodeClassName (m_name_buf, length);
        }

        COceanNode ReadEncryptedObject (CObject rio, string class_ref, int flags, int id1, int id2)
        {
            COceanNode node;
            if (!m_OceanMap.TryGetValue (id1, out node))
                throw new InvalidFormatException();
            if (node != null)
            {
                node.Offset = DecodeOffset (id1);
                node.Size   = DecodeSize (id2);
            }
            return node;
        }

        public int ReadInt32 ()
        {
            return m_input.ReadInt32();
        }

        public long ReadInt64 ()
        {
            return m_input.ReadInt64();
        }

        public ushort ReadUInt16 ()
        {
            return m_input.ReadUInt16();
        }

        public byte ReadByte ()
        {
            return m_input.ReadUInt8();
        }

        public int Read (byte[] buffer, int offset, int count)
        {
            return m_input.Read (buffer, offset, count);
        }

        public byte[] ReadBytes (int count)
        {
            return m_input.ReadBytes (count);
        }

        public bool ReadBool ()
        {
            return m_input.ReadUInt8() != 0;
        }

        public string ReadString ()
        {
            int nLength = ReadStringLength();
            if (0 == nLength)
                return "";
            if (nLength < 0)
                throw new InvalidFormatException();
            var buffer = m_input.ReadBytes (nLength);
            if (buffer.Length != nLength)
                throw new EndOfStreamException();
            return Encodings.cp932.GetString (buffer);
        }

        public int ReadCount ()
        {
            int count = ReadUInt16();
            if (count != 0xFFFF)
                return count;
            return ReadInt32();
        }

        public int ReadShortCount ()
        {
            int count = ReadByte();
            if (count != 0xFF)
                return count;
            return ReadUInt16();
        }

        int ReadStringLength ()
        {
            // First, try to read a one-byte length
            int length = ReadByte();
            if (length < 0xFF)
                return length;

            // Try a two-byte length
            length = ReadUInt16();
            if (0xFFFE == length)
                throw new NotSupportedException ("[RIO] Unicode strings not supported");
            if (length < 0xFFFF)
                return length;

            // 4-byte length
            return ReadInt32();
        }

        public byte[] ReadEncrypted (uint key)
        {
            uint size1 = m_input.ReadUInt32() ^ 0xC92E568B;
            uint size2 = m_input.ReadUInt32() ^ 0xC92E568F;
            size2 >>= 3;
            size1 = ~size1;
            if (size1 != size2)
                throw new InvalidFormatException ("Invalid encrypted chunk");
            var ici_data = new byte[size1];
            int dst = 0;
            while (dst < ici_data.Length)
            {
                ushort checksum = 0;
                int portion = Math.Min (0x20, ici_data.Length - dst);
                portion = m_input.Read (ici_data, dst, portion);
                for (int i = portion; i > 0; --i)
                {
                    byte b = (byte)(ici_data[dst] ^ key);
                    ici_data[dst++] = b;
                    checksum += (ushort)(b * i);
                    uint bit = key;
                    bit = (bit >> 15) & 1;
                    key = ~(bit + key*2 + 0xA3B376C9u);
                }
                if (portion < 0x20)
                    break;
                ushort chunk_sum = m_input.ReadUInt16();
                if (chunk_sum != checksum)
                    throw new InvalidFormatException ("Encrypted chunk checksum mismatch");
            }
            return ici_data;
        }

        static uint DecodeOffset (int offset)
        {
            return (uint)offset - 0xA2FB6AD1;
        }

        static uint DecodeSize (int size)
        {
            uint a = (uint)size - 0xE7B5D9F8;
            uint b = a >> 13;
            return (a - (b & 0xFFF)) << 19 | b;
        }

        static string DecodeClassName (byte[] enc, int length)
        {
            using (var output = new MemoryStream())
            using (var input = new MemoryStream (enc, 0, length))
            using (var bits = new LsbBitStream (input))
            {
                if (0 == bits.GetNextBit())
                    output.WriteByte ((byte)'C');
                for (;;)
                {
                    int b = bits.GetNextBit();
                    if (-1 == b)
                        break;
                    int c;
                    if (0 == b)
                    {
                        int idx = bits.GetBits (4);
                        if (-1 == idx)
                            break;
                        c = CharMap1[idx];
                    }
                    else if (bits.GetNextBit() != 0)
                    {
                        int idx = bits.GetBits (5);
                        if (-1 == idx)
                            break;
                        c = CharMap3[idx];
                    }
                    else
                    {
                        int idx = bits.GetBits (4);
                        if (-1 == idx)
                            break;
                        if (idx != 0)
                        {
                            c = CharMap2[idx];
                        }
                        else
                        {
                            c = bits.GetBits (8);
                            if (-1 == c)
                                break;
                        }
                    }
                    output.WriteByte ((byte)c);
                }
                var buf = output.GetBuffer();
                return Encodings.cp932.GetString (buf, 0, (int)output.Length);
            }
        }

        static readonly char[] CharMap1 = {
            'e', 'a', 'i', 't', 'r', 'o', 's', 'd', 'u', 'c', 'm', 'n', 'S', 'g', 'l', 'R' };
        static readonly char[] CharMap2 = {
            '\x1', 'C', 'O', 'F', 'L', 'f', 'B', 'M', 'x', 'p', 'h', 'y', 'A', 'V', 'b', 'I' };
        static readonly char[] CharMap3 = {
            'E', 'H', 'T', 'D', 'P', 'W', 'X', 'k', 'q', 'v', 'N', 'j', 'w', 'G', 'z', '0',
            '2', 'U', '_', 'K', '1', '5', 'J', 'Q', 'Z', '4', '6', '7', '8', '3', '9', '\x0' };

        static readonly Dictionary<string, string> s_basicTypeList = new Dictionary<string, string>
        {
            { "バイト",     "byte"   },
            { "短正整数",   "short"  },
            { "短整数",     "ushort" },
            { "正整数",     "int"    },
            { "整数",       "uint"   },
            { "色",         "Color"  },
        };

        static readonly Dictionary<string, IObjectFactory> s_classTable = new Dictionary<string, IObjectFactory>
        {
            { "CObjectArcMan", new CObjectFactory<CObjectArcMan>() },
            { "CrelicUnitedGameProject", new CObjectFactory<CrelicUnitedGameProject>() },
            { "CStdb", new CObjectFactory<CStdb>() },
        };
    }

    internal abstract class CObject
    {
        public int              Flags;
        public string           ClassName;

        public abstract void Deserialize (CRioArchive arc);
    }

    internal class CStringArray : CObject, IReadOnlyList<string>
    {
        string[]    m_data = new string[0];

        public int Count { get { return m_data.Length; } }

        public string this[int index]
        {
            get { return m_data[index]; }
            set { m_data[index] = value; }
        }

        public void SetSize (int count)
        {
            Array.Resize (ref m_data, count);
        }

        public override void Deserialize (CRioArchive arc)
        {
            int count = arc.ReadCount();
            SetSize (count);
            for (int i = 0; i < count; ++i)
                m_data[i] = arc.ReadString();
        }

        public IEnumerator<string> GetEnumerator ()
        {
            foreach (var s in m_data)
                yield return s;
        }

        IEnumerator IEnumerable.GetEnumerator ()
        {
            return m_data.GetEnumerator();
        }
    }

    internal class CPtrArray<CType> : CObject, IReadOnlyList<CType> where CType : CObject, new()
    {
        public CType[]  m_data = new CType[0];

        public int Count { get { return m_data.Length; } }

        public CType this[int index]
        {
            get { return m_data[index]; }
            set { m_data[index] = value; }
        }

        public void SetSize (int count)
        {
            Array.Resize (ref m_data, count);
        }

        public override void Deserialize (CRioArchive arc)
        {
            int count = arc.ReadCount();
            SetSize (count);
            for (int i = 0; i < count; ++i)
            {
                if (arc.ReadBool())
                {
                    var obj = new CType();
                    m_data[i] = obj;
                    obj.Deserialize (arc);
                }
            }

        }

        public IEnumerator<CType> GetEnumerator ()
        {
            foreach (var item in m_data)
                yield return item;
        }

        IEnumerator IEnumerable.GetEnumerator ()
        {
            return m_data.GetEnumerator ();
        }
    }

    internal class CInstallSource : CObject
    {
        public ushort   Version;
        public int      field_14;
        public int      field_18;
        public string   RioName;    // rio filename [dst]
        public long     RioOffset;  // rio offset
        public long     RioSize;    // rio size
        public int      field_A8;
        public int      field_B0;
        public byte[]   field_D4;

        public override void Deserialize (CRioArchive arc)
        {
            Version = arc.ReadUInt16();
            if (Version >= 7)
            {
                field_14 = arc.ReadInt32();
                field_18 = arc.ReadInt32();
                arc.ReadByte();
                arc.ReadString();
            }
            arc.ReadString(); // registry branch
            arc.ReadString(); // disk name
            arc.ReadString(); // rio filename [src]
            arc.ReadString();
            arc.ReadString();
            arc.ReadInt64(); // rio offset [=0]
            arc.ReadInt64(); // rio size
            if (Version < 6)
            {
                arc.ReadInt32();
                arc.ReadInt32();
            }
            else
            {
                arc.ReadInt32();
            }
            RioName = arc.ReadString();
            RioOffset = arc.ReadInt64();
            RioSize = arc.ReadInt64();
            if (Version < 6)
            {
                arc.ReadInt64();
            }
            arc.ReadInt32();
            arc.ReadString();
            arc.ReadInt32();
            arc.ReadInt32();
            arc.ReadInt32();
            arc.ReadInt32();
            arc.ReadInt32();
            arc.ReadString();
            int count = arc.ReadCount();
            arc.ReadBytes (count*4);
            PrepareBuffer(); // sub_10011700 (this);
            arc.Read (field_D4, 0, field_D4.Length);
        }

        void PrepareBuffer ()
        {
            field_B0 = (int)((RioSize + 0xFFFF) >> 16);
            field_A8 = 16;
            int length = (field_B0 + 7) >> 3;
            field_D4 = new byte[length];
        }
    }

    internal class CObjectArcMan : CObject
    {
        public int      Version;
        public string   Title;
        public CPtrArray<CInstallSource> ArcList = new CPtrArray<CInstallSource>();
        public int      field_14 = 0x1873BE26;
        public int      field_1C;
        public int      field_20;
        public int      TocOffset;  // RioTocOffset
        public int      TocSize;    // RioTocSize
        public int      field_38 = 0x14;
        public string   RioFileName;
        public CStringArray field_80 = new CStringArray();
        public int      field_98 = 0x30;

        public override void Deserialize (CRioArchive arc)
        {
            Version = arc.ReadInt32();
            field_14 = arc.ReadInt32();
            arc.ReadByte();
            arc.ReadByte();
            if (Version < 10)
            {
                field_1C = 0;
                field_20 = 0;
            }
            else
            {
                field_1C = arc.ReadInt32();
                field_20 = arc.ReadInt32();
            }
            arc.ReadInt32();
            arc.ReadInt32();
            arc.ReadInt32();
            if (Version >= 6)
            {
                TocOffset = arc.ReadInt32();
                TocSize   = arc.ReadInt32();
                arc.ReadInt32();
            }
            if (Version >= 8)
                field_38 = arc.ReadInt32();
            Title = arc.ReadString();
            arc.ReadInt32();
            arc.ReadString();
            arc.ReadInt32();
            arc.ReadString();
            arc.ReadString(); // registry branch
            arc.ReadString();
            arc.ReadInt32();
            arc.ReadString();
            field_80.Deserialize (arc);
            arc.ReadInt32();
            if (Version >= 9)
                RioFileName = arc.ReadString();
            if (Version >= 7)
                arc.ReadString(); // InstallManual
            if (Version >= 5)
                field_98 = arc.ReadInt32();
            ArcList.Deserialize (arc); // CPtrArray::Serialize
            for (int i = 0; i < ArcList.Count; ++i)
            {
                var entry = ArcList[i];
                if (entry != null)
                {
                    entry.field_14 = field_1C;
                    entry.field_18 = field_20;
                }
            }
        }
    }

    internal class CrelicUnitedGameProject : CObject
    {
        public int          Version;
        public CObject      field_08;
        public CObject      field_0C;
        public CObject      field_10;
        public CObject      field_14;
        public CObject      field_18;
        public CObject      field_1C;
        public CObject      field_24;
        public CObject      field_28;
        public CObject      field_2C;
        public CObject      field_30;
        public CUnknown1    field_34 = new CUnknown1();
        public CObject      field_38;

        internal const uint RioKey = 0x7E6B8CE2;

        public override void Deserialize (CRioArchive arc)
        {
            if (arc.IsEncrypted)
            {
                var data = arc.ReadEncrypted (RioKey);
                using (var input = new BinMemoryStream (data))
                {
                    var prev_source = arc.SetSource (input);
                    try
                    {
                        ReadRelic (arc);
                    }
                    finally
                    {
                        arc.SetSource (prev_source);
                    }
                }
            }
            else
                ReadRelic (arc);
        }

        void ReadRelic (CRioArchive arc)
        {
            Version = arc.ReadInt32();
            if (Version >= 0x24)
            {
                field_24 = arc.ReadRioReference ("CDatabaseBase"); // UnivUI
                field_28 = arc.ReadRioReference ("CDatabaseBase");
                field_10 = arc.ReadRioReference ("CBoxOcean"); // rvmm
                field_14 = arc.ReadRioReference ("CObjectOcean"); // UnivUI
                field_18 = arc.ReadRioReference ("CObjectOcean"); // UnivUI
                field_0C = arc.ReadRioReference ("CProcessOcean"); // Vm60
                if (Version >= 0x25)
                    field_30 = arc.ReadRioReference ("CStdb"); // UnivUI
                if (Version >= 0x26)
                    field_2C = arc.ReadRioReference ("CRio"); // UnivUI
                if (Version >= 0x27)
                    field_1C = arc.ReadRioReference ("CRio");
                if (Version >= 0x29)
                    field_38 = arc.ReadRioReference ("CRio");
                field_34.Deserialize (arc);
                if (Version >= 0x28)
                    field_08 = arc.ReadRioReference ("CRio");
            }
            else if (Version >= 0x20)
            {
                field_0C = arc.ReadRioReference ("CProcessOcean");
                field_10 = arc.ReadRioReference ("CBoxOcean");
                field_14 = arc.ReadRioReference ("CObjectOcean");
                field_18 = arc.ReadRioReference ("CObjectOcean");
                field_1C = arc.ReadRioReference ("CSoundManEx");
                if (Version >= 0x23)
                    field_24 = arc.ReadRioReference ("CDatabaseBase");
                if (Version >= 0x22)
                    field_28 = arc.ReadRioReference ("CDatabaseBase");
                if (Version >= 0x21)
                    field_34.Deserialize (arc);
            }
            else
                throw new NotSupportedException (string.Format ("rUGP schema {0} not supported", Version));
        }
    }

    internal class CUnknown1 : CObject
    {
        public int          Version = 0;
        public string       field_04; // registry branch
        public string       field_08; // version
        public string       field_0C;
        public string       field_14;
        public int          field_18 = 1000;
        public string       field_1C; // copyright
        public string       field_10;
        public int          field_20 = 1;
        public int          field_24 = 1;
        public byte[]       field_28;
        public int          field_38;
        public string       field_3C;
        public string       field_40;
        public string       field_44;
        public string       field_48;
        public string       field_4C;
        public string       field_50;

        public override void Deserialize (CRioArchive arc)
        {
            Version = arc.ReadInt32();
            if (Version >= 2)
                field_04 = arc.ReadString();
            field_08 = arc.ReadString();
            field_0C = arc.ReadString();
            field_14 = arc.ReadString();
            field_1C = arc.ReadString();
            field_18 = arc.ReadInt32();
            if (0 == Version)
               return;
            if (Version >= 2)
            {
                field_28 = arc.ReadBytes (16);
                field_38 = arc.ReadInt32();
            }
            field_3C = arc.ReadString();
            field_40 = arc.ReadString();
            if (Version >= 3)
                field_44 = arc.ReadString();
            if (Version >= 4)
            {
                field_10 = arc.ReadString();
                field_20 = arc.ReadInt32();
            }
            if (Version >= 5)
            {
                field_24 = arc.ReadInt32();
            }
            else
            {
                if (field_28.ToUInt16 (0) < 0x7D3)
                    field_24 = 2;
                else
                    field_24 = 1;
            }
            if (Version >= 6)
            {
                field_48 = arc.ReadString();
                field_4C = arc.ReadString();
                field_50 = arc.ReadString();
            }
        }
    }

    internal class CStdb : CObject
    {
        public string   field_0C;

        public override void Deserialize (CRioArchive arc)
        {
            field_0C = arc.ReadString();
        }
    }

    internal class CBoxOcean : CObject
    {
        public CObject  field_10;

        public override void Deserialize (CRioArchive arc)
        {
            field_10 = arc.ReadRioReference ("CFrameBuffer");
        }
    }

    internal class COceanNode : CObject
    {
        public string   Name;
        public CObject  Parent;
        public uint     Offset;
        public uint     Size;

        public COceanNode (string name)
        {
            Name = name;
        }

        public override void Deserialize (CRioArchive arc)
        {
            throw new NotImplementedException ("COceanNode.Deserialize not impelemented");
        }
    }

    internal interface IObjectFactory
    {
        CObject CreateObject ();
    }

    internal class CObjectFactory<CType> : IObjectFactory where CType : CObject, new()
    {
        public CObject CreateObject ()
        {
            return new CType();
        }
    }
}