//! \file       ArcWAG.cs
//! \date       Tue Aug 11 08:28:28 2015
//! \brief      Xuse/Eternal resource archive.
//
// Copyright (C) 2015-2016 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.Generic;
using System.ComponentModel.Composition;
using System.IO;
using System.Linq;
using System.Text.RegularExpressions;
using GameRes.Utility;

namespace GameRes.Formats.Xuse
{
    internal class WagArchive : ArcFile
    {
        public readonly byte[] Key;

        public WagArchive (ArcView arc, ArchiveFormat impl, ICollection<Entry> dir, byte[] key)
            : base (arc, impl, dir)
        {
            Key = key;
        }
    }

    [Export(typeof(ArchiveFormat))]
    public class WagOpener : ArchiveFormat
    {
        public override string         Tag { get { return "WAG"; } }
        public override string Description { get { return "Xuse/Eternal resource archive"; } }
        public override uint     Signature { get { return 0x40474157; } } // 'WAG@'
        public override bool  IsHierarchic { get { return true; } }
        public override bool      CanWrite { get { return false; } }

        public WagOpener ()
        {
            Extensions = new string[] { "wag", "4ag", "004" };
            Signatures = new uint[] { 0x40474157, 0x34464147 }; // 'GAF4'
        }

        public override ArcFile TryOpen (ArcView file)
        {
            int version = file.View.ReadUInt16 (4);
            if (0x300 != version && 0x200 != version)
                return null;
            int count = file.View.ReadInt32 (0x46);
            if (!IsSaneCount (count))
                return null;

            var reader = new IndexReader (file, version, count);
            var dir = reader.ReadIndex();
            if (null == dir)
                return null;
            return new WagArchive (file, this, dir, reader.DataKey);
        }

        public override Stream OpenEntry (ArcFile arc, Entry entry)
        {
            var warc = arc as WagArchive;
            if (null == warc)
                return arc.File.CreateStream (entry.Offset, entry.Size);
            var data = arc.File.View.ReadBytes (entry.Offset, entry.Size);
            Decrypt ((uint)entry.Offset, warc.Key, data);
            return new MemoryStream (data);
        }

        static private byte[] GenerateKey (byte[] keyword)
        {
            return GenerateKey (keyword, keyword.Length);
        }

        static private byte[] GenerateKey (byte[] keyword, int length)
        {
            int hash = 0;
            for (int i = 0; i < length; ++i)
                hash = (((sbyte)keyword[i] + i) ^ hash) + length;

            int key_length = (hash & 0xFF) + 0x40;

            for (int i = 0; i < length; ++i)
                hash += (sbyte)keyword[i];

            byte[] key = new byte[key_length--];
            key[1] = (byte)(hash >> 8);
            hash &= 0xF;
            key[0] = (byte)hash;
            key[2] = 0x46;
            key[3] = 0x88;

            for (int i = 4; i < key_length; ++i)
            {
                hash += (((sbyte)keyword[i % length] ^ hash) + i) & 0xFF;
                key[i] = (byte)hash;
            }
            return key;
        }

        static private void Decrypt (uint offset, byte[] key, byte[] index)
        {
            Decrypt (offset, key, index, 0, index.Length);
        }

        static private void Decrypt (uint offset, byte[] key, byte[] index, int pos, int length)
        {
            uint key_last = (uint)key.Length-1;
            for (uint i = 0; i < length; ++i)
                index[pos+i] ^= key[(offset + i) % key_last];
        }

        internal class IndexReader
        {
            ArcView     m_file;
            int         m_version;
            int         m_count;
            byte[]      m_data_key;

            public byte[] DataKey { get { return m_data_key; } }

            public IndexReader (ArcView file, int version, int count)
            {
                m_file = file;
                m_version = version;
                m_count = count;
            }

            byte[]      m_chunk_buf = new byte[0x40];

            public List<Entry> ReadIndex ()
            {
                byte[] title = m_file.View.ReadBytes (6, 0x40);
                int title_length = Array.IndexOf<byte> (title, 0);
                if (-1 == title_length)
                    title_length = title.Length;
                string arc_filename = Path.GetFileName (m_file.Name);
                if (0x200 != m_version)
                    arc_filename = arc_filename.ToLowerInvariant();
                string base_filename = Path.GetFileNameWithoutExtension (arc_filename);

                byte[] name_key = GenerateKey (Encodings.cp932.GetBytes (arc_filename));

                uint index_offset = 0x200 + (uint)name_key.Select (x => (int)x).Sum();
                for (int i = 0; i < name_key.Length; ++i)
                {
                    index_offset ^= name_key[i];
                    index_offset = Binary.RotR (index_offset, 1);
                }
                for (int i = 0; i < name_key.Length; ++i)
                {
                    index_offset ^= name_key[i];
                    index_offset = Binary.RotR (index_offset, 1);
                }
                index_offset %= 0x401;

                index_offset += 0x4A;
                byte[] index = m_file.View.ReadBytes (index_offset, (uint)(4*m_count));
                if (index.Length != 4*m_count)
                    return null;

                byte[] index_key = new byte[index.Length];
                for (int i = 0; i < index_key.Length; ++i)
                {
                    int v = name_key[(i+1) % name_key.Length] ^ (name_key[i % name_key.Length] + i);
                    index_key[i] = (byte)(m_count + v);
                }
                Decrypt (index_offset, index_key, index);
                m_data_key = GenerateKey (title, title_length);
                var dir = new List<Entry> (m_count);
                int current_offset = 0;
                uint next_offset = LittleEndian.ToUInt32 (index, current_offset);
                for (int i = 0; i < m_count; ++i)
                {
                    current_offset += 4;
                    uint entry_offset = next_offset;
                    if (entry_offset >= m_file.MaxOffset)
                        return null;
                    if (i + 1 == m_count)
                        next_offset = (uint)m_file.MaxOffset;
                    else
                        next_offset = LittleEndian.ToUInt32 (index, current_offset);
                    uint entry_size = next_offset - entry_offset;
                    var entry = ParseEntry (entry_offset, entry_size);
                    if (string.IsNullOrEmpty (entry.Name))
                        entry.Name = string.Format ("{0}#{1:D4}", base_filename, i);
                    dir.Add (entry);
                }
                return dir;
            }

            Entry ParseEntry (uint entry_offset, uint entry_size)
            {
                ReadChunk (entry_offset, 8);
                if (0x200 == m_version)
                    return ParseEntryV2 (entry_offset, entry_size);
                else
                    return ParseEntryV3 (entry_offset, entry_size);
            }

            void ReadChunk (uint offset, int chunk_size)
            {
                if (chunk_size > m_chunk_buf.Length)
                    m_chunk_buf = new byte[chunk_size];
                if (chunk_size != m_file.View.Read (offset, m_chunk_buf, 0, (uint)chunk_size))
                    throw new InvalidFormatException();
                Decrypt (offset, m_data_key, m_chunk_buf, 0, chunk_size);
            }

            Entry ParseEntryV2 (uint entry_offset, uint entry_size)
            {
                var data_size = LittleEndian.ToUInt32 (m_chunk_buf, 0);
                if (data_size >= entry_size)
                    throw new InvalidFormatException();
                var name_length = LittleEndian.ToInt32 (m_chunk_buf, 4);
                entry_offset += 0x10;
                var entry = new Entry();
                if (name_length > 0)
                {
                    ReadChunk (entry_offset+data_size, name_length);
                    if ('|' == m_chunk_buf[name_length-1])
                        --name_length;
                    entry.Name = Encodings.cp932.GetString (m_chunk_buf, 0, name_length);
                    entry.Type = FormatCatalog.Instance.GetTypeFromName (entry.Name);
                }
                entry.Offset = entry_offset;
                entry.Size = data_size;
                return entry;
            }

            Entry ParseEntryV3 (uint entry_offset, uint entry_size)
            {
                if (!Binary.AsciiEqual (m_chunk_buf, "DSET"))
                    throw new InvalidFormatException();

                uint chunk_offset = entry_offset + 10;
                int chunk_count = LittleEndian.ToInt32 (m_chunk_buf, 4);
                var entry = new Entry();
                string filename = null;
                for (int chunk = 0; chunk < chunk_count; ++chunk)
                {
                    ReadChunk (chunk_offset, 8);
                    int chunk_size = LittleEndian.ToInt32 (m_chunk_buf, 4);
                    if (chunk_size <= 0)
                        throw new InvalidFormatException();
                    if (Binary.AsciiEqual (m_chunk_buf, "PICT"))
                    {
                        if (string.IsNullOrEmpty (entry.Type))
                        {
                            entry.Type = "image";
                            entry_offset = chunk_offset + 0x10;
                            entry_size = (uint)chunk_size - 6;
                        }
                    }
                    else if (null == filename && Binary.AsciiEqual (m_chunk_buf, "FTAG"))
                    {
                        ReadChunk (chunk_offset+10, chunk_size-2);
                        filename = Encodings.cp932.GetString (m_chunk_buf, 0, chunk_size-2);
                    }
                    chunk_offset += 10 + (uint)chunk_size;
                }
                if (!string.IsNullOrEmpty (filename))
                    entry.Name = DriveRe.Replace (filename, "");
                entry.Offset = entry_offset;
                entry.Size = entry_size;
                return entry;
            }

            static readonly Regex DriveRe = new Regex (@"^(?:.+:)?\\+");
        }
    }
}