//! \file       ArcEncrypted.cs
//! \date       Thu Jan 14 03:27:52 2016
//! \brief      Encrypted AZ system resource archives.
//
// 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.Compression;
using GameRes.Utility;
using System;
using System.Collections.Generic;
using System.ComponentModel.Composition;
using System.IO;
using System.Linq;
using System.Security.Cryptography;

namespace GameRes.Formats.AZSys
{
    [Serializable]
    public class EncryptionScheme
    {
        public readonly uint    IndexKey;
        public readonly uint?   ContentKey;

        public static readonly uint[] DefaultSeed = { 0x2F4D7DFE, 0x47345292, 0x1BA5FE82, 0x7BC04525 };

        public EncryptionScheme (uint ikey, uint ckey)
        {
            IndexKey = ikey;
            ContentKey = ckey;
        }

        public EncryptionScheme (uint[] iseed)
        {
            IndexKey = GenerateKey (iseed);
            ContentKey = null;
        }

        public EncryptionScheme (uint[] iseed, byte[] cseed)
        {
            IndexKey = GenerateKey (iseed);
            ContentKey = GenerateContentKey (cseed);
        }

        public static uint GenerateKey (uint[] seed)
        {
            if (null == seed)
                throw new ArgumentNullException ("seed");
            if (seed.Length < 4)
                throw new ArgumentException();
            byte[] seed_bytes = new byte[0x10];
            Buffer.BlockCopy (seed, 0, seed_bytes, 0, 0x10);
            uint key = Crc32.UpdateCrc (~seed[0], seed_bytes, 0, seed_bytes.Length)
                     ^ Crc32.UpdateCrc (~(seed[1] & 0xFFFF), seed_bytes, 0, seed_bytes.Length)
                     ^ Crc32.UpdateCrc (~(seed[1] >> 16), seed_bytes, 0, seed_bytes.Length)
                     ^ Crc32.UpdateCrc (~seed[2], seed_bytes, 0, seed_bytes.Length)
                     ^ Crc32.UpdateCrc (~seed[3], seed_bytes, 0, seed_bytes.Length);
            return seed[0] ^ ~key;
        }

        public static uint GenerateContentKey (byte[] env_bytes)
        {
            if (null == env_bytes)
                throw new ArgumentNullException ("env_bytes");
            if (env_bytes.Length < 0x10)
                throw new ArgumentException();
            uint crc = Crc32.Compute (env_bytes, 0, 0x10);
            var sfmt = new FastMersenneTwister (crc);
            var seed = new uint[4];
            seed[0] = sfmt.GetRand32();
            seed[1] = sfmt.GetRand32() & 0xFFFF;
            seed[1] |= sfmt.GetRand32() << 16;
            seed[2] = sfmt.GetRand32();
            seed[3] = sfmt.GetRand32();
            return GenerateKey (seed);
        }
    }

    [Serializable]
    public class AzScheme : ResourceScheme
    {
        public Dictionary<string, EncryptionScheme> KnownSchemes;
    }

    internal class AzArchive : ArcFile
    {
        public readonly uint SysenvKey;
        public readonly uint RegularKey;

        public AzArchive (ArcView arc, ArchiveFormat impl, ICollection<Entry> dir, uint syskey, uint regkey)
            : base (arc, impl, dir)
        {
            SysenvKey = syskey;
            RegularKey = regkey;
        }
    }

    public abstract class ArcEncryptedBase : ArchiveFormat
    {
        internal List<Entry> ParseIndex (Stream input, int count, long base_offset, long max_offset)
        {
            using (var zstream = new ZLibStream (input, CompressionMode.Decompress))
            using (var index = new BinaryReader (zstream))
            {
                var dir = new List<Entry> (count);
                var name_buffer = new byte[0x20];
                for (int i = 0; i < count; ++i)
                {
                    uint offset = index.ReadUInt32();
                    uint size   = index.ReadUInt32();
                    uint crc    = index.ReadUInt32();
                    index.ReadInt32();
                    if (name_buffer.Length != index.Read (name_buffer, 0, name_buffer.Length))
                        return null;
                    var name = Binary.GetCString (name_buffer, 0, 0x20);
                    if (0 == name.Length)
                        return null;
                    var entry = FormatCatalog.Instance.Create<Entry> (name);
                    entry.Offset = base_offset + offset;
                    entry.Size   = size;
                    if (!entry.CheckPlacement (max_offset))
                        return null;
                    dir.Add (entry);
                }
                return dir;
            }
        }

        internal bool DecryptAsb (byte[] data)
        {
            int packed_size = LittleEndian.ToInt32 (data, 4);
            if (packed_size <= 4 || packed_size > data.Length-0x10)
                return false;

            uint unpacked_size = LittleEndian.ToUInt32 (data, 8);
            uint key = unpacked_size ^ 0x9E370001;
            unsafe
            {
                fixed (byte* raw = &data[0x10])
                {
                    uint* data32 = (uint*)raw;
                    for (int i = packed_size/4; i > 0; --i)
                        *data32++ -= key;
                }
            }
            return true;
        }
    }

    [Export(typeof(ArchiveFormat))]
    public class ArcEncryptedOpener : ArcEncryptedBase
    {
        public override string         Tag { get { return "ARC/AZ/encrypted"; } }
        public override string Description { get { return "AZ system encrypted resource archive"; } }
        public override uint     Signature { get { return 0; } }
        public override bool  IsHierarchic { get { return false; } }
        public override bool      CanWrite { get { return false; } }

        public static Dictionary<string, EncryptionScheme> KnownSchemes = new Dictionary<string, EncryptionScheme>
        {
            { "Default", new EncryptionScheme (EncryptionScheme.DefaultSeed) },
        };

        public override ResourceScheme Scheme
        {
            get { return new AzScheme { KnownSchemes = KnownSchemes }; }
            set { KnownSchemes = ((AzScheme)value).KnownSchemes; }
        }

        public ArcEncryptedOpener ()
        {
            Extensions = new string[] { "arc" };
            Signatures = new uint[] { 0x53EA06EB, 0x74F98F2F };
        }

        EncryptionScheme CurrentScheme;

        public override ArcFile TryOpen (ArcView file)
        {
            byte[] header_encrypted = file.View.ReadBytes (0, 0x30);
            if (header_encrypted.Length < 0x30)
                return null;
            byte[] header = new byte[header_encrypted.Length];
            if (CurrentScheme != null)
            {
                try
                {
                    Buffer.BlockCopy (header_encrypted, 0, header, 0, header.Length);
                    Decrypt (header, 0, CurrentScheme.IndexKey);
                    if (Binary.AsciiEqual (header, 0, "ARC\0"))
                    {
                        var arc = ReadIndex (file, header, CurrentScheme);
                        if (null != arc)
                            return arc;
                    }
                }
                catch { /* ignore parse errors */ }
            }
            foreach (var scheme in KnownSchemes.Values)
            {
                Buffer.BlockCopy (header_encrypted, 0, header, 0, header.Length);
                Decrypt (header, 0, scheme.IndexKey);
                if (Binary.AsciiEqual (header, 0, "ARC\0"))
                {
                    var arc = ReadIndex (file, header, scheme);
                    if (null != arc)
                        CurrentScheme = new EncryptionScheme (arc.SysenvKey, arc.RegularKey);
                    return arc;
                }
            }
            return null;
        }

        public override Stream OpenEntry (ArcFile arc, Entry entry)
        {
            var azarc = arc as AzArchive;
            if (null == azarc)
                return base.OpenEntry (arc, entry);
            var data = arc.File.View.ReadBytes (entry.Offset, entry.Size);
            if (entry.Name.Equals ("sysenv.tbl", StringComparison.InvariantCultureIgnoreCase))
            {
                Decrypt (data, entry.Offset, azarc.SysenvKey);
                return UnpackData (data);
            }
            Decrypt (data, entry.Offset, azarc.RegularKey);
            if (data.Length > 0x14 && Binary.AsciiEqual (data, 0, "ASB\0") && DecryptAsb (data))
            {
                var asb = UnpackData (data, 0x10);
                var header = new byte[0x10];
                Buffer.BlockCopy (data, 0, header, 0, 0x10);
                return new PrefixStream (header, asb);
            }
            return new MemoryStream (data);
        }

        uint ReadSysenvSeed (ArcView file, IEnumerable<Entry> dir, uint key)
        {
            var entry = dir.FirstOrDefault (e => e.Name.Equals ("sysenv.tbl", StringComparison.InvariantCultureIgnoreCase));
            if (null == entry)
                return key;
            var data = file.View.ReadBytes (entry.Offset, entry.Size);
            if (data.Length <= 4)
                throw new InvalidFormatException ("Invalid sysenv.tbl size");
            Decrypt (data, entry.Offset, key);
            uint adler32 = LittleEndian.ToUInt32 (data, 0);
            if (adler32 != Adler32.Compute (data, 4, data.Length-4))
                throw new InvalidEncryptionScheme();
            using (var input = new MemoryStream (data, 4, data.Length-4))
            using (var sysenv_stream = new ZLibStream (input, CompressionMode.Decompress))
            {
                var seed = new byte[0x10];
                if (0x10 != sysenv_stream.Read (seed, 0, 0x10))
                    throw new InvalidFormatException ("Invalid sysenv.tbl size");
                return EncryptionScheme.GenerateContentKey (seed);
            }
        }

        Stream UnpackData (byte[] data, int index = 0)
        {
            int length = data.Length - index;
            if (length <= 4)
                return new MemoryStream (data, index, length);
            uint adler32 = LittleEndian.ToUInt32 (data, index);
            if (adler32 != Adler32.Compute (data, index+4, length-4))
                return new MemoryStream (data, index, length);
            var input = new MemoryStream (data, index+4, length-4);
            return new ZLibStream (input, CompressionMode.Decompress);
        }

        AzArchive ReadIndex (ArcView file, byte[] header, EncryptionScheme scheme)
        {
            int ext_count = LittleEndian.ToInt32 (header, 4);
            int count = LittleEndian.ToInt32 (header, 8);
            uint index_length = LittleEndian.ToUInt32 (header, 12);
            if (ext_count < 1 || ext_count > 8 || !IsSaneCount (count) || index_length >= file.MaxOffset)
                return null;
            var packed_index = file.View.ReadBytes (header.Length, index_length);
            if (packed_index.Length != index_length)
                return null;
            Decrypt (packed_index, header.Length, scheme.IndexKey);
            uint checksum = LittleEndian.ToUInt32 (packed_index, 0);
            if (checksum != Adler32.Compute (packed_index, 4, packed_index.Length-4))
            {
                if (checksum != Crc32.Compute (packed_index, 4, packed_index.Length-4))
                    throw new InvalidFormatException ("Index checksum mismatch");
            }
            using (var input = new MemoryStream (packed_index, 4, packed_index.Length-4))
            {
                var dir = ParseIndex (input, count, header.Length + index_length, file.MaxOffset);
                if (null == dir)
                    return null;
                uint content_key = GetContentKey (file, dir, scheme);
                return new AzArchive (file, this, dir, scheme.IndexKey, content_key);
            }
        }

        static void Decrypt (byte[] data, long offset, uint key)
        {
            ulong hash = key * 0x9E370001ul;
            if (0 != (offset & 0x3F))
            {
                hash = Binary.RotL (hash, (int)offset);
            }
            for (uint i = 0; i < data.Length; ++i)
            {
                data[i] ^= (byte)hash;
                hash = Binary.RotL (hash, 1);
            }
        }

        uint GetContentKey (ArcView file, List<Entry> dir, EncryptionScheme scheme)
        {
            if (null != scheme.ContentKey)
                return scheme.ContentKey.Value;

            if ("system.arc".Equals (Path.GetFileName (file.Name), StringComparison.InvariantCultureIgnoreCase))
            {
                return ReadSysenvSeed (file, dir, scheme.IndexKey);
            }
            else
            {
                var system_arc = VFS.CombinePath (VFS.GetDirectoryName (file.Name), "system.arc");
                using (var arc = VFS.OpenView (system_arc))
                {
                    var header = arc.View.ReadBytes (0, 0x30);
                    Decrypt (header, 0, scheme.IndexKey);
                    using (var arc_file = ReadIndex (arc, header, scheme))
                    {
                        return ReadSysenvSeed (arc, arc_file.Dir, scheme.IndexKey);
                    }
                }
            }
        }
    }

    [Export(typeof(ArchiveFormat))]
    public class ArcIsaacEncryptedOpener : ArcEncryptedBase
    {
        public override string         Tag { get { return "ARC/AZ/ISAAC"; } }
        public override string Description { get { return "AZ system encrypted resource archive"; } }
        public override uint     Signature { get { return 0; } }
        public override bool  IsHierarchic { get { return false; } }
        public override bool      CanWrite { get { return false; } }

        public ArcIsaacEncryptedOpener ()
        {
            Extensions = new string[] { "arc" };
        }

        public override ArcFile TryOpen (ArcView file)
        {
            byte[] header_encrypted = file.View.ReadBytes (0, 0x30);
            if (header_encrypted.Length < 0x30)
                return null;
            byte[] header = new byte[header_encrypted.Length];
            Buffer.BlockCopy (header_encrypted, 0, header, 0, header.Length);

            var cipher = new AzIsaacEncryption ((uint)file.MaxOffset);
            cipher.Decrypt (header, 0, header.Length, 0);
            if (!Binary.AsciiEqual (header, 0, "ARC\0"))
                return null;

            int ext_count = LittleEndian.ToInt32 (header, 4);
            int count = LittleEndian.ToInt32 (header, 8);
            uint index_length = LittleEndian.ToUInt32 (header, 12);
            if (ext_count < 1 || ext_count > 8 || !IsSaneCount (count) || index_length >= file.MaxOffset)
                return null;

            var packed_index = file.View.ReadBytes (0x30, index_length);
            if (packed_index.Length != index_length)
                return null;
            cipher.Decrypt (packed_index, 0, packed_index.Length, 0x30);

            using (var input = new MemoryStream (packed_index))
            {
                var dir = ParseIndex (input, count, header.Length + index_length, file.MaxOffset);
                if (null == dir)
                    return null;
                return new ArcFile (file, this, dir);
            }
        }

        public override Stream OpenEntry (ArcFile arc, Entry entry)
        {
            var data = arc.File.View.ReadBytes (entry.Offset, entry.Size);
            var cipher = new AzIsaacEncryption (entry.Size);
            cipher.Decrypt (data, 0, data.Length, 0);
            if (data.Length > 0x14 && Binary.AsciiEqual (data, 0, "ASB\0") && DecryptAsb (data))
            {
                var header = new byte[0x10];
                Buffer.BlockCopy (data, 0, header, 0, 0x10);
                Stream input = new MemoryStream (data, 0x10, data.Length-0x10);
                input = new ZLibStream (input, CompressionMode.Decompress);
                return new PrefixStream (header, input);
            }
            return new MemoryStream (data);
        }

        /// <summary>
        /// Calculate SHA1 sum of archive file.
        /// </summary>
        public byte[] CalculateSum (Stream arc)
        {
            using (var sha1 = SHA1.Create())
                return sha1.ComputeHash (arc);
        }
    }

    internal class AzIsaacEncryption
    {
        uint[]      m_key = new uint[0x100];

        public AzIsaacEncryption (uint seed)
        {
            var isaac = new Isaac64Cipher (seed);
            for (int i = 0; i < m_key.Length; ++i)
            {
                m_key[i] = isaac.GetRand32();
            }
        }

        public void Decrypt (byte[] data, int index, int length, ushort offset)
        {
            for (int i = 0; i < length; ++i)
            {
                data[index + i] ^= (byte)Binary.RotL (m_key[offset & 0xFF] ^ 0x1000193, offset >> 8);
                ++offset;
            }
        }
    }

    /// <summary>
    /// ISAAC 64-bit pseudorandom number generator.
    /// </summary>
    internal class Isaac64Cipher
    {
        int         m_count;
        ulong[]     m_entropy = new ulong[0x100];
        ulong[]     m_state   = new ulong[0x100];

        public Isaac64Cipher (uint seed)
        {
            unsafe
            {
                fixed (ulong* e = m_entropy)
                {
                    uint* e32 = (uint*)e;
                    *e32 = seed ^ 0x9E370001u;
                    for (uint i = 1; i < 0x200u; ++i)
                    {
                        e32[i] = i - 0x61C88647u * (e32[i-1] ^ (e32[i-1] >> 30));
                    }
                }
            }
            Init();
        }

        ulong aa, bb, cc;
        ulong a, b, c, d, e, f, g, h;

        void Mix ()
        {
            a -= e; f ^= h >> 9;  h += a;
            b -= f; g ^= a << 9;  a += b;
            c -= g; h ^= b >> 23; b += c;
            d -= h; a ^= c << 15; c += d;
            e -= a; b ^= d >> 14; d += e;
            f -= b; c ^= e << 20; e += f;
            g -= c; d ^= f >> 17; f += g;
            h -= d; e ^= g << 14; g += h;
        }

        void Init ()
        {
            aa = bb = cc = 0;
            a = b = c = d = e = f = g = h = 0x9E3779B97F4A7C13ul;

            int i;
            for (i = 0; i < 4; ++i)
            {
                Mix();
            }

            for (i = 0; i < 0x100; i += 8)
            {
                a += m_entropy[i  ]; b += m_entropy[i+1]; c += m_entropy[i+2]; d += m_entropy[i+3];
                e += m_entropy[i+4]; f += m_entropy[i+5]; g += m_entropy[i+6]; h += m_entropy[i+7];

                Mix();
                m_state[i  ] = a; m_state[i+1] = b; m_state[i+2] = c; m_state[i+3] = d;
                m_state[i+4] = e; m_state[i+5] = f; m_state[i+6] = g; m_state[i+7] = h;
            }

            for (i = 0; i < 0x100; i += 8)
            {
                a += m_state[i  ]; b += m_state[i+1]; c += m_state[i+2]; d += m_state[i+3];
                e += m_state[i+4]; f += m_state[i+5]; g += m_state[i+6]; h += m_state[i+7];

                Mix();
                m_state[i  ] = a; m_state[i+1] = b; m_state[i+2] = c; m_state[i+3] = d;
                m_state[i+4] = e; m_state[i+5] = f; m_state[i+6] = g; m_state[i+7] = h;
            }
            Shuffle();
            m_count = 0x100;
        }

        void RngStep (ulong mix, ref int m, ref int m2, ref int r)
        {
            ulong x = m_state[m];
            aa = mix + m_state[m2++];
            ulong y = m_state[(x >> 3) & 0xFF] + aa + bb;
            m_state[m++] = y;
            m_entropy[r++] = bb = m_state[(y >> 11) & 0xFF] + x;
        }

        void Shuffle ()
        {
            int m1 = 0;
            int r = 0;
            bb += ++cc;
            int mend, m2;
            mend = m2 = 0x80;
            while (m1 < mend)
            {
                RngStep(~(aa ^ (aa << 21)), ref m1, ref m2, ref r);
                RngStep(  aa ^ (aa >> 5)  , ref m1, ref m2, ref r);
                RngStep(  aa ^ (aa << 12) , ref m1, ref m2, ref r);
                RngStep(  aa ^ (aa >> 33) , ref m1, ref m2, ref r);
            }
            m2 = 0;
            while (m2 < mend)
            {
                RngStep(~(aa ^ (aa << 21)), ref m1, ref m2, ref r);
                RngStep(  aa ^ (aa >> 5)  , ref m1, ref m2, ref r);
                RngStep(  aa ^ (aa << 12) , ref m1, ref m2, ref r);
                RngStep(  aa ^ (aa >> 33) , ref m1, ref m2, ref r);
            }
        }

        public uint GetRand32 ()
        {
            if (0 == m_count--)
            {
                Shuffle();
                m_count = 0xFF;
            }
            ulong num = m_entropy[m_count];
            return (uint)num ^ (uint)(num >> 32);
        }
    }
}