//! \file       ArcINT.cs
//! \date       Fri Jul 11 09:32:36 2014
//! \brief      Frontwing games archive.
//

using System;
using System.IO;
using System.Linq;
using System.Text;
using System.ComponentModel.Composition;
using System.Collections.Generic;
using System.Diagnostics;
using Simias.Encryption;
using System.Runtime.InteropServices;
using GameRes.Formats.Strings;
using GameRes.Formats.Properties;

namespace GameRes.Formats
{
    public class FrontwingArchive : ArcFile
    {
        public readonly Blowfish Encryption;

        public FrontwingArchive (ArcView arc, ArchiveFormat impl, ICollection<Entry> dir, Blowfish cipher)
            : base (arc, impl, dir)
        {
            Encryption = cipher;
        }
    }

    public class IntEncryptionInfo
    {
        public uint?    Key      { get; set; }
        public string   Scheme   { get; set; }
        public string   Password { get; set; }

        public IntEncryptionInfo () { }
    }

    [Export(typeof(ArchiveFormat))]
    public class IntOpener : ArchiveFormat
    {
        public override string Tag { get { return "INT"; } }
        public override string Description { get { return arcStrings.INTDescription; } }
        public override uint Signature { get { return 0x0046494b; } }
        public override bool IsHierarchic { get { return false; } }

        public override ArcFile TryOpen (ArcView file)
        {
            uint entry_count = file.View.ReadUInt32 (4);
            if (0 == entry_count || 0 != ((entry_count - 1) >> 0x14))
            {
                Trace.WriteLine (string.Format ("Invalid entry count ({0})", entry_count));
                return null;
            }
            if (file.View.AsciiEqual (8, "__key__.dat\x00"))
            {
                uint? key = QueryEncryptionInfo();
                if (null == key)
                    throw new UnknownEncryptionScheme();
                return OpenEncrypted (file, entry_count, key.Value);
            }

            long current_offset = 8;
            var dir = new List<Entry>();
            for (uint i = 0; i < entry_count; ++i)
            {
                string name = file.View.ReadString (current_offset, 0x40);
                var entry = FormatCatalog.Instance.CreateEntry (name);
                entry.Offset = file.View.ReadUInt32 (current_offset+0x40);
                entry.Size   = file.View.ReadUInt32 (current_offset+0x44);
                if (!entry.CheckPlacement (file.MaxOffset))
                    return null;
                dir.Add (entry);
                current_offset += 0x48;
            }
            return new ArcFile (file, this, dir);
        }

        private ArcFile OpenEncrypted (ArcView file, uint entry_count, uint main_key)
        {
            if (1 == entry_count)
                return null; // empty archive
            long current_offset = 8;
            var twister = new Twister();

            // [@@L1]   = 32-bit key
            // [@@L1+4] = 0 if key is available, -1 otherwise
            uint key_data = file.View.ReadUInt32 (current_offset+0x44);
            uint twist_key = twister.Twist (key_data);
            // [@@L0] = 32-bit twist key
            byte[] blowfish_key = BitConverter.GetBytes (twist_key);
            if (!BitConverter.IsLittleEndian)
                Array.Reverse (blowfish_key);

            var blowfish = new Blowfish (blowfish_key);
            var dir = new List<Entry>();
            byte[] name_info = new byte[0x40];
            for (uint i = 1; i < entry_count; ++i)
            {
                current_offset += 0x48;
                file.View.Read (current_offset, name_info, 0, 0x40);
                uint eax = file.View.ReadUInt32 (current_offset+0x40);
                uint edx = file.View.ReadUInt32 (current_offset+0x44);
                eax += i;
                blowfish.Decipher (ref eax, ref edx);
                uint key = twister.Twist (main_key + i);
                string name = DecipherName (name_info, key);

                var entry = FormatCatalog.Instance.CreateEntry (name);
                entry.Offset = eax;
                entry.Size   = edx;
                if (!entry.CheckPlacement (file.MaxOffset))
                    return null;
                dir.Add (entry);
            }
            return new FrontwingArchive (file, this, dir, blowfish);
        }

        private Stream OpenEncryptedEntry (FrontwingArchive arc, Entry entry)
        {
            using (var view = arc.File.CreateViewAccessor (entry.Offset, entry.Size))
            {
                byte[] data = new byte[entry.Size];
                // below is supposedly faster version of
                //arc.File.View.Read (entry.Offset, data, 0, entry.Size);
                unsafe
                {
                    byte* ptr = view.GetPointer (entry.Offset);
                    try {
                        Marshal.Copy (new IntPtr(ptr), data, 0, data.Length);
                    } finally {
                        view.SafeMemoryMappedViewHandle.ReleasePointer();
                    }
                }
                arc.Encryption.Decipher (data, data.Length/8*8);
                return new MemoryStream (data, false);
            }
        }

        public override Stream OpenEntry (ArcFile arc, Entry entry)
        {
            if (arc is FrontwingArchive)
                return OpenEncryptedEntry (arc as FrontwingArchive, entry);
            else
                return base.OpenEntry (arc, entry);
        }

        public string DecipherName (byte[] name, uint key)
        {
            key += (key >> 8) + (key >> 16) + (key >> 24);
            key &= 0xff;
            key %= 0x34;
            int count = 0;
            for (int i = 0; i < name.Length; ++i)
            {
                byte al = name[i];
                if (0 == al)
                    break;
                byte bl = (byte)key;
                ++count;
                uint edx = al;
                al |= 0x20;
                al -= 0x61;
                if (al < 0x1a)
                {
                    if (0 != (edx & 0x20))
                        al += 0x1a;
                    al = (byte)~al;
                    al += 0x34;
                    if (al >= bl)
                        al -= bl;
                    else
                        al = (byte)(al - bl + 0x34);
                    if (al >= 0x1a)
                        al += 6;
                    al += 0x41;
                    name[i] = al;
                }
                ++key;
                if (0x34 == key)
                    key = 0;
            }
            return Encodings.cp932.GetString (name, 0, count);
        }

        class Twister
        {
            const uint TwisterLength = 0x270;
            uint[]  m_twister = new uint[TwisterLength];
            uint    m_twister_pos = 0;

            public uint Twist (uint key)
            {
                Init (key);
                return Next();
            }

            public void Init (uint key)
            {
                uint edx = key;
                for (int i = 0; i < TwisterLength; ++i)
                {
                    uint ecx = edx * 0x10dcd + 1;
                    m_twister[i] = (edx & 0xffff0000) | (ecx >> 16);
                    edx *= 0x1C587629;
                    edx += 0x10dce;
                }
                m_twister_pos = 0;
            }

            public uint Next ()
            {
                uint ecx = m_twister[m_twister_pos];
                uint edx = m_twister_pos + 1;
                if (TwisterLength == edx)
                    edx = 0;
                uint edi = m_twister[edx];
                edi = ((edi ^ ecx) & 0x7FFFFFFF) ^ ecx;
                bool carry = 0 != (edi & 1);
                edi >>= 1;
                if (carry)
                    edi ^= 0x9908B0DF;
                ecx = m_twister_pos + 0x18d;
                if (ecx >= TwisterLength)
                    ecx -= TwisterLength;
                edi ^= m_twister[ecx];
                m_twister[m_twister_pos] = edi;
                m_twister_pos = edx;
                uint eax = edi ^ (edi >> 11);
                eax = ((eax & 0xFF3A58AD) << 7)  ^ eax;
                eax = ((eax & 0xFFFFDF8C) << 15) ^ eax;
                eax = (eax >> 18) ^ eax;
                return eax;
            }
        }

        public static uint EncodePassPhrase (string password)
        {
            byte[] pass_bytes = Encodings.cp932.GetBytes (password);
            uint key = 0xffffffff;
            foreach (var c in pass_bytes)
            {
                uint val = (uint)c << 24;
                key ^= val;
                for (int i = 0; i < 8; ++i)
                {
                    bool carry = 0 != (key & 0x80000000);
                    key <<= 1;
                    if (carry)
                        key ^= 0x4C11DB7;
                }
                key = ~key;
            }
            return key;
        }

        public struct KeyData
        {
            public uint     Key;
            public string   Passphrase;
        }

        public static readonly Dictionary<string, KeyData> KnownSchemes = new Dictionary<string, KeyData> {
            { "Grisaia no Kajitsu",               new KeyData { Key=0x1DAD9120, Passphrase="FW-6JD55162" }},
            { "Shukufuku no Campanella",          new KeyData { Key=0x4260E643, Passphrase="CAMPANELLA" }},
            { "Makai Tenshi Djibril -Episode 4-", new KeyData { Key=0xA5A166AA, Passphrase="FW_MAKAI-TENSHI_DJIBRIL4" }},
            { "Sengoku Tenshi Djibril (trial)",   new KeyData { Key=0xef870610, Passphrase="FW-8O9B6WDS" }},
        };

        uint? QueryEncryptionInfo ()
        {
            var widget = new GUI.WidgetINT (Settings.Default.INTEncryption ?? new IntEncryptionInfo());
            var args = new ParametersRequestEventArgs
            {
                Notice = arcStrings.INTNotice,
                InputWidget = widget,
            };
            FormatCatalog.Instance.InvokeParametersRequest (this, args);
            if (!args.InputResult)
                throw new OperationCanceledException();

            Settings.Default.INTEncryption = widget.Info;
            return widget.GetKey();
        }

        public override ResourceOptions GetOptions ()
        {
            return new ResourceOptions {
                Widget = new GUI.WidgetINT (Settings.Default.INTEncryption ?? new IntEncryptionInfo())
            };
        }
    }
}