//! \file       ArcPFS.cs
//! \date       Tue Dec 27 22:27:58 2016
//! \brief      Artemis 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.Generic;
using System.ComponentModel.Composition;
using System.IO;
using System.Security.Cryptography;

namespace GameRes.Formats.Artemis
{
    [Export(typeof(ArchiveFormat))]
    public class PfsOpener : ArchiveFormat
    {
        public override string         Tag { get { return "PFS"; } }
        public override string Description { get { return "Artemis engine resource archive"; } }
        public override uint     Signature { get { return 0; } }
        public override bool  IsHierarchic { get { return true; } }
        public override bool      CanWrite { get { return false; } }

        public PfsOpener ()
        {
            Extensions = new string[] { "pfs", "000", "001", "002", "003" };
        }

        public override ArcFile TryOpen (ArcView file)
        {
            if (!file.View.AsciiEqual (0, "pf"))
                return null;
            int version = file.View.ReadByte (2) - '0';
            if (8 != version)
                return null;
            uint index_size = file.View.ReadUInt32 (3);
            int count = file.View.ReadInt32 (7);
            if (!IsSaneCount (count) || 7L + index_size > file.MaxOffset)
                return null;

            var index = file.View.ReadBytes (7, index_size);
            int index_offset = 4;
            var dir = new List<Entry> (count);
            for (int i = 0; i < count; ++i)
            {
                int name_length = index.ToInt32 (index_offset);
                var name = Encodings.cp932.GetString (index, index_offset+4, name_length);
                index_offset += name_length + 8;
                var entry = FormatCatalog.Instance.Create<Entry> (name);
                entry.Offset = index.ToUInt32 (index_offset);
                entry.Size   = index.ToUInt32 (index_offset+4);
                if (!entry.CheckPlacement (file.MaxOffset))
                    return null;
                index_offset += 8;
                dir.Add (entry);
            }
            using (var sha1 = SHA1.Create())
            {
                var key = sha1.ComputeHash (index); // calculated for archive versions 4, 5, 8 and 9
                return new PfsArchive (file, this, dir, key);
            }
        }

        public override Stream OpenEntry (ArcFile arc, Entry entry)
        {
            var parc = arc as PfsArchive;
            var input = arc.File.CreateStream (entry.Offset, entry.Size);
            if (null == parc)
                return input;
            return new ByteStringEncryptedStream (input, parc.Key);
        }
    }

    internal class PfsArchive : ArcFile
    {
        public readonly byte[] Key;

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