//
// Copyright (c) 2012 Francois Valdy
// Copyright (c) 2018 Alexander Vostres
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//       http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
using System.IO;
using System.Text;
using ILRepacking.Steps.Win32Resources.PE;

namespace ILRepacking.Steps.Win32Resources
{
    internal class RsrcReader
    {
        internal static ResourceDirectory ReadResourceDirectory(byte[] b, uint baseAddress)
        {
            var dr = new MemoryStream(b);
            return ReadResourceDirectory(new BinaryReader(dr), baseAddress);
        }
        private static ResourceDirectory ReadResourceDirectory(BinaryReader dr, uint baseAddress)
        {
            var d = ReadResourceDirectoryTable(dr);
            int ne = d.NumNameEntries + d.NumIdEntries;
            for (int i = 0; i < ne; i++)
                d.Entries.Add(ReadResourceEntry(dr, baseAddress));
            return d;
        }
        private static ResourceEntry ReadResourceEntry(BinaryReader dr, uint baseAddress)
        {
            var re = new ResourceEntry();
            uint id = dr.ReadUInt32();
            uint offset = dr.ReadUInt32();
            long pos = dr.BaseStream.Position;
            if ((id & 0x80000000) != 0)
            {
                dr.BaseStream.Position = (id & 0x7fffffff);
                var b = new StringBuilder();
                int c;
                while ((c = dr.Read()) > 0)
                    b.Append((char) c);
                re.Name = b.ToString();
            }
            else
            {
                re.Id = id;
            }
            if ((offset & 0x80000000) != 0)
            {
                dr.BaseStream.Position = (offset & 0x7fffffff);
                re.Directory = ReadResourceDirectory(dr, baseAddress);
            }
            else
            {
                dr.BaseStream.Position = offset;
                uint rva = dr.ReadUInt32();
                uint size = dr.ReadUInt32();
                uint cp = dr.ReadUInt32();
                uint res = dr.ReadUInt32();
                re.CodePage = cp;
                re.Reserved = res;
                dr.BaseStream.Position = (rva - baseAddress);
                re.Data = dr.ReadBytes((int)size);
            }
            dr.BaseStream.Position = pos;
            return re;
        }
        private static ResourceDirectory ReadResourceDirectoryTable(BinaryReader dr)
        {
            var t = new ResourceDirectory
            {
                Characteristics = dr.ReadUInt32(),
                TimeDateStamp = dr.ReadUInt32(),
                MajorVersion = dr.ReadUInt16(),
                MinVersion = dr.ReadUInt16(),
                NumNameEntries = dr.ReadUInt16(),
                NumIdEntries = dr.ReadUInt16()
            };
            return t;
        }

        public static ResourceDirectory ReadResourceDirectory(string fileName)
        {
            using (var stream = File.Open(fileName, FileMode.Open, FileAccess.Read, FileShare.Read))
            {
                var reader = new ImageReader(stream);
                var data = reader.GetSectionData(".rsrc");
                if (data == null)
                {
                    return new ResourceDirectory();
                }
                return ReadResourceDirectory(data.Data, data.VirtualAddress);
            }
        }
    }
}