/*
    Copyright (C) 2011-2015 de4dot@gmail.com

    This file is part of de4dot.

    de4dot is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    de4dot is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with de4dot.  If not, see <http://www.gnu.org/licenses/>.
*/

using System;
using System.Collections.Generic;
using dnlib.IO;
using dnlib.DotNet;
using dnlib.DotNet.Emit;
using de4dot.blocks;

namespace de4dot.code.deobfuscators.CryptoObfuscator {
	class MethodBodyReader : MethodBodyReaderBase {
		ModuleDefMD module;
		ushort maxStackSize;
		GenericParamContext gpContext;

		public MethodBodyReader(ModuleDefMD module, IBinaryReader reader)
			: base(reader) {
			this.module = module;
		}

		public void Read(MethodDef method) {
			this.gpContext = GenericParamContext.Create(method);
			this.parameters = method.Parameters;
			SetLocals(GetLocals(method));

			maxStackSize = (ushort)reader.ReadInt32();
			ReadInstructionsNumBytes(reader.ReadUInt32());
			ReadExceptionHandlers();
		}

		void ReadExceptionHandlers() {
			int totalSize = reader.ReadInt32();
			if (totalSize == 0)
				return;
			reader.ReadInt32();
			ReadExceptionHandlers((totalSize - 4) / 24);
		}

		static IList<Local> GetLocals(MethodDef method) {
			if (method.Body == null)
				return new List<Local>();
			return method.Body.Variables;
		}

		protected override IField ReadInlineField(Instruction instr) {
			return module.ResolveToken(reader.ReadUInt32(), gpContext) as IField;
		}

		protected override IMethod ReadInlineMethod(Instruction instr) {
			return module.ResolveToken(reader.ReadUInt32(), gpContext) as IMethod;
		}

		protected override MethodSig ReadInlineSig(Instruction instr) {
			var sas = module.ResolveStandAloneSig(MDToken.ToRID(reader.ReadUInt32()), gpContext);
			return sas == null ? null : sas.MethodSig;
		}

		protected override string ReadInlineString(Instruction instr) {
			return module.ReadUserString(reader.ReadUInt32());
		}

		protected override ITokenOperand ReadInlineTok(Instruction instr) {
			return module.ResolveToken(reader.ReadUInt32(), gpContext) as ITokenOperand;
		}

		protected override ITypeDefOrRef ReadInlineType(Instruction instr) {
			return module.ResolveToken(reader.ReadUInt32(), gpContext) as ITypeDefOrRef;
		}

		void ReadExceptionHandlers(int numExceptionHandlers) {
			exceptionHandlers = new ExceptionHandler[numExceptionHandlers];
			for (int i = 0; i < exceptionHandlers.Count; i++)
				exceptionHandlers[i] = ReadExceptionHandler();
		}

		ExceptionHandler ReadExceptionHandler() {
			var eh = new ExceptionHandler((ExceptionHandlerType)reader.ReadUInt32());

			uint tryOffset = reader.ReadUInt32();
			eh.TryStart = GetInstructionThrow(tryOffset);
			eh.TryEnd = GetInstruction(tryOffset + reader.ReadUInt32());

			uint handlerOffset = reader.ReadUInt32();
			eh.HandlerStart = GetInstructionThrow(handlerOffset);
			eh.HandlerEnd = GetInstruction(handlerOffset + reader.ReadUInt32());

			switch (eh.HandlerType) {
			case ExceptionHandlerType.Catch:
				eh.CatchType = module.ResolveToken(reader.ReadUInt32(), gpContext) as ITypeDefOrRef;
				break;

			case ExceptionHandlerType.Filter:
				eh.FilterStart = GetInstructionThrow(reader.ReadUInt32());
				break;

			case ExceptionHandlerType.Finally:
			case ExceptionHandlerType.Fault:
			default:
				reader.ReadUInt32();
				break;
			}

			return eh;
		}

		public override void RestoreMethod(MethodDef method) {
			base.RestoreMethod(method);
			method.Body.MaxStack = maxStackSize;
		}
	}
}