/*
    Copyright (C) 2011 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 Mono.Cecil;
using Mono.Cecil.Cil;

namespace de4dot.blocks {
	class Blocks {
		MethodDefinition method;
		IList<VariableDefinition> locals;
		MethodBlocks methodBlocks;

		public MethodBlocks MethodBlocks {
			get { return methodBlocks; }
		}

		public IList<VariableDefinition> Locals {
			get { return locals; }
		}

		public MethodDefinition Method {
			get { return method; }
		}

		public Blocks(MethodDefinition method) {
			var body = method.Body;
			this.method = method;
			this.locals = body.Variables;
			methodBlocks = new InstructionListParser(body.Instructions, body.ExceptionHandlers).parse();
		}

		public void deobfuscateLeaveObfuscation() {
			foreach (var scopeBlock in getAllScopeBlocks(methodBlocks))
				scopeBlock.deobfuscateLeaveObfuscation();
		}

		public void deobfuscate() {
			foreach (var scopeBlock in getAllScopeBlocks(methodBlocks))
				scopeBlock.deobfuscate(this);

			removeDeadBlocks();

			foreach (var scopeBlock in getAllScopeBlocks(methodBlocks)) {
				scopeBlock.mergeBlocks();
				scopeBlock.repartitionBlocks();
				scopeBlock.deobfuscateLeaveObfuscation();
			}
		}

		IEnumerable<ScopeBlock> getAllScopeBlocks(ScopeBlock scopeBlock) {
			var list = new List<ScopeBlock>();
			list.Add(scopeBlock);
			list.AddRange(scopeBlock.getAllScopeBlocks());
			return list;
		}

		void removeDeadBlocks() {
			int numDeadBlocks = new DeadBlocksRemover(methodBlocks).remove();
			if (numDeadBlocks > 0)
				Log.v("Removed {0} dead block(s)", numDeadBlocks);
		}

		class DeadBlocksRemover {
			MethodBlocks methodBlocks;
			Dictionary<BaseBlock, bool> checkedBaseBlocks = new Dictionary<BaseBlock, bool>();
			Dictionary<ScopeBlock, bool> checkedScopeBlocks = new Dictionary<ScopeBlock, bool>();
			Stack<BaseBlock> baseBlocksToCheck = new Stack<BaseBlock>();
			Stack<ScopeBlock> scopeBlocksToCheck = new Stack<ScopeBlock>();

			public DeadBlocksRemover(MethodBlocks methodBlocks) {
				this.methodBlocks = methodBlocks;
			}

			public int remove() {
				addScopeBlock(methodBlocks);
				processAll();
				return removeDeadBlocks();
			}

			class ScopeBlockInfo {
				public ScopeBlock scopeBlock;
				public IList<BaseBlock> deadBlocks = new List<BaseBlock>();
				public ScopeBlockInfo(ScopeBlock scopeBlock) {
					this.scopeBlock = scopeBlock;
				}
			}

			int removeDeadBlocks() {
				int numDeadBlocks = 0;

				var infos = new Dictionary<ScopeBlock, ScopeBlockInfo>();
				var deadBlocksDict = new Dictionary<BaseBlock, bool>();
				foreach (var baseBlock in findDeadBlocks()) {
					deadBlocksDict[baseBlock] = true;
					ScopeBlock parent = (ScopeBlock)baseBlock.Parent;
					ScopeBlockInfo info;
					if (!infos.TryGetValue(parent, out info))
						infos[parent] = info = new ScopeBlockInfo(parent);
					info.deadBlocks.Add(baseBlock);
					numDeadBlocks++;
				}

				foreach (var info in infos.Values)
					info.scopeBlock.removeAllDeadBlocks(info.deadBlocks, deadBlocksDict);

				return numDeadBlocks;
			}

			IList<BaseBlock> findDeadBlocks() {
				var deadBlocks = new List<BaseBlock>();

				foreach (var bb in methodBlocks.getAllBaseBlocks()) {
					if (!checkedBaseBlocks.ContainsKey(bb))
						deadBlocks.Add(bb);
				}

				return deadBlocks;
			}

			void addScopeBlock(ScopeBlock scopeBlock) {
				scopeBlocksToCheck.Push(scopeBlock);
			}

			void processAll() {
				bool didSomething;
				do {
					didSomething = false;
					while (baseBlocksToCheck.Count > 0) {
						processBaseBlock(baseBlocksToCheck.Pop());
						didSomething = true;
					}
					while (scopeBlocksToCheck.Count > 0) {
						processScopeBlock(scopeBlocksToCheck.Pop());
						didSomething = true;
					}
				} while (didSomething);
			}

			void processBaseBlock(BaseBlock baseBlock) {
				if (baseBlock == null || checkedBaseBlocks.ContainsKey(baseBlock))
					return;
				checkedBaseBlocks[baseBlock] = true;

				if (baseBlock is Block) {
					var block = (Block)baseBlock;
					foreach (var block2 in block.getTargets())
						addBaseBlock(block2);
				}
				else if (baseBlock is ScopeBlock) {
					var scopeBlock = (ScopeBlock)baseBlock;
					addScopeBlock(scopeBlock);
					if (scopeBlock.BaseBlocks != null && scopeBlock.BaseBlocks.Count > 0)
						addBaseBlock(scopeBlock.BaseBlocks[0]);
				}
				else
					throw new ApplicationException(string.Format("Unknown BaseBlock type {0}", baseBlock.GetType()));
			}

			// Add a block to be processed later, including all its enclosing ScopeBlocks.
			void addBaseBlock(BaseBlock baseBlock) {
				for (BaseBlock bb = baseBlock; bb != null; bb = bb.Parent)
					baseBlocksToCheck.Push(bb);
			}

			void processScopeBlock(ScopeBlock scopeBlock) {
				if (scopeBlock == null || checkedScopeBlocks.ContainsKey(scopeBlock))
					return;
				checkedScopeBlocks[scopeBlock] = true;
				addBaseBlock(scopeBlock);

				if (scopeBlock is TryBlock) {
					var tryBlock = (TryBlock)scopeBlock;
					foreach (var handler in tryBlock.TryHandlerBlocks)
						addScopeBlock(handler);
				}
				else if (scopeBlock is TryHandlerBlock) {
					var tryHandlerBlock = (TryHandlerBlock)scopeBlock;
					addScopeBlock(tryHandlerBlock.FilterHandlerBlock);
					addScopeBlock(tryHandlerBlock.HandlerBlock);
				}
			}
		}

		public void getCode(out IList<Instruction> allInstructions, out IList<ExceptionHandler> allExceptionHandlers) {
			new CodeGenerator(methodBlocks).getCode(out allInstructions, out allExceptionHandlers);
		}
	}
}