// Copyright (c) 2011 AlphaSierraPapa for the SharpDevelop Team
// 
// 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.Linq;
using System.Threading;

using ICSharpCode.Decompiler;
using ICSharpCode.Decompiler.FlowAnalysis;
using ICSharpCode.Decompiler.ILAst;
using Mono.Cecil;
using Mono.Cecil.Cil;

namespace ICSharpCode.Decompiler.Disassembler
{
	/// <summary>
	/// Disassembles a method body.
	/// </summary>
	public sealed class MethodBodyDisassembler
	{
		readonly ITextOutput output;
		readonly bool detectControlStructure;
		readonly CancellationToken cancellationToken;
		
		public MethodBodyDisassembler(ITextOutput output, bool detectControlStructure, CancellationToken cancellationToken)
		{
			if (output == null)
				throw new ArgumentNullException("output");
			this.output = output;
			this.detectControlStructure = detectControlStructure;
			this.cancellationToken = cancellationToken;
		}
		
		public void Disassemble(MethodBody body, MethodDebugSymbols debugSymbols)
		{
			// start writing IL code
			MethodDefinition method = body.Method;
			output.WriteLine("// Method begins at RVA 0x{0:x4}", method.RVA);
			output.WriteLine("// Code size {0} (0x{0:x})", body.CodeSize);
			output.WriteLine(".maxstack {0}", body.MaxStackSize);
            if (method.DeclaringType.Module.Assembly != null && method.DeclaringType.Module.Assembly.EntryPoint == method)
                output.WriteLine (".entrypoint");
			
			if (method.Body.HasVariables) {
				output.Write(".locals ");
				if (method.Body.InitLocals)
					output.Write("init ");
				output.WriteLine("(");
				output.Indent();
				foreach (var v in method.Body.Variables) {
					output.WriteDefinition("[" + v.Index + "] ", v);
					v.VariableType.WriteTo(output);
					if (!string.IsNullOrEmpty(v.Name)) {
						output.Write(' ');
						output.Write(DisassemblerHelpers.Escape(v.Name));
					}
					if (v.Index + 1 < method.Body.Variables.Count)
						output.Write(',');
					output.WriteLine();
				}
				output.Unindent();
				output.WriteLine(")");
			}
			output.WriteLine();
			
			if (detectControlStructure && body.Instructions.Count > 0) {
				Instruction inst = body.Instructions[0];
				HashSet<int> branchTargets = GetBranchTargets(body.Instructions);
				WriteStructureBody(new ILStructure(body), branchTargets, ref inst, debugSymbols, method.Body.CodeSize);
			} else {
				foreach (var inst in method.Body.Instructions) {
					var startLocation = output.Location;
					inst.WriteTo(output);
					
					if (debugSymbols != null) {
						// add IL code mappings - used in debugger
						debugSymbols.SequencePoints.Add(
							new SequencePoint() {
								StartLocation = output.Location,
								EndLocation = output.Location,
								ILRanges = new ILRange[] { new ILRange(inst.Offset, inst.Next == null ? method.Body.CodeSize : inst.Next.Offset) }
							});
					}
					
					output.WriteLine();
				}
				if (method.Body.HasExceptionHandlers) {
					output.WriteLine();
					foreach (var eh in method.Body.ExceptionHandlers) {
						eh.WriteTo(output);
						output.WriteLine();
					}
				}
			}
		}
		
		HashSet<int> GetBranchTargets(IEnumerable<Instruction> instructions)
		{
			HashSet<int> branchTargets = new HashSet<int>();
			foreach (var inst in instructions) {
				Instruction target = inst.Operand as Instruction;
				if (target != null)
					branchTargets.Add(target.Offset);
				Instruction[] targets = inst.Operand as Instruction[];
				if (targets != null)
					foreach (Instruction t in targets)
						branchTargets.Add(t.Offset);
			}
			return branchTargets;
		}
		
		void WriteStructureHeader(ILStructure s)
		{
			switch (s.Type) {
				case ILStructureType.Loop:
					output.Write("// loop start");
					if (s.LoopEntryPoint != null) {
						output.Write(" (head: ");
						DisassemblerHelpers.WriteOffsetReference(output, s.LoopEntryPoint);
						output.Write(')');
					}
					output.WriteLine();
					break;
				case ILStructureType.Try:
					output.WriteLine(".try");
					output.WriteLine("{");
					break;
				case ILStructureType.Handler:
					switch (s.ExceptionHandler.HandlerType) {
						case ExceptionHandlerType.Catch:
						case ExceptionHandlerType.Filter:
							output.Write("catch");
							if (s.ExceptionHandler.CatchType != null) {
								output.Write(' ');
								s.ExceptionHandler.CatchType.WriteTo(output, ILNameSyntax.TypeName);
							}
							output.WriteLine();
							break;
						case ExceptionHandlerType.Finally:
							output.WriteLine("finally");
							break;
						case ExceptionHandlerType.Fault:
							output.WriteLine("fault");
							break;
						default:
							throw new NotSupportedException();
					}
					output.WriteLine("{");
					break;
				case ILStructureType.Filter:
					output.WriteLine("filter");
					output.WriteLine("{");
					break;
				default:
					throw new NotSupportedException();
			}
			output.Indent();
		}
		
		void WriteStructureBody(ILStructure s, HashSet<int> branchTargets, ref Instruction inst, MethodDebugSymbols debugSymbols, int codeSize)
		{
			bool isFirstInstructionInStructure = true;
			bool prevInstructionWasBranch = false;
			int childIndex = 0;
			while (inst != null && inst.Offset < s.EndOffset) {
				int offset = inst.Offset;
				if (childIndex < s.Children.Count && s.Children[childIndex].StartOffset <= offset && offset < s.Children[childIndex].EndOffset) {
					ILStructure child = s.Children[childIndex++];
					WriteStructureHeader(child);
					WriteStructureBody(child, branchTargets, ref inst, debugSymbols, codeSize);
					WriteStructureFooter(child);
				} else {
					if (!isFirstInstructionInStructure && (prevInstructionWasBranch || branchTargets.Contains(offset))) {
						output.WriteLine(); // put an empty line after branches, and in front of branch targets
					}
					var startLocation = output.Location;
					inst.WriteTo(output);
					
					// add IL code mappings - used in debugger
					if (debugSymbols != null) {
						debugSymbols.SequencePoints.Add(
							new SequencePoint() {
								StartLocation = startLocation,
								EndLocation = output.Location,
								ILRanges = new ILRange[] { new ILRange(inst.Offset, inst.Next == null ? codeSize : inst.Next.Offset) }
							});
					}
					
					output.WriteLine();
					
					prevInstructionWasBranch = inst.OpCode.FlowControl == FlowControl.Branch
						|| inst.OpCode.FlowControl == FlowControl.Cond_Branch
						|| inst.OpCode.FlowControl == FlowControl.Return
						|| inst.OpCode.FlowControl == FlowControl.Throw;
					
					inst = inst.Next;
				}
				isFirstInstructionInStructure = false;
			}
		}
		
		void WriteStructureFooter(ILStructure s)
		{
			output.Unindent();
			switch (s.Type) {
				case ILStructureType.Loop:
					output.WriteLine("// end loop");
					break;
				case ILStructureType.Try:
					output.WriteLine("} // end .try");
					break;
				case ILStructureType.Handler:
					output.WriteLine("} // end handler");
					break;
				case ILStructureType.Filter:
					output.WriteLine("} // end filter");
					break;
				default:
					throw new NotSupportedException();
			}
		}
	}
}