// Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
// This code is distributed under MIT X11 license (for details please see \doc\license.txt)

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using Mono.Cecil;

namespace ICSharpCode.Decompiler.ILAst
{
	public static class PatternMatching
	{
		public static bool Match(this ILNode node, ILCode code)
		{
			ILExpression expr = node as ILExpression;
			return expr != null && expr.Prefixes == null && expr.Code == code;
		}
		
		public static bool Match<T>(this ILNode node, ILCode code, out T operand)
		{
			ILExpression expr = node as ILExpression;
			if (expr != null && expr.Prefixes == null && expr.Code == code && expr.Arguments.Count == 0) {
				operand = (T)expr.Operand;
				return true;
			}
			operand = default(T);
			return false;
		}
		
		public static bool Match<T>(this ILNode node, ILCode code, T operand)
		{
			ILExpression expr = node as ILExpression;
			if (expr != null && expr.Prefixes == null && expr.Code == code) {
				Debug.Assert(expr.Arguments.Count == 0);
				return operand.Equals(expr.Operand);
			}
			return false;
		}
		
		public static bool Match(this ILNode node, ILCode code, out List<ILExpression> args)
		{
			ILExpression expr = node as ILExpression;
			if (expr != null && expr.Prefixes == null && expr.Code == code) {
				Debug.Assert(expr.Operand == null);
				args = expr.Arguments;
				return true;
			}
			args = null;
			return false;
		}
		
		public static bool Match(this ILNode node, ILCode code, out ILExpression arg)
		{
			List<ILExpression> args;
			if (node.Match(code, out args) && args.Count == 1) {
				arg = args[0];
				return true;
			}
			arg = null;
			return false;
		}
		
		public static bool Match<T>(this ILNode node, ILCode code, out T operand, out List<ILExpression> args)
		{
			ILExpression expr = node as ILExpression;
			if (expr != null && expr.Prefixes == null && expr.Code == code) {
				operand = (T)expr.Operand;
				args = expr.Arguments;
				return true;
			}
			operand = default(T);
			args = null;
			return false;
		}
		
		public static bool Match<T>(this ILNode node, ILCode code, out T operand, out ILExpression arg)
		{
			List<ILExpression> args;
			if (node.Match(code, out operand, out args) && args.Count == 1) {
				arg = args[0];
				return true;
			}
			arg = null;
			return false;
		}
		
		public static bool Match<T>(this ILNode node, ILCode code, out T operand, out ILExpression arg1, out ILExpression arg2)
		{
			List<ILExpression> args;
			if (node.Match(code, out operand, out args) && args.Count == 2) {
				arg1 = args[0];
				arg2 = args[1];
				return true;
			}
			arg1 = null;
			arg2 = null;
			return false;
		}
		
		public static bool MatchSingle<T>(this ILBasicBlock bb, ILCode code, out T operand, out ILExpression arg, out ILLabel fallLabel)
		{
			if (bb.Body.Count == 1) {
				if (bb.Body[0].Match(code, out operand, out arg)) {
					fallLabel = bb.FallthoughGoto != null ? (ILLabel)bb.FallthoughGoto.Operand : null;
					return true;
				}
			}
			operand = default(T);
			arg = null;
			fallLabel = null;
			return false;
		}
		
		public static bool MatchLast<T>(this ILBasicBlock bb, ILCode code, out T operand, out ILExpression arg, out ILLabel fallLabel)
		{
			if (bb.Body.LastOrDefault().Match(code, out operand, out arg)) {
				fallLabel = bb.FallthoughGoto != null ? (ILLabel)bb.FallthoughGoto.Operand : null;
				return true;
			}
			operand = default(T);
			arg = null;
			fallLabel = null;
			return false;
		}
		
		public static bool MatchThis(this ILNode node)
		{
			ILVariable v;
			return node.Match(ILCode.Ldloc, out v) && v.IsParameter && v.OriginalParameter.Index == -1;
		}
		
		public static bool MatchLdloc(this ILNode node, ILVariable expectedVar)
		{
			ILVariable v;
			return node.Match(ILCode.Ldloc, out v) && v == expectedVar;
		}
	}
}