//
// BinaryExpression.cs
//
// Author:
//   Jb Evain (jbevain@novell.com)
//   Miguel de Icaza (miguel@novell.com)
//
// Contains code from the Mono C# compiler:
//   Marek Safar (marek.safar@seznam.cz)
//   Martin Baulig (martin@ximian.com)
//   Raja Harinath (harinath@gmail.com)
//
// (C) 2001-2003 Ximian, Inc.
// (C) 2004-2008 Novell, Inc. (http://www.novell.com)
//
// 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.Reflection;
using System.Reflection.Emit;

namespace System.Linq.Expressions {

	public sealed class BinaryExpression : Expression {

		Expression left;
		Expression right;
		LambdaExpression conversion;
		MethodInfo method;
		bool lift_to_null, is_lifted;

		public Expression Left {
			get { return left; }
		}

		public Expression Right {
			get { return right; }
		}

		public MethodInfo Method {
			get { return method; }
		}

		public bool IsLifted {
			get { return is_lifted;  }
		}

		public bool IsLiftedToNull {
			get { return lift_to_null; }
		}

		public LambdaExpression Conversion {
			get { return conversion; }
		}

		internal BinaryExpression (ExpressionType node_type, Type type, Expression left, Expression right)
			: base (node_type, type)
		{
			this.left = left;
			this.right = right;
		}

		internal BinaryExpression (ExpressionType node_type, Type type, Expression left, Expression right, MethodInfo method)
			: base (node_type, type)
		{
			this.left = left;
			this.right = right;
			this.method = method;
		}

		internal BinaryExpression (ExpressionType node_type, Type type, Expression left, Expression right, bool lift_to_null,
					   bool is_lifted, MethodInfo method, LambdaExpression conversion) : base (node_type, type)
		{
			this.left = left;
			this.right = right;
			this.method = method;
			this.conversion = conversion;
			this.lift_to_null = lift_to_null;
			this.is_lifted = is_lifted;
		}

		void EmitMethod (EmitContext ec)
		{
			left.Emit (ec);
			right.Emit (ec);
			ec.ig.Emit (OpCodes.Call, Method);
		}

		static MethodInfo GetMethodNoPar (Type t, string name)
		{
			MethodInfo [] methods = t.GetMethods ();
			foreach (MethodInfo m in methods){
				if (m.Name != name)
					continue;
				if (m.GetParameters ().Length == 0)
					return m;
			}
			throw new Exception (String.Format ("Internal error: method {0} with no parameters not found on {1}",
							    name, t));
		}

		LocalBuilder EmitStored (EmitContext ec, Expression expr)
		{
			LocalBuilder lb = ec.ig.DeclareLocal (expr.Type);
			expr.Emit (ec);
			ec.ig.Emit (OpCodes.Stloc, lb);

			return lb;
		}
		
		void EmitLogical (EmitContext ec, bool and, bool short_circuit)
		{
			ILGenerator ig = ec.ig;
			if (IsLifted){
				LocalBuilder ret = ig.DeclareLocal (Type);
				LocalBuilder vleft = null, vright = null;
				MethodInfo has_value = left.Type.GetMethod ("get_HasValue");
				MethodInfo get_value = GetMethodNoPar (left.Type, "get_Value");

				vleft = EmitStored (ec, left);
				if (!short_circuit)
					vright = EmitStored (ec, right);
				
				Label left_is_null = ig.DefineLabel ();
				Label left_is_false = ig.DefineLabel ();
				Label right_is_null = ig.DefineLabel ();
				Label create  = ig.DefineLabel ();
				Label exit = ig.DefineLabel ();
				Label both_are_null = ig.DefineLabel ();
				
				// Check left
				
				ig.Emit (OpCodes.Ldloca, vleft);
				ig.Emit (OpCodes.Call, has_value);
				ig.Emit (OpCodes.Brfalse, left_is_null);
				
				ig.Emit (OpCodes.Ldloca, vleft);
				ig.Emit (OpCodes.Call, get_value);					
				ig.Emit (OpCodes.Dup);
				
				left_is_false = ig.DefineLabel ();
				ig.Emit (and ? OpCodes.Brfalse : OpCodes.Brtrue, create);
				
				// Deal with right
				if (short_circuit)
					vright = EmitStored (ec, right);
				
				ig.Emit (OpCodes.Ldloca, vright);
				ig.Emit (OpCodes.Call, has_value);
				ig.Emit (OpCodes.Brfalse, right_is_null);
				
				ig.Emit (OpCodes.Ldloca, vright);
				ig.Emit (OpCodes.Call, get_value);

				ig.Emit (and ? OpCodes.And : OpCodes.Or);
				ig.Emit (OpCodes.Br, create);

			// left_is_null:
				ig.MarkLabel (left_is_null);
				ig.Emit (OpCodes.Ldloca, vright);
				ig.Emit (OpCodes.Call, has_value);
				ig.Emit (OpCodes.Brfalse, both_are_null);
				ig.Emit (OpCodes.Ldloca, vright);
				ig.Emit (OpCodes.Call, get_value);
				ig.Emit (OpCodes.Dup);
				ig.Emit (and ? OpCodes.Brfalse : OpCodes.Brtrue, create);

			// right_is_null:
				ig.MarkLabel (right_is_null);
				ig.Emit (OpCodes.Pop);

			// both_are_null:
				ig.MarkLabel (both_are_null);
				ig.Emit (OpCodes.Ldloca, ret);
				ig.Emit (OpCodes.Initobj, Type);
				ig.Emit (OpCodes.Ldloc, ret);
				ig.Emit (OpCodes.Br, exit);
				
			// create:
				ig.MarkLabel (create);
				ig.Emit (OpCodes.Newobj, Type.GetConstructors ()[0]);

			// exit:
				ig.MarkLabel (exit);
			} else {
				left.Emit (ec);
				right.Emit (ec);
				ig.Emit (and ? OpCodes.And : OpCodes.Or);
			}
			
		}

		void EmitCoalesce (EmitContext ec)
		{
			ILGenerator ig = ec.ig;
			
			LocalBuilder vleft;
			LocalBuilder vright;
					
			MethodInfo has_value = left.Type.GetMethod ("get_HasValue");
			
			Label exit = ig.DefineLabel ();
			Label try_right = ig.DefineLabel ();
			Label setup_null = ig.DefineLabel ();

			vleft = EmitStored (ec, left);
			if (IsNullable (left.Type)){
				ig.Emit (OpCodes.Ldloca, vleft);
				ig.Emit (OpCodes.Call, has_value);
			} else 
				ig.Emit (OpCodes.Ldloc, vleft);
			
			ig.Emit (OpCodes.Brfalse, try_right);
			ig.Emit (OpCodes.Ldloc, vleft);
			ig.Emit (OpCodes.Br, exit);
			
		// try_right;
			ig.MarkLabel (try_right);
			vright = EmitStored (ec, right);
			if (IsNullable (right.Type)){
				ig.Emit (OpCodes.Ldloca, vright);
				ig.Emit (OpCodes.Call, has_value);
			} else
				ig.Emit (OpCodes.Ldloc, vright);
			
			ig.Emit (OpCodes.Brfalse, setup_null);
			ig.Emit (OpCodes.Ldloc, vright);
			ig.Emit (OpCodes.Br, exit);

		// setup_null:
			ig.MarkLabel (setup_null);
			LocalBuilder ret = ig.DeclareLocal (Type);
			ig.Emit (OpCodes.Ldloca, ret);
			ig.Emit (OpCodes.Initobj, Type);
			
		// exit:
			ig.MarkLabel (exit);
		}
		
		internal override void Emit (EmitContext ec)
		{
			ILGenerator ig = ec.ig;
			OpCode opcode;

			if (method != null){
				EmitMethod (ec);
				return;
			}

			switch (NodeType){
			case ExpressionType.And:
				EmitLogical (ec, true, false);
				return;
				
			case ExpressionType.Or:
				EmitLogical (ec, false, false);
				return;

			case ExpressionType.AndAlso:
				Console.WriteLine ("LINQ/BinaryExpression: AndAlso code path not yet reviewed");
				EmitLogical (ec, true, true);
				return;

			case ExpressionType.OrElse:
				Console.WriteLine ("LINQ/BinaryExpression: OrElse code path not yet reviewed");
				EmitLogical (ec, false, true);
				return;

			case ExpressionType.Coalesce:
				EmitCoalesce (ec);
				return;

			case ExpressionType.Power:
				left.Emit (ec);
				right.Emit (ec);
				ig.Emit (OpCodes.Call, typeof (System.Math).GetMethod ("Pow"));
				return;
			}
			
			Label? empty_value = null;
			LocalBuilder ret = null;

			if (IsLifted){
				LocalBuilder vleft, vright;

				empty_value = ig.DefineLabel ();
				ret = ig.DeclareLocal (Type);

				vleft = EmitStored (ec, left);
				vright = EmitStored (ec, right);

				MethodInfo has_value = left.Type.GetMethod ("get_HasValue");
				MethodInfo get_value = GetMethodNoPar (left.Type, "get_Value");

				ig.Emit (OpCodes.Ldloca, vleft);
				ig.Emit (OpCodes.Call, has_value);
				ig.Emit (OpCodes.Brfalse, empty_value.Value);
				ig.Emit (OpCodes.Ldloca, vright);
				ig.Emit (OpCodes.Call, has_value);
				ig.Emit (OpCodes.Brfalse, empty_value.Value);
				ig.Emit (OpCodes.Ldloca, vleft);
				ig.Emit (OpCodes.Call, get_value);
				ig.Emit (OpCodes.Ldloca, vright);
				ig.Emit (OpCodes.Call, get_value);
			} else {
				left.Emit (ec);
				right.Emit (ec);
			}

			bool is_unsigned = IsUnsigned (left.Type);

			switch (NodeType){
			case ExpressionType.Add:
				opcode = OpCodes.Add;
				break;

			case ExpressionType.AddChecked:
				if (left.Type == typeof (int) || left.Type == typeof (long))
					opcode = OpCodes.Add_Ovf;
				else if (is_unsigned)
					opcode = OpCodes.Add_Ovf_Un;
				else
					opcode = OpCodes.Add;
				break;

			case ExpressionType.Subtract:
				opcode = OpCodes.Sub;
				break;

			case ExpressionType.SubtractChecked:
				if (left.Type == typeof (int) || left.Type == typeof (long))
					opcode = OpCodes.Sub_Ovf;
				else if (is_unsigned)
					opcode = OpCodes.Sub_Ovf_Un;
				else
					opcode = OpCodes.Sub;
				break;

			case ExpressionType.Multiply:
				opcode = OpCodes.Mul;
				break;

			case ExpressionType.MultiplyChecked:
				if (left.Type == typeof (int) || left.Type == typeof (long))
					opcode = OpCodes.Mul_Ovf;
				else if (is_unsigned)
					opcode = OpCodes.Mul_Ovf_Un;
				else
					opcode = OpCodes.Mul;
				break;

			case ExpressionType.Divide:
				if (is_unsigned)
					opcode = OpCodes.Div_Un;
				else
					opcode = OpCodes.Div;
				break;

			case ExpressionType.Modulo:
				if (is_unsigned)
					opcode = OpCodes.Rem_Un;
				else
					opcode = OpCodes.Rem;
				break;

			case ExpressionType.RightShift:
				if (is_unsigned)
					opcode = OpCodes.Shr_Un;
				else
					opcode = OpCodes.Shr;
				break;

			case ExpressionType.LeftShift:
				opcode = OpCodes.Shl;
				break;

			case ExpressionType.And:
				opcode = OpCodes.And;
				break;

			case ExpressionType.Or:
				opcode = OpCodes.Or;
				break;

			case ExpressionType.ExclusiveOr:
				opcode = OpCodes.Xor;
				break;

			case ExpressionType.GreaterThan:
				if (is_unsigned)
					opcode = OpCodes.Cgt_Un;
				else
					opcode = OpCodes.Cgt;
				break;
				
			case ExpressionType.GreaterThanOrEqual:
				Type le = left.Type;
				
				if (is_unsigned || (le == typeof (double) || le == typeof (float)))
					ig.Emit (OpCodes.Clt_Un);
				else
					ig.Emit (OpCodes.Clt);
				
				ig.Emit (OpCodes.Ldc_I4_0);
				
				opcode = OpCodes.Ceq;
				break;
				
			case ExpressionType.LessThan:
				if (is_unsigned)
					opcode = OpCodes.Clt_Un;
				else
					opcode = OpCodes.Clt;
				break;
				
			case ExpressionType.LessThanOrEqual:
				Type lt = left.Type;
				
				if (is_unsigned || (lt == typeof (double) || lt == typeof (float)))
					ig.Emit (OpCodes.Cgt_Un);
				else
					ig.Emit (OpCodes.Cgt);
				ig.Emit (OpCodes.Ldc_I4_0);
				
				opcode = OpCodes.Ceq;
				break;
				
			case ExpressionType.Equal:
				opcode = OpCodes.Ceq;
				break;
				
			case ExpressionType.NotEqual:
				ig.Emit (OpCodes.Ceq);
				ig.Emit (OpCodes.Ldc_I4_0);
				
				opcode = OpCodes.Ceq;
				break;
				
			default:
				throw new Exception (String.Format ("Internal error: BinaryExpression contains non-Binary nodetype {0}", NodeType));
			}
			ig.Emit (opcode);
			
			if (IsLifted){
				ig.Emit (OpCodes.Newobj, left.Type.GetConstructors ()[0]);
				
				Label skip = ig.DefineLabel ();
				ig.Emit (OpCodes.Br_S, skip);
				ig.MarkLabel (empty_value.Value);
				ig.Emit (OpCodes.Ldloc, ret);
				ig.Emit (OpCodes.Ldloca, ret);
				ig.Emit (OpCodes.Initobj, Type);
				
				ig.MarkLabel (skip);
			}
		}
	}
}