// File: SymbolExtensions.cs
// Author: Samuel Jack
// Article: "Getting the MethodInfo of a generic method using Lambda expressions"
// URL: http://blog.functionalfun.net/2009/10/getting-methodinfo-of-generic-method.html

using System.Linq.Expressions;
using System.Reflection;
using System;

namespace PixelCrushers.DialogueSystem { // Put in DialogueSystem namespace to prevent conflicts.

	public static class SymbolExtensions
	{
		/// <summary>
		/// Given a lambda expression that calls a method, returns the method info.
		/// </summary>
		/// <typeparam name="T"></typeparam>
		/// <param name="expression">The expression.</param>
		/// <returns></returns>
		public static MethodInfo GetMethodInfo(Expression<Action> expression)
		{
			return GetMethodInfo((LambdaExpression)expression);
		}
		
		/// <summary>
		/// Given a lambda expression that calls a method, returns the method info.
		/// </summary>
		/// <typeparam name="T"></typeparam>
		/// <param name="expression">The expression.</param>
		/// <returns></returns>
		public static MethodInfo GetMethodInfo<T>(Expression<Action<T>> expression)
		{
			return GetMethodInfo((LambdaExpression)expression);
		}
		
		/// <summary>
		/// Given a lambda expression that calls a method, returns the method info.
		/// </summary>
		/// <typeparam name="T"></typeparam>
		/// <param name="expression">The expression.</param>
		/// <returns></returns>
		public static MethodInfo GetMethodInfo<T, TResult>(Expression<Func<T, TResult>> expression)
		{
			return GetMethodInfo((LambdaExpression)expression);
		}
		
		/// <summary>
		/// Given a lambda expression that calls a method, returns the method info.
		/// </summary>
		/// <param name="expression">The expression.</param>
		/// <returns></returns>
		public static MethodInfo GetMethodInfo(LambdaExpression expression)
		{
			MethodCallExpression outermostExpression = expression.Body as MethodCallExpression;
			
			if (outermostExpression == null)
			{
				throw new ArgumentException("Invalid Expression. Expression should consist of a Method call only.");
			}
			
			return outermostExpression.Method;
		}
	}

}