using System;
using System.Collections.Generic;
using System.Linq.Expressions;

namespace EC.Utils
{
	/// <summary>
	/// 动态Lamada
	/// 版 本：V3.0.0
	/// 版 权：EasyCode
	/// 作 者：LXC
	/// </summary>
	public partial class ExtLinq<T> where T : new()
	{
		private List<Expression> m_lstExpression = null;
		private ParameterExpression m_Parameter = null;

		public ExtLinq()
		{
			m_lstExpression = new List<Expression>();
			m_Parameter = Expression.Parameter(typeof(T), "x");
		}

		public void CreateExpression(string strPropertyName, object strValue, SearchMethod expressType)
		{
			Expression expRes = null;
			MemberExpression member = Expression.PropertyOrField(m_Parameter, strPropertyName);
			if (expressType == SearchMethod.Contains)
			{
				expRes = Expression.Call(member, typeof(string).GetMethod("Contains"), Expression.Constant(strValue));
			}
			else if (expressType == SearchMethod.Equal)
			{
				expRes = Expression.Equal(member, Expression.Constant(strValue, member.Type));
			}
			else if (expressType == SearchMethod.NotEqual)
			{
				expRes = Expression.NotEqual(member, Expression.Constant(strValue, member.Type));
			}
			else if (expressType == SearchMethod.LessThan)
			{
				expRes = Expression.LessThan(member, Expression.Constant(strValue, member.Type));
			}
			else if (expressType == SearchMethod.LessThanOrEqual)
			{
				expRes = Expression.LessThanOrEqual(member, Expression.Constant(strValue, member.Type));
			}
			else if (expressType == SearchMethod.GreaterThan)
			{
				expRes = Expression.GreaterThan(member, Expression.Constant(strValue, member.Type));
			}
			else if (expressType == SearchMethod.GreaterThanOrEqual)
			{
				expRes = Expression.GreaterThanOrEqual(member, Expression.Constant(strValue, member.Type));
			}
			m_lstExpression.Add(expRes);
		}

		public void CreateExpression(string strPropertyName, List<object> lstValue)
		{
			Expression expRes = null;
			MemberExpression member = Expression.PropertyOrField(m_Parameter, strPropertyName);
			foreach (var oValue in lstValue)
			{
				if (expRes == null)
				{
					expRes = Expression.Equal(member, Expression.Constant(oValue, member.Type));
				}
				else
				{
					expRes = Expression.Or(expRes, Expression.Equal(member, Expression.Constant(oValue, member.Type)));
				}
			}
			m_lstExpression.Add(expRes);
		}

		public Expression<Func<T, bool>> GetLambda()
		{
			Expression whereExpr = null;
			foreach (var expr in this.m_lstExpression)
			{
				if (whereExpr == null)
					whereExpr = expr;
				else
					whereExpr = Expression.And(whereExpr, expr);
			}
			if (whereExpr == null)
				return null;
			return Expression.Lambda<Func<T, bool>>(whereExpr, m_Parameter);
		}
	}

	public enum SearchMethod
	{
		Contains,           //like
		Equal,              //等于
		NotEqual,           //不等于
		LessThan,           //小于
		LessThanOrEqual,    //小于等于
		GreaterThan,        //大于
		GreaterThanOrEqual  //大于等于
	}
}