using Microsoft.EntityFrameworkCore;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using System.Reflection;
using System.Text;

using static System.Linq.Expressions.Expression;


namespace PartSource.Services.Extensions
{
	public static class IQueryableExtensions
	{
		public static IQueryable<T> ApplyQueryDto<T>(this IQueryable<T> queryable, T dto)
		{
			foreach (PropertyInfo property in typeof(T).GetProperties())
			{
				object value = property.GetValue(dto);

				if (IsFilterableValue(value))
				{
					queryable = queryable.Where(property, value);
				}
			}

			return queryable;
		}

		private static IQueryable<T> Where<T>(this IQueryable<T> queryable, PropertyInfo property, object value)
		{
			if (property == null || value == null)
			{
				return queryable;
			}

			MemberExpression functions = Property(null, typeof(EF).GetProperty(nameof(EF.Functions)));
			MethodInfo likeMethodInfo = typeof(DbFunctionsExtensions).GetMethod(nameof(DbFunctionsExtensions.Like), new Type[] { functions.Type, typeof(string), typeof(string) });

			ParameterExpression lambdaParameter = Parameter(typeof(T), "x");
			Expression expressionProperty = Property(lambdaParameter, property.Name);

			if (property.PropertyType != typeof(string))
			{
				expressionProperty = Call(expressionProperty, typeof(object).GetMethod(nameof(object.ToString), new Type[0]));
			}

			MethodCallExpression methodCall = Call(
					   null,
					   likeMethodInfo,
					   functions,
					   expressionProperty,
					   Constant(value.ToString()));

			return queryable.Where(Lambda<Func<T, bool>>(methodCall, lambdaParameter));
		}

		private static bool IsFilterableValue(object value)
		{
			switch (value)
			{
				case int i:
					if (i == default) return false;
					break;

				case DateTime d:
					if (d == default) return false;
					break;

				case string s:
					if (string.IsNullOrEmpty(s)) return false;
					break;

				default:
					if (value == null) return false;
					break;
			}

			return true;
		}
	}
}