using Microsoft.EntityFrameworkCore.Query;
using Microsoft.EntityFrameworkCore.Query.Internal;
using Microsoft.EntityFrameworkCore.Storage;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using System.Text;

namespace YLShipBuildLandMap.Entity.Extensions
{
    public static class QueryableExtensions
    {
        private static readonly TypeInfo QueryCompilerTypeInfo = typeof(QueryCompiler).GetTypeInfo();

        private static readonly FieldInfo QueryCompilerField = typeof(EntityQueryProvider).GetTypeInfo().DeclaredFields.First(x => x.Name == "_queryCompiler");
        private static readonly FieldInfo QueryModelGeneratorField = typeof(QueryCompiler).GetTypeInfo().DeclaredFields.First(x => x.Name == "_queryModelGenerator");
        private static readonly FieldInfo DataBaseField = QueryCompilerTypeInfo.DeclaredFields.Single(x => x.Name == "_database");
        private static readonly PropertyInfo DatabaseDependenciesField = typeof(Microsoft.EntityFrameworkCore.Storage.Database).GetTypeInfo().DeclaredProperties.Single(x => x.Name == "Dependencies");

        /// <summary>
        /// 获取本次查询SQL语句
        /// </summary>
        /// <typeparam name="TEntity"></typeparam>
        /// <param name="query"></param>
        /// <returns></returns>
        /*public static string ToSql<TEntity>(this IQueryable<TEntity> query)
        {
            var queryCompiler = (QueryCompiler)QueryCompilerField.GetValue(query.Provider);
            var queryModelGenerator = (QueryModelGenerator)QueryModelGeneratorField.GetValue(queryCompiler);
            var queryModel = queryModelGenerator.ParseQuery(query.Expression);
            var database = DataBaseField.GetValue(queryCompiler);
            var databaseDependencies = (DatabaseDependencies)DatabaseDependenciesField.GetValue(database);
            var queryCompilationContext = databaseDependencies.QueryCompilationContextFactory.Create(false);
            var modelVisitor = (RelationalQueryModelVisitor)queryCompilationContext.CreateQueryModelVisitor();
            modelVisitor.CreateQueryExecutor<TEntity>(queryModel);
            var sql = modelVisitor.Queries.First().ToString();

            return sql;
        }*/
    }
}