using Ant.Core;
using Ant.Core.Visitors;
using Ant.Data;
using Ant.Infrastructure;
using Ant.Mapper;
using Ant.ORM;
using Ant.Query.Mapping;
using Ant.Query.QueryState;
using Ant.Query.Visitors;
using System.Collections;
using System.Collections.Generic;
using System.Data;
using System.Data.SqlClient;
using System.Diagnostics;

namespace Ant.Query.Internals
{
    class InternalQuery<T> : IEnumerable<T>, IEnumerable
    {
        Queryable<T> _query; DbCommandFactor _commandFactor;

        internal InternalQuery(Queryable<T> query)
        {
            this._query = query;
            this._commandFactor = GenerateCommandFactor();
        }
        /// <summary>
        /// 创建执行SQL语句的工厂
        /// </summary>
        /// <returns></returns>
        DbCommandFactor GenerateCommandFactor()
        {
            IQueryState qs = QueryExpressionVisitor.VisitQueryExpression(this._query.QueryExpression);
            MappingData data = qs.GenerateMappingData();//解析Lambda表达式

            IObjectActivator objectActivator;
            if (this._query._trackEntity)
                objectActivator = data.ObjectActivatorCreator.CreateObjectActivator(this._query.DbContext);
            else
                objectActivator = data.ObjectActivatorCreator.CreateObjectActivator();

            IDbExpressionTranslator translator = this._query.DbContext.DbContextServiceProvider.CreateDbExpressionTranslator();
            List<DbParam> parameters;
            string cmdText = translator.Translate(data.SqlQuery, out parameters);//解析SQL语句

            DbCommandFactor commandFactor = new DbCommandFactor(objectActivator, cmdText, parameters.ToArray());
            commandFactor.StrSql = SqlDataAccess.AppendDbCommandInfo(cmdText, parameters.ToArray());
            commandFactor.SqlConnection = this._query.db.ConnectionString;
            return commandFactor;
        }
        /// <summary>
        /// 
        /// </summary>
        /// <returns></returns>
        public IEnumerator<T> GetEnumerator()
        {
            // DbCommandFactor commandFactor = this.GenerateCommandFactor();
            var enumerator = QueryEnumeratorCreator.CreateEnumerator<T>(this._query.db, _commandFactor);//用于返回数据对象
            return enumerator;
        }
        IEnumerator IEnumerable.GetEnumerator()
        {
            return this.GetEnumerator();
        }
        /// <summary>
        /// 为了获取SQL语句
        /// </summary>
        /// <returns></returns>
        public override string ToString()
        {
            //DbCommandFactor commandFactor = this.GenerateCommandFactor();
            return SqlDataAccess.AppendDbCommandInfo(_commandFactor.CommandText, _commandFactor.Parameters);//返回SQL语句用于记日志;
        }

        /// <summary>
        /// 获取数据库连接
        /// </summary>
        /// <returns></returns>
        public string GetDataConnection()
        {
            return _commandFactor.SqlConnection;
        }
    }
}