using Ant.Core;
using Ant.Data;
using Ant.DbExpressions;
using Ant.Infrastructure;
using Ant.ORM;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Ant.SqlServer
{
    /// <summary>
    /// ORM首先调该类进行SQL语句的解析（ORM的入口）
    /// </summary>
    class DbExpressionTranslator : IDbExpressionTranslator
    {
        public static readonly DbExpressionTranslator Instance = new DbExpressionTranslator();
        /// <summary>
        /// 返回拼接的SQL语句
        /// </summary>
        /// <param name="expression"></param>
        /// <param name="parameters"></param>
        /// <returns></returns>
        public string Translate(DbExpression expression, out List<DbParam> parameters)
        {
            SqlGenerator generator = SqlGenerator.CreateInstance();//构建SQL数据库类
            expression.Accept(generator);

            parameters = generator.Parameters;
            string sql = generator.SqlBuilder.ToSql();

            return sql;
        }
    }

    /// <summary>
    /// ORM实现SQL2012数据库的带分页查询类
    /// </summary>
    class DbExpressionTranslator_OffsetFetch : IDbExpressionTranslator
    {
        public static readonly DbExpressionTranslator_OffsetFetch Instance = new DbExpressionTranslator_OffsetFetch();
        /// <summary>
        /// 返回拼接的SQL语句
        /// </summary>
        /// <param name="expression"></param>
        /// <param name="parameters"></param>
        /// <returns></returns>
        public string Translate(DbExpression expression, out List<DbParam> parameters)
        {
            SqlGenerator_OffsetFetch generator = new SqlGenerator_OffsetFetch();
            expression.Accept(generator);

            parameters = generator.Parameters;
            string sql = generator.SqlBuilder.ToSql();

            return sql;
        }
    }
}