using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using FireBirdUtil.DataTypes;
using FirebirdSql.Data.FirebirdClient;
using System.Data;

namespace FireBirdUtil.SqlUtils
{
	public class SqlExecuteBaseUtil
	{
		/// <summary>
		/// 执行非查询命令(如果事务参数不为null，则在事务中执行)
		/// </summary>
		public static void ExecuteNonQuery(FbConnection connection, FbTransaction transaction, string commandText)
		{
			using (FbCommand fbCmd = connection.CreateCommand()) {
				if (transaction != null)
					fbCmd.Transaction = transaction;
				fbCmd.CommandText = GetReplaceNullSql(commandText);
				fbCmd.ExecuteNonQuery();
			}
		}

		/// <summary>
		/// 执行查询命令【根据返回的单个值处理后的值】(如果事务参数不为null，则在事务中执行)
		/// </summary>
		/// <typeparam name="TResult">处理后的结果类型</typeparam>
		public static TResult ExecuteScalar<TResult>(FbConnection connection, FbTransaction transaction, string commandText, Func<object, TResult> DealResult)
		{
#if DEBUG
			if (DealResult == null)
				throw new ArgumentException("DealResult参数不允许为null");
#endif
			TResult result;
			using (FbCommand fbCmd = connection.CreateCommand()) {
				if (transaction != null)
					fbCmd.Transaction = transaction;
				fbCmd.CommandText = GetReplaceNullSql(commandText);
				var obj = fbCmd.ExecuteScalar();
				result = DealResult(obj);
			}
			return result;
		}

		/// <summary>
		/// 执行查询命令(如果事务参数不为null，则在事务中执行)
		/// </summary>
		public static DataTable ExecuteReader(FbConnection connection, FbTransaction transaction, string commandText)
		{
			DataTable table;
			using (FbCommand fbCmd = connection.CreateCommand()) {
				if (transaction != null)
					fbCmd.Transaction = transaction;
				fbCmd.CommandText = GetReplaceNullSql(commandText);
				var reader = fbCmd.ExecuteReader();
				table = CreateDataTable(reader);
			}
			return table;
		}

		/// <summary>
		/// 如果null由引号包括，则去掉null前后的引号。即：用null代替'null'
		/// </summary>
		private static string GetReplaceNullSql(string sql)
		{
			var tmp = sql.ToLower();
			var index = tmp.IndexOf("'null'");
			if (index < 0)
				return sql;
			string old = sql.Substring(index, 6);
			sql = sql.Replace(old, "null");
			sql = GetReplaceNullSql(sql);
			return sql;
		}

		private static DataTable CreateDataTable(FbDataReader reader)
		{
			if (reader.IsClosed)
				throw new ApplicationException("查询命令已结束");

			var dataTable = new DataTable();
			dataTable.Load(reader);

			return dataTable;
		}

	}
}