// Copyright (c) 2020 Oracle and/or its affiliates.
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License, version 2.0, as
// published by the Free Software Foundation.
//
// This program is also distributed with certain software (including
// but not limited to OpenSSL) that is licensed under separate terms,
// as designated in a particular file or component or in included license
// documentation.  The authors of MySQL hereby grant you an
// additional permission to link the program and your derivative works
// with the separately licensed software that they have included with
// MySQL.
//
// Without limiting anything contained in the foregoing, this file,
// which is part of MySQL Connector/NET, is also subject to the
// Universal FOSS Exception, version 1.0, a copy of which can be found at
// http://oss.oracle.com/licenses/universal-foss-exception.
//
// This program is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
// See the GNU General Public License, version 2.0, for more details.
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using Microsoft.EntityFrameworkCore.Query;
using Microsoft.EntityFrameworkCore.Query.SqlExpressions;
using System;
using System.Collections.Generic;
using System.Reflection;

namespace MySql.EntityFrameworkCore.Query.Internal
{
  internal class MySQLDateTimeMemberTranslator : IMemberTranslator
  {
    private static readonly Dictionary<string, (string Part, int Divisor)> _datePartMapping
        = new Dictionary<string, (string, int)>
        {
                { nameof(DateTime.Year), ("year", 1) },
                { nameof(DateTime.Month), ("month", 1) },
                { nameof(DateTime.Day), ("day", 1) },
                { nameof(DateTime.Hour), ("hour", 1) },
                { nameof(DateTime.Minute), ("minute", 1) },
                { nameof(DateTime.Second), ("second", 1) },
                { nameof(DateTime.Millisecond), ("microsecond", 1000) },
        };
    private readonly MySQLSqlExpressionFactory _sqlExpressionFactory;

    public MySQLDateTimeMemberTranslator(ISqlExpressionFactory sqlExpressionFactory)
    {
      _sqlExpressionFactory = (MySQLSqlExpressionFactory)sqlExpressionFactory;
    }

    public virtual SqlExpression Translate(SqlExpression instance, MemberInfo member, Type returnType)
    {
      var declaringType = member.DeclaringType;

      if (declaringType == typeof(DateTime)
          || declaringType == typeof(DateTimeOffset))
      {
        var memberName = member.Name;

        if (_datePartMapping.TryGetValue(memberName, out var datePart))
        {
          var extract = _sqlExpressionFactory.Function(
              "EXTRACT",
              new[]
              {
                _sqlExpressionFactory.ComplexFunctionArgument(
                    new [] {
                        _sqlExpressionFactory.Fragment($"{datePart.Part} FROM"),
                        instance
                    },
                    typeof(string))
              },
              returnType);

          if (datePart.Divisor != 1)
          {
            return _sqlExpressionFactory.MySqlIntegerDivide(
                extract,
                _sqlExpressionFactory.Constant(datePart.Divisor));
          }

          return extract;
        }

        switch (memberName)
        {
          case nameof(DateTime.DayOfYear):
            return _sqlExpressionFactory.Function(
            "DAYOFYEAR",
            new[] { instance },
            returnType);

          case nameof(DateTime.Date):
            return _sqlExpressionFactory.Function(
                "CONVERT",
                new[]{
                  instance,
                  _sqlExpressionFactory.Fragment("date")
                },
                returnType);

          case nameof(DateTime.TimeOfDay):
            return _sqlExpressionFactory.Convert(instance, returnType);

          case nameof(DateTime.Now):
            return _sqlExpressionFactory.Function(
                declaringType == typeof(DateTimeOffset)
                    ? "UTC_TIMESTAMP"
                    : "CURRENT_TIMESTAMP",
                Array.Empty<SqlExpression>(), returnType);

          case nameof(DateTime.UtcNow):
            return _sqlExpressionFactory.Function(
                "UTC_TIMESTAMP",
                Array.Empty<SqlExpression>(),
                returnType);

          case nameof(DateTime.Today):
            return _sqlExpressionFactory.Function(
                declaringType == typeof(DateTimeOffset)
                    ? "UTC_DATE"
                    : "CURDATE",
                Array.Empty<SqlExpression>(),
                returnType);
        }
      }

      return null;
    }
  }
}
