DateTimeParser.h

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/*
 * Copyright 2022 HEAVY.AI, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#pragma once

#include "Shared/StringTransform.h"
#include "sqltypes.h"

#include <optional>
#include <ostream>
#include <string_view>

template <SQLTypes SQL_TYPE>
std::optional<int64_t> dateTimeParseOptional(std::string_view, unsigned const dim);

template <>
std::optional<int64_t> dateTimeParseOptional<kDATE>(std::string_view, unsigned const dim);

template <>
std::optional<int64_t> dateTimeParseOptional<kTIME>(std::string_view, unsigned const dim);

template <>
std::optional<int64_t> dateTimeParseOptional<kTIMESTAMP>(std::string_view,
                                                         unsigned const dim);

template <SQLTypes SQL_TYPE>
int64_t dateTimeParse(std::string_view const s, unsigned const dim) {
  if (auto const time = dateTimeParseOptional<SQL_TYPE>(s, dim)) {
    return *time;
  } else {
    throw std::runtime_error(cat("Invalid ", toString(SQL_TYPE), " string (", s, ')'));
  }
}

class DateTimeParser {
 public:
  enum class FormatType { Date, Time, Timezone };
  std::optional<int64_t> parse(std::string_view const, unsigned dim);
  void setFormatType(FormatType);
  std::string_view unparsed() const;

  struct DateTime {
    int64_t Y{1970};        // Full year
    unsigned m{1};          // month (1-12)
    unsigned d{1};          // day of month (1-31)
    unsigned H{0};          // hour (0-23)
    unsigned M{0};          // minute (0-59)
    unsigned S{0};          // second (0-61)
    unsigned n{0};          // fraction of a second in nanoseconds (0-999999999)
    int z{0};               // timezone offset in seconds
    std::optional<bool> p;  // true if pm, false if am, nullopt if unspecified

    int64_t getTime(unsigned const dim) const;
    friend std::ostream& operator<<(std::ostream&, DateTime const&);
  };

 private:
  DateTime dt_;
  FormatType format_type_;
  std::string_view unparsed_;

  bool parseWithFormat(std::string_view format, std::string_view& str);
  void resetDateTime();
  bool updateDateTimeAndStr(char const field, std::string_view&);
};