Converter: Datetimes in different time zones

// GraalJS Script (engine type: 2)

//////// START "main()" /////////////////////////////////////////////////////////////////
main();
function main(){ 

//// == Config Retrieving / 工程コンフィグの参照 ==
const strInputDt         = configs.get( "StrConfA1" ); // required
  if( strInputDt       === "" ){
    throw new Error( "\n AutomatedTask ConfigError:" +
                     " Config {A1: Input Datetime data} is empty \n" );
  }
const strInputTz         = configs.get( "StrConfA2" ); // hour
  let numInputTz         = engine.getTimeZoneOffsetInMinutes() /60;
  if( strInputTz       !== "" ){
      numInputTz         = parseFloat( strInputTz );
  }
const dtPocketOutput     = configs.getObject( "SelectConfB1" );
const strOutputTz        = configs.get( "StrConfB2" ); // hour
  let numOutputTz        = engine.getTimeZoneOffsetInMinutes() /60;
  if( strOutputTz      !== "" ){
      numOutputTz        = parseFloat( strOutputTz );
  }
engine.log( " AutomatedTask: Workflow Platform offset: " +
            (engine.getTimeZoneOffsetInMinutes() /60) );
engine.log( " AutomatedTask: Input Datetime as: " + numInputTz );
engine.log( " AutomatedTask: Output Datetime as: " + numOutputTz );
const numPocketTimestamp = configs.getObject( "SelectConfC" );


//// == Data Retrieving / ワークフローデータの参照 ==
// (Nothing. Retrieved via Expression Language in Config Retrieving)


//// == Calculating / 演算 ==
let dateUniversalTmp = toJsDate( strInputDt );
                                 // DATE Data in Platform time
let dateUniversal    = new Date( dateUniversalTmp.getTime() +
                                 engine.getTimeZoneOffsetInMinutes() *60 *1000 -
                                 numInputTz *60 *60 *1000 );
                                 // Corrects the difference from the Platform time
let numMsecUniversal = dateUniversal.getTime();
engine.log( " AutomatedTask: Timestamp: " + numMsecUniversal );
let dateShifted      = new Date( dateUniversal.getTime() -
                                 engine.getTimeZoneOffsetInMinutes() *60 *1000 +
                                 numOutputTz *60 *60 *1000 );
                                 // Shifts the time forward/back with timezone

//// == Data Updating / ワークフローデータへの代入 ==
engine.setData( dtPocketOutput,      new java.sql.Timestamp( dateShifted.getTime() ) );
if( numPocketTimestamp !== null ){
  engine.setData( numPocketTimestamp,  new java.math.BigDecimal( numMsecUniversal /1000 ) );
} // Millisec will exceed the numerical limit of workflow platform


} //////// END "main()" /////////////////////////////////////////////////////////////////



function toJsDate( bpmsDateOrDatetimeStr ){
  // BPMS Date:     "2020-04-01"  (subtype "Y/M" "M/D" "Y", not supported)
  // BPMS Datetime: "2020-04-01 23:59"
  let year       = 0;
  let monthIndex = 0;
  let day        = 0;
  let hours      = 0;
  let minutes    = 0;

  //  The ECMA/JavaScript Date object has a large number of methods.
  // "Date.parse" is danger (strongly discouraged)
  // - new Date("2014-11-10") // Mon Nov 10 2014 09:00:00 GMT+0900 (JST)
  // - new Date(2014, 10, 10) // Mon Nov 10 2014 00:00:00 GMT+0900 (JST)
  let arrDatetime = bpmsDateOrDatetimeStr.split(" ");
  if( arrDatetime.length === 1 ){
    let arrDateParts = arrDatetime[0].split("-");
    year       = parseInt(arrDateParts[0], 10);
    monthIndex = parseInt(arrDateParts[1], 10) - 1;
    day        = parseInt(arrDateParts[2], 10);
  }
  if( arrDatetime.length === 2 ){
    let arrDateParts = arrDatetime[0].split("-");
    let arrTimeParts = arrDatetime[1].split(":");
    year       = parseInt(arrDateParts[0], 10);
    monthIndex = parseInt(arrDateParts[1], 10) - 1;
    day        = parseInt(arrDateParts[2], 10);
    hours      = parseInt(arrTimeParts[0], 10);
    minutes    = parseInt(arrTimeParts[1], 10);
  }
  return new Date( year, monthIndex, day, hours, minutes );
}



/*
Notes:
- Convert datetime data using two time zone offsets.
    - Offset values are set in Hour. Decimal notation is also possible. (PST:"-8", JST:"+9")
    - https://en.wikipedia.org/wiki/Time_zone
- To customize the notification text according to the recipient's timezone, etc.
- Can be converted even in the standard automation "Update Data".
    - Setting Example of "Output Datetime" (EL syntax)
        - "#q_dtInputDatetime.addHours( #q_numOutputOffset - #q_numInputOffset )"
        - Assumption: Integer Hour is input in Numeric type data
    - M227: Auto Executing Data Binding, Arithmetic Operations
        - https://questetra.zendesk.com/hc/en-us/articles/360002260571-M227
    - R2270: Numeric Output via EL syntax
        - https://questetra.zendesk.com/hc/en-us/articles/360024292572-R2270
    - Update Data
        - https://support.questetra.com/bpmn-icons/service-task-data-assignment/

Notes-ja:
- 2つのタイムゾーンOffset値を用いて、時刻型データを変換します。
    - Offset値はHour単位で設定します。小数表記も可能です。（日本標準時: "+9" 太平洋標準時: "-8"）
    - https://ja.wikipedia.org/wiki/%E6%99%82%E9%96%93%E5%B8%AF_(%E6%A8%99%E6%BA%96%E6%99%82)
- 受信者のタイムゾーンにあわせて通知文をカスタマイズしたい場合などに。
- 標準で組み込まれている自動工程［データ更新］でも、時刻の自動変換は可能です。
    - "Output Datetime" の設定例 （EL式）
        - "#q_dtInputDatetime.addHours( #q_numOutputOffset - #q_numInputOffset )"
        - （数値型データに整数Hourが入力される前提）
    - M227: 業務データの結合や四則演算が自動実行されるように設定する
        - https://questetra.zendesk.com/hc/ja/articles/360002260571-M227
    - R2270: EL式による数値としての出力（データ設定式）
        - https://questetra.zendesk.com/hc/ja/articles/360024292572-R2270
    - データ更新
        - https://support.questetra.com/ja/bpmn-icons/service-task-data-assignment/
*/


/*
APPENDIX
- Not only Datetime type data but also process start datetime can be converted.
    - "#{#q_dtInputDatetime}"
    - "#{processInstanceStartDatetime}"
- "Date type + static hh:mm" is also acceptable. (processes the string "YYYY-MM-DD hh:mm")
    - "#{#q_date} 00:00"
- The timestamp obtained by this Addon is Unix epoch.
    - Seconds since 1 January 1970 UTC
    - Not the same as the ECMAScript epoch (elapsed Milliseconds), Unix is 1/1000 of ECMAScript

APPENDIX-ja
- 日時型データだけでなく、プロセス開始時刻等も変換できます。
    - "#{#q_dtInputDatetime}"
    - "#{processInstanceStartDatetime}"
- "日付型データ＋固定時刻文字列" による指定も可能です。（"YYYY-MM-DD hh:mm" の文字列を処理します）
    - "#{#q_date} 00:00"
    - "#{processInstanceStartDatetime}"
- このAddonによって取得されるタイムスタンプは Unix epoch （"経過秒数"）です。
    - 協定世界時 (UTC) の1970年1月1日からの経過秒数
    - Unix epoch（"経過秒数"）は ECMAScript epoch（"経過ミリ秒数"）の1000分の1となります
*/