/*
 This file is part of GNU Taler
 (C) 2021 Taler Systems S.A.

 GNU Taler is free software; you can redistribute it and/or modify it under the
 terms of the GNU General Public License as published by the Free Software
 Foundation; either version 3, or (at your option) any later version.

 GNU Taler 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 for more details.

 You should have received a copy of the GNU General Public License along with
 GNU Taler; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
 */

/**
*
* @author Sebastian Javier Marchano (sebasjm)
*/

import { h, Component } from "preact";

interface Props {
  closeFunction?: () => void;
  dateReceiver?: (d: Date) => void;
  opened?: boolean;
}
interface State {
  displayedMonth: number;
  displayedYear: number;
  selectYearMode: boolean;
  currentDate: Date;
}

// inspired by https://codepen.io/m4r1vs/pen/MOOxyE
export class DatePicker extends Component<Props, State> {

  closeDatePicker() {
    this.props.closeFunction && this.props.closeFunction(); // Function gets passed by parent
  }

  /**
  * Gets fired when a day gets clicked.
  * @param {object} e The event thrown by the <span /> element clicked
  */
  dayClicked(e: any) {

    const element = e.target; // the actual element clicked

    if (element.innerHTML === '') return false; // don't continue if <span /> empty

    // get date from clicked element (gets attached when rendered)
    const date = new Date(element.getAttribute('data-value'));

    // update the state
    this.setState({ currentDate: date });
    this.passDateToParent(date)
  }

  /**
  * returns days in month as array
  * @param {number} month the month to display
  * @param {number} year the year to display
  */
  getDaysByMonth(month: number, year: number) {

    const calendar = [];

    const date = new Date(year, month, 1); // month to display

    const firstDay = new Date(year, month, 1).getDay(); // first weekday of month
    const lastDate = new Date(year, month + 1, 0).getDate(); // last date of month

    let day: number | null = 0;

    // the calendar is 7*6 fields big, so 42 loops
    for (let i = 0; i < 42; i++) {

      if (i >= firstDay && day !== null) day = day + 1;
      if (day !== null && day > lastDate) day = null;

      // append the calendar Array
      calendar.push({
        day: (day === 0 || day === null) ? null : day, // null or number
        date: (day === 0 || day === null) ? null : new Date(year, month, day), // null or Date()
        today: (day === now.getDate() && month === now.getMonth() && year === now.getFullYear()) // boolean
      });
    }

    return calendar;
  }

  /**
  * Display previous month by updating state
  */
  displayPrevMonth() {
    if (this.state.displayedMonth <= 0) {
      this.setState({
        displayedMonth: 11,
        displayedYear: this.state.displayedYear - 1
      });
    }
    else {
      this.setState({
        displayedMonth: this.state.displayedMonth - 1
      });
    }
  }

  /**
  * Display next month by updating state
  */
  displayNextMonth() {
    if (this.state.displayedMonth >= 11) {
      this.setState({
        displayedMonth: 0,
        displayedYear: this.state.displayedYear + 1
      });
    }
    else {
      this.setState({
        displayedMonth: this.state.displayedMonth + 1
      });
    }
  }

  /**
  * Display the selected month (gets fired when clicking on the date string)
  */
  displaySelectedMonth() {
    if (this.state.selectYearMode) {
      this.toggleYearSelector();
    }
    else {
      if (!this.state.currentDate) return false;
      this.setState({
        displayedMonth: this.state.currentDate.getMonth(),
        displayedYear: this.state.currentDate.getFullYear()
      });
    }
  }

  toggleYearSelector() {
    this.setState({ selectYearMode: !this.state.selectYearMode });
  }

  changeDisplayedYear(e: any) {
    const element = e.target;
    this.toggleYearSelector();
    this.setState({ displayedYear: parseInt(element.innerHTML, 10), displayedMonth: 0 });
  }

  /**
  * Pass the selected date to parent when 'OK' is clicked
  */
  passSavedDateDateToParent() {
    this.passDateToParent(this.state.currentDate)
  }
  passDateToParent(date: Date) {
    if (typeof this.props.dateReceiver === 'function') this.props.dateReceiver(date);
    this.closeDatePicker();
  }

  componentDidUpdate() {
    if (this.state.selectYearMode) {
      document.getElementsByClassName('selected')[0].scrollIntoView(); // works in every browser incl. IE, replace with scrollIntoViewIfNeeded when browsers support it
    }
  }

  constructor() {
    super();

    this.closeDatePicker = this.closeDatePicker.bind(this);
    this.dayClicked = this.dayClicked.bind(this);
    this.displayNextMonth = this.displayNextMonth.bind(this);
    this.displayPrevMonth = this.displayPrevMonth.bind(this);
    this.getDaysByMonth = this.getDaysByMonth.bind(this);
    this.changeDisplayedYear = this.changeDisplayedYear.bind(this);
    this.passDateToParent = this.passDateToParent.bind(this);
    this.toggleYearSelector = this.toggleYearSelector.bind(this);
    this.displaySelectedMonth = this.displaySelectedMonth.bind(this);


    this.state = {
      currentDate: now,
      displayedMonth: now.getMonth(),
      displayedYear: now.getFullYear(),
      selectYearMode: false
    }
  }

  render() {

    const { currentDate, displayedMonth, displayedYear, selectYearMode } = this.state;

    return (
      <div>
        <div class={`datePicker ${  this.props.opened && "datePicker--opened"}`} >

          <div class="datePicker--titles">
            <h3 style={{
              color: selectYearMode ? 'rgba(255,255,255,.87)' : 'rgba(255,255,255,.57)'
            }} onClick={this.toggleYearSelector}>{currentDate.getFullYear()}</h3>
            <h2 style={{
              color: !selectYearMode ? 'rgba(255,255,255,.87)' : 'rgba(255,255,255,.57)'
            }} onClick={this.displaySelectedMonth}>
              {dayArr[currentDate.getDay()]}, {monthArrShort[currentDate.getMonth()]} {currentDate.getDate()}
            </h2>
          </div>

          {!selectYearMode && <nav>
            <span onClick={this.displayPrevMonth} class="icon"><i style={{ transform: 'rotate(180deg)' }} class="mdi mdi-forward" /></span>
            <h4>{monthArrShortFull[displayedMonth]} {displayedYear}</h4>
            <span onClick={this.displayNextMonth} class="icon"><i class="mdi mdi-forward" /></span>
          </nav>}

          <div class="datePicker--scroll">

            {!selectYearMode && <div class="datePicker--calendar" >

              <div class="datePicker--dayNames">
                {['S', 'M', 'T', 'W', 'T', 'F', 'S'].map((day,i) => <span key={i}>{day}</span>)}
              </div>

              <div onClick={this.dayClicked} class="datePicker--days">

                {/*
                  Loop through the calendar object returned by getDaysByMonth().
                */}

                {this.getDaysByMonth(this.state.displayedMonth, this.state.displayedYear)
                  .map(
                    day => {
                      let selected = false;

                      if (currentDate && day.date) selected = (currentDate.toLocaleDateString() === day.date.toLocaleDateString());

                      return (<span key={day.day}
                        class={(day.today ? 'datePicker--today ' : '') + (selected ? 'datePicker--selected' : '')}
                        disabled={!day.date}
                        data-value={day.date}
                      >
                        {day.day}
                      </span>)
                    }
                  )
                }

              </div>

            </div>}

            {selectYearMode && <div class="datePicker--selectYear">

              {yearArr.map(year => (
                <span key={year} class={(year === displayedYear) ? 'selected' : ''} onClick={this.changeDisplayedYear}>
                  {year}
                </span>
              ))}

            </div>}

          </div>
        </div>

        <div class="datePicker--background" onClick={this.closeDatePicker} style={{
          display: this.props.opened ? 'block' : 'none'
        }}
        />

      </div>
    )
  }
}


const monthArrShortFull = [
  'January',
  'February',
  'March',
  'April',
  'May',
  'June',
  'July',
  'August',
  'September',
  'October',
  'November',
  'December'
]

const monthArrShort = [
  'Jan',
  'Feb',
  'Mar',
  'Apr',
  'May',
  'Jun',
  'Jul',
  'Aug',
  'Sep',
  'Oct',
  'Nov',
  'Dec'
]

const dayArr = [
  'Sun',
  'Mon',
  'Tue',
  'Wed',
  'Thu',
  'Fri',
  'Sat'
]

const now = new Date()

const yearArr: number[] = []

for (let i = 2010; i <= now.getFullYear() + 10; i++) {
  yearArr.push(i);
}