/**
@license
Copyright (c) 2022 trading_peter
This program is available under Apache License Version 2.0
*/

import '@tp/tp-icon/tp-icon.js';
import { FormElement } from '@tp/helpers/form-element';
import { LitElement, html, css, svg } from 'lit';
import { zonedTimeToUtc } from 'date-fns-tz';

class TpDatePicker extends FormElement(LitElement) {
  static get styles() {
    return [
      css`
        :host {
          display: block;
        }

        .header {
          display: grid;
          grid-template-columns: 1fr 1fr;
          align-items: center;
        }

        .header > div {
          display: flex;
          align-items: center;
          justify-content: space-around;
          padding: 5px 10px;
        }

        .header > div > div {
          display: flex;
          align-items: center;
        }

        .right {
          display: flex;
          justify-content: end;
        }

        .grid {
          display: grid;
          grid-template-columns: repeat(7, 1fr);
          grid-template-rows: repeat(7, 1fr);
        }

        .grid > div {
          display: flex;
          align-items: center;
          justify-content: center;
          min-width: 42px;
          height: 42px;
          padding: 2px;
        }

        .day {
          font-weight: bold;
        }

        div[part~="filler"] {
          opacity: 0.5;
        }

        .year-overlay {
          display: grid;
          grid-template-columns: 1fr;
          grid-row-gap: 5px;
          position: absolute;
          inset: 0;
          overflow: auto;
          background: white;
          opacity: 0;
          transition: 300ms opacity ease-in-out;
          pointer-events: none;
        }

        .year-overlay[visible] {
          opacity: 1;
          pointer-events: all;
        }

        .year-overlay > div {
          text-align: center;
          cursor: pointer;
        }

        .year-overlay > div:hover {
          background: var(--date-picker-hover-color);
        }

        .number {
          width: 40px;
          height: 40px;
          border-radius: 40px;
          display: flex;
          align-items: center;
          justify-content: center;
        }

        .number:hover,
        .number[part~="selected"] {
          background: var(--tp-datepicker-day-hover-bg, #fff);
          color: var(--tp-datepicker-day-hover-color, #000);
          cursor: pointer;
        }

        .number[part~="today"] {
          background: var(--tp-datepicker-today-bg, #fff);
          color: var(--tp-datepicker-today-color, #000);
        }

        .pointer {
          cursor: pointer;
        }
      `
    ];
  }

  render() {
    let { month, year, dayNames, value, yearsForward, yearsBackwards } = this;

    const today = new Date();

    if ((!month && month !== 0) || (!year && year !== 0)) {
      month = today.getMonth();
      year = today.getFullYear();
    }

    const years = Array(yearsForward + yearsBackwards).fill().map((_, i) => today.getFullYear()-yearsBackwards+i).reverse();
    const curMonth = this.getMonthDates(month, year);

    return html`
      <div class="header">
        <div>
          <div>
            <tp-icon .icon=${TpDatePicker.iconPrev} @click=${() => this.previousMonth()}></tp-icon>
          </div>
          <div>${this.monthNames[month]}</div>
          <div class="right">
            <tp-icon .icon=${TpDatePicker.iconNext} @click=${() => this.nextMonth()}></tp-icon>
          </div>
        </div>
        <div>
          <div>
            <tp-icon .icon=${TpDatePicker.iconPrev} @click=${() => this.previousYear()}></tp-icon>
          </div>
          <div class="pointer" @click=${this.showYearOverlay}>${year}</div>
          <div class="right">
            <tp-icon .icon=${TpDatePicker.iconNext} @click=${() => this.nextYear()}></tp-icon>
          </div>
        </div>
      </div>
      <div class="grid" @click=${e => this.selectDate(e)}>
        ${dayNames.map(label => html`
          <div class="day" part="day">${label}</div>
        `)}
        ${curMonth.map(d => {
          const matchesValue = this.equalDate(d, value);
          const isToday = this.equalDate(d, today);
          return html`
            <div .date=${d} part="date ${d.getMonth() !== month ? 'filler' : 'of-month'}"><div class="number" part="number ${matchesValue ? 'selected' : ''} ${isToday ? 'today' : ''} ${d.getMonth() === month ? 'of-month' : ''}">${d.getDate()}</div></div>
          `
        })}
      </div>
      <div class="year-overlay" ?visible=${this.showYearSelector} @click=${this.selectYear}>
        ${years.map(y => html`
          <div .value=${y}>${y}</div>
        `)}
      </div>
    `;
  }

  static get properties() {
    return {
      value: { type: Date },
      today: { type: Date },
      month: { type: Number },
      year: { type: Number },
      monthNames: { type: Array },
      dayNames: { type: Array },
      timeZone: { type: String },
      yearsForward: { type: Number },
      yearsBackwards: { type: Number },
      showYearSelector: { type: Boolean },
    };
  }

  static get iconNext() {
    return svg`
      <path fill="var(--tp-icon-color)" d="M8.59,16.58L13.17,12L8.59,7.41L10,6L16,12L10,18L8.59,16.58Z" />
    `
  }

  static get iconPrev() {
    return svg`
      <path fill="var(--tp-icon-color)" d="M15.41,16.58L10.83,12L15.41,7.41L14,6L8,12L14,18L15.41,16.58Z" />
    `
  }

  constructor() {
    super();

    this.today = new Date();
    this.month = this.today.getMonth();
    this.year = this.today.getFullYear();
    this.yearsForward = 10;
    this.yearsBackwards = 100;

    this.dayNames = [
      'Mo',
      'Tue',
      'Wed',
      'Th',
      'Fr',
      'Sat',
      'Sun',
    ];

    this.monthNames = [
      'January',
      'February',
      'March',
      'April',
      'May',
      'June',
      'July',
      'August',
      'September',
      'October',
      'November',
      'December'
    ]
  }

  shouldUpdate(changes) {
    if (changes.has('value')) {
      this.month = this.value.getMonth();
      this.year = this.value.getFullYear();
    }

    return true;
  }

  equalDate(d, value) {
    if (!value) return false;
    return d.getDate() === value.getDate() && d.getFullYear() === value.getFullYear() && d.getMonth() === value.getMonth();
  }

  selectDate(e) {
    for (const el of e.composedPath()) {
      if (el.date !== undefined) {
        this.value = this.timeZone ? zonedTimeToUtc(el.date, this.timeZone) : el.date;
        this.dispatchEvent(new CustomEvent('value-changed', { detail: this.value, bubbles: true, composed: true }));
        return;
      }
    }
  }

  previousMonth() {
    let prevYear = this.year;
    let prevMonth = this.month - 1;

    if (prevMonth < 0) {
      prevYear -= 1;
      prevMonth = 11;
    }

    this.month = prevMonth;
    this.year = prevYear;
  }

  nextMonth() {
    let nextYear = this.year;
    let nextMonth = this.month + 1;

    if (nextMonth > 11) {
      nextYear += 1;
      nextMonth = 0;
    }

    this.month = nextMonth;
    this.year = nextYear;
  }

  previousYear() {
    this.year -= 1;
  }

  nextYear() {
    this.year += 1;
  }

  getMonthDates(month = null, year = null) {
    month = month !== null ? month : new Date().getMonth();
    year = year || new Date().getFullYear();

    const firstOfMonth = new Date();
    firstOfMonth.setFullYear(year);
    firstOfMonth.setMonth(month);
    firstOfMonth.setDate(1);
    firstOfMonth.setHours(0);
    firstOfMonth.setMinutes(0);
    firstOfMonth.setSeconds(0);

    const lastOfMonth = new Date();
    lastOfMonth.setDate(1);
    lastOfMonth.setFullYear(year);
    lastOfMonth.setMonth(month + 1);
    lastOfMonth.setDate(lastOfMonth.getDate() - 1);
    lastOfMonth.setHours(0);
    lastOfMonth.setMinutes(0);
    lastOfMonth.setSeconds(0);

    const dates = [];

    while (firstOfMonth.getDay() > 1) {
      firstOfMonth.setDate(firstOfMonth.getDate() - 1);
      dates.push(new Date(firstOfMonth));
    }

    dates.reverse();

    for (let i = 1; i <= lastOfMonth.getDate(); ++i) {
      const d = new Date();
      d.setFullYear(year);
      d.setMonth(month);
      d.setDate(i);
      d.setHours(0);
      d.setMinutes(0);
      d.setSeconds(0);
      dates.push(d);
    }

    // Make sure we always fill 42 date get guarantee equal size of the date picker.
    while (dates.length < 42) {
      lastOfMonth.setDate(lastOfMonth.getDate() + 1);
      dates.push(new Date(lastOfMonth));
    }

    return dates;
  }

  showYearOverlay() {
    this.showYearSelector = true;
  }

  selectYear(e) {
    const elList = e.composedPath();
    elList.forEach(el => {
      if (el.value) {
        this.year = el.value;
        this.showYearSelector = false;
      }
    });
  }
}

window.customElements.define('tp-date-picker', TpDatePicker);