///
/// Copyright 2015-2026 Micro Focus or one of its affiliates.
///
/// 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.
///

import { inject, Injectable, OnDestroy } from '@angular/core';
import { BehaviorSubject, Subscription } from 'rxjs';
import {
  DatePickerHeaderEvent,
  DateTimePickerService,
  YearRange,
} from '../date-time-picker.service';
import { gridify, range } from '../date-time-picker.utils';

@Injectable()
export class YearViewService implements OnDestroy {
  private readonly _datepicker = inject(DateTimePickerService);

  grid$ = new BehaviorSubject<YearViewItem[][]>([[]]);
  focused$ = new BehaviorSubject<number>(null);

  private _year: number = new Date().getFullYear();

  private readonly _subscription = new Subscription();

  constructor() {
    const year = this._datepicker.year$.subscribe(_year => this.createYearGrid(_year));

    const event = this._datepicker.headerEvent$.subscribe(_event =>
      _event === DatePickerHeaderEvent.Next ? this.goToNextDecade() : this.goToPreviousDecade()
    );

    this._subscription.add(year);
    this._subscription.add(event);
  }

  ngOnDestroy(): void {
    this._subscription.unsubscribe();
  }

  setFocus(year: number): void {
    this.focused$.next(year);
    this.createYearGrid(year);
  }

  goToPreviousDecade(): void {
    this.createYearGrid(this._year - 10);
  }

  goToNextDecade(): void {
    this.createYearGrid(this._year + 10);
  }

  private createYearGrid(year: number = this._year): void {
    this._year = year;

    // get the years to display
    const decade = this.getDecade(year);

    const currentYear = new Date().getFullYear();

    // produce items in the correct format
    const items: YearViewItem[] = decade.range.map(_year => {
      return {
        year: _year,
        isCurrentYear: _year === currentYear,
        isActiveYear: _year === this._datepicker.year$.value,
      };
    });

    // update the header text
    this._datepicker.setHeader(decade.start + ' - ' + decade.end);

    // create the grid
    this.grid$.next(gridify(items, 4));
  }

  /**
   * Get the years in the current decade to display
   */
  private getDecade(year: number): YearRange {
    // figure the start and end points
    const start = year - (year % 10);
    const end = start + 9;

    this._datepicker.yearRange = { start, end, range: range(start, end) };

    // create an array containing all the numbers between the start and end points
    return this._datepicker.yearRange;
  }
}

export interface YearViewItem {
  year: number;
  isCurrentYear: boolean;
  isActiveYear: boolean;
}