import {
  DatepickerFormatOptions,
  YearsCalendarViewModel,
  CalendarCellViewModel
} from '../models';
import { shiftDate, formatDate } from 'ngx-bootstrap/chronos';
import { createMatrix } from '../utils/matrix-utils';

const height = 4;
const width = 4;
export const yearsPerCalendar = height * width;
export const initialYearShift = (Math.floor(yearsPerCalendar / 2) - 1) * -1;
const shift = { year: 1 };

export function formatYearsCalendar(
  viewDate: Date,
  formatOptions: DatepickerFormatOptions,
  previousInitialDate?: Date
): YearsCalendarViewModel {
  const initialDate = calculateInitialDate(viewDate, previousInitialDate);
  const matrixOptions = { width, height, initialDate, shift };
  const yearsMatrix = createMatrix<
    CalendarCellViewModel
  >(matrixOptions, date => ({
    date,
    label: formatDate(date, formatOptions.yearLabel, formatOptions.locale)
  }));
  const yearTitle = formatYearRangeTitle(yearsMatrix, formatOptions);

  return {
    years: yearsMatrix,
    monthTitle: '',
    yearTitle,
    hideLeftArrow: false,
    hideRightArrow: false,
    disableLeftArrow: false,
    disableRightArrow: false
  };
}

function calculateInitialDate(viewDate: Date, previousInitialDate?: Date): Date {
  if (previousInitialDate
    && viewDate.getFullYear() >= previousInitialDate.getFullYear()
    && viewDate.getFullYear() < previousInitialDate.getFullYear() + yearsPerCalendar) {
    return previousInitialDate;
  }

  return shiftDate(viewDate, { year: initialYearShift });
}

function formatYearRangeTitle(
  yearsMatrix: CalendarCellViewModel[][],
  formatOptions: DatepickerFormatOptions
): string {
  const from = formatDate(
    yearsMatrix[0][0].date,
    formatOptions.yearTitle,
    formatOptions.locale
  );
  const to = formatDate(
    yearsMatrix[height - 1][width - 1].date,
    formatOptions.yearTitle,
    formatOptions.locale
  );

  return `${from} - ${to}`;
}