import { Component, EventEmitter, Inject, Input, LOCALE_ID, Output } from '@angular/core';

import * as dateFns from 'date-fns';

@Component({
    selector: 'novo-calendar-date-change',
    template: `
    <div class="cal-date-change">
        <i class="bhi-arrow-left" (click)="subtractDate()" ></i>
        <span [ngSwitch]="view">
            <span *ngSwitchCase="'month'">{{ ( viewDate | month:locale ) + ' ' + ( viewDate | year:locale ) }}</span>
            <span *ngSwitchCase="'week'">{{ ( startOfWeek | monthday:locale:'long' ) + ' - ' + ( endOfWeek | endofweekdisplay:startOfWeek:locale:'long' ) }}</span>
            <span *ngSwitchCase="'day'">{{ ( viewDate | weekday:locale:'long' ) + ', ' + ( viewDate | month:locale ) + ' ' + ( viewDate | dayofmonth:locale ) }}</span>
        </span>
        <i class="bhi-arrow-right" (click)="addDate()"></i>
    </div>
  `
})
export class NovoCalendarDateChangeElement {

    /**
     * The current view
     */
    @Input() view: string;

    /**
     * The current view date
     */
    @Input() viewDate: Date;

    @Input() locale: string;

    /**
     * Called when the view date is changed
     */
    @Output() viewDateChange: EventEmitter<Date> = new EventEmitter();

    constructor( @Inject(LOCALE_ID) locale: string) {
        this.locale = locale;
    }

    /**
     * @hidden
     */
    subtractDate(): void {
        this.changeDate(-1);
    }

    addDate(): void {
        this.changeDate(1);
    }

    changeDate(unit: number): void {
        const addFn: any = {
            day: dateFns.addDays,
            week: dateFns.addWeeks,
            month: dateFns.addMonths
        }[this.view];

        this.viewDateChange.emit(addFn(this.viewDate, unit));
    }

    get startOfWeek() {
        return dateFns.startOfWeek(this.viewDate);
    }

    get endOfWeek() {
        return dateFns.endOfWeek(this.viewDate);
    }

}