import { IEventBus, CalendarView } from '../types/CalendarTypes';
import { CoreEvents } from '../constants/CoreEvents';
import { DateService } from '../utils/DateService';
import { Configuration } from '../configurations/CalendarConfig';

/**
 * NavigationButtons - Manages navigation button UI and navigation logic
 *
 * RESPONSIBILITY:
 * ===============
 * This manager owns all logic related to the <swp-nav-group> UI element
 * and performs the actual navigation calculations.
 *
 * RESPONSIBILITIES:
 * - Handles button clicks on swp-nav-button elements
 * - Validates navigation actions (prev, next, today)
 * - Calculates next/previous dates based on current view
 * - Emits NAVIGATION_COMPLETED events with new date
 * - Manages button UI listeners
 *
 * EVENT FLOW:
 * ===========
 * User clicks button → calculateNewDate() → emit NAVIGATION_COMPLETED → GridManager re-renders
 */
export class NavigationButtons {
  private eventBus: IEventBus;
  private buttonListeners: Map<Element, EventListener> = new Map();
  private dateService: DateService;
  private config: Configuration;
  private currentDate: Date = new Date();
  private currentView: CalendarView = 'week';

  constructor(
    eventBus: IEventBus,
    dateService: DateService,
    config: Configuration
  ) {
    this.eventBus = eventBus;
    this.dateService = dateService;
    this.config = config;
    this.setupButtonListeners();
    this.subscribeToEvents();
  }

  /**
   * Subscribe to events
   */
  private subscribeToEvents(): void {
    // Listen for view changes
    this.eventBus.on(CoreEvents.VIEW_CHANGED, (e: Event) => {
      const detail = (e as CustomEvent).detail;
      this.currentView = detail.currentView;
    });
  }

  /**
   * Setup click listeners on all navigation buttons
   */
  private setupButtonListeners(): void {
    const buttons = document.querySelectorAll('swp-nav-button[data-action]');

    buttons.forEach(button => {
      const clickHandler = (event: Event) => {
        event.preventDefault();
        const action = button.getAttribute('data-action');
        if (action && this.isValidAction(action)) {
          this.handleNavigation(action);
        }
      };

      button.addEventListener('click', clickHandler);
      this.buttonListeners.set(button, clickHandler);
    });
  }

  /**
   * Handle navigation action
   */
  private handleNavigation(action: string): void {
    switch (action) {
      case 'prev':
        this.navigatePrevious();
        break;
      case 'next':
        this.navigateNext();
        break;
      case 'today':
        this.navigateToday();
        break;
    }
  }

  /**
   * Navigate in specified direction
   */
  private navigate(direction: 'next' | 'prev'): void {
    const offset = direction === 'next' ? 1 : -1;
    let newDate: Date;

    switch (this.currentView) {
      case 'week':
        newDate = this.dateService.addWeeks(this.currentDate, offset);
        break;
      case 'month':
        newDate = this.dateService.addMonths(this.currentDate, offset);
        break;
      case 'day':
        newDate = this.dateService.addDays(this.currentDate, offset);
        break;
      default:
        newDate = this.dateService.addWeeks(this.currentDate, offset);
    }

    this.currentDate = newDate;

    this.eventBus.emit(CoreEvents.NAVIGATION_COMPLETED, {
      direction: direction === 'next' ? 'next' : 'previous',
      newDate: newDate,
      periodLabel: this.getCurrentPeriodLabel()
    });
  }

  /**
   * Navigate to next period
   */
  private navigateNext(): void {
    this.navigate('next');
  }

  /**
   * Navigate to previous period
   */
  private navigatePrevious(): void {
    this.navigate('prev');
  }

  /**
   * Navigate to today
   */
  private navigateToday(): void {
    this.currentDate = new Date();

    this.eventBus.emit(CoreEvents.NAVIGATION_COMPLETED, {
      direction: 'today',
      newDate: this.currentDate,
      periodLabel: this.getCurrentPeriodLabel()
    });
  }

  /**
   * Get ISO week start (Monday)
   */
  private getISOWeekStart(date: Date): Date {
    const weekBounds = this.dateService.getWeekBounds(date);
    return this.dateService.startOfDay(weekBounds.start);
  }

  /**
   * Get week end (Sunday)
   */
  private getWeekEnd(date: Date): Date {
    const weekBounds = this.dateService.getWeekBounds(date);
    return this.dateService.endOfDay(weekBounds.end);
  }

  /**
   * Get current period label
   */
  private getCurrentPeriodLabel(): string {
    switch (this.currentView) {
      case 'week':
      case 'day':
        const weekStart = this.getISOWeekStart(this.currentDate);
        const weekEnd = this.getWeekEnd(this.currentDate);
        return this.dateService.formatDateRange(weekStart, weekEnd);
      case 'month':
        return this.dateService.formatMonthYear(this.currentDate);
      default:
        const defaultWeekStart = this.getISOWeekStart(this.currentDate);
        const defaultWeekEnd = this.getWeekEnd(this.currentDate);
        return this.dateService.formatDateRange(defaultWeekStart, defaultWeekEnd);
    }
  }

  /**
   * Validate if string is a valid navigation action
   */
  private isValidAction(action: string): boolean {
    return ['prev', 'next', 'today'].includes(action);
  }
}