import { eventBus } from '../core/EventBus';
import { calendarConfig } from '../core/CalendarConfig';
import { CalendarTypeFactory } from '../factories/CalendarTypeFactory';
import { CoreEvents } from '../constants/CoreEvents';
import { HeaderRenderContext } from '../renderers/HeaderRenderer';
import { ResourceCalendarData } from '../types/CalendarTypes';

/**
 * HeaderManager - Handles all header-related event logic
 * Separates event handling from rendering concerns
 */
export class HeaderManager {
  private headerEventListener: ((event: Event) => void) | null = null;
  private headerMouseLeaveListener: ((event: Event) => void) | null = null;
  private cachedCalendarHeader: HTMLElement | null = null;

  constructor() {
    // Bind methods for event listeners
    this.setupHeaderDragListeners = this.setupHeaderDragListeners.bind(this);
    this.destroy = this.destroy.bind(this);
    
    // Listen for navigation events to update header
    this.setupNavigationListener();
  }

  /**
   * Initialize header with initial date
   */
  public initializeHeader(currentDate: Date, resourceData: ResourceCalendarData | null = null): void {
    this.updateHeader(currentDate, resourceData);
  }

  /**
   * Get cached calendar header element
   */
  private getCalendarHeader(): HTMLElement | null {
    if (!this.cachedCalendarHeader) {
      this.cachedCalendarHeader = document.querySelector('swp-calendar-header');
    }
    return this.cachedCalendarHeader;
  }

  /**
   * Setup header drag event listeners
   */
  public setupHeaderDragListeners(): void {
    const calendarHeader = this.getCalendarHeader();
    if (!calendarHeader) return;

    // Clean up existing listeners first
    this.removeEventListeners();

    // Throttle for better performance
    let lastEmitTime = 0;
    const throttleDelay = 16; // ~60fps

    this.headerEventListener = (event: Event) => {
      const now = Date.now();
      if (now - lastEmitTime < throttleDelay) {
        return; // Throttle events for better performance
      }
      lastEmitTime = now;

      const target = event.target as HTMLElement;
      
      // Optimized element detection - handle day headers and all-day columns
      const dayHeader = target.closest('swp-day-header');
      const allDayColumn = target.closest('swp-allday-column');
      
      if (dayHeader || allDayColumn) {
        const hoveredElement = (dayHeader || allDayColumn) as HTMLElement;
        const targetDate = hoveredElement.dataset.date;
        
        // Get header renderer for coordination
        const calendarType = calendarConfig.getCalendarMode();
        const headerRenderer = CalendarTypeFactory.getHeaderRenderer(calendarType);
        
        eventBus.emit('header:mouseover', {
          element: hoveredElement,
          targetDate,
          headerRenderer
        });
      }
    };

    // Header mouseleave listener
    this.headerMouseLeaveListener = (event: Event) => {
      eventBus.emit('header:mouseleave', {
        element: event.target as HTMLElement
      });
    };

    // Add event listeners
    calendarHeader.addEventListener('mouseover', this.headerEventListener);
    calendarHeader.addEventListener('mouseleave', this.headerMouseLeaveListener);
  }

  /**
   * Remove event listeners from header
   */
  private removeEventListeners(): void {
    const calendarHeader = this.getCalendarHeader();
    if (!calendarHeader) return;

    if (this.headerEventListener) {
      calendarHeader.removeEventListener('mouseover', this.headerEventListener);
    }
    
    if (this.headerMouseLeaveListener) {
      calendarHeader.removeEventListener('mouseleave', this.headerMouseLeaveListener);
    }
  }

  /**
   * Setup navigation event listener
   */
  private setupNavigationListener(): void {
    eventBus.on(CoreEvents.NAVIGATION_COMPLETED, (event) => {
      const { currentDate, resourceData } = (event as CustomEvent).detail;
      this.updateHeader(currentDate, resourceData);
    });

    // Also listen for date changes (including initial setup)
    eventBus.on(CoreEvents.DATE_CHANGED, (event) => {
      const { currentDate } = (event as CustomEvent).detail;
      this.updateHeader(currentDate, null);
    });

    // Listen for workweek header updates after grid rebuild
    eventBus.on('workweek:header-update', (event) => {
      const { currentDate } = (event as CustomEvent).detail;
      this.clearCache(); // Clear cache since DOM was cleared
      this.updateHeader(currentDate, null);
    });

  }

  /**
   * Update header content for navigation
   */
  private updateHeader(currentDate: Date, resourceData: ResourceCalendarData | null = null): void {
    const calendarHeader = this.getOrCreateCalendarHeader();
    if (!calendarHeader) return;

    // Clear existing content
    calendarHeader.innerHTML = '';

    // Render new header content
    const calendarType = calendarConfig.getCalendarMode();
    const headerRenderer = CalendarTypeFactory.getHeaderRenderer(calendarType);
    
    const context: HeaderRenderContext = {
      currentWeek: currentDate,
      config: calendarConfig,
      resourceData: resourceData
    };

    headerRenderer.render(calendarHeader, context);

    // Re-setup event listeners
    this.setupHeaderDragListeners();

    // Notify other managers that header was rebuilt
    eventBus.emit('header:rebuilt', {
      headerElement: calendarHeader
    });
  }

  /**
   * Get or create calendar header element
   */
  private getOrCreateCalendarHeader(): HTMLElement | null {
    let calendarHeader = this.getCalendarHeader();
    
    if (!calendarHeader) {
      // Find grid container and create header
      const gridContainer = document.querySelector('swp-grid-container');
      if (gridContainer) {
        calendarHeader = document.createElement('swp-calendar-header');
        // Insert header as first child
        gridContainer.insertBefore(calendarHeader, gridContainer.firstChild);
        this.cachedCalendarHeader = calendarHeader;
      }
    }
    
    return calendarHeader;
  }

  /**
   * Clear cached header reference
   */
  public clearCache(): void {
    this.cachedCalendarHeader = null;
  }

  /**
   * Clean up resources and event listeners
   */
  public destroy(): void {
    this.removeEventListeners();
    
    // Clear references
    this.headerEventListener = null;
    this.headerMouseLeaveListener = null;
    
    this.clearCache();
  }
}