Calendar/src/managers/ScrollManager.ts

// Custom scroll management for calendar week container

import { eventBus } from '../core/EventBus';
import { calendarConfig } from '../core/CalendarConfig';
import { EventTypes } from '../constants/EventTypes';

/**
 * Manages scrolling functionality for the calendar using native scrollbars
 */
export class ScrollManager {
  private scrollableContent: HTMLElement | null = null;
  private calendarContainer: HTMLElement | null = null;
  private timeAxis: HTMLElement | null = null;
  private calendarHeader: HTMLElement | null = null;
  private resizeObserver: ResizeObserver | null = null;

  constructor() {
    this.init();
  }

  private init(): void {
    this.subscribeToEvents();
  }

  /**
   * Public method to initialize scroll after grid is rendered
   */
  public initialize(): void {
    this.setupScrolling();
  }

  private subscribeToEvents(): void {
    // Handle navigation animation completion - sync time axis position
    eventBus.on(EventTypes.NAVIGATION_ANIMATION_COMPLETE, () => {
      this.syncTimeAxisPosition();
      this.setupScrolling();
    });

    
    // Handle window resize
    window.addEventListener('resize', () => {
      this.updateScrollableHeight();
    });
  }

  /**
   * Setup scrolling functionality after grid is rendered
   */
  private setupScrolling(): void {
    this.findElements();
    
    if (this.scrollableContent && this.calendarContainer) {
      this.setupResizeObserver();
      this.updateScrollableHeight();
      this.setupScrollSynchronization();
    }

    // Setup horizontal scrolling synchronization
    if (this.scrollableContent && this.calendarHeader) {
      this.setupHorizontalScrollSynchronization();
    }
  }

  /**
   * Find DOM elements needed for scrolling
   */
  private findElements(): void {
    this.scrollableContent = document.querySelector('swp-scrollable-content');
    this.calendarContainer = document.querySelector('swp-calendar-container');
    this.timeAxis = document.querySelector('swp-time-axis');
    this.calendarHeader = document.querySelector('swp-calendar-header');
   
  }

  /**
   * Scroll to specific position
   */
  scrollTo(scrollTop: number): void {
    if (!this.scrollableContent) return;
    
    this.scrollableContent.scrollTop = scrollTop;
  }

  /**
   * Scroll to specific hour
   */
  scrollToHour(hour: number): void {
    const gridSettings = calendarConfig.getGridSettings();
    const hourHeight = gridSettings.hourHeight;
    const dayStartHour = gridSettings.dayStartHour;
    const scrollTop = (hour - dayStartHour) * hourHeight;
    
    this.scrollTo(scrollTop);
  }

  /**
   * Setup ResizeObserver to monitor container size changes
   */
  private setupResizeObserver(): void {
    if (!this.calendarContainer) return;

    // Clean up existing observer
    if (this.resizeObserver) {
      this.resizeObserver.disconnect();
    }

    this.resizeObserver = new ResizeObserver((entries) => {
      for (const entry of entries) {
        this.updateScrollableHeight();
      }
    });

    this.resizeObserver.observe(this.calendarContainer);
  }

  /**
   * Calculate and update scrollable content height dynamically
   */
  private updateScrollableHeight(): void {
    if (!this.scrollableContent || !this.calendarContainer) return;

    // Get calendar container height
    const containerRect = this.calendarContainer.getBoundingClientRect();
    
    // Find navigation height
    const navigation = document.querySelector('swp-calendar-nav');
    const navHeight = navigation ? navigation.getBoundingClientRect().height : 0;
    
    // Find calendar header height
    const calendarHeaderElement = document.querySelector('swp-calendar-header');
    const headerHeight = calendarHeaderElement ? calendarHeaderElement.getBoundingClientRect().height : 80;
    
    // Calculate available height for scrollable content
    const availableHeight = containerRect.height - headerHeight;
    
    // Calculate available width (container width minus time-axis)
    const availableWidth = containerRect.width - 60; // 60px time-axis
    
    // Set the height and width on scrollable content
    if (availableHeight > 0) {
      this.scrollableContent.style.height = `${availableHeight}px`;
    }
    if (availableWidth > 0) {
      this.scrollableContent.style.width = `${availableWidth}px`;
    }
  }

  /**
   * Setup scroll synchronization between scrollable content and time axis
   */
  private setupScrollSynchronization(): void {
    if (!this.scrollableContent || !this.timeAxis) return;

    // Throttle scroll events for better performance
    let scrollTimeout: number | null = null;

    this.scrollableContent.addEventListener('scroll', () => {
      if (scrollTimeout) {
        cancelAnimationFrame(scrollTimeout);
      }

      scrollTimeout = requestAnimationFrame(() => {
        this.syncTimeAxisPosition();
      });
    });
  }

  /**
   * Synchronize time axis position with scrollable content
   */
  private syncTimeAxisPosition(): void {
    if (!this.scrollableContent || !this.timeAxis) return;

    const scrollTop = this.scrollableContent.scrollTop;
    const timeAxisContent = this.timeAxis.querySelector('swp-time-axis-content');
    
    if (timeAxisContent) {
      // Use transform for smooth performance
      (timeAxisContent as HTMLElement).style.transform = `translateY(-${scrollTop}px)`;
      
      // Debug logging (can be removed later)
      if (scrollTop % 100 === 0) { // Only log every 100px to avoid spam
      }
    }
  }

  /**
   * Setup horizontal scroll synchronization between scrollable content and calendar header
   */
  private setupHorizontalScrollSynchronization(): void {
    if (!this.scrollableContent || !this.calendarHeader) return;


    // Listen to horizontal scroll events
    this.scrollableContent.addEventListener('scroll', () => {
      this.syncCalendarHeaderPosition();
    });
  }

  /**
   * Synchronize calendar header position with scrollable content horizontal scroll
   */
  private syncCalendarHeaderPosition(): void {
    if (!this.scrollableContent || !this.calendarHeader) return;

    const scrollLeft = this.scrollableContent.scrollLeft;
    
    // Use transform for smooth performance
    this.calendarHeader.style.transform = `translateX(-${scrollLeft}px)`;
    
    // Debug logging (can be removed later)
    if (scrollLeft % 100 === 0) { // Only log every 100px to avoid spam
    }
  }

  /**
   * Cleanup resources
   */
  destroy(): void {
    if (this.resizeObserver) {
      this.resizeObserver.disconnect();
      this.resizeObserver = null;
    }
  }
}