Calendar/src/renderers/EventRenderer.ts

// Event rendering strategy interface and implementations

import { CalendarEvent } from '../types/CalendarTypes';
import { calendarConfig } from '../core/CalendarConfig';
import { SwpEventElement } from '../elements/SwpEventElement';
import { PositionUtils } from '../utils/PositionUtils';
import { ColumnBounds } from '../utils/ColumnDetectionUtils';
import { DragColumnChangeEventPayload, DragMoveEventPayload, DragStartEventPayload } from '../types/EventTypes';
import { DateService } from '../utils/DateService';

/**
 * Interface for event rendering strategies
 */
export interface EventRendererStrategy {
  renderEvents(events: CalendarEvent[], container: HTMLElement): void;
  clearEvents(container?: HTMLElement): void;
  handleDragStart?(payload: DragStartEventPayload): void;
  handleDragMove?(payload: DragMoveEventPayload): void;
  handleDragAutoScroll?(eventId: string, snappedY: number): void;
  handleDragEnd?(eventId: string, originalElement: HTMLElement, draggedClone: HTMLElement, finalColumn: ColumnBounds, finalY: number): void;
  handleEventClick?(eventId: string, originalElement: HTMLElement): void;
  handleColumnChange?(payload: DragColumnChangeEventPayload): void;
  handleNavigationCompleted?(): void;
}

/**
 * Date-based event renderer
 */
export class DateEventRenderer implements EventRendererStrategy {

  private dateService: DateService;
  private draggedClone: HTMLElement | null = null;
  private originalEvent: HTMLElement | null = null;

  constructor() {
    const timezone = calendarConfig.getTimezone?.();
    this.dateService = new DateService(timezone);
  }
 
  private applyDragStyling(element: HTMLElement): void {
    element.classList.add('dragging');
    element.style.removeProperty("margin-left");
  }


  /**
   * Update clone timestamp based on new position
   */
  private updateCloneTimestamp(payload: DragMoveEventPayload): void {
    if (payload.draggedClone.dataset.allDay === "true" || !payload.columnBounds) return;

    const gridSettings = calendarConfig.getGridSettings();
    const { hourHeight, dayStartHour, snapInterval } = gridSettings;
    
    if (!payload.draggedClone.dataset.originalDuration) {
      throw new DOMException("missing clone.dataset.originalDuration");
    }

    // Calculate snapped start minutes
    const minutesFromGridStart = (payload.snappedY / hourHeight) * 60;
    const snappedStartMinutes = this.calculateSnappedMinutes(
      minutesFromGridStart, dayStartHour, snapInterval
    );

    // Calculate end minutes
    const originalDuration = parseInt(payload.draggedClone.dataset.originalDuration);
    const endTotalMinutes = snappedStartMinutes + originalDuration;

    // Update UI
    this.updateTimeDisplay(payload.draggedClone, snappedStartMinutes, endTotalMinutes);
    
    // Update data attributes
    this.updateDateTimeAttributes(
      payload.draggedClone,
      new Date(payload.columnBounds.date),
      snappedStartMinutes,
      endTotalMinutes
    );
  }

  /**
   * Calculate snapped minutes from grid start
   */
  private calculateSnappedMinutes(minutesFromGridStart: number, dayStartHour: number, snapInterval: number): number {
    const actualStartMinutes = (dayStartHour * 60) + minutesFromGridStart;
    return Math.round(actualStartMinutes / snapInterval) * snapInterval;
  }

  /**
   * Update time display in the UI
   */
  private updateTimeDisplay(element: HTMLElement, startMinutes: number, endMinutes: number): void {
    const timeElement = element.querySelector('swp-event-time');
    if (!timeElement) return;

    const startTime = this.formatTimeFromMinutes(startMinutes);
    const endTime = this.formatTimeFromMinutes(endMinutes);
    timeElement.textContent = `${startTime} - ${endTime}`;
  }

  /**
   * Update data-start and data-end attributes with ISO timestamps
   */
  private updateDateTimeAttributes(element: HTMLElement, columnDate: Date, startMinutes: number, endMinutes: number): void {
    const startDate = this.dateService.createDateAtTime(columnDate, startMinutes);

    let endDate = this.dateService.createDateAtTime(columnDate, endMinutes);

    // Handle cross-midnight events
    if (endMinutes >= 1440) {
      const extraDays = Math.floor(endMinutes / 1440);
      endDate = this.dateService.addDays(endDate, extraDays);
    }

    // Convert to UTC before storing as ISO string
    element.dataset.start = this.dateService.toUTC(startDate);
    element.dataset.end = this.dateService.toUTC(endDate);
  }

  /**
   * Format minutes since midnight to time string
   */
  private formatTimeFromMinutes(totalMinutes: number): string {
    return this.dateService.minutesToTime(totalMinutes);
  }

  /**
   * Handle drag start event
   */
  public handleDragStart(payload: DragStartEventPayload): void {

    this.originalEvent = payload.draggedElement;;

    // Use the clone from the payload instead of creating a new one
    this.draggedClone = payload.draggedClone;

    if (this.draggedClone) {
      // Apply drag styling 
      this.applyDragStyling(this.draggedClone);

      // Add to current column's events layer (not directly to column)
      const eventsLayer = payload.columnBounds?.element.querySelector('swp-events-layer');
      if (eventsLayer) {
        eventsLayer.appendChild(this.draggedClone);
      }
    }

    // Make original semi-transparent
    this.originalEvent.style.opacity = '0.3';
    this.originalEvent.style.userSelect = 'none';

  }

  /**
   * Handle drag move event
   */
  public handleDragMove(payload: DragMoveEventPayload): void {
    if (!this.draggedClone) return;

    // Update position - snappedY is already the event top position
    // Add +1px to match the initial positioning offset from SwpEventElement
    this.draggedClone.style.top = (payload.snappedY + 1) + 'px';

    // Update timestamp display
    this.updateCloneTimestamp(payload);

  }

  /**
   * Handle drag auto-scroll event
   */
  public handleDragAutoScroll(eventId: string, snappedY: number): void {
    if (!this.draggedClone) return;

    // Update position directly using the calculated snapped position
    this.draggedClone.style.top = snappedY + 'px';

    // Update timestamp display
    //this.updateCloneTimestamp(this.draggedClone, snappedY); //TODO: Commented as, we need to move all this scroll logic til scroll manager away from eventrenderer
  }

  /**
   * Handle column change during drag
   */
  public handleColumnChange(dragColumnChangeEvent: DragColumnChangeEventPayload): void {
    if (!this.draggedClone) return;

    const eventsLayer = dragColumnChangeEvent.newColumn.element.querySelector('swp-events-layer');
    if (eventsLayer && this.draggedClone.parentElement !== eventsLayer) {
      eventsLayer.appendChild(this.draggedClone);
      
      // Recalculate timestamps with new column date
      const currentTop = parseFloat(this.draggedClone.style.top) || 0;
      const mockPayload: DragMoveEventPayload = {
        draggedElement: dragColumnChangeEvent.originalElement,
        draggedClone: this.draggedClone,
        mousePosition: dragColumnChangeEvent.mousePosition,
        mouseOffset: { x: 0, y: 0 },
        columnBounds: dragColumnChangeEvent.newColumn,
        snappedY: currentTop
      };
      
      this.updateCloneTimestamp(mockPayload);
    }
  }

  /**
   * Handle drag end event
   */
  public handleDragEnd(eventId: string, originalElement: HTMLElement, draggedClone: HTMLElement, finalColumn: ColumnBounds, finalY: number): void {
    if (!draggedClone || !originalElement) {
      console.warn('Missing draggedClone or originalElement');
      return;
    }

    // Fade out original
    this.fadeOutAndRemove(originalElement);

    // Remove clone prefix and normalize clone to be a regular event
    const cloneId = draggedClone.dataset.eventId;
    if (cloneId && cloneId.startsWith('clone-')) {
      draggedClone.dataset.eventId = cloneId.replace('clone-', '');
    }

    // Fully normalize the clone to be a regular event
    draggedClone.classList.remove('dragging');

    // Clean up instance state
    this.draggedClone = null;
    this.originalEvent = null;
  }

  /**
   * Handle navigation completed event
   */
  public handleNavigationCompleted(): void {
    // Default implementation - can be overridden by subclasses
  }

  /**
   * Fade out and remove element  
   */
  private fadeOutAndRemove(element: HTMLElement): void {
    element.style.transition = 'opacity 0.3s ease-out';
    element.style.opacity = '0';

    setTimeout(() => {
      element.remove();
    }, 300);
  }


  renderEvents(events: CalendarEvent[], container: HTMLElement): void {
    // Filter out all-day events - they should be handled by AllDayEventRenderer
    const timedEvents = events.filter(event => !event.allDay);

    // Find columns in the specific container for regular events
    const columns = this.getColumns(container);

    columns.forEach(column => {
      const columnEvents = this.getEventsForColumn(column, timedEvents);
      const eventsLayer = column.querySelector('swp-events-layer');
      
      if (eventsLayer) {
        // Simply render each event - no overlap handling
        columnEvents.forEach(event => {
          const element = this.renderEvent(event);
          eventsLayer.appendChild(element);
        });
      }
    });
  }

  private renderEvent(event: CalendarEvent): HTMLElement {
    const swpEvent = SwpEventElement.fromCalendarEvent(event);
    return swpEvent.getElement();
  }

  protected calculateEventPosition(event: CalendarEvent): { top: number; height: number } {
    // Delegate to PositionUtils for centralized position calculation
    return PositionUtils.calculateEventPosition(event.start, event.end);
  }

  clearEvents(container?: HTMLElement): void {
    const selector = 'swp-event';
    const existingEvents = container
      ? container.querySelectorAll(selector)
      : document.querySelectorAll(selector);

    existingEvents.forEach(event => event.remove());
  }

  protected getColumns(container: HTMLElement): HTMLElement[] {
    const columns = container.querySelectorAll('swp-day-column');
    return Array.from(columns) as HTMLElement[];
  }

  protected getEventsForColumn(column: HTMLElement, events: CalendarEvent[]): CalendarEvent[] {
    const columnDate = column.dataset.date;
    if (!columnDate) {
      return [];
    }

    const columnEvents = events.filter(event => {
      const eventDateStr = this.dateService.formatISODate(event.start);
      const matches = eventDateStr === columnDate;

      return matches;
    });

    return columnEvents;
  }
}