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';
import { EventStackManager } from '../managers/EventStackManager';
import { EventLayoutCoordinator, GridGroupLayout, StackedEventLayout } from '../managers/EventLayoutCoordinator';

/**
 * 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 stackManager: EventStackManager;
  private layoutCoordinator: EventLayoutCoordinator;
  private draggedClone: HTMLElement | null = null;
  private originalEvent: HTMLElement | null = null;

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



  /**
   * 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 && payload.columnBounds) {
      // 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);

        // Set initial position to prevent "jump to top" effect
        // Calculate absolute Y position from original element
        const originalRect = this.originalEvent.getBoundingClientRect();
        const columnRect = payload.columnBounds.boundingClientRect;
        const initialTop = originalRect.top - columnRect.top;

        this.draggedClone.style.top = `${initialTop}px`;
      }
    }

    // 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 || !payload.columnBounds) return;

    // Delegate to SwpEventElement to update position and timestamps
    const swpEvent = this.draggedClone as SwpEventElement;
    const columnDate = this.dateService.parseISO(payload.columnBounds.date);
    swpEvent.updatePosition(columnDate, payload.snappedY);
  }

  /**
   * 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 swpEvent = this.draggedClone as SwpEventElement;
      const columnDate = this.dateService.parseISO(dragColumnChangeEvent.newColumn.date);
      swpEvent.updatePosition(columnDate, currentTop);
    }
  }

  /**
   * 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');
    draggedClone.style.pointerEvents = ''; // Re-enable pointer events

    // 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') as HTMLElement;

      if (eventsLayer) {
        this.renderColumnEvents(columnEvents, eventsLayer);
      }
    });
  }

  /**
   * Render events in a column using combined stacking + grid algorithm
   */
  private renderColumnEvents(columnEvents: CalendarEvent[], eventsLayer: HTMLElement): void {
    if (columnEvents.length === 0) return;

    // Get layout from coordinator
    const layout = this.layoutCoordinator.calculateColumnLayout(columnEvents);

    // Render grid groups
    layout.gridGroups.forEach(gridGroup => {
      this.renderGridGroup(gridGroup, eventsLayer);
    });

    // Render stacked events
    layout.stackedEvents.forEach(stackedEvent => {
      const element = this.renderEvent(stackedEvent.event);
      this.stackManager.applyStackLinkToElement(element, stackedEvent.stackLink);
      this.stackManager.applyVisualStyling(element, stackedEvent.stackLink.stackLevel);
      eventsLayer.appendChild(element);
    });
  }
  /**
   * Render events in a grid container (side-by-side with column sharing)
   */
  private renderGridGroup(gridGroup: GridGroupLayout, eventsLayer: HTMLElement): void {
    const groupElement = document.createElement('swp-event-group');

    // Add grid column class based on number of columns (not events)
    const colCount = gridGroup.columns.length;
    groupElement.classList.add(`cols-${colCount}`);

    // Add stack level class for margin-left offset
    groupElement.classList.add(`stack-level-${gridGroup.stackLevel}`);

    // Position from layout
    groupElement.style.top = `${gridGroup.position.top}px`;

    // Add stack-link attribute for drag-drop (group acts as a stacked item)
    const stackLink = {
      stackLevel: gridGroup.stackLevel
    };
    this.stackManager.applyStackLinkToElement(groupElement, stackLink);

    // Apply visual styling (margin-left and z-index) using StackManager
    this.stackManager.applyVisualStyling(groupElement, gridGroup.stackLevel);

    // Render each column
    const earliestEvent = gridGroup.events[0];
    gridGroup.columns.forEach(columnEvents => {
      const columnContainer = this.renderGridColumn(columnEvents, earliestEvent.start);
      groupElement.appendChild(columnContainer);
    });

    eventsLayer.appendChild(groupElement);
  }

  /**
   * Render a single column within a grid group
   * Column may contain multiple events that don't overlap
   */
  private renderGridColumn(columnEvents: CalendarEvent[], containerStart: Date): HTMLElement {
    const columnContainer = document.createElement('div');
    columnContainer.style.position = 'relative';

    columnEvents.forEach(event => {
      const element = this.renderEventInGrid(event, containerStart);
      columnContainer.appendChild(element);
    });

    return columnContainer;
  }

  /**
   * Render event within a grid container (absolute positioning within column)
   */
  private renderEventInGrid(event: CalendarEvent, containerStart: Date): HTMLElement {
    const element = SwpEventElement.fromCalendarEvent(event);

    // Calculate event height
    const position = this.calculateEventPosition(event);

    // Calculate relative top offset if event starts after container start
    // (e.g., if container starts at 07:00 and event starts at 08:15, offset = 75 min)
    const timeDiffMs = event.start.getTime() - containerStart.getTime();
    const timeDiffMinutes = timeDiffMs / (1000 * 60);
    const gridSettings = calendarConfig.getGridSettings();
    const relativeTop = timeDiffMinutes > 0 ? (timeDiffMinutes / 60) * gridSettings.hourHeight : 0;

    // Events in grid columns are positioned absolutely within their column container
    element.style.position = 'absolute';
    element.style.top = `${relativeTop}px`;
    element.style.height = `${position.height - 3}px`;
    element.style.left = '0';
    element.style.right = '0';

    return element;
  }


  private renderEvent(event: CalendarEvent): HTMLElement {
    const element = SwpEventElement.fromCalendarEvent(event);

    // Apply positioning (moved from SwpEventElement.applyPositioning)
    const position = this.calculateEventPosition(event);
    element.style.position = 'absolute';
    element.style.top = `${position.top + 1}px`;
    element.style.height = `${position.height - 3}px`;
    element.style.left = '2px';
    element.style.right = '2px';

    return element;
  }

  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 eventSelector = 'swp-event';
    const groupSelector = 'swp-event-group';

    const existingEvents = container
      ? container.querySelectorAll(eventSelector)
      : document.querySelectorAll(eventSelector);

    const existingGroups = container
      ? container.querySelectorAll(groupSelector)
      : document.querySelectorAll(groupSelector);

    existingEvents.forEach(event => event.remove());
    existingGroups.forEach(group => group.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 [];
    }

    // Create start and end of day for interval overlap check
    const columnStart = this.dateService.parseISO(`${columnDate}T00:00:00`);
    const columnEnd = this.dateService.parseISO(`${columnDate}T23:59:59.999`);

    const columnEvents = events.filter(event => {
      // Interval overlap: event overlaps with column day if event.start < columnEnd AND event.end > columnStart
      const overlaps = event.start < columnEnd && event.end > columnStart;
      return overlaps;
    });

    return columnEvents;
  }
}