// Event rendering strategy interface and implementations

import { CalendarEvent } from '../types/CalendarTypes';
import { calendarConfig } from '../core/CalendarConfig';
import { DateCalculator } from '../utils/DateCalculator';
import { eventBus } from '../core/EventBus';
import { OverlapDetector, OverlapResult } from '../utils/OverlapDetector';
import { SwpEventElement } from '../elements/SwpEventElement';
import { TimeFormatter } from '../utils/TimeFormatter';
import { PositionUtils } from '../utils/PositionUtils';
import { DragOffset, StackLinkData } from '../types/DragDropTypes';

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

/**
 * Base class for event renderers with common functionality
 */
export abstract class BaseEventRenderer implements EventRendererStrategy {
  protected dateCalculator: DateCalculator;

  // Drag and drop state
  private draggedClone: HTMLElement | null = null;
  private originalEvent: HTMLElement | null = null;

  // Resize manager

  constructor(dateCalculator?: DateCalculator) {
    if (!dateCalculator) {
      DateCalculator.initialize(calendarConfig);
    }
    this.dateCalculator = dateCalculator || new DateCalculator();
  }

  // ============================================
  // NEW OVERLAP DETECTION SYSTEM
  // All new functions prefixed with new_
  // ============================================

  protected overlapDetector = new OverlapDetector();

  /**
   * Ny hovedfunktion til at håndtere event overlaps
   * @param events - Events der skal renderes i kolonnen
   * @param container - Container element at rendere i
   */
  protected handleEventOverlaps(events: CalendarEvent[], container: HTMLElement): void {
    if (events.length === 0) return;

    if (events.length === 1) {
      const element = this.renderEvent(events[0]);
      container.appendChild(element);
      return;
    }

    // Track hvilke events der allerede er blevet processeret
    const processedEvents = new Set<string>();

    // Gå gennem hvert event og find overlaps
    events.forEach((currentEvent, index) => {
      // Skip events der allerede er processeret som del af en overlap gruppe
      if (processedEvents.has(currentEvent.id)) {
        return;
      }

      const remainingEvents = events.slice(index + 1);
      const overlappingEvents = this.overlapDetector.resolveOverlap(currentEvent, remainingEvents);

      if (overlappingEvents.length > 0) {
        // Der er overlaps - opret stack links
        const result = this.overlapDetector.decorateWithStackLinks(currentEvent, overlappingEvents);
        this.renderOverlappingEvents(result, container);

        // Marker alle events i overlap gruppen som processeret
        overlappingEvents.forEach(event => processedEvents.add(event.id));
      } else {
        // Intet overlap - render normalt
        const element = this.renderEvent(currentEvent);
        container.appendChild(element);
        processedEvents.add(currentEvent.id);
      }
    });
  }


  /**
   * Cleanup method for proper resource management
   */
  public destroy(): void {
    this.draggedClone = null;
    this.originalEvent = null;
  }


  /**
   * Apply common drag styling to an element
   */
  private applyDragStyling(element: HTMLElement): void {
    element.classList.add('dragging');
  }


  /**
   * Update clone timestamp based on new position
   */
  private updateCloneTimestamp(clone: HTMLElement, snappedY: number): void {

    //important as events can pile up, so they will still fire after event has been converted to another rendered type
    if (clone.dataset.allDay == "true") return;

    const gridSettings = calendarConfig.getGridSettings();
    const hourHeight = gridSettings.hourHeight;
    const dayStartHour = gridSettings.dayStartHour;
    const snapInterval = gridSettings.snapInterval;

    // Calculate minutes from grid start (not from midnight)
    const minutesFromGridStart = (snappedY / hourHeight) * 60;

    // Add dayStartHour offset to get actual time
    const actualStartMinutes = (dayStartHour * 60) + minutesFromGridStart;

    // Snap to interval
    const snappedStartMinutes = Math.round(actualStartMinutes / snapInterval) * snapInterval;

    // Use cached original duration (no recalculation)
    const cachedDuration = parseInt(clone.dataset.originalDuration || '60');
    const endTotalMinutes = snappedStartMinutes + cachedDuration;

    // Update dataset with reference date for performance
    const referenceDate = new Date('1970-01-01T00:00:00');
    const startDate = new Date(referenceDate);
    startDate.setMinutes(startDate.getMinutes() + snappedStartMinutes);

    const endDate = new Date(referenceDate);
    endDate.setMinutes(endDate.getMinutes() + endTotalMinutes);

    clone.dataset.start = startDate.toISOString();
    clone.dataset.end = endDate.toISOString();
    // Update display
    const timeElement = clone.querySelector('swp-event-time');
    if (timeElement) {
      const startTime = TimeFormatter.formatTimeFromMinutes(snappedStartMinutes);
      const endTime = TimeFormatter.formatTimeFromMinutes(endTotalMinutes);
      timeElement.textContent = `${startTime} - ${endTime}`;
    }
  }

  /**
   * Handle drag start event
   */
  public handleDragStart(originalElement: HTMLElement, eventId: string, mouseOffset: DragOffset, column: string): void {
    this.originalEvent = originalElement;

    // Remove stacking styling during drag will be handled by new system

    // Create SwpEventElement from existing DOM element and clone it
    const originalSwpEvent = SwpEventElement.fromExistingElement(originalElement);
    const clonedSwpEvent = originalSwpEvent.createClone();

    // Get the cloned DOM element
    this.draggedClone = clonedSwpEvent.getElement();

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

    // Add to current column's events layer (not directly to column)
    const columnElement = document.querySelector(`swp-day-column[data-date="${column}"]`);
    if (columnElement) {
      const eventsLayer = columnElement.querySelector('swp-events-layer');
      if (eventsLayer) {
        eventsLayer.appendChild(this.draggedClone);
      } else {
        // Fallback to column if events layer not found
        columnElement.appendChild(this.draggedClone);
      }
    }

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

  }

  /**
   * Handle drag move event
   */
  public handleDragMove(eventId: string, snappedY: number, column: string, mouseOffset: DragOffset): void {
    if (!this.draggedClone) return;

    // Update position
    this.draggedClone.style.top = snappedY + 'px';

    // Update timestamp display
    this.updateCloneTimestamp(this.draggedClone, 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);
  }

  /**
   * Handle column change during drag
   */
  public handleColumnChange(eventId: string, newColumn: string): void {
    if (!this.draggedClone) return;

    // Move clone to new column's events layer
    const newColumnElement = document.querySelector(`swp-day-column[data-date="${newColumn}"]`);
    if (newColumnElement) {
      const eventsLayer = newColumnElement.querySelector('swp-events-layer');
      if (eventsLayer && this.draggedClone.parentElement !== eventsLayer) {
        eventsLayer.appendChild(this.draggedClone);
      } else if (!eventsLayer && this.draggedClone.parentElement !== newColumnElement) {
        // Fallback to column if events layer not found
        newColumnElement.appendChild(this.draggedClone);
      }
    }
  }

  /**
   * Handle drag end event
   */
  public handleDragEnd(eventId: string, originalElement: HTMLElement, draggedClone: HTMLElement, finalColumn: string, finalY: number): void {

    if (!draggedClone || !originalElement) {
      console.warn('Missing draggedClone or originalElement');
      return;
    }

    // Check om original event var del af en stack
    const originalStackLink = originalElement.dataset.stackLink;

    if (originalStackLink) {
      try {
        const stackData = JSON.parse(originalStackLink);

        // Saml ALLE event IDs fra hele stack chain
        const allStackEventIds: Set<string> = new Set();

        // Recursive funktion til at traversere stack chain
        const traverseStack = (linkData: StackLinkData, visitedIds: Set<string>) => {
          if (linkData.prev && !visitedIds.has(linkData.prev)) {
            visitedIds.add(linkData.prev);
            const prevElement = document.querySelector(`swp-time-grid [data-event-id="${linkData.prev}"]`) as HTMLElement;
            if (prevElement?.dataset.stackLink) {
              try {
                const prevLinkData = JSON.parse(prevElement.dataset.stackLink);
                traverseStack(prevLinkData, visitedIds);
              } catch (e) { }
            }
          }

          if (linkData.next && !visitedIds.has(linkData.next)) {
            visitedIds.add(linkData.next);
            const nextElement = document.querySelector(`swp-time-grid [data-event-id="${linkData.next}"]`) as HTMLElement;
            if (nextElement?.dataset.stackLink) {
              try {
                const nextLinkData = JSON.parse(nextElement.dataset.stackLink);
                traverseStack(nextLinkData, visitedIds);
              } catch (e) { }
            }
          }
        };

        // Start traversering fra original event's stackLink
        traverseStack(stackData, allStackEventIds);

        // Fjern original eventId da det bliver flyttet
        allStackEventIds.delete(eventId);

        // Find alle stack events og fjern dem
        const stackEvents: CalendarEvent[] = [];
        let container: HTMLElement | null = null;

        allStackEventIds.forEach(id => {
          const element = document.querySelector(`swp-time-grid [data-event-id="${id}"]`) as HTMLElement;
          if (element) {
            // Gem container reference fra første element
            if (!container) {
              container = element.closest('swp-events-layer') as HTMLElement;
            }

            const event = this.elementToCalendarEvent(element);
            if (event) {
              stackEvents.push(event);
            }

            // Fjern elementet
            element.remove();
          }
        });

        // Re-render stack events hvis vi fandt nogle
        if (stackEvents.length > 0 && container) {
          this.handleEventOverlaps(stackEvents, container);
        }
      } catch (e) {
        console.warn('Failed to parse stackLink data:', e);
      }
    }

    // Remove original event from any existing groups first
    this.removeEventFromExistingGroups(originalElement);

    // 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');
    // Behold z-index hvis det er et stacked event

    // Update dataset with new times after successful drop (only for timed events)
    if (draggedClone.dataset.displayType !== 'allday') {
      const newEvent = this.elementToCalendarEvent(draggedClone);
      if (newEvent) {
        draggedClone.dataset.start = newEvent.start.toISOString();
        draggedClone.dataset.end = newEvent.end.toISOString();
      }
    }

    // Detect overlaps with other events in the target column and reposition if needed
    this.handleDragDropOverlaps(draggedClone, finalColumn);

    // Fjern stackLink data fra dropped element
    if (draggedClone.dataset.stackLink) {
      delete draggedClone.dataset.stackLink;
    }

    // Clean up instance state (no longer needed since we get elements as parameters)
    this.draggedClone = null;
    this.originalEvent = null;

  }

  /**
   * Handle event click (when drag threshold not reached)
   */
  public handleEventClick(eventId: string, originalElement: HTMLElement): void {
    console.log('handleEventClick:', eventId);

    // Clean up any drag artifacts from failed drag attempt
    if (this.draggedClone) {
      this.draggedClone.classList.remove('dragging');
      this.draggedClone.remove();
      this.draggedClone = null;
    }

    // Restore original element styling if it was modified
    if (this.originalEvent) {
      this.originalEvent.style.opacity = '';
      this.originalEvent.style.userSelect = '';
      this.originalEvent = null;
    }

    // Emit a clean click event for other components to handle
    eventBus.emit('event:clicked', {
      eventId: eventId,
      element: originalElement
    });
  }

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

  /**
   * Handle overlap detection and re-rendering after drag-drop
   */
  private handleDragDropOverlaps(droppedElement: HTMLElement, targetColumn: string): void {
    const targetColumnElement = document.querySelector(`swp-day-column[data-date="${targetColumn}"]`);
    if (!targetColumnElement) return;

    const eventsLayer = targetColumnElement.querySelector('swp-events-layer') as HTMLElement;
    if (!eventsLayer) return;

    // Convert dropped element to CalendarEvent with new position
    const droppedEvent = this.elementToCalendarEvent(droppedElement);
    if (!droppedEvent) return;

    // Get existing events in the column (excluding the dropped element)
    const existingEvents = this.getEventsInColumn(eventsLayer, droppedElement.dataset.eventId);

    // Find overlaps with the dropped event
    const overlappingEvents = this.overlapDetector.resolveOverlap(droppedEvent, existingEvents);

    if (overlappingEvents.length > 0) {
      // Remove only affected events from DOM
      const affectedEventIds = [droppedEvent.id, ...overlappingEvents.map(e => e.id)];
      eventsLayer.querySelectorAll('swp-event').forEach(el => {
        const eventId = (el as HTMLElement).dataset.eventId;
        if (eventId && affectedEventIds.includes(eventId)) {
          el.remove();
        }
      });

      // Re-render affected events with overlap handling
      const affectedEvents = [droppedEvent, ...overlappingEvents];
      this.handleEventOverlaps(affectedEvents, eventsLayer);
    } else {
      // Reset z-index for non-overlapping events
      droppedElement.style.zIndex = '';
    }
  }

  /**
   * Get all events in a column as CalendarEvent objects
   */
  private getEventsInColumn(eventsLayer: HTMLElement, excludeEventId?: string): CalendarEvent[] {
    const eventElements = eventsLayer.querySelectorAll('swp-event');
    const events: CalendarEvent[] = [];

    eventElements.forEach(el => {
      const element = el as HTMLElement;
      const eventId = element.dataset.eventId;

      // Skip the excluded event (e.g., the dropped event)
      if (excludeEventId && eventId === excludeEventId) {
        return;
      }

      const event = this.elementToCalendarEvent(element);
      if (event) {
        events.push(event);
      }
    });

    return events;
  }

  /**
   * Remove event from any existing groups and cleanup empty containers
   * In the new system, this is handled automatically by re-rendering overlaps
   */
  private removeEventFromExistingGroups(eventElement: HTMLElement): void {
    // With the new system, overlap relationships are recalculated on drop
    // No need to manually track and remove from groups
  }

  /**
   * Convert DOM element to CalendarEvent - handles both normal and 1970 reference dates
   */
  private elementToCalendarEvent(element: HTMLElement): CalendarEvent | null {
    const eventId = element.dataset.eventId;
    const title = element.dataset.title;
    const type = element.dataset.type;
    const start = element.dataset.start;
    const end = element.dataset.end;

    if (!eventId || !title || !type || !start || !end) {
      return null;
    }

    let startDate = new Date(start);
    let endDate = new Date(end);

    // Check if we have 1970 reference date (from drag operations)
    if (startDate.getFullYear() === 1970) {
      // Find the parent column to get the actual date
      const columnElement = element.closest('swp-day-column') as HTMLElement;
      if (columnElement && columnElement.dataset.date) {
        const columnDate = new Date(columnElement.dataset.date);

        // Keep the time portion from the 1970 dates, but use the column's date
        startDate = new Date(
          columnDate.getFullYear(),
          columnDate.getMonth(),
          columnDate.getDate(),
          startDate.getHours(),
          startDate.getMinutes()
        );

        endDate = new Date(
          columnDate.getFullYear(),
          columnDate.getMonth(),
          columnDate.getDate(),
          endDate.getHours(),
          endDate.getMinutes()
        );
      }
    }

    return {
      id: eventId,
      title: title,
      start: startDate,
      end: endDate,
      type: type,
      allDay: false,
      syncStatus: 'synced',
      metadata: {
        duration: element.dataset.duration
      }
    };
  }

  /**
   * Handle conversion to all-day event
   */

  /**
   * 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);
    
    console.log('🎯 EventRenderer: Filtering events', {
      totalEvents: events.length,
      timedEvents: timedEvents.length,
      filteredOutAllDay: events.length - timedEvents.length
    });
    
    // 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) {
   
        this.handleEventOverlaps(columnEvents, eventsLayer as HTMLElement);
      }
    });
  }

  // Abstract methods that subclasses must implement
  protected abstract getColumns(container: HTMLElement): HTMLElement[];
  protected abstract getEventsForColumn(column: HTMLElement, events: CalendarEvent[]): CalendarEvent[];


  protected renderEvent(event: CalendarEvent): HTMLElement {
    const swpEvent = SwpEventElement.fromCalendarEvent(event);
    const eventElement = swpEvent.getElement();

    // Setup resize handles on first mouseover only
    eventElement.addEventListener('mouseover', () => {
      if (eventElement.dataset.hasResizeHandlers !== 'true') {
        eventElement.dataset.hasResizeHandlers = 'true';
      }
    }, { once: true });

    return eventElement;
  }

  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, swp-event-group';
    const existingEvents = container
      ? container.querySelectorAll(selector)
      : document.querySelectorAll(selector);

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

  /**
   * Renderer overlappende events baseret på OverlapResult
   * @param result - OverlapResult med events og stack links
   * @param container - Container at rendere i
   */
  protected renderOverlappingEvents(result: OverlapResult, container: HTMLElement): void {
    // Iterate direkte gennem stackLinks - allerede sorteret fra decorateWithStackLinks
    for (const [eventId, stackLink] of result.stackLinks.entries()) {
      const event = result.overlappingEvents.find(e => e.id === eventId);
      if (!event) continue;

      const element = this.renderEvent(event);

      // Gem stack link information på DOM elementet
      element.dataset.stackLink = JSON.stringify({
        prev: stackLink.prev,
        next: stackLink.next,
        stackLevel: stackLink.stackLevel
      });

      // Check om dette event deler kolonne med foregående (samme start tid)
      if (stackLink.prev) {
        const prevEvent = result.overlappingEvents.find(e => e.id === stackLink.prev);
        if (prevEvent && prevEvent.start.getTime() === event.start.getTime()) {
          // Samme start tid - del kolonne (side by side)
          this.new_applyColumnSharingStyling([element]);
        } else {
          // Forskellige start tider - stack vertikalt
          this.new_applyStackStyling(element, stackLink.stackLevel);
        }
      } else {
        // Første event i stack
        this.new_applyStackStyling(element, stackLink.stackLevel);
      }

      container.appendChild(element);
    }
  }

  /**
   * Applicerer stack styling (margin-left og z-index)
   * @param element - Event element
   * @param stackLevel - Stack niveau
   */
  protected new_applyStackStyling(element: HTMLElement, stackLevel: number): void {
    element.style.marginLeft = `${stackLevel * 15}px`;
    element.style.zIndex = `${100 + stackLevel}`;
  }

  /**
   * Applicerer column sharing styling (flexbox)
   * @param elements - Event elements der skal dele plads
   */
  protected new_applyColumnSharingStyling(elements: HTMLElement[]): void {
    elements.forEach(element => {
      element.style.flex = '1';
      element.style.minWidth = '50px';
    });
  }
}

/**
 * Date-based event renderer
 */
export class DateEventRenderer extends BaseEventRenderer {
  constructor(dateCalculator?: DateCalculator) {
    super(dateCalculator);
    this.setupDragEventListeners();
  }

  /**
   * Setup drag event listeners - placeholder method
   */
  private setupDragEventListeners(): void {
    // Drag event listeners are handled by EventRendererManager
    // This method exists for compatibility
  }

  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 = DateCalculator.formatISODate(event.start);
      const matches = eventDateStr === columnDate;


      return matches;
    });

    return columnEvents;
  }
}

/**
 * Resource-based event renderer
 */
export class ResourceEventRenderer extends BaseEventRenderer {
  protected getColumns(container: HTMLElement): HTMLElement[] {
    const columns = container.querySelectorAll('swp-resource-column');
    return Array.from(columns) as HTMLElement[];
  }

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

    const columnEvents = events.filter(event => {
      return event.resource?.name === resourceName;
    });

    return columnEvents;
  }

  // ============================================
  // NEW OVERLAP DETECTION SYSTEM
  // All new functions prefixed with new_
  // ============================================

  protected overlapDetector = new OverlapDetector();

}