// 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, EventGroup, StackLink } from '../managers/EventStackManager';

/**
 * 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 draggedClone: HTMLElement | null = null;
  private originalEvent: HTMLElement | null = null;

  constructor() {
    const timezone = calendarConfig.getTimezone?.();
    this.dateService = new DateService(timezone);
    this.stackManager = new EventStackManager();
  }
 
  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) {
      // 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 || !payload.columnBounds) return;

    // Delegate to SwpEventElement to update position and timestamps
    const swpEvent = this.draggedClone as SwpEventElement;
    const columnDate = new Date(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 = new Date(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');

    // 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;

    console.log('[EventRenderer] Rendering column with', columnEvents.length, 'events');

    // Step 1: Calculate stack levels for ALL events first (to understand overlaps)
    const allStackLinks = this.stackManager.createOptimizedStackLinks(columnEvents);

    console.log('[EventRenderer] All stack links:');
    columnEvents.forEach(event => {
      const link = allStackLinks.get(event.id);
      console.log(`  Event ${event.id} (${event.title}): stackLevel=${link?.stackLevel ?? 'none'}`);
    });

    // Step 2: Find grid candidates (start together ±15 min)
    const groups = this.stackManager.groupEventsByStartTime(columnEvents);
    const gridGroups = groups.filter(group => {
      if (group.events.length <= 1) return false;
      group.containerType = this.stackManager.decideContainerType(group);
      return group.containerType === 'GRID';
    });

    console.log('[EventRenderer] Grid groups:', gridGroups.length);
    gridGroups.forEach((g, i) => {
      console.log(`  Grid group ${i}:`, g.events.map(e => e.id));
    });

    // Step 3: Render grid groups and track which events have been rendered
    const renderedIds = new Set<string>();

    gridGroups.forEach((group, index) => {
      console.log(`[EventRenderer] Rendering grid group ${index} with ${group.events.length} events:`, group.events.map(e => e.id));

      // Calculate grid group stack level by finding what it overlaps OUTSIDE the group
      const gridStackLevel = this.calculateGridGroupStackLevel(group, columnEvents, allStackLinks);

      console.log(`  Grid group stack level: ${gridStackLevel}`);

      this.renderGridGroup(group, eventsLayer, gridStackLevel);
      group.events.forEach(e => renderedIds.add(e.id));
    });

    // Step 4: Get remaining events (not in grid)
    const remainingEvents = columnEvents.filter(e => !renderedIds.has(e.id));

    console.log('[EventRenderer] Remaining events for stacking:');
    remainingEvents.forEach(event => {
      const link = allStackLinks.get(event.id);
      console.log(`  Event ${event.id} (${event.title}): stackLevel=${link?.stackLevel ?? 'none'}`);
    });

    // Step 5: Render remaining stacked/single events
    remainingEvents.forEach(event => {
      const element = this.renderEvent(event);
      const stackLink = allStackLinks.get(event.id);

      console.log(`[EventRenderer] Rendering stacked event ${event.id}, stackLink:`, stackLink);

      if (stackLink) {
        // Apply stack link to element (for drag-drop)
        this.stackManager.applyStackLinkToElement(element, stackLink);

        // Apply visual styling
        this.stackManager.applyVisualStyling(element, stackLink.stackLevel);
        console.log(`  Applied margin-left: ${stackLink.stackLevel * 15}px, stack-link:`, stackLink);
      }

      eventsLayer.appendChild(element);
    });
  }


  /**
   * Calculate stack level for a grid group based on what it overlaps OUTSIDE the group
   */
  private calculateGridGroupStackLevel(
    group: EventGroup,
    allEvents: CalendarEvent[],
    stackLinks: Map<string, StackLink>
  ): number {
    const groupEventIds = new Set(group.events.map(e => e.id));

    // Find all events OUTSIDE this group
    const outsideEvents = allEvents.filter(e => !groupEventIds.has(e.id));

    // Find the highest stackLevel of any event that overlaps with ANY event in the grid group
    let maxOverlappingLevel = -1;

    for (const gridEvent of group.events) {
      for (const outsideEvent of outsideEvents) {
        if (this.stackManager.doEventsOverlap(gridEvent, outsideEvent)) {
          const outsideLink = stackLinks.get(outsideEvent.id);
          if (outsideLink) {
            maxOverlappingLevel = Math.max(maxOverlappingLevel, outsideLink.stackLevel);
          }
        }
      }
    }

    // Grid group should be one level above the highest overlapping event
    return maxOverlappingLevel + 1;
  }

  /**
   * Render events in a grid container (side-by-side)
   */
  private renderGridGroup(group: EventGroup, eventsLayer: HTMLElement, stackLevel: number): void {
    const groupElement = document.createElement('swp-event-group');

    // Add grid column class based on event count
    const colCount = group.events.length;
    groupElement.classList.add(`cols-${colCount}`);

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

    // Position based on earliest event
    const earliestEvent = group.events[0];
    const position = this.calculateEventPosition(earliestEvent);
    groupElement.style.top = `${position.top + 1}px`;

    // Add z-index based on stack level
    groupElement.style.zIndex = `${this.stackManager.calculateZIndex(stackLevel)}`;

    // Add stack-link attribute for drag-drop (group acts as a stacked item)
    const stackLink: StackLink = {
      stackLevel: stackLevel
      // prev/next will be handled by drag-drop manager if needed
    };
    this.stackManager.applyStackLinkToElement(groupElement, stackLink);

    // NO height on the group - it should auto-size based on children

    // Render each event within the grid
    group.events.forEach(event => {
      const element = this.renderEventInGrid(event, earliestEvent.start);
      groupElement.appendChild(element);
    });

    eventsLayer.appendChild(groupElement);
  }

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

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

    // Events in grid are positioned relatively - NO top offset needed
    // The grid container itself is positioned absolutely with the correct top
    element.style.position = 'relative';
    element.style.height = `${position.height - 3}px`;

    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 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;
  }
}