import { IEventBus, ICalendarEvent } from '../../types/CalendarTypes';
import { IGridConfig } from '../../core/IGridConfig';
import { CoreEvents } from '../../constants/CoreEvents';
import { HeaderDrawerManager } from '../../core/HeaderDrawerManager';
import { EventService } from '../../storage/events/EventService';
import { DateService } from '../../core/DateService';
import {
  IDragEnterHeaderPayload,
  IDragMoveHeaderPayload,
  IDragLeaveHeaderPayload
} from '../../types/DragTypes';

/**
 * HeaderDrawerRenderer - Handles rendering of items in the header drawer
 *
 * Listens to drag events from DragDropManager and creates/manages
 * swp-header-item elements in the header drawer.
 *
 * Uses subgrid for column alignment with parent swp-calendar-header.
 * Position items via gridArea for explicit row/column placement.
 */
export class HeaderDrawerRenderer {
  private currentItem: HTMLElement | null = null;
  private container: HTMLElement | null = null;
  private sourceElement: HTMLElement | null = null;
  private wasExpandedBeforeDrag = false;

  constructor(
    private eventBus: IEventBus,
    private gridConfig: IGridConfig,
    private headerDrawerManager: HeaderDrawerManager,
    private eventService: EventService,
    private dateService: DateService
  ) {
    this.setupListeners();
  }

  /**
   * Render allDay events into the header drawer
   */
  async render(container: HTMLElement, filter: Record<string, string[]>): Promise<void> {
    const drawer = container.querySelector('swp-header-drawer');
    if (!drawer) return;

    const visibleDates = filter['date'] || [];
    if (visibleDates.length === 0) return;

    // Fetch events for date range
    const startDate = new Date(visibleDates[0]);
    const endDate = new Date(visibleDates[visibleDates.length - 1]);
    endDate.setHours(23, 59, 59, 999);

    const events = await this.eventService.getByDateRange(startDate, endDate);

    // Filter to allDay events only (allDay !== false)
    const allDayEvents = events.filter(event => event.allDay !== false);

    // Clear existing items
    drawer.innerHTML = '';

    // Render each allDay event
    allDayEvents.forEach(event => {
      const item = this.createHeaderItem(event, visibleDates);
      if (item) drawer.appendChild(item);
    });

    // Expand drawer if there are items
    if (allDayEvents.length > 0) {
      this.headerDrawerManager.expand();
    }
  }

  /**
   * Create a header item element for an allDay event
   * Supports multi-day events with column span
   */
  private createHeaderItem(event: ICalendarEvent, visibleDates: string[]): HTMLElement | null {
    const startDateKey = this.dateService.getDateKey(event.start);
    const endDateKey = this.dateService.getDateKey(event.end);

    const startColIndex = visibleDates.indexOf(startDateKey);
    const endColIndex = visibleDates.indexOf(endDateKey);

    // Event skal mindst starte eller slutte inden for synlige datoer
    if (startColIndex === -1 && endColIndex === -1) return null;

    const item = document.createElement('swp-header-item');
    item.dataset.eventId = event.id;
    item.dataset.itemType = 'event';
    item.dataset.start = event.start.toISOString();
    item.dataset.end = event.end.toISOString();
    item.textContent = event.title;

    // Color class
    const colorClass = this.getColorClass(event);
    if (colorClass) item.classList.add(colorClass);

    // Grid position (1-indexed, clamp til synlige kolonner)
    const col = Math.max(0, startColIndex) + 1;
    const endCol = (endColIndex !== -1 ? endColIndex : visibleDates.length - 1) + 2;
    item.style.gridArea = `1 / ${col} / 2 / ${endCol}`;

    return item;
  }

  /**
   * Get color class based on event metadata or type
   */
  private getColorClass(event: ICalendarEvent): string {
    if (event.metadata?.color) {
      return `is-${event.metadata.color}`;
    }
    const typeColors: Record<string, string> = {
      'customer': 'is-blue',
      'vacation': 'is-green',
      'break': 'is-amber',
      'meeting': 'is-purple',
      'blocked': 'is-red'
    };
    return typeColors[event.type] || 'is-blue';
  }

  /**
   * Setup event listeners for drag events
   */
  private setupListeners(): void {
    this.eventBus.on(CoreEvents.EVENT_DRAG_ENTER_HEADER, (e) => {
      const payload = (e as CustomEvent<IDragEnterHeaderPayload>).detail;
      this.handleDragEnter(payload);
    });

    this.eventBus.on(CoreEvents.EVENT_DRAG_MOVE_HEADER, (e) => {
      const payload = (e as CustomEvent<IDragMoveHeaderPayload>).detail;
      this.handleDragMove(payload);
    });

    this.eventBus.on(CoreEvents.EVENT_DRAG_LEAVE_HEADER, (e) => {
      const payload = (e as CustomEvent<IDragLeaveHeaderPayload>).detail;
      this.handleDragLeave(payload);
    });

    this.eventBus.on(CoreEvents.EVENT_DRAG_END, () => {
      this.handleDragEnd();
    });

    this.eventBus.on(CoreEvents.EVENT_DRAG_CANCEL, () => {
      this.cleanup();
    });
  }

  /**
   * Handle drag entering header zone - create preview item
   */
  private handleDragEnter(payload: IDragEnterHeaderPayload): void {
    this.container = document.querySelector('swp-header-drawer');
    if (!this.container) return;

    // Remember if drawer was already expanded
    this.wasExpandedBeforeDrag = this.headerDrawerManager.isExpanded();

    // Expand drawer with animation
    this.headerDrawerManager.expand();

    // Store reference to source element
    this.sourceElement = payload.element;

    // Create header item
    const item = document.createElement('swp-header-item');
    item.dataset.eventId = payload.eventId;
    item.dataset.itemType = payload.itemType;
    item.dataset.date = payload.sourceDate;
    item.dataset.duration = String(payload.duration);
    item.textContent = payload.title;

    // Apply color class if present
    if (payload.colorClass) {
      item.classList.add(payload.colorClass);
    }

    // Add dragging state
    item.classList.add('dragging');

    // Initial placement (duration determines column span)
    // gridArea format: "row / col-start / row+1 / col-end"
    const col = payload.sourceColumnIndex + 1;
    const endCol = col + payload.duration;
    item.style.gridArea = `1 / ${col} / 2 / ${endCol}`;

    this.container.appendChild(item);
    this.currentItem = item;

    // Hide original element while in header
    payload.element.style.visibility = 'hidden';
  }

  /**
   * Handle drag moving within header - update column position
   */
  private handleDragMove(payload: IDragMoveHeaderPayload): void {
    if (!this.currentItem) return;

    // Update column position (duration=1 for now)
    const col = payload.columnIndex + 1;
    const duration = parseInt(this.currentItem.dataset.duration || '1', 10);
    const endCol = col + duration;

    this.currentItem.style.gridArea = `1 / ${col} / 2 / ${endCol}`;
    this.currentItem.dataset.date = payload.dateKey;
  }

  /**
   * Handle drag leaving header - remove preview and restore source
   */
  private handleDragLeave(_payload: IDragLeaveHeaderPayload): void {
    this.cleanup();
  }

  /**
   * Handle drag end - finalize the item (it stays in header)
   * Note: EventRenderer handles removing the original element from the grid
   * via EVENT_DRAG_END with target === 'header'
   */
  private handleDragEnd(): void {
    if (!this.currentItem) return;

    // Remove dragging state
    this.currentItem.classList.remove('dragging');

    // TODO: Emit event to persist allDay=true change

    // Clear references
    this.currentItem = null;
    this.sourceElement = null;
  }

  /**
   * Cleanup preview item and restore source visibility
   */
  private cleanup(): void {
    // Remove preview item
    this.currentItem?.remove();
    this.currentItem = null;

    // Restore source element visibility
    if (this.sourceElement) {
      this.sourceElement.style.visibility = '';
      this.sourceElement = null;
    }

    // Collapse drawer if it wasn't expanded before drag
    if (!this.wasExpandedBeforeDrag) {
      this.headerDrawerManager.collapse();
    }
  }
}