// Event rendering strategy interface and implementations

import { CalendarEvent } from '../types/CalendarTypes';
import { ALL_DAY_CONSTANTS } from '../core/CalendarConfig';
import { CalendarConfig } from '../core/CalendarConfig';
import { DateCalculator } from '../utils/DateCalculator';
import { eventBus } from '../core/EventBus';
import { CoreEvents } from '../constants/CoreEvents';

/**
 * Interface for event rendering strategies
 */
export interface EventRendererStrategy {
  renderEvents(events: CalendarEvent[], container: HTMLElement, config: CalendarConfig): void;
  clearEvents(container?: HTMLElement): void;
}

/**
 * Base class for event renderers with common functionality
 */
export abstract class BaseEventRenderer implements EventRendererStrategy {
  protected dateCalculator: DateCalculator;
  protected config: CalendarConfig;
  
  // Drag and drop state
  private draggedClone: HTMLElement | null = null;
  private originalEvent: HTMLElement | null = null;

  constructor(config: CalendarConfig, dateCalculator?: DateCalculator) {
    this.config = config;
    if (!dateCalculator) {
      DateCalculator.initialize(config);
    }
    this.dateCalculator = dateCalculator || new DateCalculator();
  }
  
  /**
   * Setup listeners for drag events from DragDropManager
   */
  protected setupDragEventListeners(): void {
    // Handle drag start
    eventBus.on('drag:start', (event) => {
      const { originalElement, eventId, mouseOffset, column } = (event as CustomEvent).detail;
      this.handleDragStart(originalElement, eventId, mouseOffset, column);
    });
    
    // Handle drag move
    eventBus.on('drag:move', (event) => {
      const { eventId, snappedY, column, mouseOffset } = (event as CustomEvent).detail;
      this.handleDragMove(eventId, snappedY, column, mouseOffset);
    });
    
    // Handle drag end
    eventBus.on('drag:end', (event) => {
      const { eventId, originalElement, finalColumn, finalY } = (event as CustomEvent).detail;
      this.handleDragEnd(eventId, originalElement, finalColumn, finalY);
    });
    
    // Handle column change
    eventBus.on('drag:column-change', (event) => {
      const { eventId, newColumn } = (event as CustomEvent).detail;
      this.handleColumnChange(eventId, newColumn);
    });
    
    // Handle convert to all-day
    eventBus.on('drag:convert-to-allday', (event) => {
      const { eventId, targetDate, headerRenderer } = (event as CustomEvent).detail;
      this.handleConvertToAllDay(eventId, targetDate, headerRenderer);
    });
    
    // Handle navigation period change (when slide animation completes)
    eventBus.on(CoreEvents.PERIOD_CHANGED, () => {
      // Animate all-day height after navigation completes
      this.triggerAllDayHeightAnimation();
    });
  }
  
  /**
   * Trigger all-day height animation without creating new renderer instance
   */
  private triggerAllDayHeightAnimation(): void {
    import('./HeaderRenderer').then(({ DateHeaderRenderer }) => {
      const headerRenderer = new DateHeaderRenderer();
      headerRenderer.checkAndAnimateAllDayHeight();
    });
  }
  
  /**
   * Cleanup method for proper resource management
   */
  public destroy(): void {
    this.draggedClone = null;
    this.originalEvent = null;
  }

  /**
   * Get original event duration from data-duration attribute
   */
  private getOriginalEventDuration(originalEvent: HTMLElement): number {
    // Find the swp-event-time element with data-duration attribute
    const timeElement = originalEvent.querySelector('swp-event-time');
    if (timeElement) {
      const duration = timeElement.getAttribute('data-duration');
      if (duration) {
        const durationMinutes = parseInt(duration);
        return durationMinutes;
      }
    }
    
    // Fallback to 60 minutes if attribute not found
    return 60;
  }

  /**
   * Create a clone of an event for dragging
   */
  private createEventClone(originalEvent: HTMLElement): HTMLElement {
    const clone = originalEvent.cloneNode(true) as HTMLElement;
    
    // Prefix ID with "clone-"
    const originalId = originalEvent.dataset.eventId;
    if (originalId) {
      clone.dataset.eventId = `clone-${originalId}`;
    }
    
    // Get and cache original duration from data-duration attribute
    const originalDurationMinutes = this.getOriginalEventDuration(originalEvent);
    clone.dataset.originalDuration = originalDurationMinutes.toString();
    
    
    // Style for dragging
    clone.style.position = 'absolute';
    clone.style.zIndex = '999999';
    clone.style.pointerEvents = 'none';
    clone.style.opacity = '0.8';
    
    // Keep original dimensions (height stays the same)
    const rect = originalEvent.getBoundingClientRect();
    clone.style.width = rect.width + 'px';
    clone.style.height = rect.height + 'px';
    
    return clone;
  }
  
  /**
   * Update clone timestamp based on new position
   */
  private updateCloneTimestamp(clone: HTMLElement, snappedY: number): void {
    const gridSettings = this.config.getGridSettings();
    const hourHeight = gridSettings.hourHeight;
    const dayStartHour = gridSettings.dayStartHour;
    const snapInterval = 15; // TODO: Get from config
    
    // Calculate total minutes from top
    const totalMinutesFromTop = (snappedY / hourHeight) * 60;
    const startTotalMinutes = Math.max(
      dayStartHour * 60,
      Math.round((dayStartHour * 60 + totalMinutesFromTop) / snapInterval) * snapInterval
    );
    
    // Use cached original duration (no recalculation)
    const cachedDuration = parseInt(clone.dataset.originalDuration || '60');
    const endTotalMinutes = startTotalMinutes + cachedDuration;
    
    // Update display
    const timeElement = clone.querySelector('swp-event-time');
    if (timeElement) {
      const newTimeText = `${this.formatTime(startTotalMinutes)} - ${this.formatTime(endTotalMinutes)}`;
      timeElement.textContent = newTimeText;
      
    }
  }
  
  /**
   * Calculate event duration in minutes from element height
   */
  private getEventDuration(element: HTMLElement): number {
    const gridSettings = this.config.getGridSettings();
    const hourHeight = gridSettings.hourHeight;
    
    // Get height from style or computed
    let heightPx = parseFloat(element.style.height) || 0;
    if (!heightPx) {
      const rect = element.getBoundingClientRect();
      heightPx = rect.height;
    }
    
    return Math.round((heightPx / hourHeight) * 60);
  }
  
  /**
   * Unified time formatting method - handles both total minutes and Date objects
   */
  private formatTime(input: number | Date | string): string {
    let hours: number, minutes: number;
    
    if (typeof input === 'number') {
      // Total minutes input
      hours = Math.floor(input / 60) % 24;
      minutes = input % 60;
    } else {
      // Date or ISO string input
      const date = typeof input === 'string' ? new Date(input) : input;
      hours = date.getHours();
      minutes = date.getMinutes();
    }
    
    const period = hours >= 12 ? 'PM' : 'AM';
    const displayHours = hours > 12 ? hours - 12 : (hours === 0 ? 12 : hours);
    return `${displayHours}:${minutes.toString().padStart(2, '0')} ${period}`;
  }
  
  /**
   * Handle drag start event
   */
  private handleDragStart(originalElement: HTMLElement, eventId: string, mouseOffset: any, column: string): void {
    this.originalEvent = originalElement;
    
    // Create clone
    this.draggedClone = this.createEventClone(originalElement);
    
    // Add to current column
    const columnElement = document.querySelector(`swp-day-column[data-date="${column}"]`);
    if (columnElement) {
      columnElement.appendChild(this.draggedClone);
    }
    
    // Make original semi-transparent
    originalElement.style.opacity = '0.3';
    originalElement.style.userSelect = 'none';
    
  }
  
  /**
   * Handle drag move event
   */
  private handleDragMove(eventId: string, snappedY: number, column: string, mouseOffset: any): void {
    if (!this.draggedClone) return;
    
    // Update position
    this.draggedClone.style.top = snappedY + 'px';
    
    // Update timestamp display
    this.updateCloneTimestamp(this.draggedClone, snappedY);
    
  }
  
  /**
   * Handle column change during drag
   */
  private handleColumnChange(eventId: string, newColumn: string): void {
    if (!this.draggedClone) return;
    
    // Move clone to new column
    const newColumnElement = document.querySelector(`swp-day-column[data-date="${newColumn}"]`);
    if (newColumnElement && this.draggedClone.parentElement !== newColumnElement) {
      newColumnElement.appendChild(this.draggedClone);
    }
  }
  
  /**
   * Handle drag end event
   */
  private handleDragEnd(eventId: string, originalElement: HTMLElement, finalColumn: string, finalY: number): void {
    
    if (!this.draggedClone || !this.originalEvent) {
      return;
    }
    
    // Fade out original
    this.fadeOutAndRemove(this.originalEvent);
    
    // Remove clone prefix and normalize clone to be a regular event
    const cloneId = this.draggedClone.dataset.eventId;
    if (cloneId && cloneId.startsWith('clone-')) {
      this.draggedClone.dataset.eventId = cloneId.replace('clone-', '');
    }
    
    // Fully normalize the clone to be a regular event
    this.draggedClone.style.pointerEvents = '';
    this.draggedClone.style.opacity = '';
    this.draggedClone.style.userSelect = '';
    this.draggedClone.style.zIndex = '';
    
    
    // Clean up
    this.draggedClone = null;
    this.originalEvent = null;
    
  }
  
  /**
   * Handle conversion to all-day event
   */
  private handleConvertToAllDay(eventId: string, targetDate: string, headerRenderer: any): void {
    if (!this.draggedClone) return;
    
    // Only convert once
    if (this.draggedClone.tagName === 'SWP-ALLDAY-EVENT') return;
    
    // Transform clone to all-day format
    this.transformCloneToAllDay(this.draggedClone, targetDate);
    
    // Expand header if needed
    headerRenderer.addToAllDay(this.draggedClone.parentElement);
    
  }
  
  /**
   * Transform clone from timed to all-day event
   */
  private transformCloneToAllDay(clone: HTMLElement, targetDate: string): void {
    const calendarHeader = document.querySelector('swp-calendar-header');
    if (!calendarHeader) return;
    
    // Find all-day container
    const allDayContainer = calendarHeader.querySelector('swp-allday-container');
    if (!allDayContainer) return;
    
    // Extract all original event data
    const titleElement = clone.querySelector('swp-event-title');
    const eventTitle = titleElement ? titleElement.textContent || 'Untitled' : 'Untitled';
    
    const timeElement = clone.querySelector('swp-event-time');
    const eventTime = timeElement ? timeElement.textContent || '' : '';
    const eventDuration = timeElement ? timeElement.getAttribute('data-duration') || '' : '';
    
    // Calculate column index
    const dayHeaders = document.querySelectorAll('swp-day-header');
    let columnIndex = 1;
    dayHeaders.forEach((header, index) => {
      if ((header as HTMLElement).dataset.date === targetDate) {
        columnIndex = index + 1;
      }
    });
    
    // Create all-day event with standardized data attributes
    const allDayEvent = document.createElement('swp-allday-event');
    allDayEvent.dataset.eventId = clone.dataset.eventId || '';
    allDayEvent.dataset.title = eventTitle;
    allDayEvent.dataset.start = `${targetDate}T${eventTime.split(' - ')[0]}:00`;
    allDayEvent.dataset.end = `${targetDate}T${eventTime.split(' - ')[1]}:00`;
    allDayEvent.dataset.type = clone.dataset.type || 'work';
    allDayEvent.dataset.duration = eventDuration;
    allDayEvent.textContent = eventTitle;
    
    // Position in grid
    (allDayEvent as HTMLElement).style.gridColumn = columnIndex.toString();
    // grid-row will be set by checkAndAnimateAllDayHeight() based on actual position
    
    // Remove original clone
    if (clone.parentElement) {
      clone.parentElement.removeChild(clone);
    }
    
    // Add to all-day container
    allDayContainer.appendChild(allDayEvent);
    
    // Update reference
    this.draggedClone = allDayEvent;
    
    // Check if height animation is needed
    this.triggerAllDayHeightAnimation();
  }
  
  
  
  /**
   * 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);
  }
  
  /**
   * Convert dragged clone to all-day event preview
   */
  private convertToAllDayPreview(targetDate: string): void {
    if (!this.draggedClone) return;

    // Only convert once
    if (this.draggedClone.tagName === 'SWP-ALLDAY-EVENT') {
      return;
    }

    // Transform clone to all-day format
    this.transformCloneToAllDay(this.draggedClone, targetDate);

  }
  
  /**
   * Move all-day event to a new date container
   */
  private moveAllDayToNewDate(targetDate: string): void {
    if (!this.draggedClone) return;
    
    const calendarHeader = document.querySelector('swp-calendar-header');
    if (!calendarHeader) return;
    
    // Find the all-day container
    const allDayContainer = calendarHeader.querySelector('swp-allday-container');
    if (!allDayContainer) return;
    
    // Calculate new column index
    const dayHeaders = document.querySelectorAll('swp-day-header');
    let columnIndex = 1;
    dayHeaders.forEach((header, index) => {
      if ((header as HTMLElement).dataset.date === targetDate) {
        columnIndex = index + 1;
      }
    });
    
    // Update grid column position
    (this.draggedClone as HTMLElement).style.gridColumn = columnIndex.toString();
    
    // Move to all-day container if not already there
    if (this.draggedClone.parentElement !== allDayContainer) {
      allDayContainer.appendChild(this.draggedClone);
    }
    
  }
  renderEvents(events: CalendarEvent[], container: HTMLElement, config: CalendarConfig): void {
    
    // NOTE: Removed clearEvents() to support sliding animation
    // With sliding animation, multiple grid containers exist simultaneously
    // clearEvents() would remove events from all containers, breaking the animation
    // Events are now rendered directly into the new container without clearing

    // Separate all-day events from regular events
    const allDayEvents = events.filter(event => event.allDay);
    const regularEvents = events.filter(event => !event.allDay);
    

    // Always call renderAllDayEvents to ensure height is set correctly (even to 0)
    this.renderAllDayEvents(allDayEvents, container, config);

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

    columns.forEach(column => {
      const columnEvents = this.getEventsForColumn(column, regularEvents);
      
      const eventsLayer = column.querySelector('swp-events-layer');
      if (eventsLayer) {
        columnEvents.forEach(event => {
          this.renderEvent(event, eventsLayer, config);
        });
        
        // Debug: Verify events were actually added
        const renderedEvents = eventsLayer.querySelectorAll('swp-event');
      } else {
      }
    });
  }

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

  /**
   * Render all-day events in the header row 2
   */
  protected renderAllDayEvents(allDayEvents: CalendarEvent[], container: HTMLElement, config: CalendarConfig): void {
    
    // Find the calendar header
    const calendarHeader = container.querySelector('swp-calendar-header');
    if (!calendarHeader) {
      return;
    }

    // Find the all-day container (should always exist now)
    const allDayContainer = calendarHeader.querySelector('swp-allday-container') as HTMLElement;
    if (!allDayContainer) {
      console.warn('All-day container not found - this should not happen');
      return;
    }

    // Clear existing events
    allDayContainer.innerHTML = '';

    if (allDayEvents.length === 0) {
      // No events - container exists but is empty and hidden
      return;
    }

    // Build date to column mapping
    const dayHeaders = calendarHeader.querySelectorAll('swp-day-header');
    const dateToColumnMap = new Map<string, number>();
    
    dayHeaders.forEach((header, index) => {
      const dateStr = (header as any).dataset.date;
      if (dateStr) {
        dateToColumnMap.set(dateStr, index + 1); // 1-based column index
      }
    });

    // Calculate grid spans for all events
    const eventSpans = allDayEvents.map(event => ({
      event,
      span: this.calculateEventGridSpan(event, dateToColumnMap)
    })).filter(item => item.span.columnSpan > 0); // Remove events outside visible range

    // Simple row assignment using overlap detection
    const eventPlacements: Array<{ event: CalendarEvent, span: { startColumn: number, columnSpan: number }, row: number }> = [];
    
    eventSpans.forEach(eventItem => {
      let assignedRow = 1;
      
      // Find first row where this event doesn't overlap with any existing event
      while (true) {
        const rowEvents = eventPlacements.filter(item => item.row === assignedRow);
        const hasOverlap = rowEvents.some(rowEvent => 
          this.eventsOverlap(eventItem.span, rowEvent.span)
        );
        
        if (!hasOverlap) {
          break; // Found available row
        }
        assignedRow++;
      }
      
      eventPlacements.push({
        event: eventItem.event,
        span: eventItem.span,
        row: assignedRow
      });
    });

    // Get max row needed
    const maxRow = Math.max(...eventPlacements.map(item => item.row), 1);

    // Place events directly in the single container
    eventPlacements.forEach(({ event, span, row }) => {
      // Create the all-day event element
      const allDayEvent = document.createElement('swp-allday-event');
      allDayEvent.textContent = event.title;
      
      // Set data attributes directly from CalendarEvent
      allDayEvent.dataset.eventId = event.id;
      allDayEvent.dataset.title = event.title;
      allDayEvent.dataset.start = event.start;
      allDayEvent.dataset.end = event.end;
      allDayEvent.dataset.type = event.type;
      allDayEvent.dataset.duration = event.metadata?.duration?.toString() || '60';
      
      // Set grid position (column and row)
      (allDayEvent as HTMLElement).style.gridColumn = span.columnSpan > 1 
        ? `${span.startColumn} / span ${span.columnSpan}`
        : `${span.startColumn}`;
      (allDayEvent as HTMLElement).style.gridRow = row.toString();

      // Use event metadata for color if available
      if (event.metadata?.color) {
        (allDayEvent as HTMLElement).style.backgroundColor = event.metadata.color;
      }
      
      allDayContainer.appendChild(allDayEvent);
      
    });
    
  }

  protected renderEvent(event: CalendarEvent, container: Element, config: CalendarConfig): void {
    const eventElement = document.createElement('swp-event');
    eventElement.dataset.eventId = event.id;
    eventElement.dataset.title = event.title;
    eventElement.dataset.start = event.start;
    eventElement.dataset.end = event.end;
    eventElement.dataset.type = event.type;
    eventElement.dataset.duration = event.metadata?.duration?.toString() || '60';

    // Calculate position based on time
    const position = this.calculateEventPosition(event, config);
    eventElement.style.position = 'absolute';
    eventElement.style.top = `${position.top + 1}px`;
    eventElement.style.height = `${position.height - 3}px`; //adjusted so bottom does not cover horizontal time lines.

    // Color is now handled by CSS classes based on data-type attribute

    // Format time for display using unified method
    const startTime = this.formatTime(event.start);
    const endTime = this.formatTime(event.end);
    
    // Calculate duration in minutes
    const startDate = new Date(event.start);
    const endDate = new Date(event.end);
    const durationMinutes = (endDate.getTime() - startDate.getTime()) / (1000 * 60);

    // Create event content
    eventElement.innerHTML = `
        <swp-event-time data-duration="${durationMinutes}">${startTime} - ${endTime}</swp-event-time>
        <swp-event-title>${event.title}</swp-event-title>
    `;
    

    container.appendChild(eventElement);
  }

  protected calculateEventPosition(event: CalendarEvent, config: CalendarConfig): { top: number; height: number } {
    const startDate = new Date(event.start);
    const endDate = new Date(event.end);
    
    const gridSettings = config.getGridSettings();
    const dayStartHour = gridSettings.dayStartHour;
    const hourHeight = gridSettings.hourHeight;

    // Calculate minutes from visible day start
    const startMinutes = startDate.getHours() * 60 + startDate.getMinutes();
    const endMinutes = endDate.getHours() * 60 + endDate.getMinutes();
    const dayStartMinutes = dayStartHour * 60;

    // Calculate top position (subtract day start to align with time axis)
    const top = ((startMinutes - dayStartMinutes) / 60) * hourHeight;
    
    // Calculate height
    const durationMinutes = endMinutes - startMinutes;
    const height = (durationMinutes / 60) * hourHeight;


    return { top, height };
  }

  /**
   * Calculate grid column span for event
   */
  private calculateEventGridSpan(event: CalendarEvent, dateToColumnMap: Map<string, number>): { startColumn: number, columnSpan: number } {
    const startDate = new Date(event.start);
    const endDate = new Date(event.end);
    const startDateKey = DateCalculator.formatISODate(startDate);
    const startColumn = dateToColumnMap.get(startDateKey);
    
    if (!startColumn) {
      return { startColumn: 0, columnSpan: 0 }; // Event outside visible range
    }

    // Calculate span by checking each day
    let endColumn = startColumn;
    const currentDate = new Date(startDate);
    
    while (currentDate <= endDate) {
      currentDate.setDate(currentDate.getDate() + 1);
      const dateKey = DateCalculator.formatISODate(currentDate);
      const col = dateToColumnMap.get(dateKey);
      if (col) {
        endColumn = col;
      } else {
        break; // Event extends beyond visible range
      }
    }
    
    const columnSpan = endColumn - startColumn + 1;
    return { startColumn, columnSpan };
  }

  /**
   * Check if two events overlap in columns
   */
  private eventsOverlap(event1Span: { startColumn: number, columnSpan: number }, event2Span: { startColumn: number, columnSpan: number }): boolean {
    const event1End = event1Span.startColumn + event1Span.columnSpan - 1;
    const event2End = event2Span.startColumn + event2Span.columnSpan - 1;
    
    return !(event1End < event2Span.startColumn || event2End < event1Span.startColumn);
  }

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

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

  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 eventDate = new Date(event.start);
      const eventDateStr = DateCalculator.formatISODate(eventDate);
      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;
  }
}