import { eventBus } from '../core/EventBus';
import { CoreEvents } from '../constants/CoreEvents';
import { Configuration } from '../configurations/CalendarConfig';
import { IResizeEndEventPayload } from '../types/EventTypes';
import { PositionUtils } from '../utils/PositionUtils';

type SwpEventEl = HTMLElement & { updateHeight?: (h: number) => void };

export class ResizeHandleManager {
  private cachedEvents: SwpEventEl[] = [];
  private isResizing = false;
  private targetEl: SwpEventEl | null = null;
  
  private startY = 0;
  private startDurationMin = 0;
  private direction: 'grow' | 'shrink' = 'grow';
  
  private snapMin: number;
  private minDurationMin: number;
  private animationId: number | null = null;
  private currentHeight = 0;
  private targetHeight = 0;
  
  private unsubscribers: Array<() => void> = [];
  private pointerCaptured = false;
  private prevZ?: string;
  
  // Constants for better maintainability
  private readonly ANIMATION_SPEED = 0.35;
  private readonly Z_INDEX_RESIZING = '1000';
  private readonly EVENT_REFRESH_THRESHOLD = 0.5;

  constructor(
    private config: Configuration, 
    private positionUtils: PositionUtils
  ) {
    const grid = this.config.gridSettings;
    this.snapMin = grid.snapInterval;
    this.minDurationMin = this.snapMin;
  }

  public initialize(): void {
    this.refreshEventCache();
    this.attachHandles();
    this.attachGlobalListeners();
    this.subscribeToEventBus();
  }

  public destroy(): void {
    this.removeEventListeners();
    this.unsubscribers.forEach(unsubscribe => unsubscribe());
    this.unsubscribers = [];
  }

  private removeEventListeners(): void {
    document.removeEventListener('pointerdown', this.onPointerDown, true);
    document.removeEventListener('pointermove', this.onPointerMove, true);
    document.removeEventListener('pointerup', this.onPointerUp, true);
  }

  private refreshEventCache(): void {
    this.cachedEvents = Array.from(
      document.querySelectorAll<SwpEventEl>('swp-day-columns swp-event')
    );
  }

  private attachHandles(): void {
    this.cachedEvents.forEach(element => {
      if (!element.querySelector(':scope > swp-resize-handle')) {
        const handle = this.createResizeHandle();
        element.appendChild(handle);
      }
    });
  }

  private createResizeHandle(): HTMLElement {
    const handle = document.createElement('swp-resize-handle');
    handle.setAttribute('aria-label', 'Resize event');
    handle.setAttribute('role', 'separator');
    return handle;
  }

  private attachGlobalListeners(): void {
    document.addEventListener('pointerdown', this.onPointerDown, true);
    document.addEventListener('pointermove', this.onPointerMove, true);
    document.addEventListener('pointerup', this.onPointerUp, true);
  }

  private subscribeToEventBus(): void {
    const eventsToRefresh = [
      CoreEvents.GRID_RENDERED, 
      CoreEvents.EVENTS_RENDERED,
      CoreEvents.EVENT_CREATED, 
      CoreEvents.EVENT_UPDATED,
      CoreEvents.EVENT_DELETED
    ];

    const refresh = () => {
      this.refreshEventCache();
      this.attachHandles();
    };

    eventsToRefresh.forEach(event => {
      eventBus.on(event, refresh);
      this.unsubscribers.push(() => eventBus.off(event, refresh));
    });
  }

  private onPointerDown = (e: PointerEvent): void => {
    const handle = (e.target as HTMLElement).closest('swp-resize-handle');
    if (!handle) return;

    const element = handle.parentElement as SwpEventEl;
    this.startResizing(element, e);
  };

  private startResizing(element: SwpEventEl, event: PointerEvent): void {
    this.targetEl = element;
    this.isResizing = true;
    this.startY = event.clientY;

    const startHeight = element.offsetHeight;
    this.startDurationMin = Math.max(
      this.minDurationMin,
      Math.round(this.positionUtils.pixelsToMinutes(startHeight))
    );

    this.setZIndexForResizing(element);
    this.capturePointer(event);
    document.documentElement.classList.add('swp--resizing');
    event.preventDefault();
  }

  private setZIndexForResizing(element: SwpEventEl): void {
    const container = element.closest<HTMLElement>('swp-event-group') ?? element;
    this.prevZ = container.style.zIndex;
    container.style.zIndex = this.Z_INDEX_RESIZING;
  }

  private capturePointer(event: PointerEvent): void {
    try {
      (event.target as Element).setPointerCapture?.(event.pointerId);
      this.pointerCaptured = true;
    } catch (error) {
      console.warn('Pointer capture failed:', error);
    }
  }

  private onPointerMove = (e: PointerEvent): void => {
    if (!this.isResizing || !this.targetEl) return;

    this.updateResizeHeight(e.clientY);
  };

  private updateResizeHeight(currentY: number): void {
    const deltaY = currentY - this.startY;
    this.direction = deltaY >= 0 ? 'grow' : 'shrink';

    const startHeight = this.positionUtils.minutesToPixels(this.startDurationMin);
    const rawHeight = startHeight + deltaY;
    const minHeight = this.positionUtils.minutesToPixels(this.minDurationMin);

    this.targetHeight = Math.max(minHeight, rawHeight);

    if (this.animationId == null) {
      this.currentHeight = this.targetEl?.offsetHeight!!;
      this.animate();
    }
  }

  private animate = (): void => {
    if (!this.isResizing || !this.targetEl) {
      this.animationId = null;
      return;
    }

    const diff = this.targetHeight - this.currentHeight;
    
    if (Math.abs(diff) > this.EVENT_REFRESH_THRESHOLD) {
      this.currentHeight += diff * this.ANIMATION_SPEED;
      this.targetEl.updateHeight?.(this.currentHeight);
      this.animationId = requestAnimationFrame(this.animate);
    } else {
      this.finalizeAnimation();
    }
  };

  private finalizeAnimation(): void {
    if (!this.targetEl) return;

    this.currentHeight = this.targetHeight;
    this.targetEl.updateHeight?.(this.currentHeight);
    this.animationId = null;
  }

  private onPointerUp = (e: PointerEvent): void => {
    if (!this.isResizing || !this.targetEl) return;

    this.cleanupAnimation();
    this.snapToGrid();
    this.emitResizeEndEvent();
    this.cleanupResizing(e);
  };

  private cleanupAnimation(): void {
    if (this.animationId != null) {
      cancelAnimationFrame(this.animationId);
      this.animationId = null;
    }
  }

  private snapToGrid(): void {
    if (!this.targetEl) return;

    const currentHeight = this.targetEl.offsetHeight;
    const snapDistancePx = this.positionUtils.minutesToPixels(this.snapMin);
    const snappedHeight = Math.round(currentHeight / snapDistancePx) * snapDistancePx;
    const minHeight = this.positionUtils.minutesToPixels(this.minDurationMin);
    const finalHeight = Math.max(minHeight, snappedHeight) - 3; // Small gap to grid lines

    this.targetEl.updateHeight?.(finalHeight);
  }

  private emitResizeEndEvent(): void {
    if (!this.targetEl) return;

    const eventId = this.targetEl.dataset.eventId || '';
    const resizeEndPayload: IResizeEndEventPayload = {
      eventId,
      element: this.targetEl,
      finalHeight: this.targetEl.offsetHeight
    };
    
    eventBus.emit('resize:end', resizeEndPayload);
  }

  private cleanupResizing(event: PointerEvent): void {
    this.restoreZIndex();
    this.releasePointer(event);
    
    this.isResizing = false;
    this.targetEl = null;
    
    document.documentElement.classList.remove('swp--resizing');
    this.refreshEventCache(); // TODO: Optimize to avoid full cache refresh
  }

  private restoreZIndex(): void {
    if (!this.targetEl || this.prevZ === undefined) return;

    const container = this.targetEl.closest<HTMLElement>('swp-event-group') ?? this.targetEl;
    container.style.zIndex = this.prevZ;
    this.prevZ = undefined;
  }

  private releasePointer(event: PointerEvent): void {
    if (!this.pointerCaptured) return;

    try {
      (event.target as Element).releasePointerCapture?.(event.pointerId);
      this.pointerCaptured = false;
    } catch (error) {
      console.warn('Pointer release failed:', error);
    }
  }
}