Calendar/src/managers/DragDropManager.ts

/**
 * DragDropManager - Optimized drag and drop with consolidated position calculations
 * Reduces redundant DOM queries and improves performance through caching
 */

import { IEventBus } from '../types/CalendarTypes';
import { calendarConfig } from '../core/CalendarConfig';
import { PositionUtils } from '../utils/PositionUtils';
import { ColumnBounds, ColumnDetectionUtils } from '../utils/ColumnDetectionUtils';
import { SwpEventElement, BaseSwpEventElement } from '../elements/SwpEventElement';
import {
  DragStartEventPayload,
  DragMoveEventPayload,
  DragEndEventPayload,
  DragMouseEnterHeaderEventPayload,
  DragMouseLeaveHeaderEventPayload,
  DragMouseEnterColumnEventPayload,
  DragColumnChangeEventPayload
} from '../types/EventTypes';
import { MousePosition } from '../types/DragDropTypes';
import { CoreEvents } from '../constants/CoreEvents';

export class DragDropManager {
  private eventBus: IEventBus;

  // Mouse tracking with optimized state
  private mouseDownPosition: MousePosition = { x: 0, y: 0 };
  private currentMousePosition: MousePosition = { x: 0, y: 0 };
  private mouseOffset: MousePosition = { x: 0, y: 0 };

  // Drag state
  private originalElement!: HTMLElement | null;
  private draggedClone!: HTMLElement | null;
  private currentColumn: ColumnBounds | null = null;
  private previousColumn: ColumnBounds | null = null;
  private isDragStarted = false;

  // Hover state
  private isHoverTrackingActive = false;
  private currentHoveredEvent: HTMLElement | null = null;

  // Movement threshold to distinguish click from drag
  private readonly dragThreshold = 5; // pixels

  // Scroll compensation
  private scrollableContent: HTMLElement | null = null;
  private initialScrollTop = 0;
  private initialCloneTop = 0;
  private isScrollCompensating = false; // Track if scroll compensation is active
  private scrollListener: ((e: Event) => void) | null = null;

  // Smooth drag animation
  private dragAnimationId: number | null = null;
  private targetY = 0;
  private currentY = 0;
  private targetColumn: ColumnBounds | null = null;

  constructor(eventBus: IEventBus) {
    this.eventBus = eventBus;
    // Get config values
    const gridSettings = calendarConfig.getGridSettings();



    this.init();
  }

  /**
   * Initialize with optimized event listener setup
   */
  private init(): void {
    // Add event listeners
    document.body.addEventListener('mousemove', this.handleMouseMove.bind(this));
    document.body.addEventListener('mousedown', this.handleMouseDown.bind(this));
    document.body.addEventListener('mouseup', this.handleMouseUp.bind(this));

    const calendarContainer = document.querySelector('swp-calendar-container');

    if (calendarContainer) {
      calendarContainer.addEventListener('mouseleave', () => {
        if (this.originalElement && this.isDragStarted) {
          this.cancelDrag();
        }
      });

      // Event delegation for header enter/leave
      calendarContainer.addEventListener('mouseenter', (e) => {
        const target = e.target as HTMLElement;
        if (target.closest('swp-calendar-header')) {
          this.handleHeaderMouseEnter(e as MouseEvent);
        } else if (target.closest('swp-day-column')) {
          this.handleColumnMouseEnter(e as MouseEvent);
        } else if (target.closest('swp-event')) {
          this.handleEventMouseEnter(e as MouseEvent);
        }
      }, true); // Use capture phase

      calendarContainer.addEventListener('mouseleave', (e) => {
        const target = e.target as HTMLElement;
        if (target.closest('swp-calendar-header')) {
          this.handleHeaderMouseLeave(e as MouseEvent);
        }
        // Don't handle swp-event mouseleave here - let mousemove handle it
      }, true); // Use capture phase
    }

    // Initialize column bounds cache
    ColumnDetectionUtils.updateColumnBoundsCache();




    // Listen to resize events to update cache
    window.addEventListener('resize', () => {
      ColumnDetectionUtils.updateColumnBoundsCache();
    });

    // Listen to navigation events to update cache
    this.eventBus.on('navigation:completed', () => {
      ColumnDetectionUtils.updateColumnBoundsCache();
    });

    this.eventBus.on(CoreEvents.GRID_RENDERED, (event: Event) => {
      this.handleGridRendered(event as CustomEvent);
    });

    // Listen to edge-scroll events to control scroll compensation
    this.eventBus.on('edgescroll:started', () => {
      this.isScrollCompensating = true;
      console.log('🎬 DragDropManager: Edge-scroll started - disabling continueDrag()');
    });

    this.eventBus.on('edgescroll:stopped', () => {
      this.isScrollCompensating = false;
      console.log('🛑 DragDropManager: Edge-scroll stopped - enabling continueDrag()');
    });

  }
  private handleGridRendered(event: CustomEvent) {
    this.scrollableContent = document.querySelector('swp-scrollable-content');
    this.scrollableContent!.addEventListener('scroll', this.handleScroll.bind(this), { passive: true });
  }

  private handleMouseDown(event: MouseEvent): void {

    // Clean up drag state first
    this.cleanupDragState();
    ColumnDetectionUtils.updateColumnBoundsCache();
    //this.lastMousePosition = { x: event.clientX, y: event.clientY };
    //this.initialMousePosition = { x: event.clientX, y: event.clientY };

    // Check if mousedown is on an event
    const target = event.target as HTMLElement;
    if (target.closest('swp-resize-handle')) return;

    let eventElement = target;

    while (eventElement && eventElement.tagName !== 'SWP-GRID-CONTAINER') {
      if (eventElement.tagName === 'SWP-EVENT' || eventElement.tagName === 'SWP-ALLDAY-EVENT') {
        break;
      }
      eventElement = eventElement.parentElement as HTMLElement;
      if (!eventElement) return;
    }

    if (eventElement) {

      // Normal drag - prepare for potential dragging
      this.originalElement = eventElement;
      // Calculate mouse offset within event
      const eventRect = eventElement.getBoundingClientRect();
      this.mouseOffset = {
        x: event.clientX - eventRect.left,
        y: event.clientY - eventRect.top
      };
      this.mouseDownPosition = { x: event.clientX, y: event.clientY };

    }
  }

  /**
   * Optimized mouse move handler with consolidated position calculations
   */
  private handleMouseMove(event: MouseEvent): void {

    if (this.isScrollCompensating) return;
    
    //this.currentMouseY = event.clientY;
    // this.lastMousePosition = { x: event.clientX, y: event.clientY };

    // Check for event hover (coordinate-based) - only when mouse button is up
    if (this.isHoverTrackingActive && event.buttons === 0) {
      this.checkEventHover(event);
    }

    if (event.buttons === 1) {
      const currentPosition: MousePosition = { x: event.clientX, y: event.clientY };
      this.currentMousePosition = currentPosition; // Track current mouse position

      // Try to initialize drag if not started
      if (!this.isDragStarted && this.originalElement) {
        if (!this.initializeDrag(currentPosition)) {
          return; // Not enough movement yet
        }
      }

      // Continue drag if started //TODO: This has to be fixed... it fires way too many events, we can do better
      if (this.isDragStarted && this.originalElement && this.draggedClone) {
        //console.log("Continue drag if started", this.draggedClone);
        this.continueDrag(currentPosition);
        this.detectColumnChange(currentPosition);
      }
    }
  }

  /**
   * Try to initialize drag based on movement threshold
   * Returns true if drag was initialized, false if not enough movement
   */
  private initializeDrag(currentPosition: MousePosition): boolean {
    const deltaX = Math.abs(currentPosition.x - this.mouseDownPosition.x);
    const deltaY = Math.abs(currentPosition.y - this.mouseDownPosition.y);
    const totalMovement = Math.sqrt(deltaX * deltaX + deltaY * deltaY);

    if (totalMovement < this.dragThreshold) {
      return false; // Not enough movement
    }

    // Start drag
    this.isDragStarted = true;



    // Set high z-index on event-group if exists, otherwise on event itself
    const eventGroup = this.originalElement!.closest<HTMLElement>('swp-event-group');
    if (eventGroup) {
      eventGroup.style.zIndex = '9999';
    } else {
      this.originalElement!.style.zIndex = '9999';
    }

    const originalElement = this.originalElement as BaseSwpEventElement;
    this.currentColumn = ColumnDetectionUtils.getColumnBounds(currentPosition);
    this.draggedClone = originalElement.createClone();

    const dragStartPayload: DragStartEventPayload = {
      originalElement: this.originalElement!,
      draggedClone: this.draggedClone,
      mousePosition: this.mouseDownPosition,
      mouseOffset: this.mouseOffset,
      columnBounds: this.currentColumn
    };
    this.eventBus.emit('drag:start', dragStartPayload);

    return true;
  }


  private continueDrag(currentPosition: MousePosition): void {

    if (!this.draggedClone!.hasAttribute("data-allday")) {
      // Calculate raw position from mouse (no snapping)
      const column = ColumnDetectionUtils.getColumnBounds(currentPosition);

      if (column) {
        // Calculate raw Y position relative to column (accounting for mouse offset)
        const columnRect = column.boundingClientRect;
        const eventTopY = currentPosition.y - columnRect.top - this.mouseOffset.y;
        this.targetY = Math.max(0, eventTopY);
        this.targetColumn = column;

        // Start animation loop if not already running
        if (this.dragAnimationId === null) {
          this.currentY = parseFloat(this.draggedClone!.style.top) || 0;
          this.animateDrag();
        }
      }

    }
  }

  /**
   * Detect column change and emit event
   */
  private detectColumnChange(currentPosition: MousePosition): void {
    const newColumn = ColumnDetectionUtils.getColumnBounds(currentPosition);
    if (newColumn == null) return;

    if (newColumn.index !== this.currentColumn?.index) {
      this.previousColumn = this.currentColumn;
      this.currentColumn = newColumn;

      const dragColumnChangePayload: DragColumnChangeEventPayload = {
        originalElement: this.originalElement!,
        draggedClone: this.draggedClone!,
        previousColumn: this.previousColumn,
        newColumn,
        mousePosition: currentPosition
      };
      this.eventBus.emit('drag:column-change', dragColumnChangePayload);
    }
  }

  /**
   * Optimized mouse up handler with consolidated cleanup
   */
  private handleMouseUp(event: MouseEvent): void {
    this.stopDragAnimation();

    if (this.originalElement) {

      // Only emit drag:end if drag was actually started
      if (this.isDragStarted) {
        const mousePosition: MousePosition = { x: event.clientX, y: event.clientY };

        // Snap to grid on mouse up (like ResizeHandleManager)
        const column = ColumnDetectionUtils.getColumnBounds(mousePosition);

        if (!column) return;

        // Get current position and snap it to grid
        const snappedY = this.calculateSnapPosition(mousePosition.y, column);

        // Update clone to snapped position immediately
        if (this.draggedClone) {
          this.draggedClone.style.top = `${snappedY}px`;
        }

        // Detect drop target (swp-day-column or swp-day-header)
        const dropTarget = this.detectDropTarget(mousePosition);

        if (!dropTarget)
          throw "dropTarget is null";

        const dragEndPayload: DragEndEventPayload = {
          originalElement: this.originalElement,
          draggedClone: this.draggedClone,
          mousePosition,
          sourceColumn: this.previousColumn!!,
          finalPosition: { column, snappedY },  // Where drag ended
          target: dropTarget
        };

        console.log('DragEndEventPayload', dragEndPayload);

        this.eventBus.emit('drag:end', dragEndPayload);

        this.cleanupDragState();

      } else {
        // This was just a click - emit click event instead
        this.eventBus.emit('event:click', {
          clickedElement: this.originalElement,
          mousePosition: { x: event.clientX, y: event.clientY }
        });
      }
    }
  }
  // Add a cleanup method that finds and removes ALL clones
  private cleanupAllClones(): void {
    // Remove clones from all possible locations
    const allClones = document.querySelectorAll('[data-event-id^="clone"]');

    if (allClones.length > 0) {
      console.log(`🧹 DragDropManager: Removing ${allClones.length} clone(s)`);
      allClones.forEach(clone => clone.remove());
    }
  }

  /**
   * Cancel drag operation when mouse leaves grid container
   */
  private cancelDrag(): void {
    if (!this.originalElement) return;

    console.log('🚫 DragDropManager: Cancelling drag - mouse left grid container');

    this.cleanupAllClones();

    this.originalElement.style.opacity = '';
    this.originalElement.style.cursor = '';

    this.eventBus.emit('drag:cancelled', {
      originalElement: this.originalElement,
      reason: 'mouse-left-grid'
    });

    this.cleanupDragState();
    this.stopDragAnimation();
  }

  /**
   * Optimized snap position calculation using PositionUtils
   */
  private calculateSnapPosition(mouseY: number, column: ColumnBounds): number {
    // Calculate where the event top would be (accounting for mouse offset)
    const eventTopY = mouseY - this.mouseOffset.y;

    // Snap the event top position, not the mouse position
    const snappedY = PositionUtils.getPositionFromCoordinate(eventTopY, column);

    return Math.max(0, snappedY);
  }

  /**
   * Smooth drag animation using requestAnimationFrame
   * Emits drag:move events with current draggedClone reference on each frame
   */
  private animateDrag(): void { //TODO: this can be optimized... WAIT !!!

    if (!this.isDragStarted || !this.draggedClone || !this.targetColumn) {
      this.dragAnimationId = null;
      return;
    }

    // Smooth interpolation towards target
    const diff = this.targetY - this.currentY;
    const step = diff * 0.3; // 30% of distance per frame

    // Update if difference is significant
    if (Math.abs(diff) > 0.5) {
      this.currentY += step;

      // Emit drag:move event with current draggedClone reference
      const dragMovePayload: DragMoveEventPayload = {
        originalElement: this.originalElement!,
        draggedClone: this.draggedClone, // Always uses current reference
        mousePosition: this.currentMousePosition, // Use current mouse position!
        snappedY: this.currentY,
        columnBounds: this.targetColumn,
        mouseOffset: this.mouseOffset
      };
      this.eventBus.emit('drag:move', dragMovePayload);

      this.dragAnimationId = requestAnimationFrame(() => this.animateDrag());
    } else {
      // Close enough - snap to target
      this.currentY = this.targetY;

      // Emit final position
      const dragMovePayload: DragMoveEventPayload = {
        originalElement: this.originalElement!,
        draggedClone: this.draggedClone,
        mousePosition: this.currentMousePosition, // Use current mouse position!
        snappedY: this.currentY,
        columnBounds: this.targetColumn,
        mouseOffset: this.mouseOffset
      };
      this.eventBus.emit('drag:move', dragMovePayload);

      this.dragAnimationId = null;
    }
  }

  /**
   * Handle scroll during drag - compensate clone position
   */
  private handleScroll(): void {
    if (!this.isDragStarted || !this.draggedClone || !this.scrollableContent || !this.isScrollCompensating) return;

    // First time scrolling - save initial positions NOW!

    if(this.initialScrollTop == 0)
      this.initialScrollTop = this.scrollableContent.scrollTop;
    if(this.initialCloneTop == 0)
      this.initialCloneTop = parseFloat(this.draggedClone.style.top || '0');
    

    console.log('💾 DragDropManager: Scroll compensation started', {
      initialScrollTop: this.initialScrollTop,
      initialCloneTop: this.initialCloneTop
    });


    const currentScrollTop = this.scrollableContent.scrollTop;
    const totalScrollDelta = currentScrollTop - this.initialScrollTop;

    // Beregn ny position baseret på initial position + total scroll delta
    const newTop = this.initialCloneTop + totalScrollDelta;
    this.draggedClone.style.top = `${newTop}px`;

    console.log('📜 DragDropManager: Scroll compensation', {
      initialScrollTop: this.initialScrollTop,
      currentScrollTop,
      totalScrollDelta,
      initialCloneTop: this.initialCloneTop,
      newTop
    });
  }

  /**
   * Stop drag animation
   */
  private stopDragAnimation(): void {
    if (this.dragAnimationId !== null) {
      cancelAnimationFrame(this.dragAnimationId);
      this.dragAnimationId = null;
    }
  }

  /**
   * Clean up drag state
   */
  private cleanupDragState(): void {
    this.previousColumn = null;
    this.originalElement = null;
    this.draggedClone = null;
    this.currentColumn = null;
    this.isDragStarted = false;
  }

  /**
   * Detect drop target - whether dropped in swp-day-column or swp-day-header
   */
  private detectDropTarget(position: MousePosition): 'swp-day-column' | 'swp-day-header' | null {

    // Traverse up the DOM tree to find the target container
    let currentElement = this.draggedClone;
    while (currentElement && currentElement !== document.body) {
      if (currentElement.tagName === 'SWP-ALLDAY-CONTAINER') {
        return 'swp-day-header';
      }
      if (currentElement.tagName === 'SWP-DAY-COLUMN') {
        return 'swp-day-column';
      }
      currentElement = currentElement.parentElement as HTMLElement;
    }

    return null;
  }

  /**
   * Handle mouse enter on swp-event - activate hover tracking
   */
  private handleEventMouseEnter(event: MouseEvent): void {
    const target = event.target as HTMLElement;
    const eventElement = target.closest<HTMLElement>('swp-event');

    // Only handle hover if mouse button is up
    if (eventElement && !this.isDragStarted && event.buttons === 0) {
      // Clear any previous hover first
      if (this.currentHoveredEvent && this.currentHoveredEvent !== eventElement) {
        this.currentHoveredEvent.classList.remove('hover');
      }

      this.isHoverTrackingActive = true;
      this.currentHoveredEvent = eventElement;
      eventElement.classList.add('hover');
    }
  }

  /**
   * Handle mouse enter on calendar header - simplified using native events
   */
  private handleHeaderMouseEnter(event: MouseEvent): void {
    // Only handle if we're dragging a timed event (not all-day)
    if (!this.isDragStarted || !this.draggedClone) {
      return;
    }

    const position: MousePosition = { x: event.clientX, y: event.clientY };
    const targetColumn = ColumnDetectionUtils.getColumnBounds(position);

    if (targetColumn) {
      const calendarEvent = SwpEventElement.extractCalendarEventFromElement(this.draggedClone);

      const dragMouseEnterPayload: DragMouseEnterHeaderEventPayload = {
        targetColumn: targetColumn,
        mousePosition: position,
        originalElement: this.originalElement,
        draggedClone: this.draggedClone,
        calendarEvent: calendarEvent,
        replaceClone: (newClone: HTMLElement) => {
          this.draggedClone = newClone;
          this.dragAnimationId === null;
        }
      };
      console.log('DragMouseEnterHeaderEventPayload', dragMouseEnterPayload);
      this.eventBus.emit('drag:mouseenter-header', dragMouseEnterPayload);
    }
  }

  /**
   * Handle mouse enter on day column - for converting all-day to timed events
   */
  private handleColumnMouseEnter(event: MouseEvent): void {
    // Only handle if we're dragging an all-day event
    if (!this.isDragStarted || !this.draggedClone || !this.draggedClone.hasAttribute('data-allday')) {
      return;
    }

    console.log('🎯 DragDropManager: Mouse entered day column');

    const position: MousePosition = { x: event.clientX, y: event.clientY };
    const targetColumn = ColumnDetectionUtils.getColumnBounds(position);

    if (!targetColumn) {
      console.warn("No column detected when entering day column");
      return;
    }

    // Calculate snapped Y position
    const snappedY = this.calculateSnapPosition(position.y, targetColumn);

    // Extract CalendarEvent from the dragged clone
    const calendarEvent = SwpEventElement.extractCalendarEventFromElement(this.draggedClone);

    const dragMouseEnterPayload: DragMouseEnterColumnEventPayload = {
      targetColumn: targetColumn,
      mousePosition: position,
      snappedY: snappedY,
      originalElement: this.originalElement,
      draggedClone: this.draggedClone,
      calendarEvent: calendarEvent,
      replaceClone: (newClone: HTMLElement) => {
        this.draggedClone = newClone;
        this.dragAnimationId === null;
        this.stopDragAnimation();
      }
    };
    this.eventBus.emit('drag:mouseenter-column', dragMouseEnterPayload);
  }

  /**
   * Handle mouse leave from calendar header - simplified using native events
   */
  private handleHeaderMouseLeave(event: MouseEvent): void {
    // Only handle if we're dragging an all-day event
    if (!this.isDragStarted || !this.draggedClone || !this.draggedClone.hasAttribute("data-allday")) {
      return;
    }

    console.log('🚪 DragDropManager: Mouse left header');

    const position: MousePosition = { x: event.clientX, y: event.clientY };
    const targetColumn = ColumnDetectionUtils.getColumnBounds(position);

    if (!targetColumn) {
      console.warn("No column detected when leaving header");
      return;
    }

    const dragMouseLeavePayload: DragMouseLeaveHeaderEventPayload = {
      targetDate: targetColumn.date,
      mousePosition: position,
      originalElement: this.originalElement,
      draggedClone: this.draggedClone
    };
    this.eventBus.emit('drag:mouseleave-header', dragMouseLeavePayload);
  }

  private checkEventHover(event: MouseEvent): void {
    // Use currentHoveredEvent to check if mouse is still within bounds
    if (!this.currentHoveredEvent) return;

    const rect = this.currentHoveredEvent.getBoundingClientRect();
    const mouseX = event.clientX;
    const mouseY = event.clientY;

    // Check if mouse is still within the current hovered event
    const isStillInside = mouseX >= rect.left && mouseX <= rect.right &&
      mouseY >= rect.top && mouseY <= rect.bottom;

    // If mouse left the event
    if (!isStillInside) {
      // Only disable tracking and clear if mouse is NOT pressed (allow resize to work)
      if (event.buttons === 0) {
        this.isHoverTrackingActive = false;
        this.clearEventHover();
      }
    }
  }

  private clearEventHover(): void {
    if (this.currentHoveredEvent) {
      this.currentHoveredEvent.classList.remove('hover');
      this.currentHoveredEvent = null;
    }
  }
}