import { Injectable, signal, computed } from '@angular/core';
import type { DbResizeDirection, DbDragPreview, DbResizePreview } from '../types/dashboard.types';
import { pixelToGridPosition, clamp } from '../utils/grid.utils';

@Injectable()
export class DashboardDragService {
  // Move state
  readonly isDragging = signal(false);
  readonly draggedWidgetId = signal<string | null>(null);
  readonly dragStartCol = signal(0);
  readonly dragStartRow = signal(0);
  readonly dragPreviewCol = signal(0);
  readonly dragPreviewRow = signal(0);
  readonly dragPreviewColSpan = signal(0);
  readonly dragPreviewRowSpan = signal(0);

  // Resize state
  readonly isResizing = signal(false);
  readonly resizeWidgetId = signal<string | null>(null);
  readonly resizeDirection = signal<DbResizeDirection | null>(null);
  readonly resizeStartColSpan = signal(0);
  readonly resizeStartRowSpan = signal(0);
  readonly resizePreviewColSpan = signal(0);
  readonly resizePreviewRowSpan = signal(0);

  // Computed
  readonly isActive = computed(() => this.isDragging() || this.isResizing());

  readonly dragPreview = computed<DbDragPreview | null>(() => {
    if (!this.isDragging()) return null;
    return {
      col: this.dragPreviewCol(),
      row: this.dragPreviewRow(),
      colSpan: this.dragPreviewColSpan(),
      rowSpan: this.dragPreviewRowSpan(),
    };
  });

  readonly resizePreview = computed<DbResizePreview | null>(() => {
    if (!this.isResizing()) return null;
    return {
      colSpan: this.resizePreviewColSpan(),
      rowSpan: this.resizePreviewRowSpan(),
    };
  });

  startDrag(widgetId: string, col: number, row: number, colSpan: number, rowSpan: number): void {
    this.isDragging.set(true);
    this.draggedWidgetId.set(widgetId);
    this.dragStartCol.set(col);
    this.dragStartRow.set(row);
    this.dragPreviewCol.set(col);
    this.dragPreviewRow.set(row);
    this.dragPreviewColSpan.set(colSpan);
    this.dragPreviewRowSpan.set(rowSpan);
  }

  updateDragPreview(col: number, row: number): void {
    this.dragPreviewCol.set(col);
    this.dragPreviewRow.set(row);
  }

  endDrag(): { widgetId: string; col: number; row: number } | null {
    const widgetId = this.draggedWidgetId();
    const col = this.dragPreviewCol();
    const row = this.dragPreviewRow();

    if (!widgetId) {
      this.cancelAll();
      return null;
    }

    this.isDragging.set(false);
    this.draggedWidgetId.set(null);
    this.dragStartCol.set(0);
    this.dragStartRow.set(0);
    this.dragPreviewCol.set(0);
    this.dragPreviewRow.set(0);
    this.dragPreviewColSpan.set(0);
    this.dragPreviewRowSpan.set(0);

    return { widgetId, col, row };
  }

  startResize(
    widgetId: string,
    direction: DbResizeDirection,
    colSpan: number,
    rowSpan: number,
  ): void {
    this.isResizing.set(true);
    this.resizeWidgetId.set(widgetId);
    this.resizeDirection.set(direction);
    this.resizeStartColSpan.set(colSpan);
    this.resizeStartRowSpan.set(rowSpan);
    this.resizePreviewColSpan.set(colSpan);
    this.resizePreviewRowSpan.set(rowSpan);
  }

  updateResizePreview(colSpan: number, rowSpan: number): void {
    this.resizePreviewColSpan.set(colSpan);
    this.resizePreviewRowSpan.set(rowSpan);
  }

  endResize(): { widgetId: string; colSpan: number; rowSpan: number } | null {
    const widgetId = this.resizeWidgetId();
    const colSpan = this.resizePreviewColSpan();
    const rowSpan = this.resizePreviewRowSpan();

    if (!widgetId) {
      this.cancelAll();
      return null;
    }

    this.isResizing.set(false);
    this.resizeWidgetId.set(null);
    this.resizeDirection.set(null);
    this.resizeStartColSpan.set(0);
    this.resizeStartRowSpan.set(0);
    this.resizePreviewColSpan.set(0);
    this.resizePreviewRowSpan.set(0);

    return { widgetId, colSpan, rowSpan };
  }

  cancelAll(): void {
    this.isDragging.set(false);
    this.draggedWidgetId.set(null);
    this.dragStartCol.set(0);
    this.dragStartRow.set(0);
    this.dragPreviewCol.set(0);
    this.dragPreviewRow.set(0);
    this.dragPreviewColSpan.set(0);
    this.dragPreviewRowSpan.set(0);
    this.isResizing.set(false);
    this.resizeWidgetId.set(null);
    this.resizeDirection.set(null);
    this.resizeStartColSpan.set(0);
    this.resizeStartRowSpan.set(0);
    this.resizePreviewColSpan.set(0);
    this.resizePreviewRowSpan.set(0);
  }

  calculateGridPosition(
    event: DragEvent | MouseEvent,
    gridEl: HTMLElement,
    columns: number,
    rowHeight: number,
    gap: number,
  ): { col: number; row: number } {
    const gridRect = gridEl.getBoundingClientRect();
    return pixelToGridPosition(event.clientX, event.clientY, gridRect, columns, rowHeight, gap);
  }
}