/**
 * @license
 * Copyright Google LLC All Rights Reserved.
 *
 * Use of this source code is governed by an MIT-style license that can be
 * found in the LICENSE file at https://angular.io/license
 */

import {Injectable, Inject, NgZone, ElementRef} from '@angular/core';
import {DOCUMENT} from '@angular/common';
import {ViewportRuler} from '@angular/cdk/scrolling';
import {DragRef, DragRefConfig} from './drag-ref';
import {DropListRef} from './drop-list-ref';
import {DragDropRegistry} from './drag-drop-registry';

/** Default configuration to be used when creating a `DragRef`. */
const DEFAULT_CONFIG = {
  dragStartThreshold: 5,
  pointerDirectionChangeThreshold: 5
};

/**
 * Service that allows for drag-and-drop functionality to be attached to DOM elements.
 */
@Injectable({providedIn: 'root'})
export class DragDrop {
  constructor(
    @Inject(DOCUMENT) private _document: any,
    private _ngZone: NgZone,
    private _viewportRuler: ViewportRuler,
    private _dragDropRegistry: DragDropRegistry<DragRef, DropListRef>) {}

  /**
   * Turns an element into a draggable item.
   * @param element Element to which to attach the dragging functionality.
   * @param config Object used to configure the dragging behavior.
   */
  createDrag<T = any>(element: ElementRef<HTMLElement> | HTMLElement,
                config: DragRefConfig = DEFAULT_CONFIG): DragRef<T> {

    return new DragRef<T>(element, config, this._document, this._ngZone, this._viewportRuler,
        this._dragDropRegistry);
  }

  /**
   * Turns an element into a drop list.
   * @param element Element to which to attach the drop list functionality.
   */
  createDropList<T = any>(element: ElementRef<HTMLElement> | HTMLElement): DropListRef<T> {
    return new DropListRef<T>(element, this._dragDropRegistry, this._document, this._ngZone,
        this._viewportRuler);
  }
}