///
/// Copyright 2015-2026 Micro Focus or one of its affiliates.
///
/// Licensed under the Apache License, Version 2.0 (the "License");
/// you may not use this file except in compliance with the License.
/// You may obtain a copy of the License at
///
///      http://www.apache.org/licenses/LICENSE-2.0
///
/// Unless required by applicable law or agreed to in writing, software
/// distributed under the License is distributed on an "AS IS" BASIS,
/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
/// See the License for the specific language governing permissions and
/// limitations under the License.
///

import { DOWN_ARROW, ENTER, SPACE, UP_ARROW } from '@angular/cdk/keycodes';
import { SelectionStrategy } from '../../../directives/selection/index';

export class MultipleSelectListStrategy<T> extends SelectionStrategy<T> {
  private _lastSelection: T;

  /** Prevent the browser from highlighting text on shift click */
  mousedown(event: MouseEvent): void {
    event.preventDefault();
  }

  click(event: MouseEvent, data: T): void {
    // activate the clicked item
    this.selectionService.activate(data);

    // if the shift key is pressed we want to perform a multiple selection
    if (event.shiftKey) {
      return this.multipleSelect(data);
    }

    // otherwise perform a single toggle selection
    if (this.selectionService.isSelected(data)) {
      this.deselect(data);
      this._lastSelection = null;
    } else {
      this.select(data);
      this._lastSelection = data;
    }
  }

  keydown(event: KeyboardEvent, data: T): void {
    switch (event.which) {
      case UP_ARROW: {
        event.preventDefault();
        const sibling = this.selectionService.activateSibling(true);

        if (event.shiftKey) {
          this.select(data, sibling);
          this._lastSelection = sibling;
        }
        break;
      }

      case DOWN_ARROW: {
        event.preventDefault();
        const sibling = this.selectionService.activateSibling(false);

        if (event.shiftKey) {
          this.select(data, sibling);
          this._lastSelection = sibling;
        }
        break;
      }

      case SPACE:
      case ENTER:
        event.preventDefault();
        this.toggle(data);
        this._lastSelection = this.selectionService.isSelected(data) ? data : null;
        break;
    }
  }

  multipleSelect(data: T): void {
    // if there is no start item selected
    if (!this._lastSelection) {
      this.select(data);
      this._lastSelection = data;
      return;
    }

    // if there already is a start item then find the items in the range
    this.select(...this.getSelectedItems(this._lastSelection, data));

    // store the selection end point
    this._lastSelection = data;
  }

  private getSelectedItems(start: T, end: T): T[] {
    // get the latest dataset
    const { dataset } = this.selectionService;

    // get the indexes of the start and end point
    const startIdx = dataset.indexOf(start);
    const endIdx = dataset.indexOf(end);

    // get the region of the array that is selected - note the endIdx may be before the startIdx so account for this
    return dataset.slice(Math.min(startIdx, endIdx), Math.max(startIdx, endIdx) + 1);
  }
}