/**
 * @license
 * Copyright Google Inc. 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 {RelativeInjectorLocation} from './interfaces/injector';
import {TContainerNode, TElementNode, TNode} from './interfaces/node';
import {DECLARATION_VIEW, LView, T_HOST} from './interfaces/view';
import {getParentInjectorViewOffset} from './util/injector_utils';

/**
 * If `startTNode.parent` exists and has an injector, returns TNode for that injector.
 * Otherwise, unwraps a parent injector location number to find the view offset from the current
 * injector, then walks up the declaration view tree until the TNode of the parent injector is
 * found.
 *
 * @param location The location of the parent injector, which contains the view offset
 * @param startView The LView instance from which to start walking up the view tree
 * @param startTNode The TNode instance of the starting element
 * @returns The TNode of the parent injector
 */
export function getParentInjectorTNode(
    location: RelativeInjectorLocation, startView: LView, startTNode: TNode): TElementNode|
    TContainerNode|null {
  // If there is an injector on the parent TNode, retrieve the TNode for that injector.
  if (startTNode.parent && startTNode.parent.injectorIndex !== -1) {
    // view offset is 0
    const injectorIndex = startTNode.parent.injectorIndex;
    let tNode = startTNode.parent;
    // If tNode.injectorIndex === tNode.parent.injectorIndex, then the index belongs to a parent
    // injector.
    while (tNode.parent != null && injectorIndex == tNode.parent.injectorIndex) {
      tNode = tNode.parent;
    }
    return tNode;
  }
  let viewOffset = getParentInjectorViewOffset(location);
  // view offset is 1
  let parentView = startView;
  let parentTNode = startView[T_HOST] as TElementNode;
  // view offset is superior to 1
  while (viewOffset > 1) {
    parentView = parentView[DECLARATION_VIEW] !;
    parentTNode = parentView[T_HOST] as TElementNode;
    viewOffset--;
  }
  return parentTNode;
}