/**
 * @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 {devModeEqual} from '../change_detection/change_detection_util';

import {assertDefined, assertLessThan} from './assert';
import {ACTIVE_INDEX, LContainer} from './interfaces/container';
import {LContext, MONKEY_PATCH_KEY_NAME} from './interfaces/context';
import {ComponentDef, DirectiveDef} from './interfaces/definition';
import {NO_PARENT_INJECTOR, RelativeInjectorLocation, RelativeInjectorLocationFlags} from './interfaces/injector';
import {TContainerNode, TElementNode, TNode, TNodeFlags} from './interfaces/node';
import {RComment, RElement, RText} from './interfaces/renderer';
import {StylingContext} from './interfaces/styling';
import {CONTEXT, DECLARATION_VIEW, FLAGS, HEADER_OFFSET, HOST, HOST_NODE, LViewData, LViewFlags, PARENT, RootContext, TData, TVIEW} from './interfaces/view';



/**
 * Returns whether the values are different from a change detection stand point.
 *
 * Constraints are relaxed in checkNoChanges mode. See `devModeEqual` for details.
 */
export function isDifferent(a: any, b: any, checkNoChangesMode: boolean): boolean {
  if (ngDevMode && checkNoChangesMode) {
    return !devModeEqual(a, b);
  }
  // NaN is the only value that is not equal to itself so the first
  // test checks if both a and b are not NaN
  return !(a !== a && b !== b) && a !== b;
}

export function stringify(value: any): string {
  if (typeof value == 'function') return value.name || value;
  if (typeof value == 'string') return value;
  if (value == null) return '';
  return '' + value;
}

/**
 * Flattens an array in non-recursive way. Input arrays are not modified.
 */
export function flatten(list: any[]): any[] {
  const result: any[] = [];
  let i = 0;

  while (i < list.length) {
    const item = list[i];
    if (Array.isArray(item)) {
      if (item.length > 0) {
        list = item.concat(list.slice(i + 1));
        i = 0;
      } else {
        i++;
      }
    } else {
      result.push(item);
      i++;
    }
  }

  return result;
}

/** Retrieves a value from any `LViewData` or `TData`. */
export function loadInternal<T>(index: number, arr: LViewData | TData): T {
  ngDevMode && assertDataInRangeInternal(index + HEADER_OFFSET, arr);
  return arr[index + HEADER_OFFSET];
}

export function assertDataInRangeInternal(index: number, arr: any[]) {
  assertLessThan(index, arr ? arr.length : 0, 'index expected to be a valid data index');
}

/**
 * Takes the value of a slot in `LViewData` and returns the element node.
 *
 * Normally, element nodes are stored flat, but if the node has styles/classes on it,
 * it might be wrapped in a styling context. Or if that node has a directive that injects
 * ViewContainerRef, it may be wrapped in an LContainer. Or if that node is a component,
 * it will be wrapped in LViewData. It could even have all three, so we keep looping
 * until we find something that isn't an array.
 *
 * @param value The initial value in `LViewData`
 */
export function readElementValue(value: RElement | StylingContext | LContainer | LViewData):
    RElement {
  while (Array.isArray(value)) {
    value = value[HOST] as any;
  }
  return value;
}

/**
 * Retrieves an element value from the provided `viewData`, by unwrapping
 * from any containers, component views, or style contexts.
 */
export function getNativeByIndex(index: number, arr: LViewData): RElement {
  return readElementValue(arr[index + HEADER_OFFSET]);
}

export function getNativeByTNode(tNode: TNode, hostView: LViewData): RElement|RText|RComment {
  return readElementValue(hostView[tNode.index]);
}

export function getTNode(index: number, view: LViewData): TNode {
  return view[TVIEW].data[index + HEADER_OFFSET] as TNode;
}

export function getComponentViewByIndex(nodeIndex: number, hostView: LViewData): LViewData {
  // Could be an LViewData or an LContainer. If LContainer, unwrap to find LViewData.
  const slotValue = hostView[nodeIndex];
  return slotValue.length >= HEADER_OFFSET ? slotValue : slotValue[HOST];
}

export function isContentQueryHost(tNode: TNode): boolean {
  return (tNode.flags & TNodeFlags.hasContentQuery) !== 0;
}

export function isComponent(tNode: TNode): boolean {
  return (tNode.flags & TNodeFlags.isComponent) === TNodeFlags.isComponent;
}

export function isComponentDef<T>(def: DirectiveDef<T>): def is ComponentDef<T> {
  return (def as ComponentDef<T>).template !== null;
}

export function isLContainer(value: RElement | RComment | LContainer | StylingContext): boolean {
  // Styling contexts are also arrays, but their first index contains an element node
  return Array.isArray(value) && typeof value[ACTIVE_INDEX] === 'number';
}

/**
 * Retrieve the root view from any component by walking the parent `LViewData` until
 * reaching the root `LViewData`.
 *
 * @param component any component
 */
export function getRootView(target: LViewData | {}): LViewData {
  ngDevMode && assertDefined(target, 'component');
  let lViewData = Array.isArray(target) ? (target as LViewData) : readPatchedLViewData(target) !;
  while (lViewData && !(lViewData[FLAGS] & LViewFlags.IsRoot)) {
    lViewData = lViewData[PARENT] !;
  }
  return lViewData;
}

export function getRootContext(viewOrComponent: LViewData | {}): RootContext {
  return getRootView(viewOrComponent)[CONTEXT] as RootContext;
}

/**
 * Returns the monkey-patch value data present on the target (which could be
 * a component, directive or a DOM node).
 */
export function readPatchedData(target: any): LViewData|LContext|null {
  return target[MONKEY_PATCH_KEY_NAME];
}

export function readPatchedLViewData(target: any): LViewData|null {
  const value = readPatchedData(target);
  if (value) {
    return Array.isArray(value) ? value : (value as LContext).lViewData;
  }
  return null;
}

export function hasParentInjector(parentLocation: RelativeInjectorLocation): boolean {
  return parentLocation !== NO_PARENT_INJECTOR;
}

export function getParentInjectorIndex(parentLocation: RelativeInjectorLocation): number {
  return (parentLocation as any as number) & RelativeInjectorLocationFlags.InjectorIndexMask;
}

export function getParentInjectorViewOffset(parentLocation: RelativeInjectorLocation): number {
  return (parentLocation as any as number) >> RelativeInjectorLocationFlags.ViewOffsetShift;
}

/**
 * Unwraps a parent injector location number to find the view offset from the current injector,
 * then walks up the declaration view tree until the view is found that contains the parent
 * injector.
 *
 * @param location The location of the parent injector, which contains the view offset
 * @param startView The LViewData instance from which to start walking up the view tree
 * @returns The LViewData instance that contains the parent injector
 */
export function getParentInjectorView(
    location: RelativeInjectorLocation, startView: LViewData): LViewData {
  let viewOffset = getParentInjectorViewOffset(location);
  let parentView = startView;
  // For most cases, the parent injector can be found on the host node (e.g. for component
  // or container), but we must keep the loop here to support the rarer case of deeply nested
  // <ng-template> tags or inline views, where the parent injector might live many views
  // above the child injector.
  while (viewOffset > 0) {
    parentView = parentView[DECLARATION_VIEW] !;
    viewOffset--;
  }
  return parentView;
}

/**
 * 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 LViewData 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: LViewData, startTNode: TNode): TElementNode|
    TContainerNode|null {
  if (startTNode.parent && startTNode.parent.injectorIndex !== -1) {
    // view offset is 0
    const injectorIndex = startTNode.parent.injectorIndex;
    let parentTNode = startTNode.parent;
    while (parentTNode.parent != null && injectorIndex == parentTNode.injectorIndex) {
      parentTNode = parentTNode.parent;
    }
    return parentTNode;
  }

  let viewOffset = getParentInjectorViewOffset(location);
  let parentView = startView;
  let parentTNode = startView[HOST_NODE] as TElementNode;
  while (viewOffset > 0) {
    parentView = parentView[DECLARATION_VIEW] !;
    parentTNode = parentView[HOST_NODE] as TElementNode;
    viewOffset--;
  }
  return parentTNode;
}