import { ActivatedRoute, ActivatedRouteSnapshot, convertToParamMap, Data, ParamMap, Params, Route, UrlSegment } from '@angular/router';
import { BehaviorSubject } from 'rxjs';

/**
 * The options that are passed when creating an ActivatedRouteStub.
 */
export interface ActivatedRouteStubOptions {
  /**
   * The initial values of the parameters of the route
   */
  params?: Params;
  /**
   * The initial values of the query parameters of the route
   */
  queryParams?: Params;
  /**
   * The initial values of the data of the route
   */
  data?: Data;
  /**
   * The initial values of the title of the route
   */
  title?: string;
  /**
   * The initial fragment of the route
   */
  fragment?: string | null;
  /**
   * The initial url of the route
   */
  url?: UrlSegment[];
  /**
   * The parent of the route
   */
  parent?: ActivatedRouteStub | null;
  /**
   * The first child of the route
   */
  firstChild?: ActivatedRouteStub | null;
  /**
   * The children of the route
   */
  children?: ActivatedRouteStub[] | null;
  /**
   * The configuration of the route
   */
  routeConfig?: Route | null;
}

class ActivatedRouteSnapshotStub extends ActivatedRouteSnapshot {
  private _parent: ActivatedRouteSnapshot | null = null;
  private _root: ActivatedRouteSnapshot;
  private _firstChild: ActivatedRouteSnapshot | null = null;
  private _children: Array<ActivatedRouteSnapshot> = [];
  private _pathFromRoot: Array<ActivatedRouteSnapshot> = [];
  private _title: string | undefined;

  get parent(): ActivatedRouteSnapshot | null {
    return this._parent;
  }

  set parent(value: ActivatedRouteSnapshot | null) {
    this._parent = value;
  }

  get root(): ActivatedRouteSnapshot {
    return this._root;
  }

  set root(value: ActivatedRouteSnapshot) {
    this._root = value;
  }

  get firstChild(): ActivatedRouteSnapshot | null {
    return this._firstChild;
  }

  set firstChild(value: ActivatedRouteSnapshot | null) {
    this._firstChild = value;
  }

  get children(): Array<ActivatedRouteSnapshot> {
    return this._children;
  }

  set children(value: Array<ActivatedRouteSnapshot>) {
    this._children = value;
  }

  get pathFromRoot(): Array<ActivatedRouteSnapshot> {
    return this._pathFromRoot;
  }

  set pathFromRoot(value: Array<ActivatedRouteSnapshot>) {
    this._pathFromRoot = value;
  }

  get title(): string | undefined {
    return this._title;
  }

  set title(value: string | undefined) {
    this._title = value;
  }

  get paramMap(): ParamMap {
    return convertToParamMap(this.params);
  }

  get queryParamMap(): ParamMap {
    return convertToParamMap(this.queryParams);
  }

  constructor() {
    super();
    this._root = this;
  }
}

/**
 * A stub for ActivatedRoute. It behaves almost the same way as the actual ActivatedRoute, exposing a snapshot
 * and observables for the params, query params etc., which are kept in sync.
 *
 * In addition, this stub allows simulating a navigation by changing the params, the query params, the fragment, etc.
 * When that happens, the snapshot is modified, then the relevant observables emit the new values.
 *
 * There are some things that don't really work the same way as the real ActivatedRoute though:
 * - the handling of the firstChild and of the children is entirely under the tester's responsibility. Setting the parent
 *   of a route stub does not add this route to the children of its parent, for example.
 * - when changing the params, query params, fragment, etc., their associated observable emits unconditionally, instead of
 *   first checking if the value is actually different from before. It's thus the responsibility of the tester to not
 *   change the values if they're the same as before.
 * - the params, paramMap, queryParams and queryParamMap objects of the route snapshot change when params or query params are set
 *   on the stub route. So if the code keeps a reference to params or paramMaps, it won't see the changes.
 */
export class ActivatedRouteStub extends ActivatedRoute {
  private _firstChild: ActivatedRouteStub | null;
  private _children: Array<ActivatedRouteStub>;

  private readonly paramsSubject: BehaviorSubject<Params>;
  private readonly queryParamsSubject: BehaviorSubject<Params>;
  private readonly dataSubject: BehaviorSubject<Data>;
  private readonly fragmentSubject: BehaviorSubject<string | null>;
  private readonly urlSubject: BehaviorSubject<Array<UrlSegment>>;
  private readonly titleSubject: BehaviorSubject<string | undefined>;

  private _parent: ActivatedRouteStub | null;
  private _root: ActivatedRouteStub;
  private _pathFromRoot: Array<ActivatedRouteStub>;

  /**
   * Constructs a new instance, based on the given options.
   * If an option is not provided (or if no option is provided at all), then the route has a default value for this option
   * (empty parameters for example, null fragment, etc.)
   * If no parent is passed, then this route has no parent and is thus set as the root. Otherwise, the root and the path
   * from root are created based on the root and path from root of the given parent route.
   */
  constructor(options?: ActivatedRouteStubOptions) {
    super();

    const snapshot = new ActivatedRouteSnapshotStub();
    this.snapshot = snapshot;

    this._firstChild = options?.firstChild ?? null;
    this._children = options?.children ?? [];
    this._parent = options?.parent ?? null;
    this._root = this.parent?.root ?? this;
    this._pathFromRoot = this.parent ? [...this.parent.pathFromRoot, this] : [this];

    snapshot.params = options?.params ?? {};
    snapshot.queryParams = options?.queryParams ?? {};
    snapshot.data = options?.data ?? {};
    snapshot.title = options?.title;
    snapshot.fragment = options?.fragment ?? null;
    snapshot.url = options?.url ?? [];
    // @ts-expect-error the routeConfig is readonly, but we need to overwrite it here
    snapshot.routeConfig = options?.routeConfig ?? null;

    snapshot.firstChild = this.firstChild?.snapshot ?? null;
    snapshot.children = this.children?.map(route => route.snapshot) ?? [];
    snapshot.parent = this.parent?.snapshot ?? null;
    snapshot.root = this.root.snapshot;
    snapshot.pathFromRoot = this.pathFromRoot.map(route => route.snapshot);

    this.paramsSubject = new BehaviorSubject<Params>(this.snapshot.params);
    this.queryParamsSubject = new BehaviorSubject<Params>(this.snapshot.queryParams);
    this.dataSubject = new BehaviorSubject<Data>(this.snapshot.data);
    this.titleSubject = new BehaviorSubject<string | undefined>(this.snapshot.title);
    this.fragmentSubject = new BehaviorSubject<string | null>(this.snapshot.fragment);
    this.urlSubject = new BehaviorSubject<Array<UrlSegment>>(this.snapshot.url);

    this.params = this.paramsSubject.asObservable();
    this.queryParams = this.queryParamsSubject.asObservable();
    this.data = this.dataSubject.asObservable();
    this.fragment = this.fragmentSubject.asObservable();
    this.url = this.urlSubject.asObservable();
    // @ts-expect-error the title is readonly, but we need to be able to initialize it  here
    this.title = this.titleSubject.asObservable();
  }

  get root() {
    return this._root;
  }

  get parent(): ActivatedRouteStub | null {
    return this._parent;
  }

  get pathFromRoot(): Array<ActivatedRouteStub> {
    return this._pathFromRoot;
  }

  get firstChild(): ActivatedRouteStub | null {
    return this._firstChild;
  }

  get children(): Array<ActivatedRouteStub> {
    return this._children;
  }

  get routeConfig(): Route | null {
    return this.snapshot.routeConfig;
  }

  /**
   * Triggers a navigation with the given new parameters. All the other parts (query params etc.) stay as they are.
   * This is a shortcut to `triggerNavigation` that can be used to only change the parameters.
   */
  public setParams(params: Params): void {
    this.triggerNavigation({ params });
  }

  /**
   * Triggers a navigation with the given new parameter. The other parameters, as well as all the other parts (query params etc.)
   * stay as they are.
   * This is a shortcut to `triggerNavigation` that can be used to only change one parameter.
   */
  public setParam(name: string, value: string): void {
    this.setParams({ ...this.snapshot.params, [name]: value });
  }

  /**
   * Triggers a navigation with the given new query parameters. All the other parts (params etc.) stay as the are.
   * This is a shortcut to `triggerNavigation` that can be used to only change the query parameters.
   */
  public setQueryParams(queryParams: Params): void {
    this.triggerNavigation({ queryParams });
  }

  /**
   * Triggers a navigation with the given new parameter. The other query parameters, as well as all the other parts (params etc.)
   * stay as the are.
   * This is a shortcut to `triggerNavigation` that can be used to only change one query parameter.
   */
  public setQueryParam(name: string, value: string): void {
    this.setQueryParams({ ...this.snapshot.queryParams, [name]: value });
  }

  /**
   * Triggers a navigation with the given new data. The other parameters, as well as all the other parts (params etc.)
   * stay as the are.
   * This is a shortcut to `triggerNavigation` that can be used to only change the data.
   */
  public setData(data: Data): void {
    this.triggerNavigation({ data });
  }

  /**
   * Triggers a navigation with the given new data item. The other data, as well as all the other parts (params etc.)
   * stay as the are.
   * This is a shortcut to `triggerNavigation` that can be used to only change one data item.
   */
  public setDataItem(name: string, value: unknown): void {
    this.setData({ ...this.snapshot.data, [name]: value });
  }

  /**
   * Triggers a navigation with the given new title. The other parameters, as well as all the other parts (params etc.)
   * stay as the are.
   * This is a shortcut to `triggerNavigation` that can be used to only change the title.
   */
  public setTitle(title: string | undefined): void {
    this.triggerNavigation({ title: { value: title } });
  }

  /**
   * Triggers a navigation with the given new fragment. The other parts (params etc.)  stay as the are.
   * This is a shortcut to `triggerNavigation` that can be used to only change the fragment.
   */
  public setFragment(fragment: string | null): void {
    this.triggerNavigation({ fragment });
  }

  /**
   * Triggers a navigation with the given new url. The other parts (params etc.)  stay as the are.
   * This is a shortcut to `triggerNavigation` that can be used to only change the url.
   */
  public setUrl(url: Array<UrlSegment>): void {
    this.triggerNavigation({ url });
  }

  /**
   * Triggers a navigation based on the given options. If an option is undefined or null, it's ignored. Except for fragment, which is only
   * ignored if it's undefined, because null is a valid value for a fragment.
   *
   * The non-ignored values are used to change the snapshot of the route. Once the snapshot has been modified,
   * the observables corresponding to the updated parts emit the new value.
   *
   * So, setting params and query params will make the params and queryParams observables emit, but not the fragment, data and
   * url observables for example. This is consistent to how the router behaves.
   *
   * Note: since the title of a route can become undefined, in order to be able to distinguish between a navigation which leaves the title
   * as it is and a navigation that sets the title to undefined, a wrapper object is used for the title. So
   *
   * - `triggerNavigation({ params:... })` leaves the title as is because it's undefined in the options
   * - `triggerNavigation({ title: { value: 'test' } })` sets the title to 'test'
   * - `triggerNavigation({ title: { value: undefined } })` sets the title to undefined
   */
  public triggerNavigation(options: {
    params?: Params;
    queryParams?: Params;
    fragment?: string | null;
    data?: Data | null;
    title?: { value: string | undefined } | null;
    url?: Array<UrlSegment> | null;
  }): void {
    // set the snapshot first
    if (options.params) {
      this.snapshot.params = options.params;
    }
    if (options.queryParams) {
      this.snapshot.queryParams = options.queryParams;
    }
    if (options.fragment !== undefined) {
      this.snapshot.fragment = options.fragment;
    }
    if (options.data) {
      this.snapshot.data = options.data;
    }
    if (options.title) {
      // @ts-expect-error the title is readonly, but we need to be able to overwrite it here
      this.snapshot.title = options.title.value;
    }
    if (options.url) {
      this.snapshot.url = options.url;
    }

    // then emit everything that has changed
    if (options.params) {
      this.paramsSubject.next(this.snapshot.params);
    }
    if (options.queryParams) {
      this.queryParamsSubject.next(this.snapshot.queryParams);
    }
    if (options.fragment !== undefined) {
      this.fragmentSubject.next(this.snapshot.fragment);
    }
    if (options.data) {
      this.dataSubject.next(this.snapshot.data);
    }
    if (options.title) {
      this.titleSubject.next(this.snapshot.title);
    }
    if (options.url) {
      this.urlSubject.next(this.snapshot.url);
    }
  }

  public toString(): string {
    return 'ActivatedRouteStub';
  }
}

/**
 * Creates a new ActivatedRouteStub, by calling its constructor.
 */
export function stubRoute(options?: ActivatedRouteStubOptions): ActivatedRouteStub {
  return new ActivatedRouteStub(options);
}