import {scopedObservable, runInScopeDigest} from "./utils/angular-rx-utils";
import Observable = Rx.Observable;
import IScope = angular.IScope;
import IPromise = Rx.IPromise;

let logFn: (msg: string) => any = null;

export function setLogFn(fn: (msg: string) => any) {
  logFn = fn;
}

export abstract class StoreElement {
  pathInStore: string = null;

  log(msg: string) {
    if (this.pathInStore === null || logFn === null) {
      return;
    }

    logFn("[" + this.pathInStore + "] " + msg);
  }
}


type LoaderFn = () => IPromise<any>;

export class LoadingState<T> extends StoreElement {

  private counter = 0;

  private subject = new Rx.ReplaySubject<[number, T]>(1);

  private observable: Observable<[number, T]>;

  private lastLoadRequestedTimestamp: number = 0;

  public minimumTimeoutInMs: number;

  private loaderFn: LoaderFn = (): any => {
    throw "loaderFn not defined";
  };

  constructor(minimumTimeoutInMs: number = 5000) {
    super();
    this.minimumTimeoutInMs = minimumTimeoutInMs;
    this.observable = this.subject
      .filter(val => val[1] !== null);
  }

  public clear() {
    this.log("clear()");
    this.lastLoadRequestedTimestamp = 0;
    this.setState(this.counter++, null);
  }

  public put(value: T) {
    this.log("put(...)");
    this.setState(this.counter++, value);
  }

  public setLoaderFn(loaderFn: LoaderFn) {
    this.log("setLoaderFn(...)");
    this.loaderFn = loaderFn;
  }

  // Force

  public forceLoadAndGet(scope: IScope): IPromise<T> {
    const currentCounter = this.counter++;
    this.lastLoadRequestedTimestamp = Date.now();

    this.log("loading...");
    return this.loaderFn().then(val => {
      runInScopeDigest(scope, () => {
        this.setState(currentCounter, val);
      });
      return val;
    });
  }

  public forceLoadAndObserve(scope: IScope): Observable<T> {
    const currentCounter = this.counter;
    this.forceLoadAndGet(null);
    return this.scopedObservable(scope)
      .skipWhile((val, index, obs) => {
        return val[0] < currentCounter;
      })
      .map(val => val[1]);
  }

  // Maybe

  public maybeLoadAndGet(scope: IScope): IPromise<T> {
    if (this.isTimeoutPassed()) {
      return this.forceLoadAndGet(scope);
    } else {
      return this.get();
    }
  }

  public maybeLoadAndObserve(scope: IScope): Observable<T> {
    this.maybeLoadAndGet(null);
    return this.observe(scope);
  }

  // Passive

  public get(): IPromise<T> {
    return this.observable.take(1).map(val => val[1]).toPromise();
  }

  public observe(scope: IScope): Observable<T> {
    return this.scopedObservable(scope).map(val => val[1]);
  }

  // --------------------------------------------------------------

  private setState(counter: number, val: T) {
    this.subject.onNext([counter, val]);
  }

  private isTimeoutPassed(): boolean {
    return (Date.now() - this.lastLoadRequestedTimestamp) > this.minimumTimeoutInMs;
  }

  private scopedObservable(scope: IScope): Observable<[number, T]> {
    return scope ? scopedObservable(scope, this.observable) : this.observable;
  }
}

export class State<T> extends StoreElement {

  private subject = new Rx.ReplaySubject<T>(1);

  private observable: Observable<T>;

  constructor() {
    super();
    this.observable = this.subject
      .filter(val => val !== null);
  }

  public clear() {
    this.setState(null);
  }

  public put(value: T) {
    this.setState(value);
  }

  public get(): IPromise<T> {
    return this.observable.take(1).toPromise();
  }

  public observe(scope: IScope): Observable<T> {
    return this.scopedObservable(scope);
  }

  private setState(val: T) {
    this.subject.onNext(val);
  }

  private scopedObservable(scope: IScope): Observable<T> {
    return scope ? scopedObservable(scope, this.observable) : this.observable;
  }

}

function traverse(elem: any, path: string) {
  const values = _.toPairs(elem);
  for (let [key, value] of values) {
    let location = path.length > 0 ? path + "." + key : key;
    if (value instanceof StoreElement) {
      value.pathInStore = location;
    } else {
      traverse(value, location);
    }
  }
}

export function initStore(store: any) {
  return traverse(store, "");
}