import { Injectable, InjectionToken, Optional } from "@angular/core";
import { PLATFORM_ID, Inject } from "@angular/core";
import { isPlatformBrowser } from "@angular/common";
import { LoadingBarState } from "./loading-bar.state";
import { Subject, combineLatest } from "rxjs";
import { switchMap, map, startWith } from "rxjs/operators";
import { LOADING_BAR_CONFIG, LoadingBarConfig } from "./loading-bar.config";

@Injectable({ providedIn: "root" })
export class LoadingBarService {
    private refs: { [id: string]: LoadingBarState } = {};
    private streams$ = new Subject<void>();
    readonly value$ = this.streams$.asObservable().pipe(
        startWith(null),
        switchMap(() =>
            combineLatest(
                ...Object.keys(this.refs).map((s) => this.refs[s].value$)
            )
        ),
        map((v) => Math.max(0, ...v))
    );

    /** @deprecated use `value$` instead. */
    get progress$() {
        return this.value$;
    }

    constructor(
        @Inject(PLATFORM_ID) private platformId: Object,
        @Optional()
        @Inject(LOADING_BAR_CONFIG)
        private config: LoadingBarConfig = {}
    ) {}

    /** @deprecated use `useRef` instead. */
    start(initialValue = 2) {
        this.useRef().start(initialValue);
    }

    /** @deprecated use `useRef` instead. */
    set(value: number) {
        this.useRef().set(value);
    }

    /** @deprecated use `useRef` instead. */
    increment(value?: number) {
        this.useRef().increment(value);
    }

    /** @deprecated use `useRef` instead. */
    complete() {
        this.useRef().complete();
    }

    /** @deprecated use `useRef` instead. */
    stop() {
        this.useRef().stop();
    }

    useRef(id: string = "default"): LoadingBarState {
        if (!this.refs[id]) {
            this.refs[id] = new LoadingBarState(this.config);
            this.streams$.next();

            if (!isPlatformBrowser(this.platformId)) {
                this.refs[id].disable();
            }
        }

        return this.refs[id];
    }
}