import { Observable } from 'rxjs';
import { switchMap, take, timeout } from 'rxjs/operators';
import { HttpEvent, HttpHandler, HttpRequest } from '@angular/common/http';
import { Inject, Injectable } from '@angular/core';
import {
    AuthedClientConfig,
    AuthService,
    authServiceToken,
    clientConfigToken
} from './authed-client.config';

@Injectable()
export class AuthedHttpHandler extends HttpHandler {
    constructor(
        private delegate: HttpHandler,
        @Inject(authServiceToken) private auth: AuthService,
        @Inject(clientConfigToken) private config: AuthedClientConfig
    ) {
        super();
    }

    public handle(req: HttpRequest<any>): Observable<HttpEvent<any>> {
        return this.auth.idToken.pipe(
            take(1),
            timeout(this.config.tokenTimeout),
            switchMap(
                token =>
                    this.config.isTokenValid(token)
                        ? this.handleRequest(req, token)
                        : this.config.onMissingToken()
            )
        );
    }

    private handleRequest(
        req: HttpRequest<any>,
        token: string
    ): Observable<HttpEvent<any>> {
        return this.delegate.handle(
            // Req is immutable and must be cloned.
            req.clone({
                setHeaders: {
                    Authorization: `Bearer ${token}`
                }
            })
        );
    }
}