sprinklers3/app/state/Token.ts

import TokenClaims from "@common/TokenClaims";
import * as jwt from "jsonwebtoken";
import { computed, createAtom, IAtom, observable } from "mobx";

export class Token {
    @observable token: string | null;

    @computed get claims(): TokenClaims | null {
        if (this.token == null) {
            return null;
        }
        return jwt.decode(this.token) as any;
    }

    private isExpiredAtom: IAtom;
    private currentTime!: number;
    private expirationTimer: number | undefined;

    constructor(token: string | null = null) {
        this.token = token;
        this.isExpiredAtom = createAtom("Token.isExpired",
            this.startUpdating, this.stopUpdating);
        this.updateCurrentTime();
    }

    private updateCurrentTime = (reportChanged: boolean = true) => {
        if (reportChanged) {
            this.isExpiredAtom.reportChanged();
        }
        this.currentTime = Date.now() / 1000;
    }

    get remainingTime(): number {
        if (!this.isExpiredAtom.reportObserved()) {
            this.updateCurrentTime(false);
        }
        if (this.claims == null) {
            return Number.NEGATIVE_INFINITY;
        }
        return this.claims.exp - this.currentTime;
    }

    private startUpdating = () => {
        this.stopUpdating();
        const remaining = this.remainingTime;
        if (remaining > 0) {
            this.expirationTimer = setTimeout(this.updateCurrentTime, this.remainingTime);
        }
    }

    private stopUpdating = () => {
        if (this.expirationTimer != null) {
            clearTimeout(this.expirationTimer);
            this.expirationTimer = undefined;
        }
    }

    get isExpired() {
        return this.remainingTime <= 0;
    }

    @computed get isValid() {
        return this.token != null && !this.isExpired;
    }
}