React service that manages a queue of toasts to be displayed

ToastService.tsx

/**
* ToastService.ts
*
* Service to show in in-app status.
*/

import _ = require('lodash');
import RX = require('reactxp');

export interface ToastMessageParams {
    key: string;
    textMessage: string;
    bottomMargin?: number;
    duration?: number;
    icon?: string;
    color?: string;
    textColor?: string;
    onPress?: () => void;
}

export class ToastMessage {
    params: ToastMessageParams;
    constructor(params: ToastMessageParams) {
        this.params = params;
    }
}

class ToastService {
    showToastEvent = new RX.Types.SubscribableEvent<(message: ToastMessage) => void>();

    private _currentMessages: ToastMessage[] = [];
    private _displayedMessageKey: string = null;
    private _keyCount = 0;

    scheduleMessage(params: ToastMessageParams): void {
        this._currentMessages.push(new ToastMessage(params));
        this._showToastMessage();
    }

    scheduleTextMessage(textMessage: string): void {
        this.scheduleMessage({ key: 'key' + this._keyCount++, textMessage });
    }

    removeToastMessage(key: string): void {
        // If we are currently showing the associated toast, move on to the next toast.
        // Otherwise just remove it from the queue.
        if (this._displayedMessageKey === key) {
            this.toastDismissed();
        } else {
            _.remove(this._currentMessages, message => message.params.key === key);
        }
    }

    toastDismissed(): void {
        this._displayedMessageKey = null;
        this._showToastMessage();
    }

    private _showToastMessage(): void {
        const message = _.head(this._currentMessages);
        const isForeground = RX.App.getActivationState() === RX.Types.AppActivationState.Active;
        if (message && isForeground && !this._displayedMessageKey) {

            this.showToastEvent.fire(message);
            this._currentMessages.shift();
            this._displayedMessageKey = message.params.key;
        }
    }
}
export default new ToastService();