import { Runner } from "../commons/types/runner";
import { CookieUtils } from "../commons/utils/cookie-utils";
import { Logger } from "../commons/utils/logger";
import { SessionUtils } from "../commons/utils/session-utils";
import { SessionStartEvent } from "../event/types/session/start";
import { EventQueue } from "../commons/utils/event-queue";

/**
 * Main Bundle. Responsible for starting all products.
 *
 * @class Bundle
 */
export abstract class Bundle {
    /**
     * Add runners to the bundle.
     *
     * @static
     * @param {Runner} runner Runner to use.
     * @memberof Bundle
     */
    public static use(runner: Runner): void {
        this.runners.push(runner);
    }

    /**
     * Run the bundle.
     *
     * @static
     * @return {Promise<void>}
     * @memberof Bundle
     */
    public static async run(): Promise<void> {
        try {
            if (!CookieUtils.enabled) {
                // TODO: Here we should have some kind of metric.
                // This metric would be used to track how many PageViews we are losing from
                // disabled cookies.

                return;
            }

            this.createDataLayer();
            await EventQueue.resend();
            await this.startSession();

            for (const runner of this.runners) {
                // We need to start a background task that awaits on `runner.start`, so that
                // every error thrown in `runner.start` can be successfully logged.
                const startBackground = async (): Promise<void> => {
                    try {
                        await runner.start();
                    } catch (err) {
                        Logger.log(err);
                    }
                };

                startBackground();
            }
        } catch (err) {
            Logger.log(err);
        }
    }

    private static runners: Runner[] = [];

    /**
     * Create the default dataLayer and instantiate all
     * it's properties with default values.
     *
     * @private
     * @static
     * @memberof Bundle
     */
    private static createDataLayer(): void {
        if (!window.dataLayer) {
            window.dataLayer = [];
        }
    }

    /**
     * Start a new Session. Creates `sessionId` and `anonymousId`.
     *
     * @private
     * @static
     * @memberof Bundle
     */
    private static async startSession(): Promise<void> {
        if (!SessionUtils.isNewSession()) {
            return;
        }

        // Setting the anonymous and sessionId.
        SessionUtils.getAnonymous();
        SessionUtils.getSession();

        // This is event is sent from outside the EventRunner because all services should
        // use the same session API, so starting a session should be centralized and done
        // only once.
        await new SessionStartEvent().push();
    }
}