import * as AtomicTimer from "../../../utils/AtomicTimer";
import { floorToMinutes } from "../../../utils/TimeUtils";
import { RedisService } from "../RedisService";
import * as winston from "winston";

// TODO: unit test the hell outta this
export class ApiRequestService extends RedisService {

    // Every application may make up to 5000 requests per hour.
    // Request counts are stored in one-minute blocks which get added
    // and removed from a list.

    // expires after 1 hour
    static readonly expiry: number = 60;

    async incrApiRequest(application: string) {
        // first, increment the temporary and total counter
        let temp: number = Number(await this.client.incr("app:${application}:request:tempCounter"));
        await this.client.incr("app:${application}:request:totalCounter");

        await this.update(application, temp);
    }

    async getApiRequests(application: string): Promise<number> {
        let total: number = await this.update(application);
        if (!total) total = Number(await this.client.get("app:${application}:request:totalCounter"));

        return total;
    }

    async update(application: string, temp?: number): Promise<number> {
        // the amount of minutes passed since the unix epoch
        const now: number = floorToMinutes((await AtomicTimer.syncTime()).unix());

        // the last time the list was updated
        const last: number = Number(await this.client.get("app:${application}:request:lastUpdate"));

        const minutesPassed: number = last == 0 ? 0 : now - last;

        // retrieve the temp counter unless provided
        if (!temp) temp = Number(await this.client.get("app:${application}:request:tempCounter"));
        let total: number;

        // if the list has less entries than it should, fill it up
        const llen: number = Number(await this.client.llen("app:${application}:request:list"));
        if (llen < ApiRequestService.expiry) {
            if (llen != 0) winston.warn("Less than %s elements in in request count list for application %s", llen, application);
            for (let i = llen; i < ApiRequestService.expiry; i++) {
                await this.client.rpush("app:${application}:request:list", 0);
            }
        }

        for (let i = 0; i < minutesPassed; i++) {
            // remove the last element of the list and subtract it from the counter
            let c: number = Number(await this.client.lpop("app:${application}:request:list"));

            total = Number(await this.client.decrby("app:${application}:request:totalCounter", c));

            // push the temp counter onto the list and reset it
            await this.client.rpush("app:${application}:request:list", temp);
            await this.client.set("app:${application}:request:tempCounter", 0);
            temp = 0;
        }

        // update the last update time
        await this.client.set("app:${application}:request:lastUpdate", now);

        return total;
    }

}