export class TelegramPollingLivenessTracker {

#lastGetUpdatesAt: number;

#lastApiActivityAt: number;

#nextInFlightApiCallId = 0;

#latestInFlightApiStartedAt: number | null = null;

#inFlightApiStartedAt = new Map<number, number>();

#lastGetUpdatesStartedAt: number | null = null;

#lastGetUpdatesFinishedAt: number | null = null;

#lastGetUpdatesDurationMs: number | null = null;

constructor(private readonly options: TelegramPollingLivenessTrackerOptions = {}) {

this.#lastGetUpdatesAt = this.#now();

this.#lastApiActivityAt = this.#now();

}

get inFlightGetUpdates() {

return this.#inFlightGetUpdates;

}

noteApiCallStarted(): number {

const startedAt = this.#now();

const callId = this.#nextInFlightApiCallId;

this.#nextInFlightApiCallId += 1;

this.#inFlightApiStartedAt.set(callId, startedAt);

this.#latestInFlightApiStartedAt =

this.#latestInFlightApiStartedAt == null

? startedAt

: Math.max(this.#latestInFlightApiStartedAt, startedAt);

return callId;

}

noteApiCallSuccess(at = this.#now()) {

this.#lastApiActivityAt = at;

}

noteApiCallFinished(callId: number) {

const startedAt = this.#inFlightApiStartedAt.get(callId);

this.#inFlightApiStartedAt.delete(callId);

if (startedAt != null && this.#latestInFlightApiStartedAt === startedAt) {

this.#latestInFlightApiStartedAt = this.#resolveLatestInFlightApiStartedAt();

}

}

noteGetUpdatesStarted(payload: unknown, at = this.#now()) {

this.#lastGetUpdatesAt = at;

this.#lastGetUpdatesStartedAt = at;

this.#lastGetUpdatesDurationMs =

this.#lastGetUpdatesStartedAt == null ? null : at - this.#lastGetUpdatesStartedAt;

this.#lastGetUpdatesOutcome = Array.isArray(result) ? `ok:${result.length}` : "ok";

this.#lastApiActivityAt = at;

this.options.onPollSuccess?.(at);

}

this.#lastGetUpdatesStartedAt == null ? null : at - this.#lastGetUpdatesStartedAt;

this.#lastGetUpdatesOutcome = "error";

this.#lastGetUpdatesError = formatErrorMessage(err);

this.#lastApiActivityAt = at;

}

noteGetUpdatesFinished() {

? 0

: now - (this.#lastGetUpdatesFinishedAt ?? this.#lastGetUpdatesAt);

const elapsed = this.#inFlightGetUpdates > 0 ? activeElapsed : idleElapsed;

const apiLivenessAt =

this.#latestInFlightApiStartedAt == null

? this.#lastApiActivityAt

: Math.max(this.#lastApiActivityAt, this.#latestInFlightApiStartedAt);

const apiElapsed = now - apiLivenessAt;

if (elapsed <= params.thresholdMs || apiElapsed <= params.thresholdMs) {

if (elapsed <= params.thresholdMs) {

return null;

}

if (this.#stallDiagLoggedAt && now - this.#stallDiagLoggedAt < params.thresholdMs / 2) {

return `inFlight=${this.#inFlightGetUpdates} outcome=${this.#lastGetUpdatesOutcome} startedAt=${this.#lastGetUpdatesStartedAt ?? "n/a"} finishedAt=${this.#lastGetUpdatesFinishedAt ?? "n/a"} durationMs=${this.#lastGetUpdatesDurationMs ?? "n/a"} offset=${this.#lastGetUpdatesOffset ?? "n/a"}${error}`;

}

#resolveLatestInFlightApiStartedAt(): number | null {

let newestStartedAt: number | null = null;

for (const activeStartedAt of this.#inFlightApiStartedAt.values()) {

newestStartedAt =

newestStartedAt == null ? activeStartedAt : Math.max(newestStartedAt, activeStartedAt);

}

return newestStartedAt;

}

#now(): number {

return this.options.now?.() ?? Date.now();

}