import type EventEmitter from 'events';

const REQUEST_TIME = 'request_time';
const DB_TIME = 'db_time';
const FUNCTION_TIME = 'function_time';
const SCHEDULER_JOB_TIME = 'scheduler_job_time';
const FEATURES_CREATED_BY_PROCESSED = 'features_created_by_processed';
const EVENTS_CREATED_BY_PROCESSED = 'events_created_by_processed';
const FRONTEND_API_REPOSITORY_CREATED = 'frontend_api_repository_created';
const PROXY_REPOSITORY_CREATED = 'proxy_repository_created';
const PROXY_FEATURES_FOR_TOKEN_TIME = 'proxy_features_for_token_time';
const STAGE_ENTERED = 'stage-entered' as const;
const EXCEEDS_LIMIT = 'exceeds-limit' as const;
const REQUEST_ORIGIN = 'request_origin' as const;

type MetricEvent =
    | typeof REQUEST_TIME
    | typeof DB_TIME
    | typeof FUNCTION_TIME
    | typeof SCHEDULER_JOB_TIME
    | typeof FEATURES_CREATED_BY_PROCESSED
    | typeof EVENTS_CREATED_BY_PROCESSED
    | typeof FRONTEND_API_REPOSITORY_CREATED
    | typeof PROXY_REPOSITORY_CREATED
    | typeof PROXY_FEATURES_FOR_TOKEN_TIME
    | typeof STAGE_ENTERED
    | typeof EXCEEDS_LIMIT
    | typeof REQUEST_ORIGIN;

type RequestOriginEventPayload = {
    type: 'UI' | 'API';
    method: Request['method'];
    source?: string;
};

type MetricEventPayloads = {
    [key: string]: unknown;
    [REQUEST_ORIGIN]: RequestOriginEventPayload;
};

type MetricEventPayload<T extends MetricEvent> = MetricEventPayloads[T];

type MetricEventListener<T extends MetricEvent> = (
    payload: MetricEventPayload<T>,
) => void;

const emitMetricEvent = <T extends MetricEvent>(
    eventBus: EventEmitter,
    event: T,
    payload: MetricEventPayload<T>,
) => eventBus.emit(event, payload);

const onMetricEvent = <T extends MetricEvent>(
    eventBus: EventEmitter,
    event: T,
    listener: MetricEventListener<T>,
) => {
    eventBus.on(event, listener);
};

export {
    REQUEST_TIME,
    DB_TIME,
    SCHEDULER_JOB_TIME,
    FUNCTION_TIME,
    FEATURES_CREATED_BY_PROCESSED,
    EVENTS_CREATED_BY_PROCESSED,
    FRONTEND_API_REPOSITORY_CREATED,
    PROXY_REPOSITORY_CREATED,
    PROXY_FEATURES_FOR_TOKEN_TIME,
    STAGE_ENTERED,
    EXCEEDS_LIMIT,
    REQUEST_ORIGIN,
    type MetricEvent,
    type MetricEventPayload,
    emitMetricEvent,
    onMetricEvent,
};