import { metrics } from "@opentelemetry/api";

const meter = metrics.getMeter("@suaveplan/datetime");

/**
 * Histogram tracking the wall-clock duration of `expandRecurrence` calls in
 * milliseconds. Use this to detect expensive recurrence expansions in production.
 */
export const expandRecurrenceDuration = meter.createHistogram(
    "datetime.expand_recurrence.duration_ms",
    {
        description: "Duration of expandRecurrence() calls in milliseconds",
        unit: "ms",
    }
);

/**
 * Histogram tracking the size (number of dates emitted) by
 * `expandRecurrence`. Pairs with {@link expandRecurrenceDuration} to
 * correlate output size with latency.
 */
export const expandRecurrenceSize = meter.createHistogram(
    "datetime.expand_recurrence.size",
    {
        description: "Number of dates emitted by expandRecurrence()",
        unit: "{dates}",
    }
);

/**
 * Histogram tracking the wall-clock duration of `businessDaysBetween` calls
 * in milliseconds.
 */
export const businessDaysBetweenDuration = meter.createHistogram(
    "datetime.business_days_between.duration_ms",
    {
        description: "Duration of businessDaysBetween() calls in milliseconds",
        unit: "ms",
    }
);

/**
 * Histogram tracking the calendar-day span evaluated by
 * `businessDaysBetween` calls.
 */
export const businessDaysBetweenSize = meter.createHistogram(
    "datetime.business_days_between.size",
    {
        description: "Calendar-day span evaluated by businessDaysBetween()",
        unit: "{days}",
    }
);

/**
 * Counter tracking the cumulative number of intervals evaluated by
 * `businessDaysBetween`. Use this to monitor workload distribution.
 */
export const businessDaysBetweenTotal = meter.createCounter(
    "datetime.business_days_between.total",
    {
        description:
            "Cumulative number of day-intervals evaluated by businessDaysBetween()",
        unit: "{days}",
    }
);

/**
 * Record a `businessDaysBetween` observation.
 *
 * @param count - Number of calendar days evaluated in the call.
 */
export function recordBusinessDaysBetween(count: number): void {
    businessDaysBetweenTotal.add(count);
}

/**
 * Record an `expandRecurrence` duration observation.
 *
 * @param durationMs - Elapsed milliseconds for the expansion call.
 */
export function recordExpandRecurrence(durationMs: number): void {
    expandRecurrenceDuration.record(durationMs);
}