import type { Counter, Histogram } from "@opentelemetry/api";
import { metrics } from "@opentelemetry/api";

const METRIC_CONVERT_TOTAL = "emblem_solver.convert.total";
const METRIC_CONVERT_DURATION = "emblem_solver.convert.duration_ms";

let convertCounter: Counter | undefined;
let convertDuration: Histogram | undefined;

/** Lazy access to the `convert.total` counter. */
export function getConvertCounter(): Counter {
    if (!convertCounter) {
        const meter = metrics.getMeter("@suaveplan/emblem-solver");
        convertCounter = meter.createCounter(METRIC_CONVERT_TOTAL, {
            description: "Total number of convert() invocations",
        });
    }
    return convertCounter;
}

/** Lazy access to the `convert.duration_ms` histogram. */
export function getConvertDuration(): Histogram {
    if (!convertDuration) {
        const meter = metrics.getMeter("@suaveplan/emblem-solver");
        convertDuration = meter.createHistogram(METRIC_CONVERT_DURATION, {
            description: "Duration of convert() in milliseconds",
            unit: "ms",
        });
    }
    return convertDuration;
}

/** Internal test helper: reset the cached instruments. */
export function __resetTelemetryForTests(): void {
    convertCounter = undefined;
    convertDuration = undefined;
}

/** Internal test helper: query the cached instruments. */
export function __peekTelemetryForTests(): {
    counter: Counter | undefined;
    histogram: Histogram | undefined;
} {
    return { counter: convertCounter, histogram: convertDuration };
}