import type { Counter, Meter, MeterProvider } from "@opentelemetry/api";
import { describe, expect, it } from "@suaveplan/testing/runner";
import {
    createScalarInstruments,
    recordUiRequest,
    UI_LABEL_VALUE,
} from "./instruments.js";

interface RecordedObservation {
    readonly value: number;
    readonly attributes: Record<string, unknown>;
}

function buildRecordingProvider(): {
    readonly provider: MeterProvider;
    readonly observations: RecordedObservation[];
} {
    const observations: RecordedObservation[] = [];
    const counter = {
        add(value: number, attributes?: Record<string, unknown>): void {
            observations.push({
                value,
                attributes: { ...(attributes ?? {}) },
            });
        },
    } as unknown as Counter;
    const meter = {
        createCounter(): Counter {
            return counter;
        },
    } as unknown as Meter;
    const provider = {
        getMeter(): Meter {
            return meter;
        },
    } as unknown as MeterProvider;
    return { provider, observations };
}

describe("instruments", () => {
    it("createScalarInstruments wires a counter on the supplied provider", {
        timeout: 5000,
    }, () => {
        const { provider, observations } = buildRecordingProvider();
        const instruments = createScalarInstruments({
            meterProvider: provider,
        });
        recordUiRequest(instruments);
        expect(observations.length).toBe(1);
        expect(observations[0]?.attributes).toEqual({ ui: UI_LABEL_VALUE });
    });

    it("recordUiRequest labels per-plugin observations", {
        timeout: 5000,
    }, () => {
        const { provider, observations } = buildRecordingProvider();
        const instruments = createScalarInstruments({
            meterProvider: provider,
        });
        recordUiRequest(instruments, { plugin: "billing" });
        expect(observations[0]?.attributes).toEqual({
            ui: UI_LABEL_VALUE,
            plugin: "billing",
        });
    });

    it("falls back to the OTel global meter provider", {
        timeout: 5000,
    }, () => {
        const instruments = createScalarInstruments();
        expect(instruments.requestsTotal).toBeDefined();
        expect(instruments.meter).toBeDefined();
    });
});