import type {
    Counter,
    Histogram,
    Meter,
    MeterProvider,
} from "@opentelemetry/api";
import {
    afterEach,
    beforeEach,
    describe,
    expect,
    it,
} from "@suaveplan/testing/runner";
import {
    getInstruments,
    recordOp,
    resetInstruments,
    setStorageBrowserOpfsMeterProvider,
} from "./otel.js";

interface RecordedHistogram {
    name: string;
    samples: { value: number; attrs: Record<string, unknown> | undefined }[];
}
interface RecordedCounter {
    name: string;
    additions: { value: number; attrs: Record<string, unknown> | undefined }[];
}

class StubHistogram implements Histogram {
    public readonly entry: RecordedHistogram;
    public constructor(name: string, bag: RecordedHistogram[]) {
        this.entry = { name, samples: [] };
        bag.push(this.entry);
    }
    public record(value: number, attrs?: Record<string, unknown>): void {
        this.entry.samples.push({ value, attrs });
    }
}

class StubCounter implements Counter {
    public readonly entry: RecordedCounter;
    public constructor(name: string, bag: RecordedCounter[]) {
        this.entry = { name, additions: [] };
        bag.push(this.entry);
    }
    public add(value: number, attrs?: Record<string, unknown>): void {
        this.entry.additions.push({ value, attrs });
    }
}

class StubMeter implements Meter {
    public histograms: RecordedHistogram[] = [];
    public counters: RecordedCounter[] = [];
    public createHistogram(name: string): Histogram {
        return new StubHistogram(name, this.histograms);
    }
    public createCounter(name: string): Counter {
        return new StubCounter(name, this.counters);
    }
    public createObservableGauge(): never {
        throw new Error("unused");
    }
    public createUpDownCounter(): never {
        throw new Error("unused");
    }
    public createObservableCounter(): never {
        throw new Error("unused");
    }
    public createObservableUpDownCounter(): never {
        throw new Error("unused");
    }
    public addBatchObservableCallback(): void {}
    public removeBatchObservableCallback(): void {}
    public createGauge(): never {
        throw new Error("unused");
    }
}

class StubMeterProvider implements MeterProvider {
    public meters: StubMeter[] = [];
    public getMeter(): Meter {
        const meter = new StubMeter();
        this.meters.push(meter);
        return meter;
    }
}

describe("storage-browser-opfs otel", () => {
    let provider: StubMeterProvider;
    beforeEach(() => {
        provider = new StubMeterProvider();
        setStorageBrowserOpfsMeterProvider(provider);
    });
    afterEach(() => {
        setStorageBrowserOpfsMeterProvider(undefined);
        resetInstruments();
    });

    function findCounter(name: string): RecordedCounter | undefined {
        return provider.meters[0]?.counters.find((c) => c.name === name);
    }
    function findHistogram(name: string): RecordedHistogram | undefined {
        return provider.meters[0]?.histograms.find((h) => h.name === name);
    }

    it("recordOp emits the documented counter and histogram set", {
        timeout: 5000,
    }, () => {
        recordOp({
            op: "set",
            outcome: "success",
            durationMs: 12,
            bytes: 100,
            direction: "write",
        });
        const dur = findHistogram("storage_browser_opfs.op_duration_ms");
        expect(dur?.samples).toEqual([
            { value: 12, attrs: { op: "set", outcome: "success" } },
        ]);
        const writes = findCounter("storage_browser_opfs.writes_total");
        expect(writes?.additions).toEqual([
            { value: 1, attrs: { op: "set", outcome: "success" } },
        ]);
        const io = findHistogram("storage_browser_opfs.io_bytes");
        expect(io?.samples).toEqual([
            { value: 100, attrs: { op: "set", direction: "write" } },
        ]);
    });

    it("records error counter on a failed op", { timeout: 5000 }, () => {
        recordOp({ op: "get", outcome: "error", durationMs: 3 });
        const errs = findCounter("storage_browser_opfs.errors_total");
        expect(errs?.additions).toEqual([
            { value: 1, attrs: { op: "get", outcome: "error" } },
        ]);
    });

    it("records aborted operations on the errors counter", {
        timeout: 5000,
    }, () => {
        recordOp({ op: "get", outcome: "aborted", durationMs: 0 });
        expect(
            findCounter("storage_browser_opfs.errors_total")?.additions[0]
                ?.attrs
        ).toEqual({ op: "get", outcome: "aborted" });
    });

    it("increments reads/writes/deletes counters by op kind", {
        timeout: 5000,
    }, () => {
        recordOp({ op: "get", outcome: "success", durationMs: 1 });
        recordOp({ op: "getPartial", outcome: "success", durationMs: 1 });
        recordOp({ op: "getWithMetadata", outcome: "success", durationMs: 1 });
        recordOp({ op: "set", outcome: "success", durationMs: 1 });
        recordOp({ op: "setPartial", outcome: "success", durationMs: 1 });
        recordOp({ op: "delete", outcome: "success", durationMs: 1 });
        recordOp({ op: "clear", outcome: "success", durationMs: 1 });
        recordOp({ op: "exists", outcome: "success", durationMs: 1 });
        recordOp({ op: "list", outcome: "success", durationMs: 1 });
        expect(
            findCounter("storage_browser_opfs.reads_total")?.additions
        ).toHaveLength(3);
        expect(
            findCounter("storage_browser_opfs.writes_total")?.additions
        ).toHaveLength(2);
        expect(
            findCounter("storage_browser_opfs.deletes_total")?.additions
        ).toHaveLength(2);
    });

    it("returns a cached instrument set on repeat getInstruments calls", {
        timeout: 5000,
    }, () => {
        const a = getInstruments();
        const b = getInstruments();
        expect(a).toBe(b);
    });

    it("rebuilds the instrument set when getInstruments(true) is called", {
        timeout: 5000,
    }, () => {
        const a = getInstruments();
        const b = getInstruments(true);
        expect(a).not.toBe(b);
    });

    it("omits the io_bytes record when bytes is undefined", {
        timeout: 5000,
    }, () => {
        recordOp({ op: "list", outcome: "success", durationMs: 5 });
        expect(
            findHistogram("storage_browser_opfs.io_bytes")?.samples ?? []
        ).toHaveLength(0);
    });

    it("uses the global metrics fallback when provider is unset", {
        timeout: 5000,
    }, () => {
        setStorageBrowserOpfsMeterProvider(undefined);
        // Should not throw — falls back to the global no-op meter provider.
        const inst = getInstruments(true);
        expect(inst.meter).toBeDefined();
    });
});