import { test } from "node:test";
import assert from "node:assert/strict";

import { AVAILABILITY } from "../../src/lib/preview/contracts.js";
import { buildFixtureManifest } from "../../src/lib/preview/manifest.js";
import { createFixtureResolver } from "../../src/lib/preview/resolver.js";
import { createPreviewService } from "../../src/lib/preview/service.js";
import { PHASE } from "../../src/lib/preview/session.js";

const T0 = 1_700_000_000_000;
const SID = "svc-1";

function manifest(n = 3) {
    return buildFixtureManifest({
        rows: Array.from({ length: n }, (_, i) => ({
            providerTrackId: String(i + 1),
            title: `T${i + 1}`,
            initialAvailability: AVAILABILITY.AVAILABLE,
        })),
        createdAtMs: T0,
    });
}

/** Manual scheduler: settle windows fire only when the test says so. */
function makeScheduler() {
    let queue = new Map();
    let nextId = 1;
    const delays = [];
    return {
        delays, // every ms passed to set(), in order — for adaptive-settle asserts
        set(fn, ms) {
            const id = nextId++;
            queue.set(id, fn);
            delays.push(ms);
            return id;
        },
        clear(id) {
            queue.delete(id);
        },
        async flush() {
            const fns = [...queue.values()];
            queue.clear();
            for (const fn of fns) await fn();
            await drainMicrotasks();
        },
        pending: () => queue.size,
    };
}
const drainMicrotasks = () => new Promise((r) => setTimeout(r, 0));

/** Transport double: records every command AND behaves like the real one —
 * play/pause dispatch their media events stamped with the load's context,
 * which is exactly the wiring the service's transportFactory provides. */
function makeTransport() {
    const log = [];
    let dispatch = null;
    let ctx = null;
    const t = {
        log,
        async load(lease, c, opts) {
            ctx = c;
            log.push(["load", lease.opaqueLeaseId, c.generation, !!opts?.startPaused, opts?.startAtMs ?? 0]);
        },
        async play() {
            log.push(["play"]);
            if (ctx) dispatch({ type: "MEDIA_PLAYING", ...ctx });
        },
        async pause() {
            log.push(["pause"]);
            if (ctx) dispatch({ type: "MEDIA_PAUSED", ...ctx });
        },
        async seek(ms) {
            log.push(["seek", ms]);
        },
        async setVolume(v) {
            log.push(["setVolume", v]);
        },
        async stop() {
            ctx = null;
            log.push(["stop"]);
        },
        async dispose() {
            log.push(["dispose"]);
        },
        end() {
            if (ctx) dispatch({ type: "MEDIA_ENDED", ...ctx });
        },
        position(ms) {
            if (ctx) dispatch({ type: "MEDIA_POSITION", ...ctx, positionMs: ms });
        },
    };
    return {
        transport: t,
        factory: (d) => {
            dispatch = d;
            return t;
        },
    };
}

function makeFocus({ grant = true, pausedByPreview = true } = {}) {
    const calls = { acquire: 0, release: 0, handoff: 0, beginMainSilence: 0 };
    let live = null;
    return {
        calls,
        released: [],
        coordinator: {
            async acquirePreview() {
                calls.acquire += 1;
                if (!grant) return { granted: false, token: null };
                live = { id: `t${calls.acquire}`, pausedByPreview };
                return { granted: true, token: live };
            },
            beginMainSilence() {
                calls.beginMainSilence += 1;
            },
            release(token) {
                calls.release += 1;
                const ok = token === live;
                live = null;
                return { restored: ok && pausedByPreview };
            },
            handoffToMain() {
                calls.handoff += 1;
                live = null;
                return { restored: false, reason: "handoff" };
            },
        },
    };
}

function makeService({ plan, grant = true, n = 3 } = {}) {
    const scheduler = makeScheduler();
    const { transport, factory } = makeTransport();
    const focus = makeFocus({ grant });
    let clock = 0;
    const resolver = createFixtureResolver(
        plan ?? { 1: { opaqueLeaseId: "op-1" }, 2: { opaqueLeaseId: "op-2" }, 3: { opaqueLeaseId: "op-3" } }
    );
    const service = createPreviewService({
        resolver,
        transportFactory: factory,
        focus,
        scheduler,
        monotonicNow: () => clock,
    });
    return { service, scheduler, transport, focus, resolver, advance: (ms) => (clock += ms), manifest: manifest(n) };
}

// ------------------------------------------------------------------ open --

test("open: focus, settle, resolve, load audible, play", async () => {
    const { service, scheduler, transport, focus, manifest } = makeService();
    await service.open({ sessionId: SID, manifest });
    assert.equal(focus.calls.acquire, 1);
    assert.equal(service.getState().phase, PHASE.RESOLVING_MEDIA);
    assert.equal(scheduler.pending(), 1); // settle armed

    await scheduler.flush();
    const st = service.getState();
    assert.equal(st.phase, PHASE.PLAYING); // lease landed, played, confirmed
    const load = transport.log.find((e) => e[0] === "load");
    assert.deepEqual(load, ["load", "op-1", st.requestGeneration, false, 0]); // audible → not parked, from the top
    assert.ok(transport.log.some((e) => e[0] === "play"));
});

test("open crossfade: main is NOT silenced until the first preview clip is audible", async () => {
    const { service, scheduler, focus, manifest } = makeService();
    await service.open({ sessionId: SID, manifest });
    // Focus is granted, but the clip hasn't resolved/played — the main track
    // must still be sounding (the whole point of the deferred fade).
    assert.equal(focus.calls.beginMainSilence, 0, "no main fade through resolve/load");
    await scheduler.flush(); // resolve → load → play → MEDIA_PLAYING
    assert.equal(service.getState().phase, PHASE.PLAYING);
    assert.equal(focus.calls.beginMainSilence, 1, "main fades exactly when the preview is audible");
});

test("open crossfade: a parked (denied) open never fades the main track", async () => {
    const { service, scheduler, focus, manifest } = makeService({ grant: false });
    await service.open({ sessionId: SID, manifest });
    await scheduler.flush();
    assert.equal(focus.calls.beginMainSilence, 0, "parked preview leaves the main playing");
});

test("open with focus denied: session opens PARKED, wait state surfaced", async () => {
    const { service, scheduler, transport, manifest } = makeService({ grant: false });
    await service.open({ sessionId: SID, manifest });
    assert.equal(service.getState().desiredPlaying, false);
    await scheduler.flush();
    const load = transport.log.find((e) => e[0] === "load");
    assert.equal(load[3], true, "must load parked without focus");
    assert.ok(!transport.log.some((e) => e[0] === "play"), "no audio without focus");
});

// ------------------------------------------------------------- stepping ---

test("rapid steps: only the LAST generation ever reaches the transport", async () => {
    const { service, scheduler, transport, manifest } = makeService();
    await service.open({ sessionId: SID, manifest });
    service.step(1); // supersedes the open's pipeline before its settle fires
    service.step(1);
    const finalGen = service.getState().requestGeneration;
    await scheduler.flush();
    await scheduler.flush();
    const loads = transport.log.filter((e) => e[0] === "load");
    assert.equal(loads.length, 1, "superseded generations never loaded");
    assert.equal(loads[0][2], finalGen);
    assert.equal(loads[0][1], "op-3"); // stepped 1 → 2 → 3
});

test("failed resolve retries exactly once, then fails the item in place", async () => {
    const { service, scheduler, resolver, manifest } = makeService({
        plan: {
            1: (n) => (n === 1 ? { failure: "stale_lease", retryable: true } : { opaqueLeaseId: "op-fresh" }),
            2: { failure: "network", retryable: true }, // fails on retry too
            3: { opaqueLeaseId: "op-3" },
        },
    });
    await service.open({ sessionId: SID, manifest });
    await scheduler.flush();
    await drainMicrotasks(); // background neighbor prefetch (item 2) settles
    assert.equal(service.getState().phase, PHASE.PLAYING); // retry rescued item 1
    assert.equal(resolver.callCount("1"), 2);
    assert.equal(resolver.callCount("2"), 1, "prefetch tried item 2 once — prefetch never retries");

    service.step(1);
    await scheduler.flush();
    const st = service.getState();
    assert.equal(st.phase, PHASE.ITEM_FAILED);
    assert.equal(st.errorClass, "network");
    // 1 prefetch + 1 pipeline resolve + exactly 1 capped retry = 3, then stop
    assert.equal(resolver.callCount("2"), 3, "one capped retry in the pipeline, never a loop");
    // the failed card stays; stepping onward still works
    service.step(1);
    await scheduler.flush();
    assert.equal(service.getState().phase, PHASE.PLAYING);
    assert.equal(resolver.callCount("2"), 3, "failure is settled — no more calls");
});

// -------------------------------------------- adaptive settle / auto-play --

test("isolated steps fire the pipeline immediately; bursts pay the settle window", async () => {
    const { service, scheduler, advance, manifest } = makeService();
    await service.open({ sessionId: SID, manifest }); // isolated → 0
    service.step(1); // same instant as the open's activation → burst → 150
    advance(300);
    service.step(1); // beyond the burst window → isolated → 0
    assert.deepEqual(scheduler.delays, [0, 150, 0]);
});

test("auto-play: nearing the clip's end advances early so the next track crossfades in", async () => {
    const { service, scheduler, transport, advance, manifest } = makeService();
    await service.open({ sessionId: SID, manifest });
    await scheduler.flush();
    await drainMicrotasks(); // playing item 1, neighbour prefetched
    const genBefore = service.getState().requestGeneration;
    advance(1000); // clear the burst window: the early step must fire at once
    transport.position(29_700); // inside EARLY_ADVANCE_MS of the 30 s clip
    assert.ok(scheduler.pending() >= 1, "early advance armed");
    await scheduler.flush(); // STEP dispatched, settle armed at delay 0
    await scheduler.flush(); // pipeline: load + play item 2
    const st = service.getState();
    assert.equal(st.activeManifestIndex, 1, "advanced before the clip ended");
    assert.equal(st.phase, PHASE.PLAYING);
    assert.ok(st.requestGeneration > genBefore);
    assert.equal(st.desiredPlaying, true, "listen intent survives the auto-advance");
    assert.equal(scheduler.delays.at(-1), 0, "the early step skipped the settle window");
});

test("auto-play: the LAST playable track never advances early", async () => {
    const { service, scheduler, transport, manifest } = makeService();
    await service.open({ sessionId: SID, manifest });
    await scheduler.flush();
    service.step(1);
    await scheduler.flush();
    service.step(1);
    await scheduler.flush(); // riding on item 3 of 3
    await drainMicrotasks();
    assert.equal(service.getState().activeManifestIndex, 2);
    transport.position(29_800);
    assert.equal(scheduler.pending(), 0, "no early advance armed on the last track");
    transport.end(); // natural end still lands in the replay state
    assert.equal(service.getState().phase, PHASE.ENDED);
});

test("setVolume forwards the app volume to the transport", async () => {
    const { service, transport, manifest } = makeService();
    await service.open({ sessionId: SID, manifest });
    service.setVolume(0.35);
    service.setVolume(0); // app mute → silent previews
    assert.deepEqual(
        transport.log.filter((e) => e[0] === "setVolume"),
        [["setVolume", 0.35], ["setVolume", 0]]
    );
});

// ------------------------------------------------------- resume memory ----

test("resume: stepping back to a track picks up where it left off", async () => {
    const { service, scheduler, transport, advance, manifest } = makeService();
    await service.open({ sessionId: SID, manifest });
    await scheduler.flush();
    await drainMicrotasks(); // playing item 1
    transport.position(12_000); // listened 12 s in
    advance(300);
    service.step(1);
    await scheduler.flush();
    await drainMicrotasks(); // playing item 2 from the top
    assert.equal(transport.log.filter((e) => e[0] === "load").at(-1)[4], 0);
    advance(300);
    service.step(-1);
    await scheduler.flush();
    const back = transport.log.filter((e) => e[0] === "load").at(-1);
    assert.equal(back[1], "op-1");
    assert.equal(back[4], 12_000, "revisit resumes at the departure position");
    assert.equal(service.getState().positionMs, 12_000, "scrubber painted at the resume point");
    assert.equal(service.getState().phase, PHASE.PLAYING);
});

test("resume: a track that finished (auto-advance) restarts from the top", async () => {
    const { service, scheduler, transport, advance, manifest } = makeService();
    await service.open({ sessionId: SID, manifest });
    await scheduler.flush();
    await drainMicrotasks(); // playing item 1
    advance(1000);
    transport.position(29_700); // the anticipatory auto-advance point
    await scheduler.flush(); // early STEP
    await scheduler.flush(); // playing item 2
    assert.equal(service.getState().activeManifestIndex, 1);
    advance(300);
    service.step(-1);
    await scheduler.flush();
    const back = transport.log.filter((e) => e[0] === "load").at(-1);
    assert.equal(back[1], "op-1");
    assert.equal(back[4], 0, "a finished clip restarts from the beginning");
});

test("resume: flicking past a track does not erase its remembered position", async () => {
    const { service, scheduler, transport, advance, manifest } = makeService();
    await service.open({ sessionId: SID, manifest });
    await scheduler.flush();
    await drainMicrotasks(); // playing item 1
    transport.position(9_000);
    advance(300);
    service.step(1); // land on 2
    await scheduler.flush();
    await drainMicrotasks();
    advance(300);
    service.step(1); // land on 3 — item 2 leaves at position 0
    await scheduler.flush();
    await drainMicrotasks();
    advance(300);
    service.step(-1); // back to 2: no remembered position → from the top
    await scheduler.flush();
    assert.equal(transport.log.filter((e) => e[0] === "load").at(-1)[4], 0);
    advance(300);
    service.step(-1); // back to 1: the 9 s position survived the pass-through
    await scheduler.flush();
    const back = transport.log.filter((e) => e[0] === "load").at(-1);
    assert.equal(back[1], "op-1");
    assert.equal(back[4], 9_000);
});

// ------------------------------------------------------------- prefetch ---

test("neighbor lease prefetch: stepping forward skips the resolve", async () => {
    const { service, scheduler, resolver, manifest } = makeService();
    await service.open({ sessionId: SID, manifest });
    await scheduler.flush(); // pipeline + prefetch of item 2 kicked
    await drainMicrotasks();
    assert.equal(resolver.callCount("2"), 1, "prefetched in the background");
    service.step(1);
    await scheduler.flush();
    assert.equal(resolver.callCount("2"), 1, "no second resolve on activation");
    assert.equal(service.getState().phase, PHASE.PLAYING);
});

test("backward prefetch: stepping back to the previous track skips the resolve", async () => {
    const { service, scheduler, resolver, manifest } = makeService();
    await service.open({ sessionId: SID, manifest });
    await scheduler.flush();
    await drainMicrotasks(); // landed on 1; forward neighbour 2 prefetched
    service.step(1);
    await scheduler.flush();
    await drainMicrotasks(); // landed on 2; BOTH neighbours (1, 3) prefetched
    const before = resolver.callCount("1");
    assert.ok(before >= 2, "backward neighbour was prefetched after the step");
    service.step(-1);
    await scheduler.flush();
    assert.equal(service.getState().phase, PHASE.PLAYING);
    assert.equal(resolver.callCount("1"), before, "backward step used the prefetched lease");
});

test("pause clicked mid-step transition parks the pipeline instead of playing on", async () => {
    const { service, scheduler, transport, manifest } = makeService();
    await service.open({ sessionId: SID, manifest });
    await scheduler.flush();
    assert.equal(service.getState().phase, PHASE.PLAYING);

    service.step(1); // phase leaves PLAYING while the step resolves
    assert.equal(service.getState().phase, PHASE.RESOLVING_MEDIA);
    await service.togglePlay(); // user hits pause DURING the transition
    assert.equal(service.getState().desiredPlaying, false);
    assert.ok(transport.log.some((e) => e[0] === "pause"), "outgoing audio silenced");

    const playsBefore = transport.log.filter((e) => e[0] === "play").length;
    await scheduler.flush();
    const load = transport.log.filter((e) => e[0] === "load").at(-1);
    assert.equal(load[3], true, "the new track loads parked");
    assert.equal(
        transport.log.filter((e) => e[0] === "play").length,
        playsBefore,
        "nothing auto-plays after parking"
    );
});

test("a prefetched lease past 80% of its safe window is not trusted", async () => {
    const { service, scheduler, resolver, advance, manifest } = makeService({
        plan: {
            1: { opaqueLeaseId: "op-1", safeForMs: 10_000 },
            2: { opaqueLeaseId: "op-2", safeForMs: 10_000 },
            3: { opaqueLeaseId: "op-3" },
        },
    });
    await service.open({ sessionId: SID, manifest });
    await scheduler.flush();
    await drainMicrotasks();
    advance(9_000); // beyond 80% of the 10s safe window
    service.step(1);
    await scheduler.flush();
    assert.equal(resolver.callCount("2"), 2, "stale prefetch re-resolved");
});

// ------------------------------------------- crossfade (fade transports) --

/** Fade-capable transport double (the native transport's shape): fadeOut
 * exists, and load records the crossfadeMs it was handed. */
function makeFadeTransport() {
    const log = [];
    let dispatch = null;
    let ctx = null;
    const t = {
        log,
        async load(lease, c, opts) {
            ctx = c;
            log.push(["load", lease.opaqueLeaseId, c.generation, !!opts?.startPaused, opts?.crossfadeMs ?? 0]);
        },
        async play() {
            log.push(["play"]);
            if (ctx) dispatch({ type: "MEDIA_PLAYING", ...ctx });
        },
        async pause() {
            log.push(["pause"]);
        },
        async seek() {},
        async fadeOut(ms) {
            log.push(["fadeOut", ms]);
        },
        async stop() {
            ctx = null;
            log.push(["stop"]);
        },
        async dispose() {
            log.push(["dispose"]);
        },
    };
    return { transport: t, factory: (d) => ((dispatch = d), t) };
}

function makeFadeService({ plan, n = 3 } = {}) {
    const scheduler = makeScheduler();
    const { transport, factory } = makeFadeTransport();
    const focus = makeFocus();
    const resolver = createFixtureResolver(
        plan ?? { 1: { opaqueLeaseId: "op-1" }, 2: { opaqueLeaseId: "op-2" }, 3: { opaqueLeaseId: "op-3" } }
    );
    const service = createPreviewService({
        resolver,
        transportFactory: factory,
        focus,
        scheduler,
        monotonicNow: () => 0,
    });
    return { service, scheduler, transport, focus, manifest: manifest(n) };
}

test("fade transport: close crossfades — main returns at once, teardown waits for the tail", async () => {
    const { service, scheduler, transport, focus, manifest } = makeFadeService();
    await service.open({ sessionId: SID, manifest });
    await scheduler.flush();
    await drainMicrotasks(); // playing item 1
    const closing = service.close();
    await drainMicrotasks();
    assert.ok(transport.log.some((e) => e[0] === "fadeOut"), "the preview rings down");
    assert.equal(focus.calls.release, 1, "main resumes while the fade is still audible");
    assert.ok(!transport.log.some((e) => e[0] === "dispose"), "teardown holds for the fade tail");
    await scheduler.flush(); // the tail timer
    await closing;
    assert.ok(transport.log.some((e) => e[0] === "dispose"), "then the transport is torn down");
});

test("fade transport: outgoing keeps sounding through a step — load's crossfade owns the handover", async () => {
    const { service, scheduler, transport, manifest } = makeFadeService();
    await service.open({ sessionId: SID, manifest });
    await scheduler.flush(); // playing op-1, op-2 prefetched
    await drainMicrotasks();
    transport.log.length = 0;

    service.step(1);
    assert.ok(
        !transport.log.some((e) => e[0] === "fadeOut" || e[0] === "stop"),
        "nothing retires the outgoing at step time — it must still be sounding"
    );
    await scheduler.flush();
    const load = transport.log.find((e) => e[0] === "load");
    assert.equal(load[1], "op-2");
    assert.equal(load[4], 340, "audible step loads with the reel-slide-length crossfade");
    assert.ok(
        !transport.log.some((e) => e[0] === "fadeOut"),
        "no standalone fade — the crossfade inside load ramps the outgoing"
    );
    assert.equal(scheduler.pending(), 0, "overstay guard cleared once the load landed");
});

test("fade transport: failed resolve fades the outgoing out instead of leaving it playing", async () => {
    const { service, scheduler, transport, manifest } = makeFadeService({
        plan: {
            1: { opaqueLeaseId: "op-1" },
            2: { failure: "network", retryable: false },
            3: { opaqueLeaseId: "op-3" },
        },
    });
    await service.open({ sessionId: SID, manifest });
    await scheduler.flush();
    await drainMicrotasks();
    service.step(1);
    await scheduler.flush();
    assert.equal(service.getState().phase, PHASE.ITEM_FAILED);
    assert.deepEqual(
        transport.log.filter((e) => e[0] === "fadeOut"),
        [["fadeOut", 340]],
        "failure retires the outgoing with the standalone fade"
    );
});

test("fade transport: an overstaying resolve trips the guard and fades the outgoing", async () => {
    const { service, scheduler, transport, manifest } = makeFadeService({
        plan: {
            1: { opaqueLeaseId: "op-1" },
            2: () => new Promise(() => {}), // resolve never returns
            3: { opaqueLeaseId: "op-3" },
        },
    });
    await service.open({ sessionId: SID, manifest });
    await scheduler.flush();
    await drainMicrotasks();
    transport.log.length = 0;

    service.step(1);
    await scheduler.flush(); // settle fires, pipeline blocks on the resolve, guard armed
    assert.equal(scheduler.pending(), 1, "overstay guard is armed while the resolve hangs");
    await scheduler.flush(); // guard fires
    assert.deepEqual(
        transport.log.filter((e) => e[0] === "fadeOut"),
        [["fadeOut", 340]],
        "the outgoing is faded out rather than playing on under the new card"
    );
    assert.ok(!transport.log.some((e) => e[0] === "load"), "nothing ever loaded");
});

// ------------------------------------------------------ close/handoff -----

test("close during resolve: terminal, transport torn down, focus released once", async () => {
    const { service, scheduler, transport, focus, manifest } = makeService();
    await service.open({ sessionId: SID, manifest });
    // close BEFORE the settle window fires — mid-"resolving" phase
    const out = await service.close();
    assert.equal(service.getState().phase, PHASE.CLOSING);
    assert.equal(scheduler.pending(), 0, "settle timer cancelled");
    assert.ok(transport.log.some((e) => e[0] === "dispose"));
    assert.equal(focus.calls.release, 1);
    assert.ok(out.restored);
    // straggler flush does nothing
    await scheduler.flush();
    assert.ok(!transport.log.some((e) => e[0] === "load"));
});

test("play-full handoff: transport stopped, no restoration, main starts with the active item", async () => {
    const { service, scheduler, transport, focus, manifest } = makeService();
    await service.open({ sessionId: SID, manifest });
    await scheduler.flush();
    let started = null;
    await service.playFullTrack(async (item) => {
        started = item;
    });
    assert.equal(focus.calls.handoff, 1);
    assert.equal(started.title, "T1");
    assert.ok(transport.log.some((e) => e[0] === "stop"));
    // closing afterwards must NOT restore the pre-preview main track
    const out = await service.close();
    assert.equal(out.restored, false);
});

// -------------------------------------------------------------- controls --

test("togglePlay: pause from playing, resume from paused, replay from ended", async () => {
    const { service, scheduler, transport, manifest } = makeService();
    await service.open({ sessionId: SID, manifest });
    await scheduler.flush();
    assert.equal(service.getState().phase, PHASE.PLAYING);

    await service.togglePlay();
    assert.equal(service.getState().phase, PHASE.PAUSED);
    assert.equal(service.getState().desiredPlaying, false);
    assert.ok(transport.log.some((e) => e[0] === "pause"));

    await service.togglePlay();
    assert.equal(service.getState().phase, PHASE.PLAYING);
    assert.equal(service.getState().desiredPlaying, true);

    // ride to the LAST playable item, end its clip, and replay from ENDED
    service.step(1);
    await scheduler.flush();
    service.step(1);
    await scheduler.flush();
    assert.equal(service.getState().phase, PHASE.PLAYING);
    transport.end();
    assert.equal(service.getState().phase, PHASE.ENDED);
    await service.togglePlay(); // replay
    assert.equal(service.getState().phase, PHASE.RESOLVING_MEDIA);
    assert.equal(service.getState().desiredPlaying, true);
});