// @vitest-environment happy-dom
import { beforeEach, describe, expect, it } from "vitest";
import type { SceneRequest } from "../../src/browser/scene.js";
import { createSceneStage, type SceneStage } from "../../src/browser/scene.js";
import { rendererInputFor, sceneRequestFor } from "../../src/browser/scene-request.js";

/**
 * The transition, exercised rather than asserted.
 *
 * Every collaborator is injected — the decode, the timer, the contribution mount — so what these
 * prove is the sequence itself: readiness is awaited, the outgoing layer is never faded, a stale
 * completion is discarded, and a failure leaves the last good frame exactly where it was.
 */

const SCENE = {
  backgroundColor: "#000000",
  backgroundImage: false,
  backgroundMode: "none" as const,
  blurPixels: 0,
  darkenOpacity: 0,
  fit: "fill" as const,
  shadow: false,
};

function image(key: string, url = `https://cdn.invalid/${key}.webp`): SceneRequest {
  return { alt: "", key, kind: "native-image", scene: SCENE, url };
}

describe("scene stage", () => {
  let root: HTMLElement;
  let decodes: { url: string; resolve: () => void; reject: (error: Error) => void }[];
  let stage: SceneStage;

  function layers(): HTMLElement[] {
    return [...root.querySelectorAll(".signage-layer")] as HTMLElement[];
  }

  function opacities(): string[] {
    return layers().map((layer) => layer.style.opacity);
  }

  async function settle(): Promise<void> {
    for (let index = 0; index < 8; index += 1) {
      await new Promise((resolve) => setTimeout(resolve, 0));
    }
  }

  function resolveDecodes(): void {
    while (decodes.length > 0) {
      decodes.shift()?.resolve();
    }
  }

  beforeEach(() => {
    root = document.createElement("div");
    document.body.append(root);
    decodes = [];
    stage = createSceneStage({
      crossfadeMs: 1000,
      decodeImage: (element) =>
        new Promise<void>((resolve, reject) => {
          decodes.push({
            reject,
            resolve,
            url: element.getAttribute("src") ?? "",
          });
        }),
      root,
      // Fires immediately, so a crossfade completes without the test waiting real time. The
      // ordering the transition depends on is unaffected.
      setTimer: (handler) => {
        handler();
        return undefined;
      },
    });
  });

  it("creates exactly two layers, once, and never rebuilds them", async () => {
    const before = layers();
    expect(before).toHaveLength(2);

    const first = stage.show(image("a"));
    await settle();
    resolveDecodes();
    await first;

    const second = stage.show(image("b"));
    await settle();
    resolveDecodes();
    await second;

    // The same two elements. A renderer that rebuilt them per slide is the `v1` defect.
    expect(layers()[0]).toBe(before[0]);
    expect(layers()[1]).toBe(before[1]);
  });

  it("waits for a real decode before anything becomes visible", async () => {
    const shown = stage.show(image("a"));
    await settle();

    // The image is in the DOM and the decode has not resolved: nothing is visible yet.
    expect(decodes).toHaveLength(1);
    expect(opacities()).toEqual(["0", "0"]);

    resolveDecodes();
    await shown;
    expect(opacities().filter((opacity) => opacity === "1")).toHaveLength(1);
  });

  it("never fades the outgoing layer, so the black root cannot show through", async () => {
    const first = stage.show(image("a"));
    await settle();
    resolveDecodes();
    await first;
    const outgoing = layers().find((layer) => layer.style.opacity === "1") as HTMLElement;

    const second = stage.show(image("b"));
    await settle();
    // The incoming layer is prepared; the outgoing one is still fully opaque, underneath.
    expect(outgoing.style.opacity).toBe("1");
    resolveDecodes();
    await second;

    // Only after the fade completes does the old layer go to zero — and it is now behind, and empty.
    expect(outgoing.style.opacity).toBe("0");
    expect(outgoing.style.zIndex).toBe("1");
  });

  it("keeps the last good frame when incoming content cannot be decoded", async () => {
    const first = stage.show(image("a"));
    await settle();
    resolveDecodes();
    await first;
    const goodKey = stage.currentKey();

    const failing = stage.show(image("broken"));
    await settle();
    decodes.shift()?.reject(new Error("decode failed"));
    const outcome = await failing;

    expect(outcome).toEqual({ code: "SLIDE_DECODE_FAILED", kind: "failed" });
    // The wall still shows what it showed. A broken slide costs one slide.
    expect(stage.currentKey()).toBe(goodKey);
    expect(opacities().filter((opacity) => opacity === "1")).toHaveLength(1);
  });

  it("discards completion from a superseded transition", async () => {
    const first = stage.show(image("a"));
    await settle();
    resolveDecodes();
    await first;

    const slow = stage.show(image("b"));
    await settle();
    const fast = stage.show(image("c"));
    await settle();
    resolveDecodes();
    const [slowOutcome, fastOutcome] = await Promise.all([slow, fast]);

    // The newer transition owns the layers; the older one changes nothing.
    expect(slowOutcome.kind).toBe("superseded");
    expect(fastOutcome.kind).toBe("shown");
    expect(stage.currentKey()).toBe("c");
  });

  it("updates a mounted renderer in place rather than remounting it", async () => {
    const updates: unknown[] = [];
    let mounts = 0;
    const contributionStage = createSceneStage({
      crossfadeMs: 0,
      mountContribution: () => {
        mounts += 1;
        return Promise.resolve({
          unmount: () => undefined,
          update: (input: unknown) => {
            updates.push(input);
          },
        });
      },
      root,
      // Fires immediately, so a crossfade completes without the test waiting real time. The
      // ordering the transition depends on is unaffected.
      setTimer: (handler) => {
        handler();
        return undefined;
      },
    });

    const input = rendererInputFor(
      {
        availableUntilMs: null,
        deadlineAtMs: 5000,
        durationMs: 5000,
        id: "sel-1",
        itemId: "advent",
        itemRevision: "1",
        payload: { headline: "Sunday" },
        presentation: null,
        providerId: "fixture.announcements",
        renderer: {
          contributionId: "fixture.announcements.slide",
          contributionVersion: "1.0.0",
          kind: "contribution",
        },
        revision: 1,
        slotId: "slot-1",
        startedAtMs: 0,
        withdrawn: false,
      },
      { audienceKey: "default", localNowMs: 0, paused: false, remainingMs: null, serverNowMs: 0 },
    );
    const request: SceneRequest = {
      contributionId: "fixture.announcements.slide",
      input,
      key: "sel-1:1:default:r",
      kind: "contribution",
    };

    await contributionStage.show(request);
    const updated = await contributionStage.show({
      ...request,
      input: { ...input, payload: { headline: "Cancelled" } },
    });

    // Same key, new input: one mount, one update, no transition — which is what lets a long-running
    // screen change content without restarting animations or reloading media.
    expect(updated).toEqual({ kind: "updated" });
    expect(mounts).toBe(1);
    expect(updates).toHaveLength(1);
    await contributionStage.destroy();
  });

  it("keeps the last good frame when a renderer refuses to mount", async () => {
    const contributionStage = createSceneStage({
      crossfadeMs: 0,
      mountContribution: () => Promise.reject(new Error("renderer exploded")),
      root,
      // Fires immediately, so a crossfade completes without the test waiting real time. The
      // ordering the transition depends on is unaffected.
      setTimer: (handler) => {
        handler();
        return undefined;
      },
    });

    const outcome = await contributionStage.show({
      contributionId: "fixture.announcements.slide",
      input: {} as never,
      key: "sel-9",
      kind: "contribution",
    });

    expect(outcome).toEqual({ code: "RENDERER_MOUNT_FAILED", kind: "failed" });
    expect(contributionStage.currentKey()).toBeUndefined();
    await contributionStage.destroy();
  });

  it("unmounts a renderer deterministically when its layer is reused", async () => {
    let unmounts = 0;
    const contributionStage = createSceneStage({
      crossfadeMs: 0,
      mountContribution: () =>
        Promise.resolve({
          unmount: () => {
            unmounts += 1;
          },
        }),
      root,
      // Fires immediately, so a crossfade completes without the test waiting real time. The
      // ordering the transition depends on is unaffected.
      setTimer: (handler) => {
        handler();
        return undefined;
      },
    });

    await contributionStage.show({
      contributionId: "a.slide",
      input: {} as never,
      key: "one",
      kind: "contribution",
    });
    await contributionStage.show({
      contributionId: "a.slide",
      input: {} as never,
      key: "two",
      kind: "contribution",
    });
    await contributionStage.show({
      contributionId: "a.slide",
      input: {} as never,
      key: "three",
      kind: "contribution",
    });
    await contributionStage.destroy();

    // Three mounts, three unmounts: repeated mount and unmount leaks nothing.
    expect(unmounts).toBe(3);
  });

  it("reports blackout and slate as states of the root, so one slate implementation renders both", () => {
    stage.setBlackout(true);
    expect(root.dataset.blackout).toBe("true");
    stage.setBlackout(false);
    expect(root.dataset.blackout).toBe("false");

    stage.setSlate(true);
    expect(root.dataset.slate).toBe("true");
  });
});

describe("scene requests", () => {
  const base = {
    availableUntilMs: null,
    deadlineAtMs: 5000,
    durationMs: 5000,
    id: "sel-1",
    itemId: "welcome",
    itemRevision: "abc",
    payload: { headline: "Welcome" },
    presentation: null,
    providerId: "fixture.announcements",
    revision: 1,
    slotId: "slot-1",
    startedAtMs: 0,
    withdrawn: false,
  };
  const context = {
    audienceKey: "default",
    localNowMs: 1000,
    paused: false,
    remainingMs: null,
    serverNowMs: 9000,
  };

  it("gives a renderer both clocks, so a television with a wrong clock still counts correctly", () => {
    const input = rendererInputFor(
      {
        ...base,
        renderer: { contributionId: "a.slide", contributionVersion: "1.0.0", kind: "contribution" },
      },
      context,
    );

    expect(input.clock).toEqual({ localNowMs: 1000, serverNowMs: 9000 });
    expect(input.timing).toMatchObject({ deadlineAtMs: 5000, paused: false, startedAtMs: 0 });
    expect(input.contract).toBe("signage.slide-renderer");
    // Everything the renderer is given, and nothing else: no API client, no principal, no
    // credential, no URL.
    expect(Object.keys(input).sort()).toEqual([
      "audienceKey",
      "clock",
      "contract",
      "generation",
      "itemId",
      "itemRevision",
      "payload",
      "presentation",
      "providerId",
      "timing",
      "version",
    ]);
  });

  it("changes the key when the payload revision or pause state changes, and not when the clock does", () => {
    const selection = {
      ...base,
      renderer: { contributionId: "a.slide", contributionVersion: "1.0.0", kind: "contribution" },
    } as const;
    const first = rendererInputFor(selection, context).generation;
    const reAnchored = rendererInputFor(selection, {
      ...context,
      localNowMs: 99_999,
      serverNowMs: 99_999,
    }).generation;
    const revised = rendererInputFor({ ...selection, revision: 2 }, context).generation;
    const paused = rendererInputFor(selection, { ...context, paused: true }).generation;

    // A reconnect re-anchors the clock. Remounting a renderer for that would restart every
    // animation on the wall for no reason.
    expect(reAnchored).toBe(first);
    expect(revised).not.toBe(first);
    expect(paused).not.toBe(first);
  });

  it("declines to build a scene for a renderer the platform did not publish", () => {
    const request = sceneRequestFor(
      {
        ...base,
        renderer: {
          contributionId: "missing.slide",
          contributionVersion: "1.0.0",
          kind: "contribution",
        },
      },
      context,
      { canMountContribution: () => false },
    );

    // Ordinary rather than exceptional: the contributing module is absent, disabled, or outside
    // Signage's compatible range, and the caller keeps its last good frame.
    expect(request).toBeUndefined();
  });

  it("declines to build a native scene with no delivery URL", () => {
    const request = sceneRequestFor({ ...base, renderer: { kind: "native-image" } }, context, {
      canMountContribution: () => true,
    });

    expect(request).toBeUndefined();
  });
});