// ChangelogContent — the version history folds by version (#372).
//
// React's hooks come from the shared harness (src/test/hookHarness.ts): the
// component runs as a plain function, its state survives from one call to the
// next, `commit()` runs its effect (the fetch of the changelog), and the
// handlers of the rendered tree are called as clicks would. The markup is
// read through renderToStaticMarkup.
import { describe, it, expect, vi, beforeEach, afterEach } from "vitest";
import { isValidElement, type ReactElement, type ReactNode } from "react";

vi.mock("react", async (orig) => (await import("../../test/hookHarness")).fakeReact(await orig()));
const ctx = vi.hoisted(() => ({ language: "fr" }));
vi.mock("react-i18next", async () =>
  (await import("../../test/i18nMock")).i18nMock({ language: () => ctx.language }),
);

import { renderToStaticMarkup } from "react-dom/server";
import { hookHarness } from "../../test/hookHarness";
import ChangelogContent, { CHANGELOG_NOTES_ID_PREFIX } from "./ChangelogContent";

const harness = hookHarness();

const FR = [
  "# Journal des modifications",
  "",
  "## [Non publié]",
  "",
  "## [0.17.2] - 2026-10-18",
  "",
  "### Ajouté",
  "",
  "- **Import** : note-0172-a",
  "",
  "### Corrigé",
  "",
  "- note-0172-b",
  "",
  "## [0.17.1] - 2026-10-08",
  "",
  "### Modifié",
  "",
  "- note-0171",
  "",
  "## 0.3.2",
  "",
  "### Ajouté",
  "",
  "- note-032",
  "",
].join("\n");

const EN = FR.replace("Journal des modifications", "Changelog")
  .replace("[Non publié]", "[Unreleased]")
  .replace("note-0171", "note-0171-en");

/** FR with content under its unreleased heading, as in a development build. */
const FR_DEV = FR.replace("## [Non publié]\n", "## [Non publié]\n\n### Modifié\n\n- note-dev\n");

type AnyElement = ReactElement<Record<string, unknown> & { children?: ReactNode }>;

function find(node: ReactNode, pred: (el: AnyElement) => boolean): AnyElement[] {
  if (Array.isArray(node)) return node.flatMap((n) => find(n, pred));
  if (!isValidElement(node)) return [];
  const el = node as AnyElement;
  return [...(pred(el) ? [el] : []), ...find(el.props.children, pred)];
}

function texts(node: ReactNode): string[] {
  if (Array.isArray(node)) return node.flatMap(texts);
  if (typeof node === "string") return [node];
  if (!isValidElement(node)) return [];
  return texts((node as AnyElement).props.children);
}

interface FetchedFile {
  text: () => Promise<string>;
}

let files: Record<string, string>;
/** The bundled files, `files` by URL; any other URL fails, as an unreadable file. */
const readFiles = async (url: string): Promise<FetchedFile> => {
  if (!(url in files)) throw new Error(`unexpected fetch ${url}`);
  return { text: async () => files[url] };
};
const fetchMock = vi.fn(readFiles);

/** Lets the fetch, `text()` and the state updates that follow them settle. */
const settle = () => new Promise((resolve) => setTimeout(resolve, 0));

/** One render of the mounted component. */
function render(installedVersion: string | null = "0.17.1"): ReactNode {
  return harness.render(() => ChangelogContent({ installedVersion }) as ReactNode);
}

/** Mount, run the effect, let the file load, then render with the loaded state. */
async function mount(installedVersion: string | null = "0.17.1"): Promise<ReactNode> {
  render(installedVersion);
  harness.commit();
  await settle();
  return render(installedVersion);
}

/** The title button of `version`. */
function titleOf(tree: ReactNode, version: string): AnyElement {
  const [button] = find(
    tree,
    (e) => e.type === "button" && e.props["aria-controls"] !== undefined && texts(e.props.children).includes(version),
  );
  expect(button, `title of ${version}`).toBeDefined();
  return button;
}

/** The version titles, in order, with their state. */
function titles(tree: ReactNode): Array<[string, boolean]> {
  return find(tree, (e) => e.type === "button" && e.props["aria-controls"] !== undefined).map((e) => [
    texts(e.props.children).join(""),
    e.props["aria-expanded"] as boolean,
  ]);
}

/** The expand-all button. */
function allButton(tree: ReactNode): AnyElement {
  const [button] = find(tree, (e) => e.type === "button" && e.props["aria-controls"] === undefined);
  expect(button, "expand-all button").toBeDefined();
  return button;
}

const click = (button: AnyElement) => (button.props.onClick as () => void)();

beforeEach(() => {
  harness.clear();
  ctx.language = "fr";
  files = { "/CHANGELOG.fr.md": FR, "/CHANGELOG.md": EN };
  fetchMock.mockReset();
  fetchMock.mockImplementation(readFiles);
  vi.stubGlobal("fetch", fetchMock);
});

afterEach(() => {
  vi.unstubAllGlobals();
});

describe("ChangelogContent — loading", () => {
  it("reads the changelog of the app language", async () => {
    await mount();
    expect(fetchMock).toHaveBeenCalledWith("/CHANGELOG.fr.md");

    harness.clear();
    ctx.language = "en";
    fetchMock.mockClear();
    await mount();
    expect(fetchMock).toHaveBeenCalledWith("/CHANGELOG.md");
  });

  it("shows the empty message until the file is read, and when it cannot be read", async () => {
    expect(renderToStaticMarkup(render())).toContain("t(changelog.empty)");

    harness.clear();
    files = {};
    const html = renderToStaticMarkup(await mount());
    expect(html).toContain("t(changelog.empty)");
    expect(html).not.toContain("aria-expanded");
  });
});

describe("ChangelogContent — which versions open (#372)", () => {
  it("opens on the installed version, every other version folded", async () => {
    const tree = await mount("0.17.1");
    expect(titles(tree)).toEqual([
      ["0.17.2", false],
      ["0.17.1", true],
      ["0.3.2", false],
    ]);
    const html = renderToStaticMarkup(tree);
    expect(html).toContain("note-0171");
    expect(html).not.toContain("note-0172-a");
    expect(html).not.toContain("note-032");
  });

  it("opens on the first published version when the installed version is unknown", async () => {
    const tree = await mount(null);
    expect(titles(tree)).toEqual([
      ["0.17.2", true],
      ["0.17.1", false],
      ["0.3.2", false],
    ]);
  });

  it("opens on the first published version when the installed one is not in the file", async () => {
    const tree = await mount("0.18.0");
    expect(titles(tree).filter(([, open]) => open)).toEqual([["0.17.2", true]]);
  });

  it("hides the empty unreleased heading", async () => {
    const html = renderToStaticMarkup(await mount());
    expect(html).not.toContain("Non publié");
  });

  it("keeps an unreleased heading with content, folded, before the versions", async () => {
    files["/CHANGELOG.fr.md"] = FR_DEV;
    const tree = await mount("0.17.2");
    expect(titles(tree)).toEqual([
      ["Non publié", false],
      ["0.17.2", true],
      ["0.17.1", false],
      ["0.3.2", false],
    ]);
    expect(renderToStaticMarkup(tree)).not.toContain("note-dev");
  });

  it("shows the notes of an open version, sections and items, without bold marks", async () => {
    const html = renderToStaticMarkup(await mount("0.17.2"));
    expect(html).toContain(">Ajouté</h4>");
    expect(html).toContain(">Corrigé</h4>");
    expect(html).toContain("Import : note-0172-a");
    expect(html).not.toContain("**Import**");
    expect(html).toContain("note-0172-b");
  });
});

describe("ChangelogContent — folding by hand", () => {
  it("unfolds a folded version and folds it again on its title", async () => {
    let tree: ReactNode = await mount("0.17.1");
    click(titleOf(tree, "0.3.2"));
    tree = render();
    expect(titles(tree)).toEqual([
      ["0.17.2", false],
      ["0.17.1", true],
      ["0.3.2", true],
    ]);
    expect(renderToStaticMarkup(tree)).toContain("note-032");

    click(titleOf(tree, "0.3.2"));
    tree = render();
    expect(titleOf(tree, "0.3.2").props["aria-expanded"]).toBe(false);
    expect(renderToStaticMarkup(tree)).not.toContain("note-032");
  });

  it("folds the installed version on its title", async () => {
    let tree: ReactNode = await mount("0.17.1");
    click(titleOf(tree, "0.17.1"));
    tree = render();
    expect(titles(tree).every(([, open]) => !open)).toBe(true);
  });

  it("unfolds everything with « Expand all », then folds everything with « Collapse all »", async () => {
    let tree: ReactNode = await mount("0.17.1");
    expect(texts(allButton(tree).props.children)).toEqual(["t(changelog.expandAll)"]);

    click(allButton(tree));
    tree = render();
    expect(titles(tree).every(([, open]) => open)).toBe(true);
    expect(texts(allButton(tree).props.children)).toEqual(["t(changelog.collapseAll)"]);
    const html = renderToStaticMarkup(tree);
    for (const note of ["note-0172-a", "note-0171", "note-032"]) expect(html).toContain(note);

    click(allButton(tree));
    tree = render();
    expect(titles(tree).every(([, open]) => !open)).toBe(true);
    expect(texts(allButton(tree).props.children)).toEqual(["t(changelog.expandAll)"]);
  });

  it("offers « Collapse all » once every version is unfolded by hand", async () => {
    let tree: ReactNode = await mount("0.17.1");
    click(titleOf(tree, "0.17.2"));
    tree = render();
    expect(texts(allButton(tree).props.children)).toEqual(["t(changelog.expandAll)"]);
    click(titleOf(tree, "0.3.2"));
    tree = render();
    expect(texts(allButton(tree).props.children)).toEqual(["t(changelog.collapseAll)"]);
  });
});

describe("ChangelogContent — accessibility", () => {
  it("makes each title a button inside its heading, with its state and the notes it controls", async () => {
    const html = renderToStaticMarkup(await mount("0.17.1"));
    // Heading > button with aria-expanded and aria-controls, chevron, version.
    expect(html).toMatch(
      /<h3[^>]*><button type="button" aria-expanded="true" aria-controls="changelog-notes-1" title="t\(changelog\.hideNotes\)"[^>]*><svg[^>]*aria-hidden="true"[^>]*>.*?<\/svg>0\.17\.1<\/button><\/h3>/,
    );
    expect(html).toMatch(
      /<h3[^>]*><button type="button" aria-expanded="false" aria-controls="changelog-notes-0" title="t\(changelog\.showNotes\)"[^>]*><svg[^>]*aria-hidden="true"[^>]*>.*?<\/svg>0\.17\.2<\/button><\/h3>/,
    );
    // Every id an aria-controls names is in the page, folded or not.
    const controlled = [...html.matchAll(/aria-controls="([^"]+)"/g)].map((m) => m[1]);
    expect(controlled).toEqual([0, 1, 2].map((i) => `${CHANGELOG_NOTES_ID_PREFIX}${i}`));
    for (const id of controlled) expect(html).toContain(`id="${id}"`);
  });

  it("names the expand-all button through t, never in hard text", async () => {
    const html = renderToStaticMarkup(await mount("0.17.1"));
    expect(html).toMatch(/<button type="button"[^>]*><svg[^>]*aria-hidden="true"[^>]*>.*?<\/svg>t\(changelog\.expandAll\)<\/button>/);
  });
});

describe("ChangelogContent — language switch", () => {
  it("reloads the file of the new language and opens the installed version again", async () => {
    let tree: ReactNode = await mount("0.17.1");
    click(allButton(tree));
    ctx.language = "en";
    render();
    harness.commit();
    await settle();
    tree = render();
    expect(fetchMock).toHaveBeenLastCalledWith("/CHANGELOG.md");
    expect(titles(tree)).toEqual([
      ["0.17.2", false],
      ["0.17.1", true],
      ["0.3.2", false],
    ]);
    expect(renderToStaticMarkup(tree)).toContain("note-0171-en");
  });

  it("never lets a late answer of the previous language replace the current one", async () => {
    const pending: Array<{ url: string; resolve: (text: string) => void }> = [];
    fetchMock.mockImplementation(
      (url: string) =>
        new Promise<FetchedFile>((resolveFetch) => {
          pending.push({ url, resolve: (text) => resolveFetch({ text: async () => text }) });
        }),
    );

    render("0.17.1");
    harness.commit(); // asks for the French file
    ctx.language = "en";
    render("0.17.1");
    harness.commit(); // cancels the French one, asks for the English file
    expect(pending.map((p) => p.url)).toEqual(["/CHANGELOG.fr.md", "/CHANGELOG.md"]);

    pending[1].resolve(EN);
    await settle();
    pending[0].resolve(FR);
    await settle();
    const html = renderToStaticMarkup(render("0.17.1"));
    expect(html).toContain("note-0171-en");
    expect(html).not.toMatch(/note-0171(?!-en)/);
  });

  it("never lets a late failure of the previous language empty the current history", async () => {
    const pending: Array<{ url: string; resolve: (text: string) => void; reject: (error: Error) => void }> = [];
    fetchMock.mockImplementation(
      (url: string) =>
        new Promise<FetchedFile>((resolveFetch, rejectFetch) => {
          pending.push({ url, resolve: (text) => resolveFetch({ text: async () => text }), reject: rejectFetch });
        }),
    );

    render("0.17.1");
    harness.commit(); // asks for the French file
    ctx.language = "en";
    render("0.17.1");
    harness.commit(); // cancels the French one, asks for the English file
    expect(pending.map((p) => p.url)).toEqual(["/CHANGELOG.fr.md", "/CHANGELOG.md"]);

    pending[1].resolve(EN);
    await settle();
    pending[0].reject(new Error("the French file could not be read"));
    await settle();
    const html = renderToStaticMarkup(render("0.17.1"));
    expect(html).toContain("note-0171-en");
    expect(html).not.toContain("t(changelog.empty)");
  });
});