// DocsSubsections — unit tests (Issue #355).
//
// Same approach as FilterPanel.test.tsx: no jsdom in this project, and the
// component's only hook is `useTranslation` (mocked by `i18nMock` over a
// fixture), so it is invoked directly as a function and its React-element
// tree is walked without a renderer.

import { describe, it, expect, vi } from "vitest";

// Hoisted: the factory of `vi.mock` below reads it when the module loads.
const FIXTURE = vi.hoisted((): Record<string, unknown> => ({
  "docs.import.subsections": [
    {
      id: "import-export",
      title: "Export a CSV from your bank",
      steps: ["One subfolder per account", "Pick the widest range"],
      note: "Trailing note",
    },
    {
      id: "import-bnc",
      title: "National Bank",
      status: "No public procedure found",
      steps: ["Expected header"],
    },
  ],
}));

// The fixture stands for what the locale declares; every other key goes
// through the marked `t` (#389), as i18next returns a string for a missing key.
vi.mock("react-i18next", async () =>
  (await import("../../test/i18nMock")).i18nMock({ fixture: FIXTURE }),
);

import DocsSubsections, { readSubsections } from "./DocsSubsections";

// ---------------------------------------------------------------------------
// Minimal React-element tree walker (no renderer/DOM involved)
// ---------------------------------------------------------------------------

interface ElementNode {
  type: unknown;
  props: Record<string, unknown> & { children?: unknown };
}

type FlatNode = ElementNode | string | number;

function isElementNode(x: unknown): x is ElementNode {
  return typeof x === "object" && x !== null && "props" in x;
}

function flatten(node: unknown): FlatNode[] {
  if (Array.isArray(node)) return node.flatMap(flatten);
  if (node === null || node === undefined || typeof node === "boolean") return [];
  if (typeof node === "string" || typeof node === "number") return [node];
  if (isElementNode(node)) return [node, ...flatten(node.props.children)];
  return [];
}

function elementsOfType(root: unknown, type: string): ElementNode[] {
  return flatten(root).filter(
    (n): n is ElementNode => isElementNode(n) && n.type === type,
  );
}

function textOf(node: ElementNode): string {
  return flatten(node.props.children)
    .filter((n): n is string => typeof n === "string")
    .join("");
}

// ---------------------------------------------------------------------------
// Tests
// ---------------------------------------------------------------------------

describe("DocsSubsections", () => {
  it("renders nothing for a section without subsections", () => {
    const tree = DocsSubsections({
      sectionKey: "budget",
      registerRef: () => {},
    });
    expect(tree).toBeNull();
  });

  it("renders one block per entry with its id and registers each element", () => {
    const registered: string[] = [];
    const tree = DocsSubsections({
      sectionKey: "import",
      registerRef: (id) => registered.push(id),
    });

    const blocks = flatten(tree).filter(
      (n): n is ElementNode =>
        isElementNode(n) && typeof n.props.id === "string",
    );
    expect(blocks.map((b) => b.props.id)).toEqual([
      "import-export",
      "import-bnc",
    ]);

    // The ref callbacks are what DocsContent uses for hash navigation.
    for (const block of blocks) {
      (block.props.ref as (el: HTMLElement | null) => void)(null);
    }
    expect(registered).toEqual(["import-export", "import-bnc"]);

    const titles = elementsOfType(tree, "h4").map(textOf);
    expect(titles).toEqual(["Export a CSV from your bank", "National Bank"]);

    const steps = elementsOfType(tree, "li").map(textOf);
    expect(steps).toEqual([
      "One subfolder per account",
      "Pick the widest range",
      "Expected header",
    ]);
  });

  it("renders the status line in italic only when present, and the note only when present", () => {
    const tree = DocsSubsections({
      sectionKey: "import",
      registerRef: () => {},
    });
    const paragraphs = elementsOfType(tree, "p");
    const italics = paragraphs.filter((p) =>
      String(p.props.className).includes("italic"),
    );
    expect(italics.map(textOf)).toEqual(["No public procedure found"]);

    const notes = paragraphs.filter(
      (p) => !String(p.props.className).includes("italic"),
    );
    expect(notes.map(textOf)).toEqual(["Trailing note"]);
  });
});

describe("readSubsections", () => {
  it("returns an empty array for a missing key (i18next echoes the key)", () => {
    expect(readSubsections("docs.budget.subsections")).toEqual([]);
  });

  it("drops malformed entries", () => {
    expect(
      readSubsections([
        { id: "ok", title: "Ok", steps: [] },
        { id: "no-steps", title: "Missing steps" },
        "garbage",
        null,
      ]),
    ).toEqual([{ id: "ok", title: "Ok", steps: [] }]);
  });
});