import { readFileSync } from "node:fs";
import { expect, it } from "vitest";

// The third contract test, after `nodeEngine` and `pythonEngine`, and for the same reason: a version
// that is spelled in two places drifts, and the drift is silent until something downstream breaks.
//
// Here the two places are `package.json`'s React pin and `reactPlugin.ts`'s `target`, which tells
// babel-plugin-react-compiler which React runtime to emit memoisation against. The rule was first
// written as a comment — "`target` follows the installed React major and must move with it" — and
// the house rule this codebase was built on says a rule stated in a comment must also be enforced
// in code. So it is enforced here.
//
// The compiler does validate the option itself (an unknown target throws at build time), which
// bounds the damage: the failure mode is not a corrupt bundle but a STALE target — React moves to a
// new major and the compiler keeps emitting for the old one, with no lane saying so, because tsc
// never sees Babel's output.
//
// To move React: bump `react`, `react-dom` and `@types/react` in package.json, then follow this
// test's failures.
const readFrontend = (rel: string) =>
  readFileSync(new URL(`../../${rel}`, import.meta.url), "utf8");

const pkg = JSON.parse(readFrontend("package.json")) as {
  dependencies: Record<string, string>;
  devDependencies: Record<string, string>;
};

/** The major in a version range, whether it is exact (`19.3.0`) or a caret (`^19.3.0`). */
function major(range: string, where: string): number {
  const m = /^\D*(\d+)\./.exec(range);
  expect(m, `could not read a major from ${where}: ${range}`).not.toBeNull();
  return Number(m![1]);
}

const pinned = major(pkg.dependencies["react"]!, "react");

it("pins a plausible React major", () => {
  expect(pinned).toBeGreaterThanOrEqual(19);
});

it("keeps react-dom on the same major as react", () => {
  expect(major(pkg.dependencies["react-dom"]!, "react-dom")).toBe(pinned);
});

it("keeps the types on the same major as the runtime", () => {
  // Types a major ahead of the runtime make tsc green over APIs the shipped React does not have.
  expect(major(pkg.devDependencies["@types/react"]!, "@types/react")).toBe(pinned);
  expect(major(pkg.devDependencies["@types/react-dom"]!, "@types/react-dom")).toBe(pinned);
});

it("compiles for the React that is actually installed", () => {
  const src = readFrontend("reactPlugin.ts");
  const m = /target:\s*"(\d+)"/.exec(src);
  // A rename or a moved line lands here. Re-point the test — the contract did not go away with it.
  expect(m, 'no `target: "<major>"` in reactPlugin.ts').not.toBeNull();
  expect(
    Number(m![1]),
    `reactPlugin.ts compiles for React ${m![1]} while package.json pins ${pinned}. The React ` +
      `Compiler emits against the runtime named by \`target\`; move it with the pin.`,
  ).toBe(pinned);
});

it("keeps react-i18next on a line that supports the pinned React", () => {
  // The 14 line predates React 19: its <Trans> read `element.ref` (removed in 19) and its
  // `withTranslation` types were built on the GLOBAL JSX namespace that @types/react 19 no longer
  // declares — both latent only because this app happens to use neither export. 15 is the first
  // line that handles both, so the floor is a real contract, not a tidiness preference.
  expect(major(pkg.dependencies["react-i18next"]!, "react-i18next")).toBeGreaterThanOrEqual(15);
});