import { readFile, writeFile } from "node:fs/promises";
import path from "node:path";

import { buildContractSet } from "../generate-contract-set.ts";
import { contractSetSchema, type ContractSet } from "../../src/contracts/contract-set.ts";

/**
 * `corepack pnpm dev` never runs the build pipeline: plain `vite` serves
 * `public/release-manifest.json` verbatim. That fixture therefore has to carry
 * the same `contractSet` block `scripts/generate-build-manifest.ts` writes into
 * `dist/release-manifest.json`, because `verifyContractSet` runs unconditionally
 * at boot — in the default `MOCK` mode as much as in `HTTP` mode. When the two
 * disagree the app renders the fail-closed boot screen instead of the shell.
 *
 * Both halves of the answer live here so they cannot disagree: the generation
 * step rewrites the block, and the CI gate compares it.
 */

export const DEV_RELEASE_MANIFEST_PATH = "public/release-manifest.json";

export type DevReleaseManifestContractSet = ContractSet;

function resolveManifestPath(root: string): string {
  return path.join(root, DEV_RELEASE_MANIFEST_PATH);
}

/**
 * The contract set the build would compile, derived from
 * `EXPECTED_CONTRACT_SET_PACKAGES` exactly as `generate-build-manifest.ts`
 * derives it.
 */
export function expectedDevReleaseManifestContractSet(): DevReleaseManifestContractSet {
  return contractSetSchema.parse(
    JSON.parse(JSON.stringify(buildContractSet())),
  );
}

/**
 * Compares one manifest `contractSet` block against the compiled expectation.
 * Returns one human-readable line per disagreement; an empty array means the
 * fixture would boot.
 */
export function compareDevReleaseManifestContractSet(
  actual: unknown,
  expected: DevReleaseManifestContractSet,
): string[] {
  const parsed = contractSetSchema.safeParse(actual);
  if (!parsed.success) {
    return [
      `${DEV_RELEASE_MANIFEST_PATH} contractSet is missing or not a valid contract set: ${parsed.error.issues
        .map((issue) => `${issue.path.join(".") || "root"}: ${issue.message}`)
        .join("; ")}`,
    ];
  }
  const manifest = parsed.data;
  const failures: string[] = [];
  if (manifest.setAlgorithm !== expected.setAlgorithm) {
    failures.push(
      `setAlgorithm drift: manifest ${manifest.setAlgorithm}, build ${expected.setAlgorithm}`,
    );
  }
  if (manifest.setDigest !== expected.setDigest) {
    failures.push(
      `setDigest drift: manifest ${manifest.setDigest}, build ${expected.setDigest}`,
    );
  }
  const manifestById = new Map(
    manifest.packages.map((entry) => [entry.packageId, entry] as const),
  );
  const expectedById = new Map(
    expected.packages.map((entry) => [entry.packageId, entry] as const),
  );
  for (const [packageId, entry] of expectedById) {
    const declared = manifestById.get(packageId);
    if (!declared) {
      failures.push(
        `package missing from the manifest (boot fails with CONTRACT_SET_PACKAGE_MISSING): ${packageId}@${entry.version}`,
      );
      continue;
    }
    if (JSON.stringify(declared) !== JSON.stringify(entry)) {
      failures.push(
        `package drift for ${packageId}: manifest ${JSON.stringify(declared)}, build ${JSON.stringify(entry)}`,
      );
    }
  }
  for (const packageId of manifestById.keys()) {
    if (!expectedById.has(packageId)) {
      failures.push(
        `package declared by the manifest but not compiled into the build (boot fails with CONTRACT_SET_PACKAGE_UNEXPECTED): ${packageId}`,
      );
    }
  }
  return failures;
}

export async function readDevReleaseManifest(
  root: string = process.cwd(),
): Promise<Record<string, unknown>> {
  const raw = await readFile(resolveManifestPath(root), "utf8");
  const document: unknown = JSON.parse(raw);
  if (!document || typeof document !== "object" || Array.isArray(document)) {
    throw new TypeError(`${DEV_RELEASE_MANIFEST_PATH} must be a JSON object`);
  }
  return document as Record<string, unknown>;
}

export async function checkDevReleaseManifestContractSet(
  root: string = process.cwd(),
): Promise<readonly string[]> {
  const document = await readDevReleaseManifest(root);
  return compareDevReleaseManifestContractSet(
    document["contractSet"],
    expectedDevReleaseManifestContractSet(),
  );
}

/**
 * Rewrites only the `contractSet` block. Every other field of the hand
 * maintained fixture is preserved byte for byte by round-tripping the same
 * two-space JSON encoding the file already uses.
 */
export async function refreshDevReleaseManifestContractSet(
  root: string = process.cwd(),
): Promise<Readonly<{ changed: boolean; contractSet: DevReleaseManifestContractSet }>> {
  const target = resolveManifestPath(root);
  const document = await readDevReleaseManifest(root);
  const contractSet = expectedDevReleaseManifestContractSet();
  const previous = JSON.stringify(document["contractSet"]);
  document["contractSet"] = contractSet;
  const next = `${JSON.stringify(document, null, 2)}\n`;
  const changed = previous !== JSON.stringify(contractSet);
  if (changed) await writeFile(target, next, "utf8");
  return Object.freeze({ changed, contractSet });
}