import { createHash } from "node:crypto";
import { mkdir, writeFile } from "node:fs/promises";
import { dirname } from "node:path";

import {
  CONTRACT_SET_ALGORITHM,
  computeContractSetDigestWith,
  type ContractSetPackage,
} from "../src/contracts/contract-set-canonical.ts";
import { EXPECTED_CONTRACT_SET_PACKAGES } from "../src/features/installed-contract-contributions.ts";

/**
 * §5.4 / §17.2.2 step 2. Derives the build-time expected contract set from the
 * installed contributions and emits it as generated source for the manifest
 * writer. `TEMPLATE_FIXTURE` provenance never reaches this list, so a fixture
 * cannot influence the release digest.
 */

const OUTPUT = ".generated/frontend-runtime/contract-set.ts";

function sha256(bytes: Uint8Array): Uint8Array {
  return new Uint8Array(createHash("sha256").update(bytes).digest());
}

export function buildContractSet(
  packages: readonly ContractSetPackage[] = EXPECTED_CONTRACT_SET_PACKAGES as readonly ContractSetPackage[],
) {
  return Object.freeze({
    setAlgorithm: CONTRACT_SET_ALGORITHM,
    setDigest: computeContractSetDigestWith(packages, sha256),
    packages: Object.freeze(
      [...packages]
        .map((entry) => Object.freeze({ ...entry }))
        .sort((left, right) => (left.packageId < right.packageId ? -1 : 1)),
    ),
  });
}

async function main(): Promise<void> {
  const contractSet = buildContractSet();
  const source = [
    "// Generated by scripts/generate-contract-set.ts. Do not edit.",
    "// Regenerated from scratch on every build; never committed.",
    "",
    "import type { ContractSet } from \"../../src/contracts/contract-set.ts\";",
    "",
    `export const BUILD_CONTRACT_SET: ContractSet = ${JSON.stringify(
      contractSet,
      null,
      2,
    )} as const;`,
    "",
  ].join("\n");

  await mkdir(dirname(OUTPUT), { recursive: true });
  await writeFile(OUTPUT, source, "utf8");
  process.stdout.write(
    `contract set: ${contractSet.packages.length} package(s) ${contractSet.setDigest}\n`,
  );
}

if (process.argv[1]?.endsWith("generate-contract-set.ts")) {
  await main();
}