#!/usr/bin/env node
/**
 * derive-facts.mjs — extract mechanical facts from the parent repo and write
 * them as a typed TS module. Run as `prebuild`. The same logic also runs in
 * the content-drift cron against raw.githubusercontent.com so the deployed
 * worker can detect repo→site drift between deploys.
 *
 * This script delegates all derivation logic to facts-lib.mjs so that
 * check-facts.mjs can reuse the same code for the CI drift gate.
 */
import { writeFileSync, readFileSync, existsSync } from "node:fs";
import { dirname, resolve } from "node:path";
import { fileURLToPath } from "node:url";
import { buildFacts } from "./facts-lib.mjs";

const __dirname = dirname(fileURLToPath(import.meta.url));
const target = resolve(__dirname, "..", "lib", "facts.generated.ts");

const out = buildFacts();

// Preserve the committed `generatedAt` when every *checked* fact is unchanged,
// so a clean rebuild doesn't dirty the tracked file on every run. The drift
// gate (check-facts.mjs) ignores generatedAt + latestRelease; we mirror that
// volatile set here. Only when a real fact changes do we stamp a fresh time.
const VOLATILE = new Set(["generatedAt", "latestRelease"]);
function readCommittedFacts() {
  if (!existsSync(target)) return null;
  const src = readFileSync(target, "utf-8");
  const m = src.match(/export const FACTS\s*:\s*\w+\s*=\s*([\s\S]*?);?\s*$/);
  if (!m) return null;
  try {
    return JSON.parse(m[1]);
  } catch {
    return null;
  }
}
const committed = readCommittedFacts();
if (committed && typeof committed.generatedAt === "string") {
  const sameChecked = Object.keys(out).every(
    (k) => VOLATILE.has(k) || JSON.stringify(out[k]) === JSON.stringify(committed[k]),
  );
  if (sameChecked) out.generatedAt = committed.generatedAt;
}

// latestRelease is intentionally null at build time — populated at runtime by the drift cron.
const RUNTIME_ONLY = new Set(["latestRelease"]);
const missing = Object.entries(out).filter(
  ([k, v]) =>
    k !== "generatedAt" &&
    !RUNTIME_ONLY.has(k) &&
    (v == null || (Array.isArray(v) && v.length === 0)),
);
if (missing.length > 0) {
  console.warn("[derive-facts] missing values:", missing.map(([k]) => k).join(", "));
}


const ts = `// AUTO-GENERATED by web/scripts/derive-facts.mjs at prebuild.
// DO NOT EDIT — re-run \`npm run prebuild\` (or just \`npm run build\`) after changing the parent repo.
// To override at runtime, write the same shape to KV under key "facts:current".

export interface ProviderFact { id: string; label: string; env: string }

export interface RepoFacts {
  generatedAt: string;
  version: string | null;
  crates: string[];
  sandboxBackends: string[];
  providers: ProviderFact[];
  defaultModel: string | null;
  nodeEngines: string | null;
  toolCount: number | null;
  license: string | null;
  latestRelease: string | null;
}

export const FACTS: RepoFacts = ${JSON.stringify(out, null, 2)};
`;

writeFileSync(target, ts);
console.log(`[derive-facts] wrote ${target}`);
console.log(
  `[derive-facts] version=${out.version} crates=${out.crates.length} ` +
    `providers=${out.providers.length} sandboxes=${out.sandboxBackends.length} ` +
    `default-model=${out.defaultModel} node=${out.nodeEngines} ` +
    `tools=${out.toolCount} license=${out.license}`,
);