// Generate frontend/dist/THIRD_PARTY_LICENSES.txt: the third-party attribution file for the
// npm packages bundled into the built frontend.
//
// Self-contained (no extra dependency): it asks npm for the *production* dependency tree, then
// reads each package's own license file from node_modules and concatenates them. Run via
// `npm run licenses` (also invoked by the CMake `frontend` build target).

import { execFileSync } from "node:child_process";
import { readFileSync, readdirSync, existsSync, mkdirSync, writeFileSync } from "node:fs";
import { join, dirname } from "node:path";
import { fileURLToPath } from "node:url";

const frontendDir = join(dirname(fileURLToPath(import.meta.url)), "..");
const nodeModules = join(frontendDir, "node_modules");
const outFile = join(frontendDir, "dist", "THIRD_PARTY_LICENSES.txt");

const LICENSE_FILE = /^(licen[sc]e|copying|notice)([.-].*)?$/i;

// Set of "name@version" strings that actually ship in production (excludes devDependencies).
function productionPackages() {
  const json = execFileSync("npm", ["ls", "--omit=dev", "--all", "--json"], {
    cwd: frontendDir,
    encoding: "utf8",
    maxBuffer: 64 * 1024 * 1024,
  });
  const set = new Set();
  const walk = (deps) => {
    for (const [name, info] of Object.entries(deps || {})) {
      if (info.version) set.add(`${name}@${info.version}`);
      walk(info.dependencies);
    }
  };
  walk(JSON.parse(json).dependencies);
  return set;
}

// Map "name@version" -> package directory, by scanning every node_modules in the install tree.
function installedPackages() {
  const map = new Map();
  const scan = (nm) => {
    if (!existsSync(nm)) return;
    for (const entry of readdirSync(nm)) {
      if (entry.startsWith(".")) continue;
      if (entry.startsWith("@")) {
        for (const sub of readdirSync(join(nm, entry))) record(join(nm, entry, sub));
      } else {
        record(join(nm, entry));
      }
    }
  };
  const record = (dir) => {
    const pkgJson = join(dir, "package.json");
    if (!existsSync(pkgJson)) return;
    try {
      const pkg = JSON.parse(readFileSync(pkgJson, "utf8"));
      if (pkg.name && pkg.version) map.set(`${pkg.name}@${pkg.version}`, { dir, pkg });
    } catch { /* ignore unparseable package.json */ }
    scan(join(dir, "node_modules"));
  };
  scan(nodeModules);
  return map;
}

function findLicenseText(dir) {
  const file = readdirSync(dir).find((f) => LICENSE_FILE.test(f));
  if (!file) return null;
  try {
    return readFileSync(join(dir, file), "utf8").trimEnd();
  } catch {
    return null;
  }
}

function licenseId(pkg) {
  if (typeof pkg.license === "string") return pkg.license;
  if (pkg.license?.type) return pkg.license.type;
  if (Array.isArray(pkg.licenses)) return pkg.licenses.map((l) => l.type || l).join(" OR ");
  return "UNKNOWN";
}

function repoUrl(pkg) {
  const r = pkg.repository;
  if (typeof r === "string") return r;
  if (r?.url) return r.url.replace(/^git\+/, "").replace(/\.git$/, "");
  return pkg.homepage || "";
}

const prod = productionPackages();
const installed = installedPackages();

const blocks = [];
const missing = [];
for (const id of [...prod].sort((a, b) => a.localeCompare(b))) {
  const found = installed.get(id);
  if (!found) continue; // present in tree report but not on disk (e.g. bundled) — skip
  const { dir, pkg } = found;
  const text = findLicenseText(dir);
  if (!text) missing.push(`${id} (${licenseId(pkg)})`);
  const url = repoUrl(pkg);
  blocks.push(
    `${"=".repeat(80)}\n` +
      `${id}  —  ${licenseId(pkg)}\n` +
      (url ? `${url}\n` : "") +
      `${"=".repeat(80)}\n\n` +
      (text || `License: ${licenseId(pkg)} (no license file shipped in this package)`),
  );
}

const header =
  "Third-party software bundled in the Jungfraujoch frontend\n" +
  "=========================================================\n\n" +
  "The Jungfraujoch frontend is licensed under GPL-3.0. It bundles the following npm packages\n" +
  "(production dependencies). Each package's license and notice text follows.\n\n" +
  `Generated by scripts/generate-third-party-licenses.mjs — ${prod.size} packages.\n` +
  (missing.length
    ? `\nPackages without a bundled license file (license field shown above):\n  ${missing.join("\n  ")}\n`
    : "");

mkdirSync(dirname(outFile), { recursive: true });
writeFileSync(outFile, header + "\n" + blocks.join("\n\n") + "\n", "utf8");
console.log(`Wrote ${outFile} (${blocks.length} packages, ${missing.length} without license file).`);