#!/usr/bin/env node
// Verify that CHANGELOG.md gained at least one entry under [Unreleased]
// or that a [vX.Y.Z] block was added since main. Fails CI if not.
//
// Skip with the PR label `no-changelog` for trivial doc-only changes.

import { execSync } from "node:child_process";
import { readFileSync } from "node:fs";

const base = process.env.GITHUB_BASE_REF || "main";
let diff;
try {
  execSync(`git fetch --no-tags --depth=50 origin ${base}`, { stdio: "ignore" });
  diff = execSync(`git diff --unified=0 origin/${base}...HEAD -- CHANGELOG.md`).toString();
} catch (err) {
  console.error("Could not diff CHANGELOG.md:", err.message);
  process.exit(1);
}

const additions = diff.split("\n").filter(l => l.startsWith("+") && !l.startsWith("+++"));
const meaningful = additions.filter(l => l.replace(/^\+/, "").trim().length > 0 && !l.includes("Unreleased"));

if (meaningful.length === 0) {
  console.error("CHANGELOG.md has no new entries on this PR.");
  console.error("Either add an entry under [Unreleased], or label this PR `no-changelog`.");
  process.exit(1);
}

console.log(`OK — ${meaningful.length} CHANGELOG line(s) added.`);