#!/usr/bin/env node
/**
 * check-changelog-append-only — CI + pre-push guard (OPS44/OPS85): the
 * committed changelog record is per-file only. docs/changelog/ entries are
 * additions-only, docs/CHANGELOG-AGENTS-HISTORY.md is a frozen snapshot
 * (only its creation is allowed), and the regenerable aggregate
 * docs/CHANGELOG-AGENTS.md must never be committed — its one-time removal
 * is allowed only together with the HISTORY creation (the OPS85 migration).
 * Legitimate exceptions (D8-style restorations, HISTORY corrections) escape
 * via the documented `changelog-rewrite:` token in the PR body.
 *
 * Paths from git diff (merge-base…HEAD); body from PR_BODY env or `gh pr
 * view` when PR_NUMBER is set. The escape is honored only when the diff
 * actually touches the changelog paths, and only as a standalone line
 * (never the PR template's own checkbox text).
 */
import { execFileSync } from 'node:child_process'

import {
  assertChangelogAppendOnly,
  CHANGELOG_AGGREGATE,
  CHANGELOG_DIR,
  CHANGELOG_HISTORY,
  CHANGELOG_REWRITE_ESCAPE_RE,
} from './lib/changelog.mjs'

const base = `origin/${process.env.GITHUB_BASE_REF ?? 'main'}`

function die(message) {
  console.error(`[check-changelog-append-only] ${message}`)
  process.exit(1)
}

function git(args) {
  return execFileSync('git', args, { encoding: 'utf8' }).trim()
}

let mergeBase
try {
  mergeBase = git(['merge-base', 'HEAD', base])
} catch {
  die(`no merge-base with ${base} (shallow clone?)`)
}

function listChangedPaths() {
  const raw = execFileSync(
    'git',
    [
      'diff',
      '--no-renames',
      '--name-status',
      `${mergeBase}...HEAD`,
      '--',
      CHANGELOG_AGGREGATE,
      CHANGELOG_HISTORY,
      CHANGELOG_DIR,
    ],
    { encoding: 'utf8' },
  )

  return raw
    .split('\n')
    .map((line) => line.trim())
    .filter(Boolean)
}

function readPrBody() {
  if (process.env.PR_BODY !== undefined) {
    return process.env.PR_BODY
  }

  const prNumber = process.env.PR_NUMBER ?? process.env.GITHUB_PR_NUMBER
  if (!prNumber) return ''

  try {
    const json = execFileSync('gh', ['pr', 'view', String(prNumber), '--json', 'body'], {
      encoding: 'utf8',
    })
    const parsed = JSON.parse(json)
    return typeof parsed.body === 'string' ? parsed.body : ''
  } catch (error) {
    const detail = error instanceof Error ? error.message : String(error)
    die(`failed to read PR #${prNumber} body via gh: ${detail}`)
  }
}

const diffLines = listChangedPaths()
if (diffLines.length === 0) {
  console.log('[check-changelog-append-only] ok — no changelog diff')
  process.exit(0)
}

// --no-renames guarantees the `STATUS<TAB>path` shape (no R entries).
const changed = diffLines.map((line) => {
  const [status, path] = line.split('\t')
  return { status, path }
})

const body = readPrBody()
if (CHANGELOG_REWRITE_ESCAPE_RE.test(body)) {
  console.log('[check-changelog-append-only] ok — changelog-rewrite escape in PR body')
  process.exit(0)
}

const result = assertChangelogAppendOnly({
  changelogDiff: changed.filter(({ path }) => path.startsWith(`${CHANGELOG_DIR}/`)),
  historyDiff: changed.filter(({ path }) => path === CHANGELOG_HISTORY),
  aggregateDiff: changed.filter(({ path }) => path === CHANGELOG_AGGREGATE),
})

if (!result.ok) {
  die(result.message)
}

console.log('[check-changelog-append-only] ok — changelog is append-only')