1import { execSync } from 'child_process'
2import crypto from 'crypto'
3
4type MineOpts = {
5  cwd: string,
6  msgBase: string,
7  tgtShaPrefix: string,
8  gitEnv?: Record<string, string>,
9}
10
11const computeCommitSha = (treeSha: string, authorLine: string, committerLine: string, message: string) => {
12  const body = `tree ${treeSha}\n${authorLine}\n${committerLine}\n\n${message}\n`
13  const header = `commit ${Buffer.byteLength(body)}\0`
14  return crypto.createHash('sha1').update(header + body).digest('hex')
15}
16
17export const commitMineShaPrefix = ({cwd, msgBase, tgtShaPrefix, gitEnv}: MineOpts): string => {
18  const env = gitEnv ? {...process.env, ...gitEnv} : undefined
19  const run = (cmd: string) => execSync(cmd, {cwd, stdio: 'pipe', encoding: 'utf8', env})
20
21  const treeSha = run('git write-tree').trim()
22
23  if (!tgtShaPrefix) {
24    const sha = run(`git commit-tree ${treeSha} -m "${msgBase} #0"`).trim()
25    run(`git update-ref HEAD ${sha}`)
26    return sha
27  }
28
29  // Resolve author/committer identity (env overrides > git config fallback)
30  const cfg = (k: string) => { try { return run(`git config ${k}`).trim() } catch { return '' } }
31  const authorName = gitEnv?.GIT_AUTHOR_NAME || gitEnv?.GIT_COMMITTER_NAME || cfg('user.name')
32  const authorEmail = gitEnv?.GIT_AUTHOR_EMAIL || gitEnv?.GIT_COMMITTER_EMAIL || cfg('user.email')
33  const committerName = gitEnv?.GIT_COMMITTER_NAME || authorName
34  const committerEmail = gitEnv?.GIT_COMMITTER_EMAIL || authorEmail
35
36  // Fix timestamp so JS-computed SHA matches the final git commit-tree call
37  const ts = Math.floor(Date.now() / 1000)
38  const tzOff = -new Date().getTimezoneOffset()
39  const tz = `${tzOff >= 0 ? '+' : '-'}${String(Math.floor(Math.abs(tzOff) / 60)).padStart(2, '0')}${String(Math.abs(tzOff) % 60).padStart(2, '0')}`
40  const gitDate = `${ts} ${tz}`
41  const authorLine = `author ${authorName} <${authorEmail}> ${ts} ${tz}`
42  const committerLine = `committer ${committerName} <${committerEmail}> ${ts} ${tz}`
43
44  // Mine: pure-JS SHA1 loop (~µs/iter), then single git commit-tree for the winner
45  let nonce = 0, sha = ''
46  for (; nonce < 1_000_000; nonce++) {
47    const candidate = computeCommitSha(treeSha, authorLine, committerLine, `${msgBase} #${nonce}`)
48    if (candidate.startsWith(tgtShaPrefix)) { sha = candidate; break }
49  }
50  if (!sha) throw new Error(`mining sha prefix "${tgtShaPrefix}" failed after 1M attempts`)
51
52  const commitEnv = {...process.env, ...gitEnv, GIT_AUTHOR_DATE: gitDate, GIT_COMMITTER_DATE: gitDate} as Record<string, string>
53  const created = execSync(`git commit-tree ${treeSha} -m "${msgBase} #${nonce}"`, {cwd, stdio: 'pipe', encoding: 'utf8', env: commitEnv as any}).trim()
54  if (created !== sha) throw new Error(`mining sha mismatch: JS=${sha.slice(0,12)} git=${created.slice(0,12)}`)
55  run(`git update-ref HEAD ${sha}`)
56  console.log(`  mined sha prefix "${tgtShaPrefix}" after ${nonce + 1} attempt(s): ${sha.slice(0, 12)}`)
57  return sha
58}
59