#!/usr/bin/env node
// lib/util/test-lock.mjs
// K8 -- the test lock. The executor (wave-1 order 1) locks a step's test files
// once the test is written and seen failing, and unlocks them when the test
// passes. Two guards read the lock:
//   - pre-write-executor.mjs refuses Write/Edit/NotebookEdit on a locked file;
//   - stop-test-lock.mjs refuses "done" while the session that took the lock
//     still holds it.
// The lock lives in the repository's git directory (<git dir>/voyage/
// test-lock.json), so it can never be committed, and each worktree has its own.
//
// Usage:
//   node lib/util/test-lock.mjs lock --files <a,b> --step <N> [--cwd <dir>]
//   node lib/util/test-lock.mjs unlock [--cwd <dir>]
//   node lib/util/test-lock.mjs status [--cwd <dir>]      (JSON on stdout)
// Exit: 0 = done, 1 = refused (another step holds the lock), 2 = could not
// run (not a repository, bad usage, unreadable lock). 2 is never "unlocked".
// Paths in --files are relative to the --cwd (default: the current directory).
// The session is taken from CLAUDE_CODE_SESSION_ID, which Claude Code sets in
// Bash tool subprocesses (code.claude.com/docs/en/env-vars).
//
// Credit: locking tests during a fix is Claude Code's own hook pattern
// (hooks-guide "Block edits to protected files").

import { readFileSync, writeFileSync, mkdirSync, rmSync, existsSync, realpathSync, readdirSync } from 'node:fs';
import { join, resolve, dirname } from 'node:path';
import { fileURLToPath } from 'node:url';
import { createHash } from 'node:crypto';
import { tmpdir } from 'node:os';
import { resolveRepo, canonicalPath } from '../verification/repo-tools.mjs';

export const LOCK_VERSION = 1;

export function lockPathFor(gitDir) {
  return join(gitDir, 'voyage', 'test-lock.json');
}

/**
 * Read the lock for the repo that `start` (a file or directory) belongs to.
 * @returns {{ state: 'no-repo'|'none'|'locked'|'corrupt', lock?: object, path?: string, error?: string }}
 */
export function readLock(start) {
  const repo = resolveRepo(start);
  if (!repo) return { state: 'no-repo' };
  const path = lockPathFor(repo.gitDir);
  if (!existsSync(path)) return { state: 'none', path, repo };
  try {
    const lock = JSON.parse(readFileSync(path, 'utf8'));
    if (!lock || !Array.isArray(lock.files) || !Number.isInteger(lock.step)) {
      return { state: 'corrupt', path, repo, error: 'lock has no files/step' };
    }
    return { state: 'locked', lock, path, repo };
  } catch (e) {
    return { state: 'corrupt', path, repo, error: e.message };
  }
}

// A pointer from the session that took a lock to the lock file, so the stop
// guard finds it even after the session has moved to another directory.
const SESSION_DIR = join(tmpdir(), `voyage-test-locks-${process.getuid ? process.getuid() : 'u'}`);
const sessionPointer = (sessionId) =>
  join(SESSION_DIR, `${createHash('sha256').update(String(sessionId)).digest('hex').slice(0, 32)}.json`);

// Pointers whose lock is gone are dropped on the next lock.
function sweepPointers() {
  try {
    for (const f of readdirSync(SESSION_DIR)) {
      const p = join(SESSION_DIR, f);
      try {
        if (!existsSync(JSON.parse(readFileSync(p, 'utf8')).lock_path)) rmSync(p, { force: true });
      } catch { rmSync(p, { force: true }); }
    }
  } catch { /* no dir yet */ }
}

function writeSessionPointer(sessionId, lockPath) {
  if (!sessionId) return;
  try {
    mkdirSync(SESSION_DIR, { recursive: true });
    sweepPointers();
    writeFileSync(sessionPointer(sessionId), JSON.stringify({ lock_path: lockPath }));
  } catch { /* the cwd lookup still works */ }
}

function removeSessionPointer(sessionId) {
  if (sessionId) rmSync(sessionPointer(sessionId), { force: true });
}

/**
 * The lock this session holds, wherever it lives: { state: 'locked', lock, path }
 * or { state: 'none' }. A pointer to a lock that is gone, or that another
 * session now holds, is not this session's lock.
 */
export function lockForSession(sessionId) {
  if (!sessionId) return { state: 'none' };
  try {
    const { lock_path } = JSON.parse(readFileSync(sessionPointer(sessionId), 'utf8'));
    const lock = JSON.parse(readFileSync(lock_path, 'utf8'));
    if (lock?.session === sessionId && Array.isArray(lock.files) && Number.isInteger(lock.step)) {
      return { state: 'locked', lock, path: lock_path };
    }
  } catch { /* no pointer, or the lock is gone */ }
  return { state: 'none' };
}

// Is `file` one of the locked files? Compared as canonical real paths.
export function isLockedFile(lock, file) {
  const c = canonicalPath(file);
  return lock.files.includes(c);
}

function parseArgs(argv) {
  const out = { _: [] };
  for (let i = 0; i < argv.length; i += 1) {
    const a = argv[i];
    if (a === '--files' || a === '--step' || a === '--cwd') { out[a.slice(2)] = argv[i + 1]; i += 1; }
    else out._.push(a);
  }
  return out;
}

function fail(code, msg) {
  process.stderr.write(`[voyage] test-lock: ${msg}\n`);
  process.exit(code);
}

function main(argv) {
  const args = parseArgs(argv);
  const cmd = args._[0];
  if (!['lock', 'unlock', 'status'].includes(cmd)) fail(2, 'usage: test-lock.mjs lock --files <a,b> --step <N> | unlock | status [--cwd <dir>]');
  const cwd = resolve(args.cwd || process.cwd());
  const cur = readLock(cwd);
  if (cur.state === 'no-repo') fail(2, `not a git repository: ${cwd}`);

  if (cmd === 'status') {
    if (cur.state === 'corrupt') {
      process.stdout.write(JSON.stringify({ locked: null, state: 'corrupt', lock_path: cur.path, error: cur.error }, null, 2) + '\n');
      process.exit(2);
    }
    const l = cur.lock || {};
    process.stdout.write(JSON.stringify({
      locked: cur.state === 'locked', step: l.step ?? null, files: l.files ?? [], session: l.session ?? null,
      locked_at: l.locked_at ?? null, lock_path: cur.path,
    }, null, 2) + '\n');
    process.exit(0);
  }

  if (cmd === 'unlock') {
    if (cur.state === 'corrupt') fail(2, `unreadable lock ${cur.path} (${cur.error}); inspect it before removing it`);
    removeSessionPointer(cur.lock?.session);
    rmSync(cur.path, { force: true });
    process.exit(0);
  }

  // lock
  if (!args.files) fail(2, 'lock needs --files <a,b>');
  if (args.step === undefined || !/^\d+$/.test(String(args.step))) fail(2, 'lock needs --step <N> (a whole number)');
  const step = Number(args.step);
  if (cur.state === 'corrupt') fail(2, `unreadable lock ${cur.path} (${cur.error})`);
  if (cur.state === 'locked' && cur.lock.step !== step) {
    fail(1, `step ${cur.lock.step} holds the lock; unlock it first`);
  }
  const files = String(args.files).split(',').map((f) => f.trim()).filter(Boolean).map((f) => canonicalPath(resolve(cwd, f)));
  if (files.length === 0) fail(2, 'lock needs at least one file');
  const lock = {
    version: LOCK_VERSION,
    step,
    files: [...new Set(files)],
    session: process.env.CLAUDE_CODE_SESSION_ID || null,
    locked_at: new Date().toISOString(),
  };
  mkdirSync(dirname(cur.path), { recursive: true });
  writeFileSync(cur.path, JSON.stringify(lock, null, 2) + '\n');
  writeSessionPointer(lock.session, cur.path);
  process.exit(0);
}

function isMain() {
  try {
    return realpathSync(process.argv[1]) === realpathSync(fileURLToPath(import.meta.url));
  } catch {
    return false;
  }
}

if (isMain()) main(process.argv.slice(2));