#!/usr/bin/env node
/**
 * C5 observer-coverage-checker (brain governance, observer factor-analysis
 * spec §5.2). Warn-only — always exits 0. Two checks:
 *   1. Coverage — recent git commits but 0 observer episodes this month.
 *   2. Registration integrity — observer Stop-hook present in
 *      .claude/settings.json and .git/hooks/post-commit installed.
 * Findings are surfaced in docs/observer/STATUS.md (C4 generator); this
 * controller never blocks a commit.
 *
 * Security Guidance #40: git is invoked via execFileSync (argument array,
 * no shell) — no exec/execSync.
 */
import { readFileSync, existsSync } from 'fs';
import { join } from 'path';
import { execFileSync } from 'child_process';

const RECENT_WINDOW = '14 days ago';

/** @returns {{ok: boolean, detail: string}} */
export function checkCoverage(episodeCount, recentCommitCount) {
  if (recentCommitCount > 0 && episodeCount === 0) {
    return {
      ok: false,
      detail: `${recentCommitCount} commit(s) in the last 2 weeks but 0 observer episodes this month`,
    };
  }
  return { ok: true, detail: `${episodeCount} episode(s), ${recentCommitCount} recent commit(s)` };
}

/** @returns {{ok: boolean, detail: string}} */
export function checkRegistration(settingsJson, postCommitExists) {
  const problems = [];
  const stopHooks = (((settingsJson || {}).hooks || {}).Stop) || [];
  const hasObserverStop = stopHooks.some((entry) =>
    ((entry && entry.hooks) || []).some((h) => String((h && h.command) || '').includes('observer-stop-hook'))
  );
  if (!hasObserverStop) {
    problems.push('observer-stop-hook NOT registered in .claude/settings.json Stop hook');
  }
  if (!postCommitExists) {
    problems.push('.git/hooks/post-commit not installed (run: npx lefthook install --force)');
  }
  return {
    ok: problems.length === 0,
    detail: problems.length ? problems.join('; ') : 'Stop-hook + post-commit OK',
  };
}

function countEpisodes(root) {
  const month = new Date().toISOString().slice(0, 7);
  const file = join(root, 'docs', 'observer', `episodes-${month}.jsonl`);
  if (!existsSync(file)) return 0;
  return readFileSync(file, 'utf-8').trim().split('\n').filter(Boolean).length;
}

function countRecentCommits(root) {
  try {
    const out = execFileSync('git', ['log', `--since=${RECENT_WINDOW}`, '--oneline'], {
      cwd: root,
      encoding: 'utf-8',
      stdio: ['ignore', 'pipe', 'ignore'],
    });
    return out.trim() ? out.trim().split('\n').length : 0;
  } catch {
    return 0;
  }
}

export function runCoverageChecker(root = process.cwd()) {
  const coverage = checkCoverage(countEpisodes(root), countRecentCommits(root));
  let settings = {};
  try {
    settings = JSON.parse(readFileSync(join(root, '.claude', 'settings.json'), 'utf-8'));
  } catch {
    settings = {};
  }
  const registration = checkRegistration(settings, existsSync(join(root, '.git', 'hooks', 'post-commit')));
  return { coverage, registration };
}

if (process.argv[1] && process.argv[1].replace(/\\/g, '/').endsWith('/observer-coverage-checker.mjs')) {
  const { coverage, registration } = runCoverageChecker();
  if (!coverage.ok) console.warn(`[observer-coverage-checker] WARN — coverage: ${coverage.detail}`);
  if (!registration.ok) console.warn(`[observer-coverage-checker] WARN — registration: ${registration.detail}`);
  if (coverage.ok && registration.ok) {
    console.log(`[observer-coverage-checker] OK — ${coverage.detail}; ${registration.detail}`);
  }
  process.exit(0); // warn-only — never blocks a commit
}