#!/usr/bin/env -S bun --no-env-file --config=/dev/null
/**
 * gstack-docs-candidate — /ship's documentation-audit snapshot and its later check.
 *
 * Usage (run inside the repository):
 *   gstack-docs-candidate snapshot --out <candidate.json> --audit-id <id> --mode edit|read-only
 *                                  --base <rev> [--select <path>]... [--docs <path>]...
 *   gstack-docs-candidate compare <candidate.json>
 *   gstack-docs-candidate [snapshot|compare] --help
 *
 * snapshot saves, NUL-safely and without writing to the repository: base SHA,
 * HEAD, branch, index entries, committed (base..HEAD), staged, unstaged and
 * untracked paths, and git blob hashes of the working-tree content of every
 * selected path, docs path and dirty/untracked path. Without --select, the
 * selected paths are the committed, staged, unstaged and untracked paths.
 * --docs takes files or directories (directories expand to their tracked and
 * untracked files). It prints a short summary; the JSON file is the record.
 *
 * compare re-reads the same state and prints one JSON object: whether HEAD or
 * the index changed, which recorded paths' content changed or disappeared, and
 * which paths are newly dirty or untracked. It never decides whether a change
 * was permitted; the caller checks those paths against the child's report.
 */
import { spawnSync } from 'child_process';
import * as fs from 'fs';
import * as path from 'path';

function git(args: string[]): string {
  const r = spawnSync('git', args, { encoding: 'utf8', env: { ...process.env, GIT_OPTIONAL_LOCKS: '0' }, maxBuffer: 256 * 1024 * 1024 });
  if (r.status !== 0) throw new Error(`git ${args.join(' ')} failed: ${(r.stderr || '').trim()}`);
  return r.stdout;
}
const nul = (text: string) => text.split('\0').filter(Boolean);

function state(base: string) {
  const head = git(['rev-parse', 'HEAD']).trim();
  return {
    head,
    branch: git(['branch', '--show-current']).trim(),
    index: nul(git(['ls-files', '-s', '-z'])),
    committed: nul(git(['diff', '--name-only', '-z', base, head])),
    staged: nul(git(['diff', '--cached', '--name-only', '-z'])),
    unstaged: nul(git(['diff', '--name-only', '-z'])),
    untracked: nul(git(['ls-files', '-z', '--others', '--exclude-standard'])),
  };
}

function expand(listed: string[], paths: string[]): string[] {
  const out = new Set<string>();
  for (const p of paths) {
    const rel = p.replace(/^\.\//, '').replace(/\/+$/, '');
    const under = listed.filter(f => f === rel || f.startsWith(rel + '/'));
    if (under.length) under.forEach(f => out.add(f)); else out.add(rel);
  }
  return [...out].sort();
}

/** Git blob ids of working-tree content, computed in-process (any path bytes, nothing written); null when absent. */
function hashes(paths: string[]): Record<string, string | null> {
  const out: Record<string, string | null> = {};
  for (const p of paths) {
    if (!fs.existsSync(p) || !fs.statSync(p).isFile()) { out[p] = null; continue; }
    const content = fs.readFileSync(p);
    out[p] = new Bun.CryptoHasher('sha1').update(`blob ${content.length}\0`).update(content).digest('hex');
  }
  return out;
}

function flag(args: string[], name: string): string[] {
  const values: string[] = [];
  for (let i = 0; i < args.length; i++) if (args[i] === name) {
    const value = args[i + 1];
    if (value === undefined || value.startsWith('--')) throw new Error(`${name} needs a value`);
    values.push(value); i++;
  }
  return values;
}

function one(args: string[], name: string): string {
  const values = flag(args, name);
  if (values.length !== 1) throw new Error(`${name} is required exactly once`);
  return values[0]!;
}

const USAGE = `usage: gstack-docs-candidate snapshot --out <candidate.json> --audit-id <id> --mode edit|read-only --base <rev> [--select <path>]... [--docs <path>]...
       gstack-docs-candidate compare <candidate.json>`;

/** Each field compare needs that the record lacks or types wrongly; empty for a valid record. */
function recordProblems(record: any): string[] {
  if (!record || typeof record !== 'object' || Array.isArray(record)) return ['not a JSON object'];
  const problems: string[] = [];
  if (record.schema_version !== 1) problems.push('missing or wrong schema_version (want 1)');
  if (typeof record.base !== 'string') problems.push('missing or wrong base (want the base commit SHA string)');
  if (!record.hashes || typeof record.hashes !== 'object' || Array.isArray(record.hashes)) problems.push('missing or wrong hashes (want an object of path -> blob id)');
  return problems;
}

function main(argv: string[]): void {
  const [command, ...args] = argv;
  const topHelp = (command === '--help' || command === '-h') && !args.length;
  const commandHelp = (command === 'snapshot' || command === 'compare') && args.length === 1 && args[0] === '--help';
  if (topHelp || commandHelp) {
    console.log(USAGE);
    return;
  }
  if (command === 'snapshot') {
    const known = new Set(['--out', '--audit-id', '--mode', '--base', '--select', '--docs']);
    for (let i = 0; i < args.length; i += 2) if (!known.has(args[i]!)) throw new Error(`unknown argument: ${args[i]}`);
    const out = path.resolve(one(args, '--out'));
    const top = fs.realpathSync(git(['rev-parse', '--show-toplevel']).trim());
    if (out === top || out.startsWith(top + path.sep)) throw new Error('--out must be outside the repository');
    const mode = one(args, '--mode');
    if (mode !== 'edit' && mode !== 'read-only') throw new Error('--mode must be edit or read-only');
    const base = git(['rev-parse', '--verify', one(args, '--base') + '^{commit}']).trim();
    process.chdir(top);
    const now = state(base);
    const listed = nul(git(['ls-files', '-z', '--cached', '--others', '--exclude-standard']));
    const selected = flag(args, '--select').length ? expand(listed, flag(args, '--select'))
      : [...new Set([...now.committed, ...now.staged, ...now.unstaged, ...now.untracked])].sort();
    const docs = expand(listed, flag(args, '--docs'));
    const tracked = [...new Set([...selected, ...docs, ...now.staged, ...now.unstaged, ...now.untracked])].sort();
    const record = { schema_version: 1, audit_id: one(args, '--audit-id'), mode, base, ...now, selected, docs, hashes: hashes(tracked) };
    fs.writeFileSync(out, JSON.stringify(record, null, 2) + '\n', { mode: 0o600 });
    console.log(`CANDIDATE: ${out}`);
    console.log(`base=${base} head=${now.head} branch=${now.branch || '(detached)'} mode=${mode}`);
    console.log(`committed=${now.committed.length} staged=${now.staged.length} unstaged=${now.unstaged.length} untracked=${now.untracked.length} selected=${selected.length} docs=${docs.length} hashed=${tracked.length}`);
    for (const [label, list] of [['committed', now.committed], ['staged', now.staged], ['unstaged', now.unstaged], ['untracked', now.untracked], ['docs', docs]] as const) {
      if (list.length) console.log(`${label}: ${list.map(p => JSON.stringify(p)).join(' ')}`);
    }
    return;
  }
  if (command === 'compare') {
    if (args.length !== 1) throw new Error('compare takes exactly one candidate path');
    const file = args[0]!;
    let record: any;
    try { record = JSON.parse(fs.readFileSync(file, 'utf8')); }
    catch (error) { if ((error as NodeJS.ErrnoException).code === 'ENOENT') throw error; record = undefined; }
    const problems = record === undefined ? ['not valid JSON'] : recordProblems(record);
    if (problems.length) {
      throw new Error(`${file} is not a gstack-docs-candidate record: ${problems.join('; ')}. `
        + 'Fix: the candidate must be the record the Prepare snapshot wrote. To rebuild it, rerun the Prepare snapshot '
        + '(gstack-docs-candidate snapshot --out <path> --audit-id <id> --mode edit --base <rev> ...) only before dispatching '
        + 'the child audit. After the audit, never snapshot over it: the post-child snapshot uses a different --out '
        + '(<audit-id>-post.json).');
    }
    process.chdir(fs.realpathSync(git(['rev-parse', '--show-toplevel']).trim()));
    const now = state(record.base);
    const current = hashes(Object.keys(record.hashes));
    const content_changed = Object.keys(record.hashes).filter(p => current[p] !== record.hashes[p]).sort();
    const dirty = (s: { staged: string[]; unstaged: string[]; untracked: string[] }) => new Set([...s.staged, ...s.unstaged, ...s.untracked]);
    const before = dirty(record);
    const newly_dirty = [...dirty(now)].filter(p => !before.has(p) && !(p in record.hashes)).sort();
    const sameList = (a: string[], b: string[]) => a.length === b.length && a.every((v, i) => v === b[i]);
    console.log(JSON.stringify({
      audit_id: record.audit_id,
      head_changed: now.head !== record.head,
      index_changed: !sameList(now.index, record.index),
      content_changed,
      newly_dirty,
    }));
    return;
  }
  throw new Error(USAGE);
}

try { main(process.argv.slice(2)); }
catch (error) {
  console.error(`gstack-docs-candidate: ${error instanceof Error ? error.message : String(error)}`);
  process.exit(1);
}