import { lstatSync, readdirSync } from 'node:fs';
import { dirname, join } from 'node:path';
import { spawn } from 'node:child_process';
import { gitEnv, runGit, GIT_LIMITS } from '../../seat/src/checkout.mjs';
import { ProjectError } from './paths.mjs';
import { currentProcessing } from '../../processing-control/src/effects.mjs';

export const SAFE = ['-c', 'core.hooksPath=/dev/null', '-c', 'core.fsmonitor=false', '-c', 'core.ignorestat=false',
  '-c', 'protocol.allow=never', '-c', 'submodule.recurse=false', '-c', 'commit.gpgsign=false',
  '-c', 'maintenance.auto=false', '-c', 'gc.auto=0'];
export async function git(repo, args, identity = {}) {
  const result = await runGit([...SAFE, '-C', repo, ...args], {
    ...gitEnv(), GIT_CEILING_DIRECTORIES: dirname(repo), ...identity,
  });
  if (!result.ok) throw new ProjectError('project-git', `local git ${args[0]} refused (${result.why})`);
  return result.out.trimEnd();
}
export async function inspectGit(repo) {
  // Refuse gitdir indirection, alternates, links or hardlinks before git reads metadata.
  // Everything below .git was named by a readdir, so a name that is gone when it is read was
  // removed by a concurrent git process (for example a pack temp file). That refuses; it is
  // never skipped or retried, because the metadata did not hold still while it was checked.
  const changed = e => e.code === 'ENOENT'
    ? new ProjectError('project-repository', 'git metadata changed during inspection') : e;
  const statEntry = path => { try { return lstatSync(path); } catch (e) { throw changed(e); } };
  const namesIn = directory => { try { return readdirSync(directory); } catch (e) { throw changed(e); } };
  // Every directory takes a fresh lstat when the walk enters it, so one replaced by a link or a
  // file after its listed stat still refuses. The root is not a listed name: a missing .git
  // keeps its own error, as before.
  const walk = (directory, root = false) => {
    const st = root ? lstatSync(directory) : statEntry(directory);
    if (!st.isDirectory() || st.isSymbolicLink()) throw new ProjectError('project-repository', 'expected local .git directory');
    for (const name of namesIn(directory)) {
      const path = join(directory, name), entry = statEntry(path);
      if (entry.isDirectory()) walk(path);
      else if (!entry.isFile() || entry.nlink !== 1)
        throw new ProjectError('project-repository', 'git metadata must contain regular private files');
    }
  };
  walk(join(repo, '.git'), true);
  for (const name of ['commondir', 'objects/info/alternates', 'objects/info/http-alternates']) {
    try { lstatSync(join(repo, '.git', name)); }
    catch (e) { if (e.code === 'ENOENT') continue; throw e; }
    throw new ProjectError('project-repository', 'git metadata indirection refused');
  }
  const config = lstatSync(join(repo, '.git/config'));
  if (config.size > 65536) throw new ProjectError('project-repository', 'git config is too large');
  const list = await git(repo, ['config', '--no-includes', '--file', join(repo, '.git/config'), '--list', '--null']);
  const allowed = {
    'core.repositoryformatversion': ['0'], 'core.bare': ['false'], 'core.filemode': ['true', 'false'],
    'core.logallrefupdates': ['true'], 'core.ignorecase': ['true', 'false'],
  };
  for (const entry of list.split('\0').filter(Boolean)) {
    const split = entry.indexOf('\n'), key = entry.slice(0, split), value = entry.slice(split + 1);
    if (key.startsWith('remote.')) throw new ProjectError('project-remote', 'project repository must have no remote');
    if (['user.name', 'user.email'].includes(key)) continue;
    if (!allowed[key]?.includes(value)) throw new ProjectError('project-repository', `unsupported local git config: ${key}`);
  }
}
export async function requireClean(repo) {
  const status = await git(repo, ['status', '--porcelain=v1', '--untracked-files=all', '--ignored=matching']);
  const flags = await git(repo, ['ls-files', '-v']);
  if (status || flags.split('\n').some(line => /^[a-zS] /.test(line)))
    throw new ProjectError('project-dirty', 'pending edits, staged changes, ignored content or hidden index flags refuse');
}
export const identity = name => ({ GIT_AUTHOR_NAME: name, GIT_AUTHOR_EMAIL: `${name}@mosaic.invalid`,
  GIT_COMMITTER_NAME: name, GIT_COMMITTER_EMAIL: `${name}@mosaic.invalid` });

// Blob/log reads preserve bytes and bound memory before decoding untrusted Git data.
export async function gitBytes(repo, args, maxBytes) {
  return new Promise((resolve, reject) => {
    const processing = currentProcessing();
    processing?.guard();
    const child = spawn('git', [...SAFE, '-C', repo, ...args], {
      env: { ...gitEnv(), GIT_CEILING_DIRECTORIES: dirname(repo) },
      detached: true, stdio: ['ignore', 'pipe', 'pipe'],
    });
    processing?.track(child);
    let size = 0, failed = false, settled = false;
    const chunks = [];
    const kill = () => { try { process.kill(-child.pid, 'SIGKILL'); } catch {} };
    const timer = setTimeout(() => { failed = true; kill(); }, GIT_LIMITS.timeoutMs);
    const finish = (code) => {
      if (settled) return;
      settled = true;
      clearTimeout(timer);
      if (failed || code !== 0) reject(new ProjectError('project-git', 'bounded local Git read refused'));
      else resolve(Buffer.concat(chunks));
    };
    child.stdout.on('data', chunk => {
      size += chunk.length;
      if (size > maxBytes) { failed = true; kill(); }
      else chunks.push(chunk);
    });
    // Drain stderr without retaining repository-controlled text.
    child.stderr.on('data', () => {});
    child.on('error', () => finish(-1));
    child.on('close', finish);
  });
}