// lib/stats/claimed-order.mjs
// Which coord-queue order is this Voyage run working on? Read from the queue
// itself, never typed by the model and never guessed.
//
// Why this exists: the yardstick's `use` number joins a new-work order to a
// Voyage run. A key declared on the order before any run (a `slug:`) is not
// proof a run happened, and no order carried one. The run itself has to say
// which order it ran, so /trekbrief's stats record carries the id this module
// finds (lib/stats/stats-append.mjs adds it; the model never copies it).
//
// The contract it mirrors is repo-mailbox's claim verb (coord-order-claim.sh,
// 0.37.0), read here, never called:
//   - coord root   ${CLAUDE_COORD_DIR:-$HOME/.claude/coord}
//   - mailbox      basename of `git rev-parse --show-toplevel`; `_*` is reserved
//   - claim        `mv orders/<id>.md orders/claimed/<id>.md`, so the id is the
//                  file stem, plus a best-effort sidecar `claimed/<id>.claim`
//                  holding `claimed-at: <ISO>`
//   - close        coord-order-done.sh deletes the `.claim`, so the claim time
//                  survives only in the record this module feeds.
// A worktree's toplevel basename is the worktree's name, so the main repo's
// name (the parent of the common git dir) is searched too.
//
// Exactly one claimed order -> { order_id, order_claimed_at, order_reason: null }.
// Anything else -> order_id null (or the id with `no-claim-time`) and a reason:
// mailbox-unresolved · coord-missing · coord-unreadable · none-claimed ·
// several-claimed:N · to-mismatch · no-claim-time. It only reads, never throws,
// and starts nothing. Zero npm dependencies.

import { existsSync, readdirSync, readFileSync, realpathSync, statSync } from 'node:fs';
import { homedir } from 'node:os';
import { basename, dirname, isAbsolute, join, relative, resolve } from 'node:path';
import { execFileSync } from 'node:child_process';

const GIT_TIMEOUT_MS = 5000;
const unattributed = (order_reason) => ({ order_id: null, order_claimed_at: null, order_reason });

/** The coord root the claim script uses: CLAUDE_COORD_DIR, else $HOME/.claude/coord. */
export function resolveCoordDir(env = process.env) {
  if (env.CLAUDE_COORD_DIR) return env.CLAUDE_COORD_DIR;
  const home = env.HOME && env.HOME.length > 0 ? env.HOME : homedir();
  return join(home, '.claude', 'coord');
}

function gitLine(dir, args, env) {
  try {
    return execFileSync('git', ['-C', dir, 'rev-parse', ...args], {
      encoding: 'utf8', timeout: GIT_TIMEOUT_MS, env, stdio: ['ignore', 'pipe', 'ignore'],
    }).trim();
  } catch {
    return '';
  }
}

/**
 * The mailbox names `dir` can be filed under: the toplevel's basename (the
 * claim script's rule) and, in a linked worktree, the main repo's name. Two
 * independent git calls, so one failing never loses the other. An inherited
 * GIT_DIR / GIT_WORK_TREE would point git at another repo, so both are dropped.
 */
export function resolveMailboxes(dir, { env = {} } = {}) {
  const childEnv = { ...process.env, ...env };
  for (const key of ['GIT_DIR', 'GIT_WORK_TREE', 'GIT_COMMON_DIR', 'GIT_INDEX_FILE']) delete childEnv[key];
  const names = [];
  const top = gitLine(dir, ['--show-toplevel'], childEnv);
  if (top) names.push(basename(top));
  const common = gitLine(dir, ['--path-format=absolute', '--git-common-dir'], childEnv);
  // Only `<repo>/.git` names a repo; a submodule's `.git/modules/<x>` does not.
  if (common && basename(common) === '.git') names.push(basename(dirname(common)));
  return [...new Set(names)];
}

const isDir = (p) => existsSync(p) && statSync(p).isDirectory();

/** The one claimed order across `mailboxes`, or null and the reason it is not one. */
export function findClaimedOrder({ coordDir, mailboxes }) {
  try {
    if (!isDir(coordDir)) return unattributed('coord-missing');
    const names = (mailboxes ?? []).filter((m) => typeof m === 'string' && m !== '' && !m.startsWith('_'));
    if (names.length === 0) return unattributed('mailbox-unresolved');
    const found = [];
    for (const mailbox of names) {
      const dir = join(coordDir, mailbox, 'orders', 'claimed');
      if (!isDir(dir)) continue;
      for (const name of readdirSync(dir).sort()) {
        if (name.endsWith('.md')) found.push({ mailbox, dir, id: name.slice(0, -3) });
      }
    }
    if (found.length === 0) return unattributed('none-claimed');
    if (found.length > 1) return unattributed(`several-claimed:${found.length}`);
    const [{ mailbox, dir, id }] = found;
    const text = readFileSync(join(dir, `${id}.md`), 'utf8');
    const fm = text.match(/^---\r?\n([\s\S]*?)\r?\n---/)?.[1] ?? '';
    const to = fm.match(/^to:[ \t]*(.*?)[ \t]*$/m)?.[1];
    if (to !== undefined && to !== mailbox) return unattributed('to-mismatch');
    const claimPath = join(dir, `${id}.claim`);
    const at = existsSync(claimPath)
      ? readFileSync(claimPath, 'utf8').match(/^claimed-at:[ \t]*(\S+)[ \t]*$/m)?.[1]
      : undefined;
    if (!at) return { order_id: id, order_claimed_at: null, order_reason: 'no-claim-time' };
    return { order_id: id, order_claimed_at: at, order_reason: null };
  } catch {
    return unattributed('coord-unreadable');
  }
}

// The directory to resolve the mailbox from: `projectDir` when it is a directory
// inside `cwd` (a brief's project dir), else `cwd`. A path that walks out of cwd
// cannot move the lookup to another repo.
function baseDir(cwd, projectDir) {
  if (typeof projectDir !== 'string' || projectDir === '') return cwd;
  try {
    const abs = resolve(cwd, projectDir);
    if (!isDir(abs)) return cwd;
    const rel = relative(realpathSync(cwd), realpathSync(abs));
    return rel.startsWith('..') || isAbsolute(rel) ? cwd : abs;
  } catch {
    return cwd;
  }
}

/** The attribution a /trekbrief record carries: always the three keys. */
export function attributeOrder({ cwd = process.cwd(), env = process.env, projectDir } = {}) {
  const mailboxes = resolveMailboxes(baseDir(cwd, projectDir), { env });
  if (mailboxes.length === 0) return unattributed('mailbox-unresolved');
  return findClaimedOrder({ coordDir: resolveCoordDir(env), mailboxes });
}