// lib/stats/stats-append.mjs
// Append one command-stats record to <data dir>/<kind>-stats.jsonl.
//
// Why this exists: the commands' stats phases said "append to
// ${CLAUDE_PLUGIN_DATA}/<kind>-stats.jsonl; if it is not set, skip silently".
// The Bash tool's env carries no CLAUDE_PLUGIN_DATA, so the record was skipped
// whenever the model did not guess the directory itself — the same silent skip
// that left brief-approved at 0 records. This writer resolves the directory
// the way scripts/yardstick.mjs reads it, and a failed write is REPORTED
// (exit 1 + reason), never swallowed. Stats still never block the workflow:
// the command prose reports the failure and carries on.
//
// CLI (the record is read from stdin, so no shell quoting of JSON):
//   node lib/stats/stats-append.mjs <kind> <<'JSON'
//   { ...record... }
//   JSON
//   → prints {"written":true,"path":...} exit 0 | {"written":false,"reason":...} exit 1

import { appendFileSync, mkdirSync, readFileSync } from 'node:fs';
import { homedir } from 'node:os';
import { join } from 'node:path';

export const STATS_KINDS = Object.freeze([
  'trekbrief', 'trekresearch', 'trekplan', 'trekexecute', 'trekreview', 'trekcontinue',
]);

/**
 * The plugin data directory: CLAUDE_PLUGIN_DATA when the harness provides it,
 * otherwise the directory the hooks write to and scripts/yardstick.mjs reads.
 */
export function resolveStatsDir(env = process.env) {
  if (env.CLAUDE_PLUGIN_DATA) return env.CLAUDE_PLUGIN_DATA;
  const home = env.HOME && env.HOME.length > 0 ? env.HOME : homedir();
  return join(home, '.claude', 'plugins', 'data', 'voyage-ktg-plugin-marketplace');
}

/**
 * @returns {{ written: boolean, path: string|null, reason?: string }}
 */
export function appendStatsRecord(kind, record, env = process.env) {
  if (!STATS_KINDS.includes(kind)) {
    return { written: false, path: null, reason: `unknown kind "${kind}" (one of ${STATS_KINDS.join(', ')})` };
  }
  if (!record || typeof record !== 'object' || Array.isArray(record)) {
    return { written: false, path: null, reason: 'record must be a JSON object' };
  }
  const dir = resolveStatsDir(env);
  const path = join(dir, `${kind}-stats.jsonl`);
  try {
    mkdirSync(dir, { recursive: true });
    appendFileSync(path, JSON.stringify(record) + '\n');
  } catch (e) {
    return { written: false, path, reason: `${e.code || 'write-failed'}: ${e.message}` };
  }
  return { written: true, path };
}

if (import.meta.url === `file://${process.argv[1]}`) {
  const kind = process.argv[2];
  let record = null;
  let reason = null;
  try {
    record = JSON.parse(readFileSync(0, 'utf8'));
  } catch (e) {
    reason = `stdin is not JSON: ${e.message}`;
  }
  const r = reason ? { written: false, path: null, reason } : appendStatsRecord(kind, record);
  process.stdout.write(JSON.stringify(r) + '\n');
  process.exit(r.written ? 0 : 1);
}