#!/usr/bin/env node
/**
 * pre-agent-gate.js — Agent 派遣前置门 (P1, 2026-04-19)
 * PRE_AGENT_GATE_P1
 *
 * PreToolUse(Task) 钩子 — general-purpose + 轻量查询 → 建议改用 explore agent。
 * fail-open: exit 0 始终, 不阻断派遣。
 */
'use strict';

const fs = require('fs');
const path = require('path');

const LIGHTWEIGHT_KEYWORDS = [
  /\\bfind\\b/i, /\\blocate\\b/i, /\\bsearch\\b/i, /\\blist\\b/i,
  /\\bwhich\\b/i, /\\bwhere\\s+is\\b/i, /\\blook\\s+up\\b/i, /\\bgrep\\b/i,
  /查找/, /搜索/, /定位/, /列出/, /哪里/, /哪个文件/,
];
const SHORT_PROMPT_THRESHOLD = 200;

function getLogPath() {
  try {
    const root = require('./lib/root.js');
    return path.join(root, 'debug', 'pre-agent-gate.jsonl');
  } catch {
    return path.join(__dirname, '..', 'debug', 'pre-agent-gate.jsonl');
  }
}

function readStdinSync() {
  try {
    const raw = fs.readFileSync(0, 'utf8');
    return JSON.parse(raw);
  } catch {
    return null;
  }
}

function isLightweight(prompt) {
  if (!prompt || typeof prompt !== 'string') return false;
  if (prompt.length < SHORT_PROMPT_THRESHOLD) return true;
  return LIGHTWEIGHT_KEYWORDS.some(re => re.test(prompt));
}

function logEvent(record) {
  try {
    fs.appendFileSync(getLogPath(), JSON.stringify(record) + '\n');
  } catch {}
}

function main() {
  const input = readStdinSync();
  if (!input || !input.tool_input) {
    process.exit(0);
  }

  const ti = input.tool_input || {};
  const subagentType = ti.subagent_type || '';
  const prompt = ti.prompt || '';
  const description = ti.description || '';

  const record = {
    ts: new Date().toISOString(),
    sessionId: input.session_id || '',
    subagent_type: subagentType,
    promptLen: prompt.length,
    description,
    hint: false,
  };

  if (subagentType !== 'general-purpose') {
    logEvent(record);
    process.exit(0);
  }

  if (!isLightweight(prompt)) {
    logEvent(record);
    process.exit(0);
  }

  record.hint = true;
  logEvent(record);

  const hint = '[pre-agent-gate] 检测到轻量查询使用 general-purpose agent。' +
               '建议改用 explore agent (haiku 模型, 成本约 1/5)。' +
               '若确需 general-purpose 请忽略此提示。';

  const out = {
    hookSpecificOutput: {
      hookEventName: 'PreToolUse',
      additionalContext: hint,
    },
  };
  process.stdout.write(JSON.stringify(out));
  process.exit(0);
}

main();