'use strict';

const crypto = require('crypto');
const prom = require('./prom');

// Phase 0：验签 -> 去重 -> 只处理 contact 的 message.created -> 回一条占位消息。
// Phase 1 会把这里替换成 bridge AI 编排。
function verifySignature(rawBody, secret, signature) {
  if (!secret || !signature) return false;
  const expected = 'sha256=' + crypto.createHmac('sha256', secret).update(rawBody).digest('hex');
  const a = Buffer.from(String(signature));
  const b = Buffer.from(expected);
  return a.length === b.length && crypto.timingSafeEqual(a, b);
}

function createLibreDeskWebhook(cfg, deps = {}) {
  const client = deps.client || require('./libredesk').createLibreDeskClient(cfg);
  const agent = deps.agent || null;
  const seen = new Map();
  const TTL_MS = 10 * 60 * 1000;

  function markSeen(uuid) {
    const now = Date.now();
    for (const [key, ts] of seen) if (now - ts > TTL_MS) seen.delete(key);
    if (seen.has(uuid)) return false;
    seen.set(uuid, now);
    return true;
  }

  async function handle(body) {
    if (!body || body.event !== 'message.created') return;
    const msg = body.payload || {};
    prom.inc('bridge_webhook_events_total', { event: body.event || 'unknown' });
    if (msg.sender_type !== 'contact' || msg.private) return;
    if (!msg.uuid || !msg.conversation_uuid) return;
    if (!markSeen(msg.uuid)) return;

    const conv = await client.getConversation(msg.conversation_uuid);
    const inboxId = String(conv && conv.inbox_id);
    const allowed = cfg.libredeskWebhookInboxIds || [];
    if (allowed.length && !allowed.includes(inboxId)) {
      console.log(JSON.stringify({ ts: new Date().toISOString(), webhook: 'ignored_inbox', inbox: inboxId, conversation: msg.conversation_uuid }));
      return;
    }

    const text = String(msg.text_content || msg.content || '').trim();
    console.log(JSON.stringify({ ts: new Date().toISOString(), webhook: 'message.created', inbox: inboxId, conversation: msg.conversation_uuid, message: msg.uuid, text: text.slice(0, 120) }));

    if (agent) {
      try {
        await agent.run(conv, msg);
      } catch (err) {
        console.error(JSON.stringify({ ts: new Date().toISOString(), webhook: 'agent_error', conversation: msg.conversation_uuid, error: err.message }));
      }
    } else {
      // 没有 agent 时的占位回复（仅用于链路调试）
      const reply = `Bridge Phase 0 已收到：${text || '(空消息)'}`;
      await client.sendMessage(msg.conversation_uuid, reply, { echoId: `bridge-p0-${msg.uuid}` });
      console.log(JSON.stringify({ ts: new Date().toISOString(), webhook: 'replied', conversation: msg.conversation_uuid, reply }));
    }
  }

  return { verifySignature, handle };
}

module.exports = { createLibreDeskWebhook, verifySignature };