'use strict';

/**
 * sys-call dispatcher.
 *
 * Routes incoming sys-call messages (action='request'|'cancel') from VPS
 * to the correct channel handler, and wires the emit callback so that
 * handler replies are sent back over the WebSocket.
 *
 * Message envelope (shared by all sys-call messages):
 * {
 *   type:    'sys-call',
 *   id:      '<UUID>',
 *   api:     'channel.weixin',
 *   method:  'login',
 *   action:  'request' | 'reply' | 'notify' | 'progress' | 'event' | 'finish' | 'cancel',
 *   event:   '',
 *   code:    0,
 *   message: '',
 *   data:    {}
 * }
 */

const log = require('./logger');

// ── channel handlers ──────────────────────────────────────────────────────────
const handlers = {
  'channel.weixin': require('./channel/weixin'),
};

// ── running tasks: callId → abort() ──────────────────────────────────────────
const running = new Map();

/**
 * Handle an incoming sys-call message from VPS.
 *
 * @param {object}   msg  - parsed message object
 * @param {function} send - send(replyPayload) → forwards to VPS over WS;
 *                          caller prepends { type:'sys-call' }
 */
function handle(msg, send) {
  const { id: callId, api, method, action } = msg;

  if (!callId) {
    log.warn('sys-call', 'missing id field, ignoring');
    return;
  }

  // ── cancel ────────────────────────────────────────────────────────────────
  if (action === 'cancel') {
    const abort = running.get(callId);
    if (abort) {
      log.info('sys-call', `cancel callId=${callId}`);
      try { abort(); } catch (e) { log.warn('sys-call', `abort error: ${e.message}`); }
      running.delete(callId);
    } else {
      log.debug('sys-call', `cancel for unknown/finished callId=${callId}`);
    }
    return;
  }

  // ── request ───────────────────────────────────────────────────────────────
  if (action !== 'request') {
    log.warn('sys-call', `unexpected action=${action} callId=${callId}`);
    return;
  }

  const handler = handlers[api];
  if (!handler || typeof handler[method] !== 'function') {
    log.warn('sys-call', `unknown api=${api} method=${method}`);
    send({
      id: callId, api, method,
      action: 'finish', event: 'failed',
      code: 404, message: `unknown api: ${api}.${method}`,
    });
    return;
  }

  // emit: wraps handler replies, cleans up running map on finish
  const emit = (payload) => {
    send({ id: callId, api, method, event: '', code: 0, message: '', ...payload });
    if (payload.action === 'finish') {
      running.delete(callId);
      log.info('sys-call', `finished callId=${callId}`);
    }
  };

  log.info('sys-call', `start api=${api} method=${method} callId=${callId}`);

  let abort;
  try {
    abort = handler[method]({ callId, ...(msg.data || {}), emit });
  } catch (e) {
    log.error('sys-call', `handler threw: ${e.message}`);
    send({
      id: callId, api, method,
      action: 'finish', event: 'failed',
      code: 500, message: e.message,
    });
    return;
  }

  if (typeof abort === 'function') {
    running.set(callId, abort);
  }
}

module.exports = { handle };