Помічник для повідомлень на замовлення

function transitionAssistant(current, action, scenario) {
  const text = value => typeof value === 'string' && value.trim().length > 0 && value.length <= 2000;
  if (!scenario || typeof scenario !== 'object' || Array.isArray(scenario) ||
      !['client_initial', 'assistant_reply', 'client_confirmation', 'handoff_department'].every(key => text(scenario[key]))) {
    throw new Error('SCENARIO_INVALID');
  }
  const source = scenario.ticket;
  if (!source || typeof source !== 'object' || Array.isArray(source) ||
      typeof source.id !== 'string' || !/^DEMO-[A-Za-z0-9_-]{1,64}$/.test(source.id) ||
      !['call', 'message'].includes(source.channel) || !['high', 'standard'].includes(source.priority) ||
      !text(source.topic) || !text(source.department) ||
      ['contact', 'details'].some(key => source[key] !== undefined && !text(source[key]))) throw new Error('SCENARIO_INVALID');
  const initial = {status: 'idle', transcript: [], ticket: null, count: 0};
  if (action === 'reset') return initial;
  const state = current == null ? initial : current;
  if (!['idle', 'received', 'replied', 'captured', 'assigned'].includes(state.status) ||
      !Array.isArray(state.transcript) || ![0, 1].includes(state.count)) throw new Error('ASSISTANT_STATE');
  const transcript = state.transcript.map(entry => ({speaker: entry.speaker, text: entry.text}));
  if (action === 'start' && state.status === 'idle') {
    return {status: 'received', transcript: [{speaker: 'client', text: scenario.client_initial}], ticket: null, count: 0};
  }
  if (action === 'reply' && state.status === 'received') {
    transcript.push({speaker: 'assistant', text: scenario.assistant_reply}, {speaker: 'client', text: scenario.client_confirmation});
    return {status: 'replied', transcript, ticket: null, count: 0};
  }
  if (action === 'capture' && ['captured', 'assigned'].includes(state.status) && state.ticket) {
    return {status: state.status, transcript, ticket: {...state.ticket}, count: 1};
  }
  if (action === 'capture' && state.status === 'replied') {
    const ticket = {};
    ['id', 'channel', 'topic', 'contact', 'details', 'department', 'priority'].forEach(key => {
      if (source[key] !== undefined) ticket[key] = source[key];
    });
    const required=source.channel==='call'?['contact','vehicle','preferred_time']:['contact','delivery_address'];
    const provided=Array.isArray(scenario.provided_fields)?scenario.provided_fields:[];
    ticket.missing_fields=required.filter(key=>!provided.includes(key));
    ticket.ready_to_execute=ticket.missing_fields.length===0;
    ticket.handed_off=false;
    ticket.status = 'captured';
    return {status: 'captured', transcript, ticket, count: 1};
  }
  if (action === 'handoff' && state.status === 'captured' && state.ticket) {
    return {status: 'assigned', transcript, ticket: {...state.ticket, department: scenario.handoff_department, status: 'assigned', assigned_to: 'operator', handed_off: true}, count: 1};
  }
  if (!['start', 'reply', 'capture', 'handoff'].includes(action)) throw new Error('ASSISTANT_ACTION');
  throw new Error('ASSISTANT_ORDER');
}