// Отправка заявки на POST /api/lead и перевод ответа сервера в состояние формы.
import type { FieldErrors, LeadField, LeadRequest } from '@kvarta/shared/lead';

export const SUBMIT_TIMEOUT_MS = 10_000;

/** Что сказать посетителю после отправки. */
export type SubmitNotice = 'created' | 'clarified' | 'invalid' | 'rate_limited' | 'failed';

export type SubmitResult = {
  status: 'success' | 'error';
  notice: SubmitNotice;
  /** подсказки под полями при 400 */
  fieldErrors: FieldErrors;
};

export type SendLead = (body: LeadRequest) => Promise<SubmitResult>;

const FIELDS: readonly LeadField[] = ['name', 'phone', 'interest', 'comment'];

const success = (notice: 'created' | 'clarified'): SubmitResult => ({ status: 'success', notice, fieldErrors: {} });
const error = (notice: SubmitNotice, fieldErrors: FieldErrors = {}): SubmitResult => ({
  status: 'error',
  notice,
  fieldErrors,
});

/** Сеть, таймаут, отказ fetch. */
export const FAILED: SubmitResult = error('failed');

function pickFieldErrors(value: unknown): FieldErrors {
  if (!value || typeof value !== 'object') return {};
  const src = value as Record<string, unknown>;
  const out: FieldErrors = {};
  for (const field of FIELDS) {
    const message = src[field];
    if (typeof message === 'string' && message !== '') out[field] = message;
  }
  return out;
}

/** Ответ сервера → состояние формы. Тело может быть чем угодно, в том числе null. */
export function resultFromResponse(status: number, body: unknown): SubmitResult {
  const data = (body && typeof body === 'object' ? body : {}) as Record<string, unknown>;
  if (status === 201) return success('created');
  if (status === 200 && data.ok === true) return success(data.clarified === true ? 'clarified' : 'created');
  if (status === 400) {
    const fieldErrors = pickFieldErrors(data.fieldErrors);
    return Object.keys(fieldErrors).length > 0 ? error('invalid', fieldErrors) : FAILED;
  }
  if (status === 429) return error('rate_limited');
  // 413, 415, 5xx, 503 и всё неожиданное — «попробуйте ещё раз или позвоните»
  return FAILED;
}

export function createSendLead({
  fetchImpl = (...args: Parameters<typeof fetch>) => fetch(...args),
  timeoutMs = SUBMIT_TIMEOUT_MS,
  url = '/api/lead',
}: { fetchImpl?: typeof fetch; timeoutMs?: number; url?: string } = {}): SendLead {
  return async (body) => {
    const controller = new AbortController();
    const timer = setTimeout(() => controller.abort(), timeoutMs);
    try {
      const res = await fetchImpl(url, {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify(body),
        signal: controller.signal,
      });
      const data: unknown = await res.json().catch(() => null);
      return resultFromResponse(res.status, data);
    } catch {
      return FAILED;
    } finally {
      clearTimeout(timer);
    }
  };
}

export const sendLead: SendLead = createSendLead();