import { utmKeys, type LeadFormId, type LeadInput, type LeadResponse } from '../../shared/lead'

const ENDPOINT = '/api/leads/medical-centers-existing-physio'
const DRAFT_KEY = 'exo_medcenter_lead_draft'

const FALLBACK_ERROR =
  'Не удалось отправить форму автоматически. Данные сохранены в браузере — свяжитесь с нами по +7 939 717-80-80.'

/** Query-string UTM tags, forwarded to amoCRM with the lead. */
function collectUtm(): Record<string, string> {
  const params = new URLSearchParams(window.location.search)
  const utm: Record<string, string> = {}
  for (const key of utmKeys) {
    const value = params.get(key)
    if (value) utm[key] = value
  }
  return utm
}

export interface SubmitResult {
  ok: boolean
  error?: string
  fields?: Record<string, string>
}

export async function submitLead(
  form: LeadFormId,
  values: Omit<LeadInput, 'form' | 'utm' | 'page' | 'referrer'>,
): Promise<SubmitResult> {
  const payload: LeadInput = {
    ...values,
    form,
    page: window.location.pathname,
    referrer: document.referrer || undefined,
    utm: collectUtm(),
  }

  try {
    const response = await fetch(ENDPOINT, {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify(payload),
    })

    const body = (await response.json().catch(() => null)) as LeadResponse | null

    if (!response.ok || !body?.ok) {
      // The page must never lose a lead just because the CRM is down.
      saveDraft(payload)
      return {
        ok: false,
        error: body && !body.ok ? body.error : FALLBACK_ERROR,
        fields: body && !body.ok ? body.fields : undefined,
      }
    }

    window.dataLayer = window.dataLayer ?? []
    window.dataLayer.push({ event: 'medcenter_lead_sent', form })
    localStorage.removeItem(DRAFT_KEY)
    return { ok: true }
  } catch (error) {
    saveDraft(payload)
    console.warn('Lead endpoint error', error, payload)
    return { ok: false, error: FALLBACK_ERROR }
  }
}

function saveDraft(payload: LeadInput) {
  try {
    localStorage.setItem(DRAFT_KEY, JSON.stringify(payload))
  } catch {
    // Private-mode browsers throw on write; the visible error message is enough.
  }
}

declare global {
  interface Window {
    dataLayer?: Record<string, unknown>[]
  }
}