import { SEO_ROUTES } from '@/constants/routes'
import { createClientId } from '@/lib/createClientId'

export type TrafficSource = 'instagram' | 'telegram'

const VISITOR_KEY = 'ghabilee:visitor-id'
const ATTRIBUTION_PREFIX = 'ghabilee:attribution:'
const ATTRIBUTION_TTL_MS = 30 * 24 * 60 * 60 * 1000

const SOURCES = new Set<TrafficSource>(['instagram', 'telegram'])

interface StoredAttribution {
  source: TrafficSource
  capturedAt: number
}

const isBrowser = () => typeof window !== 'undefined'

export const parseTrafficSource = (raw: string | null | undefined): TrafficSource | null => {
  if (!raw) return null
  const value = raw.trim().toLowerCase()

  return SOURCES.has(value as TrafficSource) ? (value as TrafficSource) : null
}

export const getOrCreateVisitorId = (): string | null => {
  if (!isBrowser()) return null

  try {
    const existing = window.localStorage.getItem(VISITOR_KEY)

    if (existing && /^[0-9a-f-]{36}$/i.test(existing)) return existing

    const created = createClientId()

    window.localStorage.setItem(VISITOR_KEY, created)

    return created
  } catch {
    return null
  }
}

export const rememberEventAttribution = (eventId: string, source: TrafficSource): void => {
  if (!isBrowser() || !eventId) return

  try {
    const key = `${ATTRIBUTION_PREFIX}${eventId}`
    const existingRaw = window.localStorage.getItem(key)

    if (existingRaw) {
      const existing = JSON.parse(existingRaw) as StoredAttribution

      if (existing?.source && Date.now() - existing.capturedAt < ATTRIBUTION_TTL_MS) {
        return
      }
    }
    const payload: StoredAttribution = { source, capturedAt: Date.now() }

    window.localStorage.setItem(key, JSON.stringify(payload))
  } catch {
    // Privacy modes / full storage — attribution is best-effort.
  }
}

export const getEventAttribution = (eventId: string): TrafficSource | null => {
  if (!isBrowser() || !eventId) return null

  try {
    const raw = window.localStorage.getItem(`${ATTRIBUTION_PREFIX}${eventId}`)

    if (!raw) return null
    const stored = JSON.parse(raw) as StoredAttribution

    if (!stored?.source || !SOURCES.has(stored.source)) return null
    if (Date.now() - stored.capturedAt > ATTRIBUTION_TTL_MS) return null

    return stored.source
  } catch {
    return null
  }
}

export const buildEventShareUrl = (slug: string, source?: TrafficSource): string => {
  const path = SEO_ROUTES.EVENT_LANDING(slug)

  if (!isBrowser()) {
    return source ? `${path}?src=${source}` : path
  }
  const url = new URL(path, window.location.origin)

  if (source) url.searchParams.set('src', source)

  return url.toString()
}