interface BookingParams {
  airlineCode: string
  origin: string
  destination: string
  date: string // ISO date string
  passengers?: number
}

// Direct booking URL templates for major airlines
// date format helpers applied per-airline
const BOOKING_TEMPLATES: Record<string, (p: BookingParams & { d: string; ymd: string }) => string> = {
  FR: p => `https://www.ryanair.com/es/es/trip/flights/select?adults=${p.passengers}&teens=0&children=0&infants=0&dateOut=${p.ymd}&originIata=${p.origin}&destinationIata=${p.destination}&isReturn=false`,
  U2: p => `https://www.easyjet.com/es/search?origin=${p.origin}&destination=${p.destination}&outboundDate=${p.ymd}&adults=${p.passengers}`,
  VY: () => `https://www.vueling.com/es/reserva-tu-vuelo/busca-tu-vuelo`,
  LH: p => `https://www.lufthansa.com/es/es/offer/search?origin=${p.origin}&destination=${p.destination}&departureDate=${p.ymd}&paxAdult=${p.passengers}&cabinClass=ECONOMY&tripType=O`,
  IB: p => `https://www.iberia.com/es/?language=es&market=ES&origin=${p.origin}&destination=${p.destination}&outbound=${p.ymd}&adults=${p.passengers}&cabin=ECONOMY`,
  W6: p => `https://wizzair.com/es-es#/booking/select-flight/${p.origin}/${p.destination}/${p.ymd}/null/${p.passengers}/0/0/null`,
  NK: p => `https://www.spirit.com/book/flights?origStation=${p.origin}&destStation=${p.destination}&date=${p.ymd}&adt=${p.passengers}&chd=0&inf=0&promoCode=&tripType=OW`,
  KL: p => `https://www.klm.es/search?pax=${p.passengers}:0:0:0:0:0:0:0&cabinClass=ECONOMY&connections=${p.origin}:C%3E${p.destination}:C&bookingFlow=LEISURE`,
  AF: p => `https://www.airfrance.es/search?pax=${p.passengers}:0:0:0:0:0:0:0&cabinClass=ECONOMY&connections=${p.origin}:C%3E${p.destination}:C&bookingFlow=LEISURE`,
  TK: p => `https://www.turkishairlines.com/es-es/flights/?origin=${p.origin}&destination=${p.destination}&departureDate=${p.ymd}&adult=${p.passengers}&child=0&infant=0&tripType=O`,
  AA: p => `https://www.aa.com/booking/find-flights?origin=${p.origin}&destination=${p.destination}&departureDate=${p.ymd}&pax=${p.passengers}&tripType=OneWay&locale=es_ES`,
}

interface AirlineData {
  website: string | null
  bookingUrl: string | null
  bookingUrlTemplate: string | null
}

// Airline data cache (loaded once from API)
const airlineData = ref<Map<string, AirlineData> | null>(null)
let loadingPromise: Promise<void> | null = null

async function loadAirlineData() {
  if (airlineData.value) return
  if (loadingPromise) return loadingPromise

  loadingPromise = $fetch<{ airlines: { iata: string; website: string | null; booking_url: string | null; booking_url_template: string | null }[] }>('/api/airlines')
    .then(res => {
      const map = new Map<string, AirlineData>()
      for (const a of res.airlines) {
        map.set(a.iata, {
          website: a.website,
          bookingUrl: a.booking_url,
          bookingUrlTemplate: a.booking_url_template,
        })
      }
      airlineData.value = map
    })
    .catch(() => {
      airlineData.value = new Map()
    })

  return loadingPromise
}

function applyTemplate(template: string, params: BookingParams, pax: number, ymd: string): string {
  return template
    .replace(/\{origin\}/gi, params.origin)
    .replace(/\{destination\}/gi, params.destination)
    .replace(/\{date\}/gi, ymd)
    .replace(/\{passengers\}/gi, String(pax))
}

function buildGoogleFlightsUrl(p: BookingParams): string {
  const ymd = p.date.slice(0, 10)
  return `https://www.google.com/travel/flights?hl=es&curr=EUR&q=flights+from+${p.origin}+to+${p.destination}+on+${ymd}+one+way+${p.passengers}+passenger`
}

export function useBookingUrl() {
  // Start loading on first use
  loadAirlineData()

  function getBookingUrl(params: BookingParams): string {
    const pax = params.passengers || 1
    const ymd = params.date.slice(0, 10)
    const d = ymd.replace(/-/g, '')

    // 1. Hardcoded templates (most reliable, manually verified)
    const hardcoded = BOOKING_TEMPLATES[params.airlineCode]
    if (hardcoded) {
      return hardcoded({ ...params, passengers: pax, d, ymd })
    }

    const data = airlineData.value?.get(params.airlineCode)

    // 2. Auto-discovered template with placeholders
    if (data?.bookingUrlTemplate) {
      return applyTemplate(data.bookingUrlTemplate, params, pax, ymd)
    }

    // 3. Discovered booking page URL (no params, but lands on the right page)
    if (data?.bookingUrl) {
      return data.bookingUrl
    }

    // 4. Google Flights as universal fallback
    return buildGoogleFlightsUrl({ ...params, passengers: pax })
  }

  function getAirlineWebsite(code: string): string | null {
    return airlineData.value?.get(code)?.website || null
  }

  return { getBookingUrl, getAirlineWebsite }
}