import { NextRequest } from 'next/server'
import { CHF_COUNTRIES } from '@/lib/currency'

/**
 * Get client IP address from request headers
 */
function getClientIp(request: NextRequest): string | null {
  // Check various headers that might contain the real IP
  const forwardedFor = request.headers.get('x-forwarded-for')
  if (forwardedFor) {
    // x-forwarded-for can contain multiple IPs, take the first one
    return forwardedFor.split(',')[0].trim()
  }

  const realIp = request.headers.get('x-real-ip')
  if (realIp) {
    return realIp.trim()
  }

  const cfConnectingIp = request.headers.get('cf-connecting-ip') // Cloudflare
  if (cfConnectingIp) {
    return cfConnectingIp.trim()
  }

  // Fallback to remote address if available
  const remoteAddress = request.headers.get('remote-addr')
  if (remoteAddress) {
    return remoteAddress.trim()
  }

  return null
}

/**
 * Get country code from IP address using ip-api.com (free, no API key required)
 * Returns country code (e.g., 'CH' for Switzerland, 'SG' for Singapore), or null if detection fails
 */
export async function getCountryFromIp(request: NextRequest): Promise<string | null> {
  try {
    const ip = getClientIp(request)
    
    if (!ip) {
      console.warn('Could not determine client IP')
      return null
    }

    // Skip localhost/private IPs
    if (ip === '127.0.0.1' || ip === '::1' || ip.startsWith('192.168.') || ip.startsWith('10.') || ip.startsWith('172.')) {
      // For local development, default to Switzerland
      return 'CH'
    }

    // Use ip-api.com free service (no API key required, rate limited)
    // Returns JSON with country code
    const response = await fetch(`http://ip-api.com/json/${ip}?fields=countryCode`, {
      method: 'GET',
      headers: {
        'Accept': 'application/json',
      },
    })

    if (!response.ok) {
      console.warn(`Failed to fetch geolocation: ${response.status}`)
      return null
    }

    const data = await response.json()
    
    if (data.countryCode) {
      return data.countryCode
    }

    return null
  } catch (error) {
    console.error('Error detecting country from IP:', error)
    return null
  }
}

/**
 * Calculate shipping fee based on country
 * Returns shipping fee in the appropriate currency
 * 15 CHF for countries in CHF_COUNTRIES, 40 EUR for all other countries
 */
export function calculateShippingFee(countryCode: string | null): number {
  // 15 CHF for countries in CHF_COUNTRIES, 40 EUR for all other countries
  if (countryCode && CHF_COUNTRIES.includes(countryCode as any)) {
    return 15
  }
  return 40
}