import { NextRequest, NextResponse } from 'next/server'

/**
 * eBay API Proxy Route
 * Proxies requests to eBay Finding API to avoid CORS issues
 */

interface eBaySearchParams {
  keywords: string
  categoryId?: string
  sortOrder?: string
  maxResults?: number
}

interface eBaySearchResult {
  itemId: string
  title: string
  price: string
  currency: string
  imageUrl?: string
  viewItemUrl: string
  condition?: string
  shippingCost?: string
  affiliateLink: string
}

type MaybeArray<T> = T | T[]

const SEARCH_CACHE_TTL = 15 * 60 * 1000 // 15 minutes
const searchResponseCache = new Map<string, { results: eBaySearchResult[]; timestamp: number }>()
const inFlightSearchResponses = new Map<string, Promise<eBaySearchResult[]>>()

// Affiliate campaign ID for generating links
const AFFILIATE_CAMPAIGN_ID = process.env.EBAY_AFFILIATE_CAMPAIGN_ID?.trim() || ''

// Generate eBay affiliate link
function generateAffiliateLink(viewItemUrl: string): string {
  if (!AFFILIATE_CAMPAIGN_ID) {
    return viewItemUrl
  }

  try {
    const url = new URL(viewItemUrl)
    url.searchParams.set('mkcid', '1')
    url.searchParams.set('mkrid', '711-53200-19255-0')
    url.searchParams.set('siteid', '0')
    url.searchParams.set('campid', AFFILIATE_CAMPAIGN_ID)
    url.searchParams.set('toolid', '10001')
    url.searchParams.set('mkevt', '1')
    return url.toString()
  } catch {
    return viewItemUrl
  }
}

function first<T>(value: MaybeArray<T> | undefined): T | undefined {
  if (!value) {
    return undefined
  }

  return Array.isArray(value) ? value[0] : value
}

function normalizeItem(item: any): eBaySearchResult {
  const currentPrice = first(item.sellingStatus?.currentPrice)
  const shippingCost = first(item.shippingInfo?.shippingServiceCost)
  const condition = first(item.condition)
  const viewItemUrl = item.viewItemURL || item.viewItemUrl || ''

  return {
    itemId: item.itemId || '',
    title: item.title || 'Unknown Item',
    price: `${currentPrice?.value || '0'} ${currentPrice?.currencyId || 'USD'}`,
    currency: currentPrice?.currencyId || 'USD',
    imageUrl: first(item.galleryURL) || undefined,
    viewItemUrl,
    condition: condition?.conditionDisplayName || undefined,
    shippingCost: shippingCost?.value
      ? `${shippingCost.value} ${shippingCost.currencyId || currentPrice?.currencyId || 'USD'}`
      : undefined,
    affiliateLink: generateAffiliateLink(viewItemUrl),
  }
}

async function readEbayErrorMessage(response: Response) {
  const text = await response.text().catch(() => '')
  if (!text.trim()) {
    return `eBay API error: ${response.status}`
  }

  try {
    const parsed = JSON.parse(text) as any
    const messages = parsed?.errorMessage?.[0]?.error?.[0]
    const message = Array.isArray(messages?.message) ? messages.message[0] : messages?.message

    if (typeof message === 'string' && message.trim()) {
      const errorId = Array.isArray(messages?.errorId) ? messages.errorId[0] : messages?.errorId
      return errorId ? `eBay API error ${errorId}: ${message}` : `eBay API error: ${message}`
    }
  } catch {
    // Fall through to returning the raw text below.
  }

  return text.trim() || `eBay API error: ${response.status}`
}

function buildCacheKey(
  keywords: string,
  categoryId: string | undefined,
  sortOrder: string,
  maxResults: number,
): string {
  return [
    keywords.trim().toLowerCase(),
    categoryId || '',
    sortOrder || 'BestMatch',
    String(maxResults),
  ].join('|')
}

function getCachedSearchResults(cacheKey: string): eBaySearchResult[] | null {
  const cached = searchResponseCache.get(cacheKey)

  if (!cached) {
    return null
  }

  if (Date.now() - cached.timestamp > SEARCH_CACHE_TTL) {
    searchResponseCache.delete(cacheKey)
    return null
  }

  return cached.results
}

function setCachedSearchResults(cacheKey: string, results: eBaySearchResult[]) {
  searchResponseCache.set(cacheKey, {
    results,
    timestamp: Date.now(),
  })
}

export async function GET(request: NextRequest) {
  const { searchParams } = new URL(request.url)

  const keywords = searchParams.get('keywords')
  const categoryId = searchParams.get('categoryId') || undefined
  const sortOrder = searchParams.get('sortOrder') || 'BestMatch'
  const maxResults = parseInt(searchParams.get('maxResults') || '6', 10)
  const cacheKey = buildCacheKey(keywords || '', categoryId, sortOrder, maxResults)

  if (!keywords) {
    return NextResponse.json({ error: 'Keywords parameter is required' }, { status: 400 })
  }

  const appId = process.env.EBAY_APP_ID?.trim()

  if (!appId) {
    console.error('EBAY_APP_ID not configured')
    return NextResponse.json(
      { error: 'eBay API not configured. Please set EBAY_APP_ID environment variable.' },
      { status: 503 }
    )
  }

  const cachedResults = getCachedSearchResults(cacheKey)
  if (cachedResults) {
    return NextResponse.json(cachedResults)
  }

  const inFlight = inFlightSearchResponses.get(cacheKey)
  if (inFlight) {
    try {
      const results = await inFlight
      return NextResponse.json(results)
    } catch (error) {
      return NextResponse.json(
        { error: error instanceof Error ? error.message : 'Failed to fetch products from eBay' },
        { status: 500 }
      )
    }
  }

  // Build eBay Finding API URL
  const baseUrl = 'https://svcs.ebay.com/services/search/FindingService/v1'
  const url = new URL(baseUrl)

  url.searchParams.set('OPERATION-NAME', 'findItemsAdvanced')
  url.searchParams.set('SERVICE-VERSION', '1.0.0')
  url.searchParams.set('SECURITY-APPNAME', appId)
  url.searchParams.set('RESPONSE-DATA-FORMAT', 'JSON')
  url.searchParams.set('REST-PAYLOAD', 'true')
  url.searchParams.set('keywords', keywords)
  url.searchParams.set('sortOrder', sortOrder)
  url.searchParams.set('paginationInput.entriesPerPage', maxResults.toString())

  if (categoryId) {
    url.searchParams.set('categoryId', categoryId)
  }

  try {
    const request = (async () => {
      const response = await fetch(url.toString(), {
        method: 'GET',
        headers: {
          'Accept': 'application/json',
        },
      })

      if (!response.ok) {
        const errorMessage = await readEbayErrorMessage(response)
        throw new Error(errorMessage)
      }

      const data = await response.json()

      // Parse eBay API response
      const findItemsAdvancedResponse = data.findItemsAdvancedResponse?.[0]
      if (!findItemsAdvancedResponse) {
        return []
      }

      const searchResult = findItemsAdvancedResponse.searchResult?.[0]
      if (!searchResult || !searchResult.item || searchResult.item.length === 0) {
        return []
      }

      const items = Array.isArray(searchResult.item) ? searchResult.item : [searchResult.item]

      return items.map((item: any) => normalizeItem(item))
    })()

    inFlightSearchResponses.set(cacheKey, request)

    const results = await request
    setCachedSearchResults(cacheKey, results)
    return NextResponse.json(results)

  } catch (error) {
    console.error('Error fetching from eBay API:', error)
    return NextResponse.json(
      { error: error instanceof Error ? error.message : 'Failed to fetch products from eBay' },
      { status: 500 }
    )
  } finally {
    inFlightSearchResponses.delete(cacheKey)
  }
}