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)
  }
}