/**
 * Parts lookup utility for frontend
 *
 * Provides functions to fetch parts data by manual filename.
 * Static JSON remains the primary data source, while live eBay fallback
 * goes through the server route so credentials never reach the browser.
 */

export interface PartForPage {
  partNumber: string
  description: string
  ebayListings: Array<{
    itemId: string
    title: string
    price: string
    currency: string
    imageUrl?: string
    viewItemUrl: string
    condition?: string
    shippingCost?: string
    affiliateLink: string
  }>
}

interface ManualPartsLookup {
  [manualFilename: string]: PartForPage[]
}

interface ManualPagesParts {
  [manualFilename: string]: {
    [pageNumber: string]: PartForPage[]
  }
}

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

interface EbaySearchResponse {
  results: EbaySearchResult[]
  error?: string
}

// Cache for eBay search results
const ebaySearchCache = new Map<string, { results: EbaySearchResult[]; timestamp: number }>()
const inFlightEbaySearches = new Map<string, Promise<EbaySearchResponse>>()
const EBAY_CACHE_TTL = 15 * 60 * 1000 // 15 minutes

const GENERIC_PART_TERMS = new Set([
  'and',
  'the',
  'for',
  'with',
  'from',
  'page',
  'part',
  'parts',
  'number',
  'numbers',
  'read',
  'across',
  'refer',
  'reference',
  'shown',
  'figure',
  'fig',
  'rev',
  'revision',
  'item',
  'items',
  'assembly',
  'assy',
])

let manualPartsCache: ManualPartsLookup | null = null
let manualPagesPartsCache: ManualPagesParts | null = null

/**
 * Load parts lookup data
 */
async function loadPartsData(): Promise<{
  manualParts: ManualPartsLookup
  manualPagesParts: ManualPagesParts
}> {
  if (manualPartsCache && manualPagesPartsCache) {
    return {
      manualParts: manualPartsCache,
      manualPagesParts: manualPagesPartsCache,
    }
  }
  
  try {
    // Try to load from public data directory (relative to public folder)
    const [manualPartsResponse, manualPagesResponse] = await Promise.all([
      fetch('/manual_parts_lookup.json'),
      fetch('/manual_pages_parts.json'),
    ])
    
    if (manualPartsResponse.ok && manualPagesResponse.ok) {
      const [manualParts, manualPagesParts] = await Promise.all([
        manualPartsResponse.json(),
        manualPagesResponse.json(),
      ])
      
      manualPartsCache = manualParts
      manualPagesPartsCache = manualPagesParts
      
      return { manualParts, manualPagesParts }
    }
  } catch (error) {
    console.warn('Could not load parts data:', error)
  }
  
  // Return empty data if loading fails
  return {
    manualParts: {},
    manualPagesParts: {},
  }
}

/**
 * Search eBay for parts with caching.
 * This calls the server route so the app never needs direct eBay credentials
 * in client code.
 */
async function searchEBayForParts(
  partNumber: string,
  description?: string,
  manufacturer?: string,
): Promise<EbaySearchResponse> {
  const cacheKey = `parts:${partNumber}:${description || ''}:${manufacturer || ''}`
  
  // Check cache
  const cached = ebaySearchCache.get(cacheKey)
  if (cached && Date.now() - cached.timestamp < EBAY_CACHE_TTL) {
    return { results: cached.results as EbaySearchResult[] }
  }

  const buildQuery = () => {
    let query = partNumber

    if (description && description.length > 0 && description.length < 50) {
      const descWords = description
        .split(/\s+/)
        .filter((word) => word.length > 3)
        .slice(0, 3)
        .join(' ')

      if (descWords) {
        query += ` ${descWords}`
      }
    }

    if (manufacturer) {
      query += ` ${manufacturer}`
    }

    return `${query} vending machine`
  }

  const searchViaApi = async (categoryId?: string): Promise<EbaySearchResponse> => {
    const requestKey = `${cacheKey}:${categoryId || 'general'}`

    const inFlight = inFlightEbaySearches.get(requestKey)
    if (inFlight) {
      return inFlight
    }

    const params = new URLSearchParams({
      keywords: buildQuery(),
      maxResults: '3',
      sortOrder: 'BestMatch',
    })

    if (categoryId) {
      params.set('categoryId', categoryId)
    }

    const request = (async () => {
      try {
        const response = await fetch(`/api/ebay/search?${params.toString()}`)
        const body = await response.json().catch(() => null)

        if (!response.ok) {
          const message =
            body && typeof body.error === 'string'
              ? body.error
              : `eBay API error: ${response.status}`

          return { results: [], error: message }
        }

        const results = Array.isArray(body) ? body : []
        return { results }
      } catch (error) {
        return {
          results: [],
          error: error instanceof Error ? error.message : 'Failed to search eBay',
        }
      }
    })()

    inFlightEbaySearches.set(requestKey, request)

    try {
      return await request
    } finally {
      inFlightEbaySearches.delete(requestKey)
    }
  }

  const categorySearch = await searchViaApi('11700')
  if (categorySearch.results.length > 0) {
    ebaySearchCache.set(cacheKey, {
      results: categorySearch.results,
      timestamp: Date.now(),
    })
    return categorySearch
  }

  const generalSearch = await searchViaApi()
  if (generalSearch.results.length > 0) {
    ebaySearchCache.set(cacheKey, {
      results: generalSearch.results,
      timestamp: Date.now(),
    })
    return generalSearch
  }

  return {
    results: [],
    error: categorySearch.error || generalSearch.error,
  }
}

function normalizePartText(value: string): string {
  return value.trim().toLowerCase()
}

function isSyntheticEbayListing(listing: PartForPage['ebayListings'][number]): boolean {
  const itemId = listing.itemId?.trim() || ''
  const viewItemUrl = listing.viewItemUrl?.trim() || ''
  const imageUrl = listing.imageUrl?.trim() || ''

  return (
    imageUrl.includes('images.unsplash.com') ||
    viewItemUrl.includes('123456789') ||
    itemId.startsWith('123456789')
  )
}

function hasLiveEbayListings(listings: PartForPage['ebayListings']): boolean {
  return listings.some((listing) => !isSyntheticEbayListing(listing))
}

function scorePartForLiveSearch(part: PartForPage, index: number): number {
  const partNumber = part.partNumber.trim()
  const description = part.description.trim()
  const lowerPartNumber = normalizePartText(partNumber)
  const lowerDescription = normalizePartText(description)

  if (!partNumber) {
    return -1000
  }

  if (GENERIC_PART_TERMS.has(lowerPartNumber)) {
    return -500
  }

  let score = 0

  // Prefer actual part numbers, model numbers, and revision codes over prose.
  if (/\d/.test(partNumber)) {
    score += 30
  }
  if (/[a-z]/i.test(partNumber) && /\d/.test(partNumber)) {
    score += 20
  }
  if (/^[a-z0-9][a-z0-9\-._/ ]{2,24}$/i.test(partNumber)) {
    score += 10
  }
  if (partNumber.length >= 4 && partNumber.length <= 20) {
    score += 8
  }

  if (description && description.length <= 80) {
    score += 6
  }

  if (description && !GENERIC_PART_TERMS.has(lowerDescription)) {
    score += 4
  }

  if (lowerPartNumber.includes('rev') || lowerPartNumber.includes('figure')) {
    score -= 10
  }

  // Prefer earlier entries when scores are similar.
  score -= index * 0.01

  return score
}

function selectPartsForLiveSearch(parts: PartForPage[], limit: number): PartForPage[] {
  return parts
    .map((part, index) => ({
      part,
      score: scorePartForLiveSearch(part, index),
    }))
    .sort((a, b) => b.score - a.score)
    .slice(0, limit)
    .map(({ part }) => part)
}

async function enhancePartsData(parts: PartForPage[]): Promise<{
  parts: PartForPage[]
  error?: string
}> {
  let firstError: string | undefined

  const enhancedParts: PartForPage[] = []

  for (const part of parts) {
    const shouldRefreshListings =
      part.ebayListings.length === 0 || !hasLiveEbayListings(part.ebayListings)

    if (shouldRefreshListings) {
      const ebayResults = await searchEBayForParts(part.partNumber, part.description)

      if (ebayResults.error && !firstError) {
        firstError = ebayResults.error
      }

      enhancedParts.push({
        ...part,
        ebayListings: ebayResults.results.map((result) => ({
          itemId: result.itemId,
          title: result.title,
          price: result.price,
          currency: result.currency,
          imageUrl: result.imageUrl,
          viewItemUrl: result.viewItemUrl,
          condition: result.condition,
          shippingCost: result.shippingCost,
          affiliateLink: result.affiliateLink,
        })),
      })
      continue
    }

    enhancedParts.push(part)
  }

  return {
    parts: enhancedParts,
    error: firstError,
  }
}

function findManualParts(
  manualFilename: string,
  manualParts: ManualPartsLookup,
): PartForPage[] {
  if (manualParts[manualFilename]) {
    return manualParts[manualFilename]
  }

  const lowerFilename = manualFilename.toLowerCase()
  for (const [filename, parts] of Object.entries(manualParts)) {
    if (filename.toLowerCase() === lowerFilename) {
      return parts
    }
  }

  const filenameWithoutExt = manualFilename.replace(/\.pdf$/i, '')
  const lowerWithoutExt = filenameWithoutExt.toLowerCase()

  for (const [filename, parts] of Object.entries(manualParts)) {
    const otherWithoutExt = filename.replace(/\.pdf$/i, '').toLowerCase()
    if (
      otherWithoutExt === lowerWithoutExt ||
      otherWithoutExt.includes(lowerWithoutExt) ||
      lowerWithoutExt.includes(otherWithoutExt)
    ) {
      return parts
    }
  }

  return []
}

function findManualPagesParts(
  manualFilename: string,
  pageNumber: number,
  manualPagesParts: ManualPagesParts,
): PartForPage[] {
  if (
    manualPagesParts[manualFilename] &&
    manualPagesParts[manualFilename][pageNumber.toString()]
  ) {
    return manualPagesParts[manualFilename][pageNumber.toString()]
  }

  const lowerFilename = manualFilename.toLowerCase()
  for (const [filename, pages] of Object.entries(manualPagesParts)) {
    if (filename.toLowerCase() === lowerFilename && pages[pageNumber.toString()]) {
      return pages[pageNumber.toString()]
    }
  }

  const filenameWithoutExt = manualFilename.replace(/\.pdf$/i, '')
  const lowerWithoutExt = filenameWithoutExt.toLowerCase()

  for (const [filename, pages] of Object.entries(manualPagesParts)) {
    const otherWithoutExt = filename.replace(/\.pdf$/i, '').toLowerCase()
    if (
      otherWithoutExt === lowerWithoutExt ||
      otherWithoutExt.includes(lowerWithoutExt) ||
      lowerWithoutExt.includes(otherWithoutExt)
    ) {
      if (pages[pageNumber.toString()]) {
        return pages[pageNumber.toString()]
      }
    }
  }

  return []
}

async function getPartsForManualWithStatus(
  manualFilename: string,
): Promise<{
  parts: PartForPage[]
  error?: string
}> {
  const { manualParts } = await loadPartsData()
  const parts = findManualParts(manualFilename, manualParts)

  return { parts }
}

/**
 * Get all parts for a manual with enhanced eBay data
 */
export async function getPartsForManual(
  manualFilename: string
): Promise<PartForPage[]> {
  const result = await getPartsForManualWithStatus(manualFilename)
  return result.parts
}

/**
 * Get parts for a specific page of a manual with enhanced eBay data
 */
export async function getPartsForPage(
  manualFilename: string,
  pageNumber: number
): Promise<PartForPage[]> {
  const { manualPagesParts } = await loadPartsData()
  const parts = findManualPagesParts(manualFilename, pageNumber, manualPagesParts)

  if (parts.length === 0) {
    return []
  }

  const enhanced = await enhancePartsData(parts)
  return enhanced.parts
}

/**
 * Get top N parts for a manual (most relevant) with enhanced eBay data
 */
export async function getTopPartsForManual(
  manualFilename: string,
  limit: number = 5
): Promise<{
  parts: PartForPage[]
  error?: string
}> {
  const { parts } = await getPartsForManualWithStatus(manualFilename)

  if (parts.length === 0) {
    return { parts: [] }
  }

  const liveSearchCandidates = selectPartsForLiveSearch(parts, Math.max(limit * 2, limit))
  const { parts: enrichedParts, error } = await enhancePartsData(liveSearchCandidates)

  const sorted = enrichedParts.sort((a, b) => {
    const aHasLiveListings = hasLiveEbayListings(a.ebayListings) ? 1 : 0
    const bHasLiveListings = hasLiveEbayListings(b.ebayListings) ? 1 : 0

    if (aHasLiveListings !== bHasLiveListings) {
      return bHasLiveListings - aHasLiveListings
    }

    return b.ebayListings.length - a.ebayListings.length
  })
  
  return {
    parts: sorted.slice(0, limit),
    error,
  }
}

/**
 * Check if a manual has parts available
 */
export async function hasPartsForManual(manualFilename: string): Promise<boolean> {
  const parts = await getPartsForManual(manualFilename)
  return parts.length > 0
}

/**
 * Get a set of all manual filenames that have parts available
 * Useful for filtering
 */
export async function getManualsWithParts(): Promise<Set<string>> {
  const { manualParts } = await loadPartsData()
  const manualsWithParts = new Set<string>()

  for (const [filename, parts] of Object.entries(manualParts)) {
    if (parts.length > 0) {
      manualsWithParts.add(filename)
      // Also add variations for matching
      manualsWithParts.add(filename.toLowerCase())
      manualsWithParts.add(filename.replace(/\.pdf$/i, ''))
      manualsWithParts.add(filename.replace(/\.pdf$/i, '').toLowerCase())
    }
  }

  return manualsWithParts
}

/**
 * Clear cache (useful for development)
 */
export function clearPartsCache(): void {
  manualPartsCache = null
  manualPagesPartsCache = null
}