function normalizeText(value: unknown): string | null {
  if (typeof value !== 'string') {
    return null
  }
  const trimmed = value.trim()
  return trimmed ? trimmed : null
}

function hashText(value: string): string {
  let hash = 0
  for (let index = 0; index < value.length; index += 1) {
    hash = ((hash << 5) - hash + value.charCodeAt(index)) | 0
  }
  return Math.abs(hash).toString(16).padStart(8, '0')
}

function boundedIdentity(prefix: string, raw: string): string {
  const normalizedPrefix = prefix.trim().replace(/:+$/, '')
  const normalizedRaw = raw.trim()
  if (!normalizedRaw) {
    return `${normalizedPrefix}:${hashText(prefix)}`
  }

  const candidate = `${normalizedPrefix}:${normalizedRaw}`
  if (candidate.length <= 120) {
    return candidate
  }

  return `${normalizedPrefix}:${hashText(normalizedRaw)}`
}

function normalizeURLPath(pathname: string): string {
  const normalized = pathname.replace(/\/+$/, '')
  return normalized === '/' ? '' : normalized
}

function safeParseURL(input: string): URL | null {
  try {
    return new URL(input)
  } catch {
    return null
  }
}

function genericAIConversationPath(pathname: string): boolean {
  return /^\/(?:chat|c|conversation)(?:\/|$)/i.test(pathname)
}

export interface GenericAIPageState {
  displayName: string | null
  avatarUrl: string | null
  fingerprint: string | null
  credentialFingerprint: string | null
  currentPath: string | null
  strongAuthSignalCount: number
  loginSignalCount: number
  loggedOutSignalCount: number
  challengeSignalCount: number
}

export function genericAIPageLooksAuthenticated(
  currentURL: string,
  pageState: GenericAIPageState | null,
): boolean {
  const current = safeParseURL(currentURL)
  const currentPath = normalizeURLPath(current?.pathname ?? pageState?.currentPath ?? '')
  const strongAuthSignalCount = pageState?.strongAuthSignalCount ?? 0
  const loginSignalCount = pageState?.loginSignalCount ?? 0
  const loggedOutSignalCount = pageState?.loggedOutSignalCount ?? 0
  const challengeSignalCount = pageState?.challengeSignalCount ?? 0
  const hasCredentialFingerprint = Boolean(normalizeText(pageState?.credentialFingerprint))
  const onConversationPath = genericAIConversationPath(currentPath)

  if (challengeSignalCount > 0) {
    return false
  }

  if (loggedOutSignalCount > 0) {
    return false
  }

  if (
    loginSignalCount > 0 &&
    strongAuthSignalCount === 0 &&
    !onConversationPath &&
    !hasCredentialFingerprint
  ) {
    return false
  }

  if (loginSignalCount > 0) {
    return (strongAuthSignalCount >= 2 || hasCredentialFingerprint) && !onConversationPath
  }

  return strongAuthSignalCount > 0 || onConversationPath || hasCredentialFingerprint
}

export function buildGenericAIPageFingerprintFallback(
  platformId: string,
  pageState?: GenericAIPageState | null,
): string | null {
  const credentialFingerprint = normalizeText(pageState?.credentialFingerprint)
  if (credentialFingerprint) {
    return boundedIdentity(`${platformId}-session`, credentialFingerprint)
  }

  const fallbackFingerprint = normalizeText(pageState?.fingerprint)
  if (!fallbackFingerprint) {
    return null
  }

  const strongAuthSignalCount = pageState?.strongAuthSignalCount ?? 0
  if (strongAuthSignalCount <= 0) {
    return null
  }

  return boundedIdentity(`${platformId}-page`, fallbackFingerprint)
}