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);
}