/** Optional generation is separate from local search and never starts itself. */
export interface AiConfiguration {
  enabled: boolean;
  base_url: string;
  model: string;
  api_key: string | null;
}
const bytes = (text: string) => new TextEncoder().encode(text).length;
export function aiConfigurationProblem(config: AiConfiguration): string | null {
  if (!config.enabled) return "Optional AI is disabled.";
  let endpoint: URL;
  try {
    endpoint = new URL(config.base_url);
  } catch {
    return "Enter your OpenAI-compatible endpoint URL.";
  }
  if (
    !["http:", "https:"].includes(endpoint.protocol) ||
    endpoint.username ||
    endpoint.password ||
    endpoint.search ||
    endpoint.hash ||
    bytes(config.base_url) > 2048
  )
    return "Use an HTTP(S) endpoint without URL credentials, query or fragment.";
  if (
    !config.model.trim() ||
    bytes(config.model) > 200 ||
    /[\u0000-\u001f\u007f]/u.test(config.model)
  )
    return "Enter a model name (up to 200 bytes).";
  if (
    config.api_key &&
    (bytes(config.api_key) > 2048 ||
      /[\u0000-\u001f\u007f]/u.test(config.api_key))
  )
    return "The session API key is invalid or too long.";
  return null;
}
export function aiQuestionProblem(question: string): string | null {
  return !question.trim()
    ? "Enter a question about this passage."
    : bytes(question) > 2048
      ? "The question exceeds 2048 bytes."
      : null;
}
export function aiEndpointLabel(baseURL: string) {
  try {
    return new URL(baseURL).origin;
  } catch {
    return "your configured endpoint";
  }
}
export function aiSourceEligible(
  source?: { kind: string; number: number },
  media = false,
) {
  return (
    !media &&
    Boolean(
      source &&
        ["page", "paragraph", "line"].includes(source.kind) &&
        Number.isInteger(source.number) &&
        source.number > 0,
    )
  );
}
export class AiRevision {
  private revision = 0;
  private selection = "";
  invalidate() {
    this.revision++;
  }
  select(selection: string) {
    if (selection !== this.selection) {
      this.selection = selection;
      this.invalidate();
    }
  }
  current() {
    return this.revision;
  }
  accepts(revision: number) {
    return revision === this.revision;
  }
}