export const ATTACHMENT_MAX_BYTES = 10 * 1024 * 1024;
export const ATTACHMENT_MAX_COUNT = 4;
/** Base64 expands payload by 4/3; cap before decode to reject oversize uploads cheaply. */
export const ATTACHMENT_MAX_BASE64_LENGTH = Math.ceil(ATTACHMENT_MAX_BYTES / 3) * 4;

export const ATTACHMENT_IMAGE_MIME_TYPES = [
  "image/jpeg",
  "image/png",
  "image/webp",
  "image/gif",
] as const;

export const ATTACHMENT_FILE_MIME_TYPES = [
  "application/pdf",
  "text/plain",
  "text/markdown",
  "text/csv",
  "application/json",
] as const;

export const ATTACHMENT_ALLOWED_MIME_TYPES = [
  ...ATTACHMENT_IMAGE_MIME_TYPES,
  ...ATTACHMENT_FILE_MIME_TYPES,
] as const;

export type AttachmentMimeType = (typeof ATTACHMENT_ALLOWED_MIME_TYPES)[number];

export function isAttachmentImageMimeType(mimeType: string): boolean {
  return (ATTACHMENT_IMAGE_MIME_TYPES as readonly string[]).includes(mimeType);
}

export function isAllowedAttachmentMimeType(mimeType: string): mimeType is AttachmentMimeType {
  return (ATTACHMENT_ALLOWED_MIME_TYPES as readonly string[]).includes(mimeType);
}

export function validateThreadsSendInput(input: {
  text?: string;
  artifactIds?: string[];
}): boolean {
  const text = input.text?.trim() ?? "";
  const artifactIds = input.artifactIds ?? [];
  return Boolean(text || artifactIds.length);
}