import type { Email } from "@/lib/jmap/types";
import { buildForwardSubject } from "@/lib/subject-prefix";
import { emailExportFilename } from "@/lib/download-filename";

export interface ForwardAsAttachmentEntry {
  blobId: string;
  name: string;
  type: "message/rfc822";
  size: number;
}

export interface ForwardAsAttachmentPayload {
  subject: string;
  attachment: ForwardAsAttachmentEntry;
}

/**
 * Build the subject and synthetic attachment entry for forwarding a
 * message as a message/rfc822 attachment instead of inline-quoted text
 * (e.g. reporting spam to an upstream gateway that expects the raw
 * original as an attachment, or preserving exact formatting/headers).
 *
 * Referenced by blobId, not re-uploaded - JMAP blobs are account-scoped,
 * not per-email, so the same blobId a message already has can be attached
 * to a brand new outgoing email directly.
 *
 * Returns null when the email has no blobId (nothing to reference).
 */
export function buildForwardAsAttachmentPayload(
  email: Email,
  forwardPrefix: string,
): ForwardAsAttachmentPayload | null {
  if (!email.blobId) return null;

  return {
    subject: buildForwardSubject(email.subject, forwardPrefix),
    attachment: {
      blobId: email.blobId,
      name: emailExportFilename(email),
      type: "message/rfc822",
      size: email.size,
    },
  };
}