andrewpietiladotcom/lib/MimeHeaderFactory.js

import MimeHeader from "./MimeHeader.js";
import MessageIdMimeHeader from "./MessageIdMimeHeader.js";
import InReplyToMimeHeader from "./InReplyToMimeHeader.js";

function MimeHeaderFactory(key, value) {
    if ( value !== undefined ) {
        return new MimeHeader(`${key}: ${value}`);
    }
    if ( key.toLowerCase().startsWith("message-id:") || key.toLowerCase() === "message-id" ) {
        return new MessageIdMimeHeader(key, value);
    } else if ( key.toLowerCase().startsWith("in-reply-to:") || key.toLowercase() === "in-reply-to" ) {
        return new InReplyToMimeHeader(key, value);
    }
    return new MimeHeader(key, value);
}

export default MimeHeaderFactory;