nostr-mailing-list/handleUidFetch.ts

import type { Socket } from "node:net";
import type { ImapCommandParameters } from "./imapParsing.ts";
import { fetchAllEventsMatchingQuery, type ImapSession } from "./imapServer.ts";
import * as nip19 from "@nostr/tools/nip19";
import type { Event } from "@nostr/tools";
import {
  findUidForEvent,
  getByteLength,
  getFlags,
  parseBasicNostrMarkdown,
  parseUid,
  sendSocketMessage,
} from "./utils.ts";

const eventCache: {
  mailingList: string;
  timestamp: number;
  events: Event[];
} = {
  mailingList: "",
  timestamp: 0,
  events: [],
};

const CACHE_EXPIRY = 5 * 60 * 1000;

function buildHeaders(
  event: Event,
  session: ImapSession,
  headersRequested: string[],
): string {
  if (!session.selectedMailingList) {
    throw new Error("No mailing list selected");
  }

  let headersResponse = "\r\n";
  const subjectTag = event.tags.find((tag) =>
    tag[0].toLowerCase() === "subject"
  );

  headersResponse += `From: ${nip19.npubEncode(event.pubkey)}@nostr\r\n`;

  headersResponse += `To: ${
    nip19.npubEncode(session.selectedMailingList)
  }@nostr\r\n`;

  headersResponse += `Reply-To: ${nip19.noteEncode(event.id)}@nostr\r\n`;

  if (headersRequested.includes("SUBJECT")) {
    headersResponse += `Subject: ${
      subjectTag ? subjectTag[1] : "No subject"
    }\r\n`;
  }

  if (headersRequested.includes("DATE")) {
    headersResponse += `Date: ${
      new Date(event.created_at * 1000).toUTCString()
    }\r\n`;
  }

  const threadId = event.tags.find((tag) => tag[0] === "E");
  const messageThread = [];
  if (threadId) {
    messageThread.push(threadId[1]);
  }
  headersResponse += `Message-ID: <${event.id}@nostr>\r\n`;

  const eTags = event.tags.filter((tag) => tag[0] === "e");
  if (eTags.length > 0) {
    for (const eTag of eTags) {
      messageThread.push(eTag[1]);
    }
  }

  if (messageThread.length > 0) {
    headersResponse += `References: ${
      messageThread.map((id) => `<${id}@nostr>`).join(" ")
    }\r\n`;
    headersResponse += `In-Reply-To: <${
      messageThread[messageThread.length - 1]
    }@nostr>\r\n`;
    headersResponse += `Thread-Index: ${messageThread.join("")}@nostr\r\n`;
    headersResponse += `X-Thread-Depth: ${messageThread.length}\r\n`;
  }

  headersResponse += "Content-Type: text/html; charset=utf-8\r\n";

  headersResponse += "\r\n";
  return headersResponse;
}

function buildFullMessageBody(event: Event, session: ImapSession): string {
  if (!session.selectedMailingList) {
    throw new Error("No mailing list selected");
  }

  const subjectTag = event.tags.find((tag) =>
    tag[0].toLowerCase() === "subject"
  );
  const subject = subjectTag ? subjectTag[1] : "No subject";
  const threadTag = event.tags.find((tag) => tag[0] === "E");
  const threadId = threadTag ? threadTag[1] : event.id;

  const contentParts = [
    `From: ${nip19.npubEncode(event.pubkey)}@nostr`,
    `To: ${nip19.npubEncode(session.selectedMailingList)}@nostr`,
    `Reply-To: ${nip19.noteEncode(event.id)}@nostr`,
    `Subject: ${subject}`,
    `Date: ${new Date(event.created_at * 1000).toUTCString()}`,
    `Message-ID: <${event.id}@nostr>`,
    "Content-Type: text/html; charset=utf-8",
  ];

  const messageThread = [];

  if (threadId !== event.id) {
    messageThread.push(threadId);
  }

  const eTags = event.tags.filter((tag) => tag[0] === "e");
  if (eTags.length > 0) {
    for (const eTag of eTags) {
      messageThread.push(eTag[1]);
    }
  }

  if (messageThread.length > 0) {
    contentParts.push(
      `References: ${messageThread.map((id) => `<${id}@nostr>`).join(" ")}`,
    );
    contentParts.push(
      `In-Reply-To: <${messageThread[messageThread.length - 1]}@nostr>`,
    );
    contentParts.push(
      `Thread-Index: ${messageThread.join("")}@nostr`,
    );
    contentParts.push(
      `X-Thread-Depth: ${messageThread.length}`,
    );
  }

  contentParts.push(
    "",
    `${event.content}`,
  );

  return contentParts.join("\r\n");
}

async function handleDataItem(
  item: string | Record<string, unknown>,
  event: Event,
  session: ImapSession,
  dataPieces: string[],
) {
  if (item === "UID") return;

  if (item === "FLAGS") {
    const flags = await getFlags(session, event.id);
    dataPieces.push(`FLAGS (${flags.join(" ")})`);
    return;
  }

  if (item === "RFC822.SIZE") {
    dataPieces.push(`RFC822.SIZE ${JSON.stringify(event).length}`);
    return;
  }

  if (typeof item === "object" && item["BODY.PEEK[HEADER.FIELDS]"]) {
    const headersRequested = (item["BODY.PEEK[HEADER.FIELDS]"] as string[]).map(
      (x: string) => x.toUpperCase(),
    );
    const headersResponse = buildHeaders(event, session, headersRequested);
    dataPieces.push(
      `BODY[HEADER.FIELDS (${
        (item["BODY.PEEK[HEADER.FIELDS]"] as string[]).join(" ")
      })] {${headersResponse.length}}${headersResponse}`,
    );
    return;
  }

  if (
    typeof item === "string" &&
    item.startsWith("BODY")
  ) {
    const contentText = buildFullMessageBody(event, session);
    const contentHtml = parseBasicNostrMarkdown(contentText);
    const bodyMessage = `BODY[] {${
      getByteLength(contentHtml)
    }}\r\n${contentHtml}`;
    dataPieces.push(bodyMessage);
    return;
  }

  if (item === "BODY.PEEK[HEADER]" || item === "BODY[HEADER]") {
    const allHeadersResponse = buildHeaders(
      event,
      session,
      [
        "FROM",
        "TO",
        "SUBJECT",
        "DATE",
        "CONTENT-TYPE",
        "MESSAGE-ID",
        "THREAD-ID",
      ],
    );
    dataPieces.push(
      `BODY[HEADER] {${allHeadersResponse.length}}${allHeadersResponse}`,
    );
    return;
  }

  if (item === "BODY.PEEK[TEXT]" || item === "BODY[TEXT]") {
    dataPieces.push(`BODY[TEXT] {${event.content.length}}\r\n${event.content}`);
    return;
  }

  if (item === "ENVELOPE") {
    const subjectTag = event.tags.find((tag) =>
      tag[0].toLowerCase() === "subject"
    );
    const subject = subjectTag ? subjectTag[1] : "No subject";
    const date = new Date(event.created_at * 1000).toUTCString();

    let envelopeStr = `ENVELOPE ("${date}" "${subject}" (("" NIL "${
      nip19.npubEncode(event.pubkey)
    }" "nostr")) (("" NIL "${
      nip19.npubEncode(event.pubkey)
    }" "nostr")) (("" NIL "${nip19.npubEncode(event.pubkey)}" "nostr"))`;

    if (session.selectedMailingList) {
      envelopeStr += ` ((NIL NIL "${
        nip19.npubEncode(session.selectedMailingList)
      }" "nostr"))`;
    } else {
      envelopeStr += ` ((NIL NIL "unknown" "nostr"))`;
    }

    envelopeStr += ` NIL NIL NIL "<${event.id}@nostr>")`;
    dataPieces.push(envelopeStr);
    return;
  }

  console.log("Unknown item", item);
}

export async function handleUidFetch(
  session: ImapSession,
  socket: Socket,
  tag: string,
  uid: ImapCommandParameters,
  data_items: ImapCommandParameters,
): Promise<void> {
  try {
    if (!session.selectedMailingList) {
      sendSocketMessage(socket, `${tag} NO No mailbox selected\r\n`);
      return;
    }

    let allThreads: Event[];
    const now = Date.now();

    if (
      eventCache.mailingList === session.selectedMailingList &&
      now - eventCache.timestamp < CACHE_EXPIRY
    ) {
      allThreads = eventCache.events;
    } else {
      allThreads = await fetchAllEventsMatchingQuery([
        {
          kinds: [11, 1111],
          "#P": [session.selectedMailingList],
        },
      ]);

      eventCache.mailingList = session.selectedMailingList;
      eventCache.timestamp = now;
      eventCache.events = allThreads;
    }

    let start = 0;
    let end = 0;
    try {
      const range = parseUid(uid);
      start = range[0];
      end = range[1];
    } catch (error) {
      if (error instanceof Error) {
        sendSocketMessage(
          socket,
          `${tag} BAD Invalid UID range: ${error.message}\r\n`,
        );
      } else {
        sendSocketMessage(socket, `${tag} BAD Invalid UID range\r\n`);
      }
      return;
    }

    let counter = 1;
    const filteredEvents = allThreads.filter((event) => {
      const eventUid = findUidForEvent(event);
      return eventUid >= start && eventUid <= end;
    });

    filteredEvents.sort((a, b) => findUidForEvent(a) - findUidForEvent(b));

    for (const event of filteredEvents) {
      const eventUid = findUidForEvent(event);
      let message = `* ${counter++} FETCH (`;
      const dataPieces: string[] = [`UID ${eventUid}`];

      if (Array.isArray(data_items)) {
        for (const item of data_items) {
          await handleDataItem(item, event, session, dataPieces);
        }
      } else {
        await handleDataItem(data_items, event, session, dataPieces);
      }

      message += `${dataPieces.join(" ")})\r\n`;
      sendSocketMessage(socket, message);
    }

    sendSocketMessage(socket, `${tag} OK UID FETCH completed\r\n`);
  } catch (error) {
    console.error("Error in UID FETCH handler:", error);
    const errorMessage = error instanceof Error
      ? error.message
      : "Unknown error";
    sendSocketMessage(
      socket,
      `${tag} NO Error processing FETCH: ${errorMessage}\r\n`,
    );
  }
}