src/lib/server/endpoints/preprocessMessages.ts

import type { Message } from "$lib/types/Message";
import { format } from "date-fns";
import type { EndpointMessage } from "./endpoints";
import { downloadFile } from "../files/downloadFile";
import type { ObjectId } from "mongodb";

export async function preprocessMessages(
	messages: Message[],
	webSearch: Message["webSearch"],
	convId: ObjectId
): Promise<EndpointMessage[]> {
	return Promise.resolve(messages)
		.then((msgs) => addWebSearchContext(msgs, webSearch))
		.then((msgs) => downloadFiles(msgs, convId))
		.then((msgs) => injectClipboardFiles(msgs));
}

function addWebSearchContext(messages: Message[], webSearch: Message["webSearch"]) {
	const webSearchContext = webSearch?.contextSources
		.map(({ context }, idx) => `Source [${idx + 1}]\n${context.trim()}`)
		.join("\n\n----------\n\n");

	// No web search context available, skip
	if (!webSearch || !webSearchContext?.trim()) return messages;
	// No messages available, skip
	if (messages.length === 0) return messages;

	const lastQuestion = messages.findLast((el) => el.from === "user")?.content ?? "";
	const previousQuestions = messages
		.filter((el) => el.from === "user")
		.slice(0, -1)
		.map((el) => el.content);
	const currentDate = format(new Date(), "MMMM d, yyyy");

	const finalMessage = {
		...messages[messages.length - 1],
		content: `I searched the web using the query: ${webSearch.searchQuery}.
Today is ${currentDate} and here are the results.
When answering the question, you must reference the sources you used inline by wrapping the index in brackets like this: [1]. If multiple sources are used, you must reference each one of them without commas like this: [1][2][3].
=====================
${webSearchContext}
=====================
${previousQuestions.length > 0 ? `Previous questions: \n- ${previousQuestions.join("\n- ")}` : ""}
Answer the question: ${lastQuestion}`,
	};

	return [...messages.slice(0, -1), finalMessage];
}

async function downloadFiles(messages: Message[], convId: ObjectId): Promise<EndpointMessage[]> {
	return Promise.all(
		messages.map<Promise<EndpointMessage>>((message) =>
			Promise.all((message.files ?? []).map((file) => downloadFile(file.value, convId))).then(
				(files) => ({ ...message, files })
			)
		)
	);
}

async function injectClipboardFiles(messages: EndpointMessage[]) {
	return Promise.all(
		messages.map((message) => {
			const plaintextFiles = message.files
				?.filter((file) => file.mime === "application/vnd.chatui.clipboard")
				.map((file) => Buffer.from(file.value, "base64").toString("utf-8"));

			if (!plaintextFiles || plaintextFiles.length === 0) return message;

			return {
				...message,
				content: `${plaintextFiles.join("\n\n")}\n\n${message.content}`,
				files: message.files?.filter((file) => file.mime !== "application/vnd.chatui.clipboard"),
			};
		})
	);
}