src/lib/buildPrompt.ts

import type { BackendModel } from "./server/models";
import type { Message } from "./types/Message";
import { collections } from "$lib/server/database";
import { ObjectId } from "mongodb";
/**
 * Convert [{user: "assistant", content: "hi"}, {user: "user", content: "hello"}] to:
 *
 * <|assistant|>hi<|endoftext|><|prompter|>hello<|endoftext|><|assistant|>
 */

export async function buildPrompt(
	messages: Pick<Message, "from" | "content">[],
	model: BackendModel,
	webSearchId?: string,
	preprompt?: string
): Promise<string> {
	if (webSearchId) {
		const webSearch = await collections.webSearches.findOne({
			_id: new ObjectId(webSearchId),
		});

		if (!webSearch) throw new Error("Web search not found");

		if (webSearch.summary) {
			messages = [
				{
					from: "assistant",
					content: `The following context was found while searching the internet: ${webSearch.summary}`,
				},
				...messages,
			];
		}
	}

	return (
		model
			.chatPromptRender({ messages, preprompt })
			// Not super precise, but it's truncated in the model's backend anyway
			.split(" ")
			.slice(-(model.parameters?.truncate ?? 0))
			.join(" ")
	);
}