import { buildPrompt } from "$lib/buildPrompt";
import { authCondition } from "$lib/server/auth";
import { collections } from "$lib/server/database";
import { models } from "$lib/server/models";
import { buildSubtree } from "$lib/utils/tree/buildSubtree";
import { isMessageId } from "$lib/utils/tree/isMessageId";
import { error } from "@sveltejs/kit";
import { ObjectId } from "mongodb";

export async function GET({ params, locals }) {
	const conv =
		params.id.length === 7
			? await collections.sharedConversations.findOne({
					_id: params.id,
				})
			: await collections.conversations.findOne({
					_id: new ObjectId(params.id),
					...authCondition(locals),
				});

	if (conv === null) {
		error(404, "Conversation not found");
	}

	const messageId = params.messageId;

	const messageIndex = conv.messages.findIndex((msg) => msg.id === messageId);

	if (!isMessageId(messageId) || messageIndex === -1) {
		error(404, "Message not found");
	}

	const model = models.find((m) => m.id === conv.model);

	if (!model) {
		error(404, "Conversation model not found");
	}

	const messagesUpTo = buildSubtree(conv, messageId);

	const prompt = await buildPrompt({
		preprompt: conv.preprompt,
		messages: messagesUpTo,
		model,
	});

	const userMessage = conv.messages[messageIndex];
	const assistantMessage = conv.messages[messageIndex + 1];

	return new Response(
		JSON.stringify(
			{
				note: "This is a preview of the prompt that will be sent to the model when retrying the message. It may differ from what was sent in the past if the parameters have been updated since",
				prompt,
				model: model.name,
				parameters: {
					...model.parameters,
					return_full_text: false,
				},
				userMessage,
				...(assistantMessage ? { assistantMessage } : {}),
			},
			null,
			2
		),
		{ headers: { "Content-Type": "application/json" } }
	);
}
