src/lib/server/endpoints/openai/endpointOai.ts

import { z } from "zod";
import { openAICompletionToTextGenerationStream } from "./openAICompletionToTextGenerationStream";
import {
	openAIChatToTextGenerationSingle,
	openAIChatToTextGenerationStream,
} from "./openAIChatToTextGenerationStream";
import type { CompletionCreateParamsStreaming } from "openai/resources/completions";
import type {
	ChatCompletionCreateParamsNonStreaming,
	ChatCompletionCreateParamsStreaming,
} from "openai/resources/chat/completions";
import { buildPrompt } from "$lib/buildPrompt";
import { config } from "$lib/server/config";
import type { Endpoint } from "../endpoints";
import type OpenAI from "openai";
import { createImageProcessorOptionsValidator, makeImageProcessor } from "../images";
import type { MessageFile } from "$lib/types/Message";
import type { EndpointMessage } from "../endpoints";
// uuid import removed (no tool call ids)

export const endpointOAIParametersSchema = z.object({
	weight: z.number().int().positive().default(1),
	model: z.any(),
	type: z.literal("openai"),
	baseURL: z.string().url().default("https://api.openai.com/v1"),
	// Canonical auth token is OPENAI_API_KEY; keep HF_TOKEN as legacy alias
	apiKey: z.string().default(config.OPENAI_API_KEY || config.HF_TOKEN || "sk-"),
	completion: z
		.union([z.literal("completions"), z.literal("chat_completions")])
		.default("chat_completions"),
	defaultHeaders: z.record(z.string()).optional(),
	defaultQuery: z.record(z.string()).optional(),
	extraBody: z.record(z.any()).optional(),
	multimodal: z
		.object({
			image: createImageProcessorOptionsValidator({
				supportedMimeTypes: [
					// Restrict to the most widely-supported formats
					"image/png",
					"image/jpeg",
				],
				preferredMimeType: "image/jpeg",
				maxSizeInMB: 3,
				maxWidth: 2048,
				maxHeight: 2048,
			}),
		})
		.default({}),
	/* enable use of max_completion_tokens in place of max_tokens */
	useCompletionTokens: z.boolean().default(false),
	streamingSupported: z.boolean().default(true),
});

export async function endpointOai(
	input: z.input<typeof endpointOAIParametersSchema>
): Promise<Endpoint> {
	const {
		baseURL,
		apiKey,
		completion,
		model,
		defaultHeaders,
		defaultQuery,
		multimodal,
		extraBody,
		useCompletionTokens,
		streamingSupported,
	} = endpointOAIParametersSchema.parse(input);

	let OpenAI;
	try {
		OpenAI = (await import("openai")).OpenAI;
	} catch (e) {
		throw new Error("Failed to import OpenAI", { cause: e });
	}

	// Store router metadata if captured
	let routerMetadata: { route?: string; model?: string } = {};

	// Custom fetch wrapper to capture response headers for router metadata
	const customFetch = async (url: RequestInfo, init?: RequestInit): Promise<Response> => {
		const response = await fetch(url, init);

		// Capture router headers if present (fallback for non-streaming)
		const routeHeader = response.headers.get("X-Router-Route");
		const modelHeader = response.headers.get("X-Router-Model");

		if (routeHeader && modelHeader) {
			routerMetadata = {
				route: routeHeader,
				model: modelHeader,
			};
		}

		return response;
	};

	const openai = new OpenAI({
		apiKey: apiKey || "sk-",
		baseURL,
		defaultHeaders,
		defaultQuery,
		fetch: customFetch,
	});

	const imageProcessor = makeImageProcessor(multimodal.image);

	if (completion === "completions") {
		return async ({ messages, preprompt, continueMessage, generateSettings, conversationId }) => {
			const prompt = await buildPrompt({
				messages,
				continueMessage,
				preprompt,
				model,
			});

			const parameters = { ...model.parameters, ...generateSettings };
			const body: CompletionCreateParamsStreaming = {
				model: model.id ?? model.name,
				prompt,
				stream: true,
				max_tokens: parameters?.max_tokens,
				stop: parameters?.stop,
				temperature: parameters?.temperature,
				top_p: parameters?.top_p,
				frequency_penalty: parameters?.frequency_penalty,
				presence_penalty: parameters?.presence_penalty,
			};

			const openAICompletion = await openai.completions.create(body, {
				body: { ...body, ...extraBody },
				headers: {
					"ChatUI-Conversation-ID": conversationId?.toString() ?? "",
					"X-use-cache": "false",
				},
			});

			return openAICompletionToTextGenerationStream(openAICompletion);
		};
	} else if (completion === "chat_completions") {
		return async ({ messages, preprompt, generateSettings, conversationId, isMultimodal }) => {
			// Format messages for the chat API, handling multimodal content if supported
			let messagesOpenAI: OpenAI.Chat.Completions.ChatCompletionMessageParam[] =
				await prepareMessages(messages, imageProcessor, isMultimodal ?? model.multimodal);

			// Check if a system message already exists as the first message
			const hasSystemMessage = messagesOpenAI.length > 0 && messagesOpenAI[0]?.role === "system";

			if (hasSystemMessage) {
				// System message exists - preserve user configuration
				if (preprompt !== undefined) {
					// Prepend preprompt to existing system message if preprompt exists
					const userSystemPrompt = messagesOpenAI[0].content || "";
					messagesOpenAI[0].content =
						preprompt + (userSystemPrompt ? "\n\n" + userSystemPrompt : "");
				}
				// If no preprompt, user's system message remains unchanged
			} else {
				// No system message exists - create a new one with preprompt or empty string
				messagesOpenAI = [{ role: "system", content: preprompt ?? "" }, ...messagesOpenAI];
			}

			// Combine model defaults with request-specific parameters
			const parameters = { ...model.parameters, ...generateSettings };
			const body = {
				model: model.id ?? model.name,
				messages: messagesOpenAI,
				stream: streamingSupported,
				// Support two different ways of specifying token limits depending on the model
				...(useCompletionTokens
					? { max_completion_tokens: parameters?.max_tokens }
					: { max_tokens: parameters?.max_tokens }),
				stop: parameters?.stop,
				temperature: parameters?.temperature,
				top_p: parameters?.top_p,
				frequency_penalty: parameters?.frequency_penalty,
				presence_penalty: parameters?.presence_penalty,
			};

			// Handle both streaming and non-streaming responses with appropriate processors
			if (streamingSupported) {
				const openChatAICompletion = await openai.chat.completions.create(
					body as ChatCompletionCreateParamsStreaming,
					{
						body: { ...body, ...extraBody },
						headers: {
							"ChatUI-Conversation-ID": conversationId?.toString() ?? "",
							"X-use-cache": "false",
						},
					}
				);
				return openAIChatToTextGenerationStream(openChatAICompletion, () => routerMetadata);
			} else {
				const openChatAICompletion = await openai.chat.completions.create(
					body as ChatCompletionCreateParamsNonStreaming,
					{
						body: { ...body, ...extraBody },
						headers: {
							"ChatUI-Conversation-ID": conversationId?.toString() ?? "",
							"X-use-cache": "false",
						},
					}
				);
				return openAIChatToTextGenerationSingle(openChatAICompletion, () => routerMetadata);
			}
		};
	} else {
		throw new Error("Invalid completion type");
	}
}

async function prepareMessages(
	messages: EndpointMessage[],
	imageProcessor: ReturnType<typeof makeImageProcessor>,
	isMultimodal: boolean
): Promise<OpenAI.Chat.Completions.ChatCompletionMessageParam[]> {
	return Promise.all(
		messages.map(async (message) => {
			if (message.from === "user" && isMultimodal) {
				const imageParts = await prepareFiles(imageProcessor, message.files ?? []);
				if (imageParts.length) {
					const parts = [{ type: "text" as const, text: message.content }, ...imageParts];
					return { role: message.from, content: parts };
				}
			}
			return { role: message.from, content: message.content };
		})
	);
}

async function prepareFiles(
	imageProcessor: ReturnType<typeof makeImageProcessor>,
	files: MessageFile[]
): Promise<OpenAI.Chat.Completions.ChatCompletionContentPartImage[]> {
	const processedFiles = await Promise.all(
		files.filter((file) => file.mime.startsWith("image/")).map(imageProcessor)
	);
	return processedFiles.map((file) => ({
		type: "image_url" as const,
		image_url: {
			url: `data:${file.mime};base64,${file.image.toString("base64")}`,
			// Improves compatibility with some OpenAI-compatible servers
			// that expect an explicit detail setting.
			detail: "auto",
		},
	}));
}