import { config } from "$lib/server/config";
import { logger } from "$lib/server/logger";
import type { RouteSelection } from "./types";
import { getRoutes } from "./policy";

/** Default route when no specific heuristic matches */
export const DEFAULT_ROUTE = "default";
export const MULTIMODAL_ROUTE = "multimodal";
export const AGENTIC_ROUTE = "agentic";

/**
 * Simple heuristic-based route selection.
 *
 * This replaces the Arch Router API call with local heuristics:
 * - If image input is detected → multimodal route
 * - If tools are active → agentic route
 * - Otherwise → default route
 *
 * The actual model selection is handled by the routes.json policy file.
 */
export async function heuristicSelectRoute(
	options: {
		hasImageInput?: boolean;
		hasToolsActive?: boolean;
	} = {}
): Promise<RouteSelection> {
	const { hasImageInput = false, hasToolsActive = false } = options;

	const routes = await getRoutes();

	// Check for multimodal input
	if (hasImageInput) {
		const multimodalExists = routes.some((r) => r.name === MULTIMODAL_ROUTE);
		if (multimodalExists) {
			logger.debug({ route: MULTIMODAL_ROUTE }, "[router] heuristic: image input detected");
			return { routeName: MULTIMODAL_ROUTE };
		}
	}

	// Check for MCP servers active
	if (hasToolsActive) {
		const agenticExists = routes.some((r) => r.name === AGENTIC_ROUTE);
		if (agenticExists) {
			logger.debug({ route: AGENTIC_ROUTE }, "[router] heuristic: MCP servers active");
			return { routeName: AGENTIC_ROUTE };
		}
	}

	// Default route for general conversation. If the named route doesn't exist in the
	// policy file, resolveRouteModels falls through to LLM_ROUTER_FALLBACK_MODEL — that's
	// the right safety net, vs. silently picking an arbitrary specialized routes[0].
	const defaultRoute = config.LLM_ROUTER_DEFAULT_ROUTE || DEFAULT_ROUTE;
	logger.debug({ route: defaultRoute }, "[router] heuristic: using default route");
	return { routeName: defaultRoute };
}