// Router + match contexts. `routerContext` carries the Router instance (provided
// by RouterProvider, read by every hook). `matchContext` carries the current
// match id down the render tree so `Outlet` can find the NEXT match to render —
// the pull-based chaining that replaces a top-down state diff.
import { createContext, useContext } from 'octane';
import type { AnyRouter, RegisteredRouter } from '@tanstack/router-core';

export const routerContext = createContext<AnyRouter | undefined>(undefined);
export const getRouterContext = (): typeof routerContext => routerContext;

// The id of the nearest rendered match (undefined above the first match).
export const matchContext = createContext<string | undefined>(undefined);

// Resolve the active router: an explicitly-passed one wins, else the context.
// `useContext` is keyed by context identity (not a per-call-site slot), so it's
// safe to call from this binding code without a slot.
export function useRouter<TRouter extends AnyRouter = RegisteredRouter>(opts?: {
	router?: TRouter;
	warn?: boolean;
}): TRouter;
export function useRouter(...args: unknown[]): AnyRouter {
	const opts = (args.length && typeof args[0] !== 'symbol' ? args[0] : undefined) as
		{ router?: AnyRouter; warn?: boolean } | undefined;
	const ctx = useContext(routerContext);
	const router = opts?.router ?? ctx;
	if (!router && opts?.warn !== false) {
		throw new Error('useRouter must be used inside a <RouterProvider> component!');
	}
	return router as AnyRouter;
}