// Universal test fixture: a tiny node:http server. Tests are
// run-only (not shipped); importing node:http here is permitted in the
// `tests/` directory which is excluded from tier-purity checks in
// `src/`. The src tree stays universal.
import {
    createServer,
    type IncomingMessage,
    type Server,
    type ServerResponse,
} from "node:http";

export type RouteHandler = (
    req: IncomingMessage,
    res: ServerResponse
) => void | Promise<void>;

export interface FixtureServer {
    readonly url: string;
    readonly port: number;
    close(): Promise<void>;
}

/**
 * Stand up a localhost `node:http` server with the given route handler.
 * The returned `url` ends with `/` so it can be used as a `rootUrl`.
 */
export async function startFixtureServer(
    handler: RouteHandler
): Promise<FixtureServer> {
    const server: Server = createServer((req, res) => {
        try {
            const out = handler(req, res);
            if (out !== undefined) {
                void Promise.resolve(out).catch((err) => {
                    res.statusCode = 500;
                    res.end(String(err));
                });
            }
        } catch (err) {
            res.statusCode = 500;
            res.end(String(err));
        }
    });
    await new Promise<void>((resolve) =>
        server.listen(0, "127.0.0.1", () => resolve())
    );
    const addr = server.address();
    if (addr === null || typeof addr === "string") {
        throw new Error("fixture server did not bind to a TCP port");
    }
    const port = addr.port;
    return {
        url: `http://127.0.0.1:${port}/`,
        port,
        close: () =>
            new Promise<void>((resolve, reject) =>
                server.close((err) => (err ? reject(err) : resolve()))
            ),
    };
}