package com.ankurm.ssews;

import org.springframework.context.annotation.Configuration;
import org.springframework.messaging.simp.config.MessageBrokerRegistry;
import org.springframework.web.socket.config.annotation.EnableWebSocketMessageBroker;
import org.springframework.web.socket.config.annotation.StompEndpointRegistry;
import org.springframework.web.socket.config.annotation.WebSocketMessageBrokerConfigurer;
import org.springframework.web.socket.config.annotation.WebSocketTransportRegistration;

/**
 * Four lines of configuration that decide more than they look like they do.
 *
 * @see <a href="../../../../../docs/04-stomp.md">docs/04-stomp.md</a>
 */
@Configuration
@EnableWebSocketMessageBroker
public class WebSocketConfig implements WebSocketMessageBrokerConfigurer {

    @Override
    public void registerStompEndpoints(StompEndpointRegistry registry) {
        // No setAllowedOrigins call at all. The handshake then permits same-origin requests
        // only -- and "same origin" is decided from the Origin header, which a non-browser
        // client does not send, so curl and the Java client are allowed while a page on
        // another site is not. Add setAllowedOriginPatterns("https://app.example.com") for a
        // real cross-origin front end; setAllowedOrigins("*") is rejected outright when
        // credentials are allowed.
        registry.addEndpoint("/ws");

        // The SockJS variant is a SECOND endpoint on its own path. Registering .withSockJS()
        // on the same path does not give you both: SockJS wraps the URL in /{server}/{session}
        // and a plain WebSocket client pointed at it fails the handshake.
        registry.addEndpoint("/ws-sockjs").withSockJS();
    }

    @Override
    public void configureMessageBroker(MessageBrokerRegistry registry) {
        // The simple broker. In-memory, single JVM, no persistence, no acknowledgement, and it
        // drops everything on restart. enableStompBrokerRelay(..) swaps in RabbitMQ or ActiveMQ
        // without touching a controller -- see ../rabbitmq for the broker side.
        registry.enableSimpleBroker("/topic", "/queue");

        // Destinations a CLIENT sends to. /app/chat.send is routed to @MessageMapping; anything
        // starting with /topic or /queue goes straight to the broker and is NEVER seen by a
        // controller. Getting this backwards produces a message that vanishes with no error.
        registry.setApplicationDestinationPrefixes("/app");

        // The prefix a client subscribes under for messages addressed to it alone. The client
        // subscribes to /user/queue/whisper; the broker rewrites that to a session-scoped
        // destination that no other session can subscribe to.
        registry.setUserDestinationPrefix("/user");
    }

    @Override
    public void configureWebSocketTransport(WebSocketTransportRegistration registration) {
        // Defaults, restated so the numbers are visible in one place rather than discovered
        // when a 70 KB frame disappears. WebSocketTransportRegistration's own defaults are
        // 64 KB for both; see WebSocketLimitsTest for what exceeding them looks like.
        registration.setMessageSizeLimit(64 * 1024);
        registration.setSendBufferSizeLimit(512 * 1024);
        registration.setSendTimeLimit(20_000);
    }
}