SmsHook/app/src/main/java/com/example/smshook/HttpServer.java

package com.example.smshook;

import java.util.List;
import java.util.Map;

import fi.iki.elonen.NanoHTTPD;

public class HttpServer extends NanoHTTPD {

    public interface OnRequestListener {
        void onSmsRequest(String sender, String message);

    }

    private OnRequestListener listener;

    public void setOnRequestListener(OnRequestListener listener) {
        this.listener = listener;
    }

    private HttpServer(int port) {
        super(port);
    }

    private HttpServer(String hostname, int port) {
        super(hostname, port);
    }

    private static volatile HttpServer instance;

    //double check locking
    public static HttpServer getInstance(int port) {
        if (instance == null) {
            synchronized (HttpServer.class) {
                if (instance == null) {
                    instance = new HttpServer("0.0.0.0", port);
                }
            }
        }
        return instance;
    }

    @Override
    public Response serve(IHTTPSession session) {
        Map<String, List<String>> params = session.getParameters();
        List<String> senders = params.get("sender");
        if (senders == null || senders.isEmpty()) {
            return newFixedLengthResponse("sender is required");
        }
        List<String> messages = params.get("message");
        if (messages == null || messages.isEmpty()) {
            return newFixedLengthResponse("message is required");
        }
        String sender = senders.get(0);
        String message = messages.get(0);

        if (listener != null) {
            listener.onSmsRequest(sender, message);
        }

        return newFixedLengthResponse("ok");
    }
}