import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.function.BiConsumer;

public class Server {

    // port of server
    private final int PORT;

    // Thread pool
    ExecutorService threadPool;
    // Max Thread pool count
    private final int THREAD_COUNT = 10;

    //server
    private ServerSocket server;

    // backing container
    private Map<String, String> db;

    // boolean that tells server to stop
    private volatile boolean stop = false;

    public Server(int port){
        this.PORT = port;

        db = new HashMap<>();

        try {
            server = new ServerSocket(PORT);
        } catch (IOException e) {
            e.printStackTrace();
        }

        threadPool = Executors.newFixedThreadPool(THREAD_COUNT);
    }

    public void listen(){
        try {
            while(!stop){
                threadPool.execute(onSocket(server.accept(), onInput));
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public void stop(){
        threadPool.shutdown();
        stop = true;
    }

    private BiConsumer<String, PrintWriter> onInput = (input, output) -> {
        // incoming msg
        String[] inMessage = input.split(":");
        String identifier = inMessage[0];

        String[] keyValuePair = inMessage[1].split("-");

        String key = keyValuePair.length > 0 ? keyValuePair[0] : "";
        String value = keyValuePair.length > 1 ? keyValuePair[1] : "";

        // out going msg
        String outMessage;

        switch (identifier){
            case "Add":
                db.put(key, value);
                outMessage = "Success: Added value";
                break;
            case "AddList":
                String dbValue = db.getOrDefault(key, "");
                value = dbValue.equals("") ? value : String.format("%s,%s", dbValue, value);
                db.put(key, value);
                outMessage = "Success: Added value";
                break;
            case "Get":
                outMessage = db.getOrDefault(key, "null");
                break;
            case "GetList":
                outMessage = db.getOrDefault(key, "null");
                break;
            case "shutdown":
                stop();
                outMessage = "Shutting down Server";
                break;
            default:
                outMessage = "Error: Unknown Command";
        }
        output.println(outMessage);
    };

    private Runnable onSocket(final Socket client, BiConsumer<String, PrintWriter> onInput){
        return () -> {
            try{
                PrintWriter output = new PrintWriter(client.getOutputStream(), true);
                BufferedReader input = new BufferedReader(new InputStreamReader(client.getInputStream()));

                onInput.accept(input.readLine(), output);

                output.close();
                input.close();
                client.close();
            } catch (IOException e){
                e.printStackTrace();
            }
        };
    }
}