package bg.sofia.uni.fmi.mjt.wish.list;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;

import java.util.Map;
import java.util.HashMap;

import java.util.Set;
import java.util.HashSet;

import java.util.Iterator;

import java.util.List;
import java.util.ArrayList;
import java.util.Arrays;

import java.util.Random;
import java.util.stream.Collectors;

public class WishListServer {

    //private static final int SERVER_PORT = 7777;
    private int port;
    private static final int BUFFER_LIMIT = 1024;
    private static final int POST_PARAM_COUNT = 3;
    private static final String SERVER_HOST = "localhost";
    private static ByteBuffer buffer = ByteBuffer.allocateDirect(BUFFER_LIMIT);


    private Selector selector;
    private static Map<String, Set<String>> wishList = new HashMap<>();


    private boolean isRunning;

    public WishListServer(int port) {
        this.port = port;
        isRunning = true;
    }


    public void start() {
        try (ServerSocketChannel serverChannel = ServerSocketChannel.open();
        ) {

            serverChannel.bind(new InetSocketAddress(SERVER_HOST, port));
            serverChannel.configureBlocking(false);

            selector = Selector.open();
            serverChannel.register(selector, SelectionKey.OP_ACCEPT);

            while (this.isRunning) {
                int readyChannels = selector.select();
                if (readyChannels == 0) {
                    continue; // no channels
                }

                Set<SelectionKey> keys = selector.selectedKeys();
                Iterator<SelectionKey> iterator = keys.iterator();

                while (iterator.hasNext()) {
                    SelectionKey key = iterator.next();

                    if (key.isAcceptable()) {
                        ServerSocketChannel socketChannel = (ServerSocketChannel) key.channel();
                        SocketChannel clientSocket = socketChannel.accept();
                        clientSocket.configureBlocking(false);
                        clientSocket.register(selector, SelectionKey.OP_READ);
                    } else if (key.isReadable()) {


                        SocketChannel clientChannel = (SocketChannel) key.channel();

                        buffer.clear();
                        int rd = clientChannel.read(buffer);
                        if (rd < 0) {
                            System.out.println("client stopped communication");
                            clientChannel.close();
                            continue;
                        }

                        buffer.flip();

                        // parse the buffer
                        String serverResponse = "[ Unknown command ]";

                        // Convert buffer to String

                        byte[] byteArray = new byte[buffer.remaining()];
                        buffer.get(byteArray);
                        String reply = new String(byteArray, "UTF-8"); // buffer drain

                        List<String> parsedBuffer = Arrays.asList(reply.split(" "));
                        String commandName = parsedBuffer.get(0).toLowerCase();

                        if (commandName.equals("post-wish")) {
                            if (parsedBuffer.size() < POST_PARAM_COUNT) {
                                serverResponse = "[ Unknown command ]";
                            }

                            String gift = String.join(" ", parsedBuffer.subList(2, parsedBuffer.size()));

                            if (gift.isEmpty()) {
                                serverResponse = "[ Unknown command ]";
                            }

                            serverResponse = postWish(parsedBuffer.get(1),
                                    gift.toLowerCase());
                        } else if (commandName.equals("get-wish")) {
                            serverResponse = getWish();
                        } else if (commandName.equals("disconnect")) {
                            serverResponse = "[ Disconnected from server ]";

                            serverResponse = serverResponse + System.lineSeparator();

                            buffer.clear();
                            buffer.put(serverResponse.getBytes("UTF-8"));

                            buffer.flip();
                            clientChannel.write(buffer);

                            clientChannel.close();
                            continue;
                        }


                        // Response
                        serverResponse = serverResponse + System.lineSeparator();

                        buffer.clear();
                        buffer.put(serverResponse.getBytes("UTF-8"));

                        buffer.flip();
                        clientChannel.write(buffer);

                    }

                    iterator.remove(); // remove answered response
                }
            }

        } catch (
                IOException e) {
            System.out.println("Problem establishing connection ..");
            e.printStackTrace();
        }

    }

    private static String postWish(String username, String gift) {
        String result = "[ Gift " + gift + " for student " + username
                + " submitted successfully ]";
        if (!wishList.containsKey(username)) {
            wishList.put(username, new HashSet<>());
            wishList.get(username).add(gift);
        } else {
            // if it gift is already present
            if (wishList.get(username).contains(gift)) {
                result = "[ The same gift for student " + username + " was already submitted ]";
            } else {
                wishList.get(username).add(gift);
            }
        }


        return result;

    }

    private static String getWish() {

        if (wishList.isEmpty()) {
            return "[ There are no students present in the wish list ]";
        }

        // Get random user from hashMap and print its wishes

        // Get random user name from HashMap

        List<String> users = new ArrayList<>(wishList.keySet());
        Random random = new Random();

        String randomUser = users.get(random.nextInt(users.size()));

        Set<String> gifts = wishList.get(randomUser);
        wishList.remove(randomUser);

        return "[ " + randomUser + ": " + gifts + " ]";


    }

    public void stop() {
        this.isRunning = false;

        try {
            selector.close();
        } catch (IOException e) {
            System.out.println("Failed to close selector");
            e.printStackTrace();
        }
    }

}