package client.utils;

import client.exception.InvalidModificationException;
import commons.ws.messages.Message;
import org.apache.commons.lang3.function.FailableFunction;
import org.apache.commons.lang3.tuple.Pair;

import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.CompletableFuture;
import java.util.function.Consumer;
import java.util.function.Function;

public class WebSocketDataService<ID, Value> {
    public WebSocketDataService() {

    }

    /**
     * dataRegister maps a CompletableFuture&lt;T&gt; to its fulfilment function.
     */
    private final Map<ID, CompletableFuture<Value>> pendingRegister = new HashMap<>();
    private Function<Message, FailableFunction<Message, Pair<ID, Value>, InvalidModificationException>> parser;
    public void setMessageParser(
            Function<
                    Message,
                    FailableFunction<Message, Pair<ID, Value>, InvalidModificationException>
                    > parser) {
        this.parser = parser;
    }

    /**
     * On each WS message, the parser callback distinguishes what
     * consumer (crud function) to call. Then the pair of ID-Value
     * returned by the processor is used
     * @param message
     */
    public void onMessage(Message message) {
        Pair<ID, Value> result = parser.apply(message).apply(message);
        pendingRegister.get(result.getKey()).complete(result.getValue());
    }

    /**
     * Adds an ID-reference to the map for an object whose update is pending.
     * If the key already exists, the caller should assume there is an ongoing
     * operation on the object.
     * @param id ID of the object.
     * @return Whether the key already exists.
     */
    public boolean add(ID id, Consumer<Value> onComplete) {
        CompletableFuture<Value> future = new CompletableFuture<>();
        future.thenAccept(onComplete.andThen(_ -> pendingRegister.remove(id)));
        return pendingRegister.putIfAbsent(id, future) == null;
    }
    public boolean add(ID id) {
        return add(id, (_) -> {});
    }
}