package io.gitlab.jfronny.betterwhitelist.server;

import org.jetbrains.annotations.NotNull;

import java.util.concurrent.*;

public class ManualFuture<T> implements Future<T> {
    private Result state = Result.RUNNING;
    private T result;

    @Override
    public boolean cancel(boolean b) {
        if (state != Result.RUNNING) return false;
        cancel();
        return true;
    }

    @Override
    public boolean isCancelled() {
        return state == Result.CANCELLED;
    }

    @Override
    public boolean isDone() {
        return state == Result.DONE;
    }

    @Override
    public T get() throws InterruptedException, ExecutionException {
        while (state == Result.RUNNING) Thread.sleep(10);
        if (state == Result.CANCELLED) throw new CancellationException();
        return result;
    }

    @Override
    public T get(long l, @NotNull TimeUnit timeUnit) throws TimeoutException {
        long millis = timeUnit.toMillis(l) / 10;
        while (state == Result.RUNNING && millis-- > 0) {
            try {
                Thread.sleep(10);
            } catch (InterruptedException ignored) {
            }
        }
        if (millis <= 0) throw new TimeoutException();
        if (state == Result.CANCELLED) throw new CancellationException();
        return result;
    }

    public void cancel() {
        this.state = Result.CANCELLED;
    }

    public void complete(T result) {
        if (state != Result.RUNNING) throw new IllegalStateException("Attempted to complete non-running future");
        this.state = Result.DONE;
        this.result = result;
    }

    public void reset() {
        this.state = Result.RUNNING;
    }

    private enum Result {
        RUNNING, CANCELLED, DONE
    }
}