package org.stianloader.mrjmania;

import java.util.concurrent.Executor;
import java.util.concurrent.ForkJoinPool;

import org.jetbrains.annotations.Contract;
import org.jetbrains.annotations.NotNull;

/**
 * Polyfills regarding threads, {@link Executor}s and thread pools.
 */
public class MRJExecutors {

    private MRJExecutors() {
        throw new UnsupportedOperationException();
    }

    /**
     * Gets a {@link String} representation of the {@link #getVirtualExecutor()}
     * executor used. Or, it returns which pool is being used.
     *
     * @return A {@link String} representation of the {@link Executor} used.
     */
    @NotNull
    @Contract(pure = true)
    public static String getVirtualExecutorType() {
        return "ForkJoinPool.commonPool";
    }

    /**
     * Returns whether virtual threads are enabled/support in the given release.
     *
     * @return Returns false for Java 8 to Java 20 (as per {@link MRJMania#getMRJVersion()}), true for J21 and above.
     */
    @Contract(pure = true)
    public static boolean supportsVirtualExecutors() {
        return false;
    }

    /**
     * Returns an executor that may or may not be virtual, see {@link #supportsVirtualExecutors()}.
     *
     * <p>Note that the returned executor will be from the {@link ForkJoinPool#commonPool()}
     * by default if not virtual, so it might be unwise to use it for non-short-lived tasks
     * else it might clog up other processes.
     *
     * <p>Further, if the task is indeed virtual, it will spin up a virtual thread by
     * task. This might not be intended/great either, depending on circumstances.
     *
     * @return The virtual executor to use.
     */
    @NotNull
    @Contract(pure = true)
    public static Executor getVirtualExecutor() {
        return ForkJoinPool.commonPool()::execute;
    }
}