/*
 * Hunt - A refined core library for D programming language.
 *
 * Copyright (C) 2018-2019 HuntLabs
 *
 * Website: https://www.huntlabs.net/
 *
 * Licensed under the Apache-2.0 License.
 *
 */
module hunt.util.Common;



/**
 * Implementing this interface allows an object to be the target of
 * the "for-each loop" statement. 
 * @param (T) the type of elements returned by the iterator
 */
interface Iterable(T) {
   int opApply(scope int delegate(ref T) dg);
}

interface Iterable(K, V) {
   int opApply(scope int delegate(ref K, ref V) dg);
}


/**
 * A class implements the <code>Cloneable</code> interface to
 * indicate to the {@link java.lang.Object#clone()} method that it
 * is legal for that method to make a
 * field-for-field copy of instances of that class.
 * <p>
 * Invoking Object's clone method on an instance that does not implement the
 * <code>Cloneable</code> interface results in the exception
 * <code>CloneNotSupportedException</code> being thrown.
 * <p>
 * By convention, classes that implement this interface should override
 * <tt>Object.clone</tt> (which is protected) with a method.
 * See {@link java.lang.Object#clone()} for details on overriding this
 * method.
 * <p>
 * Note that this interface does <i>not</i> contain the <tt>clone</tt> method.
 * Therefore, it is not possible to clone an object merely by virtue of the
 * fact that it implements this interface.  Even if the clone method is invoked
 * reflectively, there is no guarantee that it will succeed.
 */
interface Cloneable {
}


interface Comparable(T) {
    // TODO: Tasks pending completion -@zxp at 12/30/2018, 10:17:44 AM
    // 
    // int opCmp(T o) nothrow;
    int opCmp(T o);

    deprecated("Use opCmp instead.")
    alias compareTo = opCmp;
}

/**
 * The <code>Runnable</code> interface should be implemented by any
 * class whose instances are intended to be executed by a thread. The
 * class must define a method of no arguments called <code>run</code>.
 * <p>
 * This interface is designed to provide a common protocol for objects that
 * wish to execute code while they are active. For example,
 * <code>Runnable</code> is implemented by class <code>Thread</code>.
 * Being active simply means that a thread has been started and has not
 * yet been stopped.
 * <p>
 * In addition, <code>Runnable</code> provides the means for a class to be
 * active while not subclassing <code>Thread</code>. A class that implements
 * <code>Runnable</code> can run without subclassing <code>Thread</code>
 * by instantiating a <code>Thread</code> instance and passing itself in
 * as the target.  In most cases, the <code>Runnable</code> interface should
 * be used if you are only planning to override the <code>run()</code>
 * method and no other <code>Thread</code> methods.
 * This is important because classes should not be subclassed
 * unless the programmer intends on modifying or enhancing the fundamental
 * behavior of the class.
 *
 * @author  Arthur van Hoff
 * @see     Callable
 */
interface Runnable {
    /**
     * When an object implementing interface <code>Runnable</code> is used
     * to create a thread, starting the thread causes the object's
     * <code>run</code> method to be called in that separately executing
     * thread.
     * <p>
     * The general contract of the method <code>run</code> is that it may
     * take any action whatsoever.
     */
    void run();
}


/**
 * A task that returns a result and may throw an exception.
 * Implementors define a single method with no arguments called
 * {@code call}.
 *
 * <p>The {@code Callable} interface is similar to {@link
 * java.lang.Runnable}, in that both are designed for classes whose
 * instances are potentially executed by another thread.  A
 * {@code Runnable}, however, does not return a result and cannot
 * throw a checked exception.
 *
 * <p>The {@link Executors} class contains utility methods to
 * convert from other common forms to {@code Callable} classes.
 *
 * @see Executor
 * @author Doug Lea
 * @param <V> the result type of method {@code call}
 */
interface Callable(V) {
    /**
     * Computes a result, or throws an exception if unable to do so.
     *
     * @return computed result
     * @throws Exception if unable to compute a result
     */
    V call();
}


/**
 * An object that executes submitted {@link Runnable} tasks. This
 * interface provides a way of decoupling task submission from the
 * mechanics of how each task will be run, including details of thread
 * use, scheduling, etc.  An {@code Executor} is normally used
 * instead of explicitly creating threads. For example, rather than
 * invoking {@code new Thread(new RunnableTask()).start()} for each
 * of a set of tasks, you might use:
 *
 * <pre> {@code
 * Executor executor = anExecutor();
 * executor.execute(new RunnableTask1());
 * executor.execute(new RunnableTask2());
 * ...}</pre>
 *
 * However, the {@code Executor} interface does not strictly require
 * that execution be asynchronous. In the simplest case, an executor
 * can run the submitted task immediately in the caller's thread:
 *
 * <pre> {@code
 * class DirectExecutor implements Executor {
 *   public void execute(Runnable r) {
 *     r.run();
 *   }
 * }}</pre>
 *
 * More typically, tasks are executed in some thread other than the
 * caller's thread.  The executor below spawns a new thread for each
 * task.
 *
 * <pre> {@code
 * class ThreadPerTaskExecutor implements Executor {
 *   public void execute(Runnable r) {
 *     new Thread(r).start();
 *   }
 * }}</pre>
 *
 * Many {@code Executor} implementations impose some sort of
 * limitation on how and when tasks are scheduled.  The executor below
 * serializes the submission of tasks to a second executor,
 * illustrating a composite executor.
 *
 * <pre> {@code
 * class SerialExecutor implements Executor {
 *   final Queue!(Runnable) tasks = new ArrayDeque<>();
 *   final Executor executor;
 *   Runnable active;
 *
 *   SerialExecutor(Executor executor) {
 *     this.executor = executor;
 *   }
 *
 *   public synchronized void execute(Runnable r) {
 *     tasks.add(() -> {
 *       try {
 *         r.run();
 *       } finally {
 *         scheduleNext();
 *       }
 *     });
 *     if (active is null) {
 *       scheduleNext();
 *     }
 *   }
 *
 *   protected synchronized void scheduleNext() {
 *     if ((active = tasks.poll()) !is null) {
 *       executor.execute(active);
 *     }
 *   }
 * }}</pre>
 *
 * The {@code Executor} implementations provided in this package
 * implement {@link ExecutorService}, which is a more extensive
 * interface.  The {@link ThreadPoolExecutor} class provides an
 * extensible thread pool implementation. The {@link Executors} class
 * provides convenient factory methods for these Executors.
 *
 * <p>Memory consistency effects: Actions in a thread prior to
 * submitting a {@code Runnable} object to an {@code Executor}
 * <a href="package-summary.html#MemoryVisibility"><i>happen-before</i></a>
 * its execution begins, perhaps in another thread.
 *
 * @since 1.5
 * @author Doug Lea
 */
interface Executor {

    /**
     * Executes the given command at some time in the future.  The command
     * may execute in a new thread, in a pooled thread, or in the calling
     * thread, at the discretion of the {@code Executor} implementation.
     *
     * @param command the runnable task
     * @throws RejectedExecutionException if this task cannot be
     * accepted for execution
     * @throws NullPointerException if command is null
     */
    void execute(Runnable command);
}



/**
 * An object that may hold resources (such as file or socket handles)
 * until it is closed. The {@link #close()} method of an {@code AutoCloseable}
 * object is called automatically when exiting a {@code
 * try}-with-resources block for which the object has been declared in
 * the resource specification header. This construction ensures prompt
 * release, avoiding resource exhaustion exceptions and errors that
 * may otherwise occur.
 *
 * @apiNote
 * <p>It is possible, and in fact common, for a base class to
 * implement AutoCloseable even though not all of its subclasses or
 * instances will hold releasable resources.  For code that must operate
 * in complete generality, or when it is known that the {@code AutoCloseable}
 * instance requires resource release, it is recommended to use {@code
 * try}-with-resources constructions. However, when using facilities such as
 * {@link java.util.stream.Stream} that support both I/O-based and
 * non-I/O-based forms, {@code try}-with-resources blocks are in
 * general unnecessary when using non-I/O-based forms.
 *
 * @author Josh Bloch
 */
interface AutoCloseable {
    /**
     * Closes this resource, relinquishing any underlying resources.
     * This method is invoked automatically on objects managed by the
     * {@code try}-with-resources statement.
     *
     * <p>While this interface method is declared to throw {@code
     * Exception}, implementers are <em>strongly</em> encouraged to
     * declare concrete implementations of the {@code close} method to
     * throw more specific exceptions, or to throw no exception at all
     * if the close operation cannot fail.
     *
     * <p> Cases where the close operation may fail require careful
     * attention by implementers. It is strongly advised to relinquish
     * the underlying resources and to internally <em>mark</em> the
     * resource as closed, prior to throwing the exception. The {@code
     * close} method is unlikely to be invoked more than once and so
     * this ensures that the resources are released in a timely manner.
     * Furthermore it reduces problems that could arise when the resource
     * wraps, or is wrapped, by another resource.
     *
     * <p><em>Implementers of this interface are also strongly advised
     * to not have the {@code close} method throw {@link
     * InterruptedException}.</em>
     *
     * This exception interacts with a thread's interrupted status,
     * and runtime misbehavior is likely to occur if an {@code
     * InterruptedException} is {@linkplain Throwable#addSuppressed
     * suppressed}.
     *
     * More generally, if it would cause problems for an
     * exception to be suppressed, the {@code AutoCloseable.close}
     * method should not throw it.
     *
     * <p>Note that unlike the {@link java.io.Closeable#close close}
     * method of {@link java.io.Closeable}, this {@code close} method
     * is <em>not</em> required to be idempotent.  In other words,
     * calling this {@code close} method more than once may have some
     * visible side effect, unlike {@code Closeable.close} which is
     * required to have no effect if called more than once.
     *
     * However, implementers of this interface are strongly encouraged
     * to make their {@code close} methods idempotent.
     *
     * @throws Exception if this resource cannot be closed
     */
    void close();
}


interface Closeable : AutoCloseable {
    
}



/**
 * An object to which {@code char} sequences and values can be appended.  The
 * {@code Appendable} interface must be implemented by any class whose
 * instances are intended to receive formatted output from a {@link
 * java.util.Formatter}.
 *
 * <p> The characters to be appended should be valid Unicode characters as
 * described in <a href="Character.html#unicode">Unicode Character
 * Representation</a>.  Note that supplementary characters may be composed of
 * multiple 16-bit {@code char} values.
 *
 * <p> Appendables are not necessarily safe for multithreaded access.  Thread
 * safety is the responsibility of classes that extend and implement this
 * interface.
 *
 * <p> Since this interface may be implemented by existing classes
 * with different styles of error handling there is no guarantee that
 * errors will be propagated to the invoker.
 *
 */
interface Appendable {

    /**
     * Appends the specified character sequence to this {@code Appendable}.
     *
     * <p> Depending on which class implements the character sequence
     * {@code csq}, the entire sequence may not be appended.  For
     * instance, if {@code csq} is a {@link java.nio.CharBuffer} then
     * the subsequence to append is defined by the buffer's position and limit.
     *
     * @param  csq
     *         The character sequence to append.  If {@code csq} is
     *         {@code null}, then the four characters {@code "null"} are
     *         appended to this Appendable.
     *
     * @return  A reference to this {@code Appendable}
     *
     * @throws  IOException
     *          If an I/O error occurs
     */
    Appendable append(string csq);

    /**
     * Appends a subsequence of the specified character sequence to this
     * {@code Appendable}.
     *
     * <p> An invocation of this method of the form {@code out.append(csq, start, end)}
     * when {@code csq} is not {@code null}, behaves in
     * exactly the same way as the invocation
     *
     * <pre>
     *     out.append(csq.subSequence(start, end)) </pre>
     *
     * @param  csq
     *         The character sequence from which a subsequence will be
     *         appended.  If {@code csq} is {@code null}, then characters
     *         will be appended as if {@code csq} contained the four
     *         characters {@code "null"}.
     *
     * @param  start
     *         The index of the first character in the subsequence
     *
     * @param  end
     *         The index of the character following the last character in the
     *         subsequence
     *
     * @return  A reference to this {@code Appendable}
     *
     * @throws  IndexOutOfBoundsException
     *          If {@code start} or {@code end} are negative, {@code start}
     *          is greater than {@code end}, or {@code end} is greater than
     *          {@code csq.length()}
     *
     * @throws  IOException
     *          If an I/O error occurs
     */
    // Appendable append(CharSequence csq, int start, int end);

    /**
     * Appends the specified character to this {@code Appendable}.
     *
     * @param  c
     *         The character to append
     *
     * @return  A reference to this {@code Appendable}
     *
     * @throws  IOException
     *          If an I/O error occurs
     */
    Appendable append(char c);
}


/**
 * A tagging interface that all event listener interfaces must extend.
 */
interface EventListener {
}


/**
 * <p>
 * A callback abstraction that handles completed/failed events of asynchronous
 * operations.
 * </p>
 * <p>
 * <p>
 * Semantically this is equivalent to an optimise Promise&lt;Void&gt;, but
 * callback is a more meaningful name than EmptyPromise
 * </p>
 */
interface Callback {
    /**
     * Instance of Adapter that can be used when the callback methods need an
     * empty implementation without incurring in the cost of allocating a new
     * Adapter object.
     */
    __gshared Callback NOOP;

    shared static this() {
        NOOP = new NoopCallback();
    }

    /**
     * <p>
     * Callback invoked when the operation completes.
     * </p>
     *
     * @see #failed(Throwable)
     */
    void succeeded();

    /**
     * <p>
     * Callback invoked when the operation fails.
     * </p>
     *
     * @param x the reason for the operation failure
     */
    void failed(Exception x);

    /**
     * @return True if the callback is known to never block the caller
     */
    bool isNonBlocking();
}

/**
*/
class NestedCallback : Callback {
    private Callback callback;

    this(Callback callback) {
        this.callback = callback;
    }

    this(NestedCallback nested) {
        this.callback = nested.callback;
    }

    Callback getCallback() {
        return callback;
    }

    void succeeded() {
        callback.succeeded();
    }

    void failed(Exception x) {
        callback.failed(x);
    }

    bool isNonBlocking() {
        return callback.isNonBlocking();
    }
}

/**
 * <p>
 * A callback abstraction that handles completed/failed events of asynchronous
 * operations.
 * </p>
 * <p>
 * <p>
 * Semantically this is equivalent to an optimise Promise&lt;Void&gt;, but
 * callback is a more meaningful name than EmptyPromise
 * </p>
 */
class NoopCallback : Callback {
    /**
     * <p>
     * Callback invoked when the operation completes.
     * </p>
     *
     * @see #failed(Throwable)
     */
    void succeeded() {
    }

    /**
     * <p>
     * Callback invoked when the operation fails.
     * </p>
     *
     * @param x the reason for the operation failure
     */
    void failed(Exception x) {
    }

    /**
     * @return True if the callback is known to never block the caller
     */
    bool isNonBlocking() {
        return false;
    }
}


/**
*/
class CompilerHelper {

    static bool isGreaterThan(int ver) pure @safe @nogc nothrow {
        return __VERSION__ >= ver;
    }

    static bool isLessThan(int ver) pure @safe @nogc nothrow {
        return __VERSION__ <= ver;
    }
}