/*
 * Licensed under the GNU Lesser General Public License Version 3
 *
 * This library is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the license, or
 * (at your option) any later version.
 *
 * This software is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library.  If not, see <http://www.gnu.org/licenses/>.
 */

// generated automatically - do not change


module gio.Cancellable;

private import gio.c.functions;
public  import gio.c.types;
private import glib.ConstructionException;
private import glib.ErrorG;
private import glib.GException;
private import glib.Source;
private import gobject.ObjectG;
private import gobject.Signals;
private import std.algorithm;


/**
 * GCancellable is a thread-safe operation cancellation stack used
 * throughout GIO to allow for cancellation of synchronous and
 * asynchronous operations.
 */
public class Cancellable : ObjectG
{
	/** the main Gtk struct */
	protected GCancellable* gCancellable;

	/** Get the main Gtk struct */
	public GCancellable* getCancellableStruct(bool transferOwnership = false)
	{
		if (transferOwnership)
			ownedRef = false;
		return gCancellable;
	}

	/** the main Gtk struct as a void* */
	protected override void* getStruct()
	{
		return cast(void*)gCancellable;
	}

	protected override void setStruct(GObject* obj)
	{
		gCancellable = cast(GCancellable*)obj;
		super.setStruct(obj);
	}

	/**
	 * Sets our main struct and passes it to the parent class.
	 */
	public this (GCancellable* gCancellable, bool ownedRef = false)
	{
		this.gCancellable = gCancellable;
		super(cast(GObject*)gCancellable, ownedRef);
	}


	/** */
	public static GType getType()
	{
		return g_cancellable_get_type();
	}

	/**
	 * Creates a new #GCancellable object.
	 *
	 * Applications that want to start one or more operations
	 * that should be cancellable should create a #GCancellable
	 * and pass it to the operations.
	 *
	 * One #GCancellable can be used in multiple consecutive
	 * operations or in multiple concurrent operations.
	 *
	 * Returns: a #GCancellable.
	 *
	 * Throws: ConstructionException GTK+ fails to create the object.
	 */
	public this()
	{
		auto p = g_cancellable_new();

		if(p is null)
		{
			throw new ConstructionException("null returned by new");
		}

		this(cast(GCancellable*) p, true);
	}

	/**
	 * Gets the top cancellable from the stack.
	 *
	 * Returns: a #GCancellable from the top
	 *     of the stack, or %NULL if the stack is empty.
	 */
	public static Cancellable getCurrent()
	{
		auto p = g_cancellable_get_current();

		if(p is null)
		{
			return null;
		}

		return ObjectG.getDObject!(Cancellable)(cast(GCancellable*) p);
	}

	/**
	 * Will set @cancellable to cancelled, and will emit the
	 * #GCancellable::cancelled signal. (However, see the warning about
	 * race conditions in the documentation for that signal if you are
	 * planning to connect to it.)
	 *
	 * This function is thread-safe. In other words, you can safely call
	 * it from a thread other than the one running the operation that was
	 * passed the @cancellable.
	 *
	 * If @cancellable is %NULL, this function returns immediately for convenience.
	 *
	 * The convention within GIO is that cancelling an asynchronous
	 * operation causes it to complete asynchronously. That is, if you
	 * cancel the operation from the same thread in which it is running,
	 * then the operation's #GAsyncReadyCallback will not be invoked until
	 * the application returns to the main loop.
	 */
	public void cancel()
	{
		g_cancellable_cancel(gCancellable);
	}

	/**
	 * Convenience function to connect to the #GCancellable::cancelled
	 * signal. Also handles the race condition that may happen
	 * if the cancellable is cancelled right before connecting.
	 *
	 * @callback is called at most once, either directly at the
	 * time of the connect if @cancellable is already cancelled,
	 * or when @cancellable is cancelled in some thread.
	 *
	 * @data_destroy_func will be called when the handler is
	 * disconnected, or immediately if the cancellable is already
	 * cancelled.
	 *
	 * See #GCancellable::cancelled for details on how to use this.
	 *
	 * Since GLib 2.40, the lock protecting @cancellable is not held when
	 * @callback is invoked.  This lifts a restriction in place for
	 * earlier GLib versions which now makes it easier to write cleanup
	 * code that unconditionally invokes e.g. g_cancellable_cancel().
	 *
	 * Params:
	 *     callback = The #GCallback to connect.
	 *     data = Data to pass to @callback.
	 *     dataDestroyFunc = Free function for @data or %NULL.
	 *
	 * Returns: The id of the signal handler or 0 if @cancellable has already
	 *     been cancelled.
	 *
	 * Since: 2.22
	 */
	public gulong connect(GCallback callback, void* data, GDestroyNotify dataDestroyFunc)
	{
		return g_cancellable_connect(gCancellable, callback, data, dataDestroyFunc);
	}

	/**
	 * Disconnects a handler from a cancellable instance similar to
	 * g_signal_handler_disconnect().  Additionally, in the event that a
	 * signal handler is currently running, this call will block until the
	 * handler has finished.  Calling this function from a
	 * #GCancellable::cancelled signal handler will therefore result in a
	 * deadlock.
	 *
	 * This avoids a race condition where a thread cancels at the
	 * same time as the cancellable operation is finished and the
	 * signal handler is removed. See #GCancellable::cancelled for
	 * details on how to use this.
	 *
	 * If @cancellable is %NULL or @handler_id is %0 this function does
	 * nothing.
	 *
	 * Params:
	 *     handlerId = Handler id of the handler to be disconnected, or %0.
	 *
	 * Since: 2.22
	 */
	public void disconnect(gulong handlerId)
	{
		g_cancellable_disconnect(gCancellable, handlerId);
	}

	/**
	 * Gets the file descriptor for a cancellable job. This can be used to
	 * implement cancellable operations on Unix systems. The returned fd will
	 * turn readable when @cancellable is cancelled.
	 *
	 * You are not supposed to read from the fd yourself, just check for
	 * readable status. Reading to unset the readable status is done
	 * with g_cancellable_reset().
	 *
	 * After a successful return from this function, you should use
	 * g_cancellable_release_fd() to free up resources allocated for
	 * the returned file descriptor.
	 *
	 * See also g_cancellable_make_pollfd().
	 *
	 * Returns: A valid file descriptor. %-1 if the file descriptor
	 *     is not supported, or on errors.
	 */
	public int getFd()
	{
		return g_cancellable_get_fd(gCancellable);
	}

	/**
	 * Checks if a cancellable job has been cancelled.
	 *
	 * Returns: %TRUE if @cancellable is cancelled,
	 *     FALSE if called with %NULL or if item is not cancelled.
	 */
	public bool isCancelled()
	{
		return g_cancellable_is_cancelled(gCancellable) != 0;
	}

	/**
	 * Creates a #GPollFD corresponding to @cancellable; this can be passed
	 * to g_poll() and used to poll for cancellation. This is useful both
	 * for unix systems without a native poll and for portability to
	 * windows.
	 *
	 * When this function returns %TRUE, you should use
	 * g_cancellable_release_fd() to free up resources allocated for the
	 * @pollfd. After a %FALSE return, do not call g_cancellable_release_fd().
	 *
	 * If this function returns %FALSE, either no @cancellable was given or
	 * resource limits prevent this function from allocating the necessary
	 * structures for polling. (On Linux, you will likely have reached
	 * the maximum number of file descriptors.) The suggested way to handle
	 * these cases is to ignore the @cancellable.
	 *
	 * You are not supposed to read from the fd yourself, just check for
	 * readable status. Reading to unset the readable status is done
	 * with g_cancellable_reset().
	 *
	 * Params:
	 *     pollfd = a pointer to a #GPollFD
	 *
	 * Returns: %TRUE if @pollfd was successfully initialized, %FALSE on
	 *     failure to prepare the cancellable.
	 *
	 * Since: 2.22
	 */
	public bool makePollfd(GPollFD* pollfd)
	{
		return g_cancellable_make_pollfd(gCancellable, pollfd) != 0;
	}

	/**
	 * Pops @cancellable off the cancellable stack (verifying that @cancellable
	 * is on the top of the stack).
	 */
	public void popCurrent()
	{
		g_cancellable_pop_current(gCancellable);
	}

	/**
	 * Pushes @cancellable onto the cancellable stack. The current
	 * cancellable can then be received using g_cancellable_get_current().
	 *
	 * This is useful when implementing cancellable operations in
	 * code that does not allow you to pass down the cancellable object.
	 *
	 * This is typically called automatically by e.g. #GFile operations,
	 * so you rarely have to call this yourself.
	 */
	public void pushCurrent()
	{
		g_cancellable_push_current(gCancellable);
	}

	/**
	 * Releases a resources previously allocated by g_cancellable_get_fd()
	 * or g_cancellable_make_pollfd().
	 *
	 * For compatibility reasons with older releases, calling this function
	 * is not strictly required, the resources will be automatically freed
	 * when the @cancellable is finalized. However, the @cancellable will
	 * block scarce file descriptors until it is finalized if this function
	 * is not called. This can cause the application to run out of file
	 * descriptors when many #GCancellables are used at the same time.
	 *
	 * Since: 2.22
	 */
	public void releaseFd()
	{
		g_cancellable_release_fd(gCancellable);
	}

	/**
	 * Resets @cancellable to its uncancelled state.
	 *
	 * If cancellable is currently in use by any cancellable operation
	 * then the behavior of this function is undefined.
	 *
	 * Note that it is generally not a good idea to reuse an existing
	 * cancellable for more operations after it has been cancelled once,
	 * as this function might tempt you to do. The recommended practice
	 * is to drop the reference to a cancellable after cancelling it,
	 * and let it die with the outstanding async operations. You should
	 * create a fresh cancellable for further async operations.
	 */
	public void reset()
	{
		g_cancellable_reset(gCancellable);
	}

	/**
	 * If the @cancellable is cancelled, sets the error to notify
	 * that the operation was cancelled.
	 *
	 * Returns: %TRUE if @cancellable was cancelled, %FALSE if it was not
	 *
	 * Throws: GException on failure.
	 */
	public bool setErrorIfCancelled()
	{
		GError* err = null;

		auto p = g_cancellable_set_error_if_cancelled(gCancellable, &err) != 0;

		if (err !is null)
		{
			throw new GException( new ErrorG(err) );
		}

		return p;
	}

	/**
	 * Creates a source that triggers if @cancellable is cancelled and
	 * calls its callback of type #GCancellableSourceFunc. This is
	 * primarily useful for attaching to another (non-cancellable) source
	 * with g_source_add_child_source() to add cancellability to it.
	 *
	 * For convenience, you can call this with a %NULL #GCancellable,
	 * in which case the source will never trigger.
	 *
	 * The new #GSource will hold a reference to the #GCancellable.
	 *
	 * Returns: the new #GSource.
	 *
	 * Since: 2.28
	 */
	public Source sourceNew()
	{
		auto p = g_cancellable_source_new(gCancellable);

		if(p is null)
		{
			return null;
		}

		return new Source(cast(GSource*) p, true);
	}

	protected class OnCancelledDelegateWrapper
	{
		static OnCancelledDelegateWrapper[] listeners;
		void delegate(Cancellable) dlg;
		gulong handlerId;

		this(void delegate(Cancellable) dlg)
		{
			this.dlg = dlg;
			this.listeners ~= this;
		}

		void remove(OnCancelledDelegateWrapper source)
		{
			foreach(index, wrapper; listeners)
			{
				if (wrapper.handlerId == source.handlerId)
				{
					listeners[index] = null;
					listeners = std.algorithm.remove(listeners, index);
					break;
				}
			}
		}
	}

	/**
	 * Emitted when the operation has been cancelled.
	 *
	 * Can be used by implementations of cancellable operations. If the
	 * operation is cancelled from another thread, the signal will be
	 * emitted in the thread that cancelled the operation, not the
	 * thread that is running the operation.
	 *
	 * Note that disconnecting from this signal (or any signal) in a
	 * multi-threaded program is prone to race conditions. For instance
	 * it is possible that a signal handler may be invoked even after
	 * a call to g_signal_handler_disconnect() for that handler has
	 * already returned.
	 *
	 * There is also a problem when cancellation happens right before
	 * connecting to the signal. If this happens the signal will
	 * unexpectedly not be emitted, and checking before connecting to
	 * the signal leaves a race condition where this is still happening.
	 *
	 * In order to make it safe and easy to connect handlers there
	 * are two helper functions: g_cancellable_connect() and
	 * g_cancellable_disconnect() which protect against problems
	 * like this.
	 *
	 * An example of how to us this:
	 * |[<!-- language="C" -->
	 * // Make sure we don't do unnecessary work if already cancelled
	 * if (g_cancellable_set_error_if_cancelled (cancellable, error))
	 * return;
	 *
	 * // Set up all the data needed to be able to handle cancellation
	 * // of the operation
	 * my_data = my_data_new (...);
	 *
	 * id = 0;
	 * if (cancellable)
	 * id = g_cancellable_connect (cancellable,
	 * G_CALLBACK (cancelled_handler)
	 * data, NULL);
	 *
	 * // cancellable operation here...
	 *
	 * g_cancellable_disconnect (cancellable, id);
	 *
	 * // cancelled_handler is never called after this, it is now safe
	 * // to free the data
	 * my_data_free (my_data);
	 * ]|
	 *
	 * Note that the cancelled signal is emitted in the thread that
	 * the user cancelled from, which may be the main thread. So, the
	 * cancellable signal should not do something that can block.
	 */
	gulong addOnCancelled(void delegate(Cancellable) dlg, ConnectFlags connectFlags=cast(ConnectFlags)0)
	{
		auto wrapper = new OnCancelledDelegateWrapper(dlg);
		wrapper.handlerId = Signals.connectData(
			this,
			"cancelled",
			cast(GCallback)&callBackCancelled,
			cast(void*)wrapper,
			cast(GClosureNotify)&callBackCancelledDestroy,
			connectFlags);
		return wrapper.handlerId;
	}

	extern(C) static void callBackCancelled(GCancellable* cancellableStruct, OnCancelledDelegateWrapper wrapper)
	{
		wrapper.dlg(wrapper.outer);
	}

	extern(C) static void callBackCancelledDestroy(OnCancelledDelegateWrapper wrapper, GClosure* closure)
	{
		wrapper.remove(wrapper);
	}
}