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// DynamicItemSource.cs
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// Christopher James Halse Rogers <raof@ubuntu.com>
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// Copyright © 2011 Christopher James Halse Rogers <raof@ubuntu.com>
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// This library is free software; you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as
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// published by the Free Software Foundation; either version 2.1 of the
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// License, or (at your option) any later version.
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// This library is distributed in the hope that it will be useful, but
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// WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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// Lesser General Public License for more details.
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// You should have received a copy of the GNU Lesser General Public
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// License along with this library; if not, write to the Free Software
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// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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using System.Collections.Generic;
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public class ItemsAvailableEventArgs : EventArgs
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public IEnumerable<Item> newItems;
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public class ItemsUnavailableEventArgs : EventArgs
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public IEnumerable<Item> unavailableItems;
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/// An item source with items which may appear or disappear at any time.
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/// Unlike the standard ItemSource, this does not get periodically polled.
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public abstract class DynamicItemSource : Item, IChildItemSource
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private object event_lock = new object ();
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private bool available_connected = false;
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private bool unavailable_connected = false;
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/// This function is called when a listener has connected to the ItemsAvailable and ItemsUnavailable event.
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/// The <typeparamref>DynamicItemSource</typeparamref> MUST NOT raise either event until this has been
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protected abstract void Enable ();
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/// This function is called when a listener has disconnected to the ItemsAvailable and ItemsUnavailable event.
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/// The <typeparamref>DynamicItemSource</typeparamref> MUST NOT raise either event after this has been
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/// called until a subsequente Enable () call is made.
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protected abstract void Disable ();
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protected bool Connected {
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get { return available_connected && unavailable_connected; }
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private EventHandler<ItemsAvailableEventArgs> itemsAvailable;
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/// The <typeparamref>DynamicItemSource</typeparamref> raises this event when
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/// new Items are available and should be added to the Universe.
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public event EventHandler<ItemsAvailableEventArgs> ItemsAvailable {
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if (available_connected) {
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throw new InvalidOperationException ("Attempt to subscribe to ItemsAvailable while a subscriber already exists");
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itemsAvailable += value;
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available_connected = true;
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if (!available_connected) {
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itemsAvailable -= value;
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available_connected = false;
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protected void RaiseItemsAvailable (ItemsAvailableEventArgs args)
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EventHandler<ItemsAvailableEventArgs> handler;
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// FIXME: This should really be a Log message rather than an exception
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throw new InvalidOperationException ("Attempted to raise ItemsAvailable without a subscriber connected.");
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handler = itemsAvailable;
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handler (this, args);
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private EventHandler<ItemsUnavailableEventArgs> itemsUnavailable;
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/// The <typeparamref>DynamicItemSource</typeparamref> raises this event when
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/// one or more items are no longer available and should be removed from the
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public event EventHandler<ItemsUnavailableEventArgs> ItemsUnavailable {
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if (unavailable_connected) {
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throw new InvalidOperationException ("Attempt to subscribe to ItemsUnavailable while a subscriber already exists");
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itemsUnavailable += value;
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unavailable_connected = true;
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if (!unavailable_connected) {
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itemsUnavailable -= value;
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unavailable_connected = false;
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protected void RaiseItemsUnavailable (ItemsUnavailableEventArgs args)
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EventHandler<ItemsUnavailableEventArgs> handler;
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// FIXME: This should really be a Log message rather than an exception
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throw new InvalidOperationException ("Attempted to raise ItemsUnavailable without a subscriber connected.");
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handler = itemsUnavailable;
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handler (this, args);
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/// Item sub-types provided/supported by this source. These include any
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/// types of items provided through ItemsAvailable, and the types of items
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/// that this source will provide children for. Please provide types as
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/// close as possible in ancestry to the static types of items this source
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/// provides/supports (e.g. FirefoxBookmarkItem instead of Item or
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public abstract IEnumerable<Type> SupportedItemTypes { get; }
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/// Provides a collection of children of an item. Item is guaranteed to be a
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/// subtype of a type in SupportedItemTypes.
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/// An empty enumerable is ok---it signifies that no children are provided for
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/// the Item argument.
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public virtual IEnumerable<Item> ChildrenOfItem (Item item)
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Do.Universe/src/Do.Universe/DynamicItemSource.cs
