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//
// ExtensionChain.cs
//
// Author:
// Lluis Sanchez Gual <lluis@xamarin.com>
//
// Copyright (c) 2014 Xamarin, Inc (http://www.xamarin.com)
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
using System;
using System.Collections.Generic;
using System.Linq;
namespace MonoDevelop.Projects
{
/// <summary>
/// A collection of extension objects
/// </summary>
public class ExtensionChain
{
Dictionary<Type,ChainedExtensionSentinel> chains = new Dictionary<Type, ChainedExtensionSentinel> ();
// Maybe an array is not the best solution here, given chains grow and decrease, a list might be better.
ChainedExtension [] extensions;
ChainedExtension defaultInsertBefore;
BatchModifier batchModifier;
public static ExtensionChain Create<T> (T[] extensions) where T:ChainedExtension
{
var c = new ExtensionChain ();
for (int n = extensions.Length - 2; n >= 0; n--)
extensions [n].InitChain (c, extensions [n + 1]);
c.extensions = extensions;
return c;
}
public T GetExtension<T> () where T:ChainedExtension, new()
{
if (!chains.TryGetValue (typeof(T), out ChainedExtensionSentinel e)) {
e = new ChainedExtensionSentinel (new T());
e.Update (this, typeof (T), -1);
chains [typeof(T)] = e;
}
return (T)e.Extension;
}
public void SetDefaultInsertionPosition (ChainedExtension insertBefore)
{
defaultInsertBefore = insertBefore;
}
public IEnumerable<ChainedExtension> GetAllExtensions ()
{
return extensions;
}
public IDisposable BatchModify () => batchModifier = new BatchModifier (this);
public void AddExtension (ChainedExtension ext, ChainedExtension insertAfter = null, ChainedExtension insertBefore = null)
{
int index = -1;
if (insertBefore != null) {
index = Array.IndexOf (extensions, insertBefore);
} else if (insertAfter != null) {
index = Array.IndexOf (extensions, insertAfter);
if (index != -1)
index++;
} else if (defaultInsertBefore != null) {
index = Array.IndexOf (extensions, defaultInsertBefore);
}
if (index == -1) {
index = extensions.Length;
}
Array.Resize (ref extensions, extensions.Length + 1);
for (int n = extensions.Length - 1; n > index; n--)
extensions [n] = extensions [n - 1];
extensions [index] = ext;
Rechain (index);
}
public void RemoveExtension (ChainedExtension ext)
{
if (extensions == null)
return;
int index = extensions.Length;
extensions = extensions.Where ((e, eindex) => {
bool shouldRemove = e == ext;
if (shouldRemove)
index = eindex;
return !shouldRemove;
}).ToArray ();
Rechain (index);
}
void Rechain (int firstChangeIndex)
{
// If we are in a batch update, only update where to start rechaining.
if (batchModifier != null) {
batchModifier.UpdateFirstIndex (firstChangeIndex);
return;
}
// Re-chain every extension
for (int n = extensions.Length - 2; n >= 0; n--)
extensions [n].InitChain (this, extensions [n + 1]);
// The first extension object in type-specific chains is a placeholder extension used only to hold
// a reference to the real first extension.
foreach (var kvp in chains) {
ChainedExtensionSentinel fex = kvp.Value;
fex.Update (this, kvp.Key, firstChangeIndex);
}
}
public void Dispose ()
{
var first = extensions [0];
extensions = null;
first.DisposeChain ();
foreach (var kvp in chains) {
// Dispose the placeholder extension just in case the extension itself registers something
// in InitializeChain that it cleans up in Dispose.
var extension = kvp.Value;
extension.Dispose ();
}
}
class ChainedExtensionSentinel
{
public ChainedExtension Extension { get; }
int extensionIndex = -1;
public ChainedExtensionSentinel (ChainedExtension extension)
{
Extension = extension;
}
public void Update (ExtensionChain chain, Type type, int firstChainChangeIndex)
{
// We only want to update an extension if we insert somewhere before the extension we found.
if (extensionIndex < firstChainChangeIndex)
return;
// Maybe it would be useful to skip extensions until min(indices), as they've already been scanned
// in a previous check
var impl = ChainedExtension.FindNextImplementation (type, chain.extensions[0], out extensionIndex);
Extension.InitChain (chain, impl);
}
public void Dispose () => Extension.Dispose ();
}
class BatchModifier : IDisposable
{
readonly ExtensionChain chain;
int minChangedIndex;
public BatchModifier (ExtensionChain chain)
{
this.chain = chain;
minChangedIndex = chain.extensions.Length;
}
public void UpdateFirstIndex (int firstChainChangeIndex)
{
// If we added a node at firstChainChangeIndex then removed that one
// it might help not to rechain in that case and reset the index.
// Maybe we can keep track of that and handle it.
// Regardless, the code is simpler this way and it should not be a bottleneck
minChangedIndex = Math.Min (firstChainChangeIndex, minChangedIndex);
}
public void Dispose ()
{
chain.batchModifier = null;
chain.Rechain (minChangedIndex);
}
}
}
}
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