8 files changed, 607 insertions, 0 deletions
diff --git a/api/logic/resources/Resource.cpp b/api/logic/resources/Resource.cpp
new file mode 100644
index 00000000..e95675d7
--- /dev/null
+++ b/api/logic/resources/Resource.cpp
@@ -0,0 +1,155 @@
+#include "Resource.h"
+
+#include <QDebug>
+
+#include "ResourceObserver.h"
+#include "ResourceHandler.h"
+
+// definition of static members of Resource
+QMap<QString, std::function<std::shared_ptr<ResourceHandler>(const QString &)>> Resource::m_handlers;
+QMap<QPair<int, int>, std::function<QVariant(QVariant)>> Resource::m_transfomers;
+QMap<QString, std::weak_ptr<Resource>> Resource::m_resources;
+
+struct NullResourceResult {};
+Q_DECLARE_METATYPE(NullResourceResult)
+class NullResourceHandler : public ResourceHandler
+{
+public:
+	explicit NullResourceHandler()
+	{
+		setResult(QVariant::fromValue<NullResourceResult>(NullResourceResult()));
+	}
+};
+
+Resource::Resource(const QString &resource)
+	: m_resource(resource)
+{
+	if (!resource.isEmpty())
+	{
+		// a valid resource identifier has the format <id>:<data>
+		Q_ASSERT(resource.contains(':'));
+		// "parse" the resource identifier into id and data
+		const QString resourceId = resource.left(resource.indexOf(':'));
+		const QString resourceData = resource.mid(resource.indexOf(':') + 1);
+
+		// create and set up the handler
+		Q_ASSERT(m_handlers.contains(resourceId));
+		m_handler = m_handlers.value(resourceId)(resourceData);
+	}
+	else
+	{
+		m_handler = std::make_shared<NullResourceHandler>();
+	}
+
+	Q_ASSERT(m_handler);
+	m_handler->init(m_handler);
+	m_handler->setResource(this);
+}
+Resource::~Resource()
+{
+	qDeleteAll(m_observers);
+}
+
+Resource::Ptr Resource::create(const QString &resource, Ptr placeholder)
+{
+	const QString storageId = storageIdentifier(resource, placeholder);
+
+	// do we already have a resource? even if m_resources contains it it might not be valid any longer (weak_ptr)
+	Resource::Ptr ptr = m_resources.contains(storageId)
+			? m_resources.value(storageId).lock()
+			: nullptr;
+	// did we have one? and is it still valid?
+	if (!ptr)
+	{
+		/* We don't want Resource to have a public constructor, but std::make_shared needs it,
+		 * so we create a subclass of Resource here that exposes the constructor as public.
+		 * The alternative would be making the allocator for std::make_shared a friend, but it
+		 * differs between different STL implementations, so that would be a pain.
+		 */
+		struct ConstructableResource : public Resource
+		{
+			explicit ConstructableResource(const QString &resource)
+				: Resource(resource) {}
+		};
+		ptr = std::make_shared<ConstructableResource>(resource);
+		ptr->m_placeholder = placeholder;
+		m_resources.insert(storageId, ptr);
+	}
+	return ptr;
+}
+
+Resource::Ptr Resource::applyTo(ResourceObserver *observer)
+{
+	m_observers.append(observer);
+	observer->setSource(shared_from_this()); // give the observer a shared_ptr for us so we don't get deleted
+	observer->resourceUpdated(); // ask the observer to poll us immediently, we might already have data
+	return shared_from_this(); // allow chaining
+}
+Resource::Ptr Resource::applyTo(QObject *target, const char *property)
+{
+	// the cast to ResourceObserver* is required to ensure the right overload gets choosen,
+	// since QObjectResourceObserver also inherits from QObject
+	return applyTo(static_cast<ResourceObserver *>(new QObjectResourceObserver(target, property)));
+}
+
+QVariant Resource::getResourceInternal(const int typeId) const
+{
+	// no result (yet), but a placeholder? delegate to the placeholder.
+	if (m_handler->result().isNull() && m_placeholder)
+	{
+		return m_placeholder->getResourceInternal(typeId);
+	}
+	const QVariant variant = m_handler->result();
+	const auto typePair = qMakePair(int(variant.type()), typeId);
+
+	// do we have an explicit transformer? use it.
+	if (m_transfomers.contains(typePair))
+	{
+		return m_transfomers.value(typePair)(variant);
+	}
+	else
+	{
+		// we do not have an explicit transformer, so we just pass the QVariant, which will automatically
+		// transform some types for us (different numbers to each other etc.)
+		return variant;
+	}
+}
+
+void Resource::reportResult()
+{
+	for (ResourceObserver *observer : m_observers)
+	{
+		observer->resourceUpdated();
+	}
+}
+void Resource::reportFailure(const QString &reason)
+{
+	for (ResourceObserver *observer : m_observers)
+	{
+		observer->setFailure(reason);
+	}
+}
+void Resource::reportProgress(const int progress)
+{
+	for (ResourceObserver *observer : m_observers)
+	{
+		observer->setProgress(progress);
+	}
+}
+
+void Resource::notifyObserverDeleted(ResourceObserver *observer)
+{
+	m_observers.removeAll(observer);
+}
+
+QString Resource::storageIdentifier(const QString &id, Resource::Ptr placeholder)
+{
+	if (placeholder)
+	{
+		return id + '#' + storageIdentifier(placeholder->m_resource, placeholder->m_placeholder);
+	}
+	else
+	{
+		return id;
+	}
+}
diff --git a/api/logic/resources/Resource.h b/api/logic/resources/Resource.h
new file mode 100644
index 00000000..63e97b88
--- /dev/null
+++ b/api/logic/resources/Resource.h
@@ -0,0 +1,132 @@
+#pragma once
+
+#include <QString>
+#include <QMap>
+#include <QVariant>
+#include <functional>
+#include <memory>
+
+#include "ResourceObserver.h"
+#include "TypeMagic.h"
+
+#include "multimc_logic_export.h"
+
+class ResourceHandler;
+
+/** Frontend class for resources
+ *
+ * Usage:
+ *	Resource::create("icon:noaccount")->applyTo(accountsAction);
+ *	Resource::create("web:http://asdf.com/image.png")->applyTo(imageLbl)->placeholder(Resource::create("icon:loading"));
+ *
+ * Memory management:
+ *	Resource caches ResourcePtrs using weak pointers, so while a resource is still existing
+ *	when a new resource is created the resources will be the same (including the same handler).
+ *
+ *	ResourceObservers keep a shared pointer to the resource, as does the Resource itself to it's
+ *	placeholder (if present). This means a resource stays valid while it's still used ("applied to" etc.)
+ *	by something. When nothing uses it anymore it gets deleted.
+ *
+ *	@note Always pass resource around using Resource::Ptr! Copy and move constructors are disabled for a reason.
+ */
+class MULTIMC_LOGIC_EXPORT Resource : public std::enable_shared_from_this<Resource>
+{
+	// only allow creation from Resource::create and disallow passing around non-pointers
+	explicit Resource(const QString &resource);
+	Resource(const Resource &) = delete;
+	Resource(Resource &&) = delete;
+public:
+	using Ptr = std::shared_ptr<Resource>;
+
+	~Resource();
+
+	/// The returned pointer needs to be stored until either Resource::applyTo or Resource::then is called, or it is passed as
+	/// a placeholder to Resource::create itself.
+	static Ptr create(const QString &resource, Ptr placeholder = nullptr);
+
+	/// Use these functions to specify what should happen when e.g. the resource changes
+	Ptr applyTo(ResourceObserver *observer);
+	Ptr applyTo(QObject *target, const char *property = nullptr);
+	template<typename Func>
+	Ptr then(Func &&func)
+	{
+		// Arg will be the functions argument with references and cv-qualifiers (const, volatile) removed
+		using Arg = TypeMagic::CleanType<typename TypeMagic::Function<Func>::Argument>;
+		// Ret will be the functions return type
+		using Ret = typename TypeMagic::Function<Func>::ReturnType;
+
+		// FunctionResourceObserver<ReturnType, ArgumentType, FunctionSignature>
+		return applyTo(new FunctionResourceObserver<Ret, Arg, Func>(std::forward<Func>(func)));
+	}
+
+	/// Retrieve the currently active resource. If it's type is different from T a conversion will be attempted.
+	template<typename T>
+	T getResource() const { return getResourceInternal(qMetaTypeId<T>()).template value<T>(); }
+
+	/// @internal Used by ResourceObserver and ResourceProxyModel
+	QVariant getResourceInternal(const int typeId) const;
+
+	/** Register a new ResourceHandler. T needs to inherit from ResourceHandler
+	 * Usage: Resource::registerHandler<MyResourceHandler>("myid");
+	 */
+	template<typename T>
+	static void registerHandler(const QString &id)
+	{
+		m_handlers.insert(id, [](const QString &res) { return std::make_shared<T>(res); });
+	}
+	/** Register a new resource transformer
+	 * Resource transformers are functions that are responsible for converting between different types,
+	 * for example converting from a QByteArray to a QPixmap. They are registered "externally" because not
+	 * all types might be available in this library, for example gui types like QPixmap.
+	 *
+	 * Usage: Resource::registerTransformer([](const InputType &type) { return OutputType(type); });
+	 *   This assumes that OutputType has a constructor that takes InputType as an argument. More
+	 *   complicated transformers can of course also be registered.
+	 *
+	 * When a ResourceObserver requests a type that's different from the actual resource type, a matching
+	 * transformer will be looked up from the list of transformers.
+	 * @note Only one-stage transforms will be performed (you can't registerTransformers for QString => int
+	 *       and int => float and expect QString to automatically be transformed into a float.
+	 */
+	template<typename Func>
+	static void registerTransformer(Func &&func)
+	{
+		using Out = typename TypeMagic::Function<Func>::ReturnType;
+		using In = TypeMagic::CleanType<typename TypeMagic::Function<Func>::Argument>;
+		static_assert(!std::is_same<Out, In>::value, "It does not make sense to transform a value to itself");
+		m_transfomers.insert(qMakePair(qMetaTypeId<In>(), qMetaTypeId<Out>()), [func](const QVariant &in)
+		{
+			return QVariant::fromValue<Out>(func(in.value<In>()));
+		});
+	}
+
+private: // half private, implementation details
+	friend class ResourceHandler;
+	// the following three functions are called by ResourceHandlers
+	/** Notifies the observers. They will call Resource::getResourceInternal which will call ResourceHandler::result
+	 * or delegate to it's placeholder.
+	 */
+	void reportResult();
+	void reportFailure(const QString &reason);
+	void reportProgress(const int progress);
+
+	friend class ResourceObserver;
+	/// Removes observer from the list of observers so that we don't attempt to notify something that doesn't exist
+	void notifyObserverDeleted(ResourceObserver *observer);
+
+private: // truly private
+	QList<ResourceObserver *> m_observers;
+	std::shared_ptr<ResourceHandler> m_handler = nullptr;
+	Ptr m_placeholder = nullptr;
+	const QString m_resource;
+
+	static QString storageIdentifier(const QString &id, Ptr placeholder = nullptr);
+	QString storageIdentifier() const;
+
+	// a list of resource handler factories, registered using registerHandler
+	static QMap<QString, std::function<std::shared_ptr<ResourceHandler>(const QString &)>> m_handlers;
+	// a list of resource transformers, registered using registerTransformer
+	static QMap<QPair<int, int>, std::function<QVariant(QVariant)>> m_transfomers;
+	// a list of resources so that we can reuse them
+	static QMap<QString, std::weak_ptr<Resource>> m_resources;
+};
diff --git a/api/logic/resources/ResourceHandler.cpp b/api/logic/resources/ResourceHandler.cpp
new file mode 100644
index 00000000..46a4422c
--- /dev/null
+++ b/api/logic/resources/ResourceHandler.cpp
@@ -0,0 +1,28 @@
+#include "ResourceHandler.h"
+
+#include "Resource.h"
+
+void ResourceHandler::setResult(const QVariant &result)
+{
+	m_result = result;
+	if (m_resource)
+	{
+		m_resource->reportResult();
+	}
+}
+
+void ResourceHandler::setFailure(const QString &reason)
+{
+	if (m_resource)
+	{
+		m_resource->reportFailure(reason);
+	}
+}
+
+void ResourceHandler::setProgress(const int progress)
+{
+	if (m_resource)
+	{
+		m_resource->reportProgress(progress);
+	}
+}
diff --git a/api/logic/resources/ResourceHandler.h b/api/logic/resources/ResourceHandler.h
new file mode 100644
index 00000000..f09d8904
--- /dev/null
+++ b/api/logic/resources/ResourceHandler.h
@@ -0,0 +1,36 @@
+#pragma once
+
+#include <QVariant>
+#include <memory>
+
+#include "multimc_logic_export.h"
+
+class Resource;
+
+/** Base class for things that can retrieve a resource.
+ *
+ * Subclass, provide a constructor that takes a single QString as argument, and
+ * call Resource::registerHandler<MyResourceHandler>("<id>"), where <id> is the
+ * prefix of the resource ("web", "icon", etc.)
+ */
+class MULTIMC_LOGIC_EXPORT ResourceHandler
+{
+public:
+	virtual ~ResourceHandler() {}
+
+	void setResource(Resource *resource) { m_resource = resource; }
+	/// reimplement this if you need to do something after you have been put in a shared pointer
+	// we do this instead of inheriting from std::enable_shared_from_this
+	virtual void init(std::shared_ptr<ResourceHandler>&) {}
+
+	QVariant result() const { return m_result; }
+
+protected: // use these methods to notify the resource of changes
+	void setResult(const QVariant &result);
+	void setFailure(const QString &reason);
+	void setProgress(const int progress);
+
+private:
+	QVariant m_result;
+	Resource *m_resource = nullptr;
+};
diff --git a/api/logic/resources/ResourceObserver.cpp b/api/logic/resources/ResourceObserver.cpp
new file mode 100644
index 00000000..4f168fd2
--- /dev/null
+++ b/api/logic/resources/ResourceObserver.cpp
@@ -0,0 +1,55 @@
+#include "ResourceObserver.h"
+
+#include <QDebug>
+
+#include "Resource.h"
+
+static const char *defaultPropertyForTarget(QObject *target)
+{
+	if (target->inherits("QLabel"))
+	{
+		return "pixmap";
+	}
+	else if (target->inherits("QAction") ||
+			 target->inherits("QMenu") ||
+			 target->inherits("QAbstractButton"))
+	{
+		return "icon";
+	}
+	// for unit tests
+	else if (target->inherits("DummyObserverObject"))
+	{
+		return "property";
+	}
+	else
+	{
+		Q_ASSERT_X(false, "ResourceObserver.cpp: defaultPropertyForTarget", "Unrecognized QObject subclass");
+		return nullptr;
+	}
+}
+
+QObjectResourceObserver::QObjectResourceObserver(QObject *target, const char *property)
+	: QObject(target), m_target(target)
+{
+	const QMetaObject *mo = m_target->metaObject();
+	m_property = mo->property(mo->indexOfProperty(
+								  property ?
+									  property
+									: defaultPropertyForTarget(target)));
+}
+void QObjectResourceObserver::resourceUpdated()
+{
+	m_property.write(m_target, getInternal(m_property.type()));
+}
+
+
+ResourceObserver::~ResourceObserver()
+{
+	m_resource->notifyObserverDeleted(this);
+}
+
+QVariant ResourceObserver::getInternal(const int typeId) const
+{
+	Q_ASSERT(m_resource);
+	return m_resource->getResourceInternal(typeId);
+}
diff --git a/api/logic/resources/ResourceObserver.h b/api/logic/resources/ResourceObserver.h
new file mode 100644
index 00000000..c42e41ba
--- /dev/null
+++ b/api/logic/resources/ResourceObserver.h
@@ -0,0 +1,73 @@
+#pragma once
+
+#include <memory>
+#include <functional>
+
+#include <QObject>
+#include <QMetaProperty>
+#include "multimc_logic_export.h"
+
+class QVariant;
+class Resource;
+
+/// Base class for things that can use a resource
+class MULTIMC_LOGIC_EXPORT ResourceObserver
+{
+public:
+	virtual ~ResourceObserver();
+
+protected: // these methods are called by the Resource when something changes
+	virtual void resourceUpdated() = 0;
+	virtual void setFailure(const QString &) {}
+	virtual void setProgress(const int) {}
+
+private:
+	friend class Resource;
+	void setSource(std::shared_ptr<Resource> resource) { m_resource = resource; }
+
+protected:
+	template<typename T>
+	T get() const { return getInternal(qMetaTypeId<T>()).template value<T>(); }
+	QVariant getInternal(const int typeId) const;
+
+private:
+	std::shared_ptr<Resource> m_resource;
+};
+
+/** Observer for QObject properties
+ *
+ * Give it a target and the name of a property, and that property will be set when the resource changes.
+ *
+ * If no name is given an attempt to find a default property for some common classes is done.
+ */
+class MULTIMC_LOGIC_EXPORT QObjectResourceObserver : public QObject, public ResourceObserver
+{
+public:
+	explicit QObjectResourceObserver(QObject *target, const char *property = nullptr);
+
+	void resourceUpdated() override;
+
+private:
+	QObject *m_target;
+	QMetaProperty m_property;
+};
+
+/** Observer for functions, lambdas etc.
+ * Template arguments:
+ *   * We need Ret and Arg in order to create the std::function
+ *   * We need Func in order to std::forward the function
+ */
+template <typename Ret, typename Arg, typename Func>
+class FunctionResourceObserver : public ResourceObserver
+{
+	std::function<Ret(Arg)> m_function;
+public:
+	template <typename T>
+	explicit FunctionResourceObserver(T &&func)
+		: m_function(std::forward<Func>(func)) {}
+
+	void resourceUpdated() override
+	{
+		m_function(get<Arg>());
+	}
+};
diff --git a/api/logic/resources/ResourceProxyModel.cpp b/api/logic/resources/ResourceProxyModel.cpp
new file mode 100644
index 00000000..f026d9a9
--- /dev/null
+++ b/api/logic/resources/ResourceProxyModel.cpp
@@ -0,0 +1,89 @@
+#include "ResourceProxyModel.h"
+
+#include <QItemSelectionRange>
+
+#include "Resource.h"
+#include "ResourceObserver.h"
+
+class ModelResourceObserver : public ResourceObserver
+{
+public:
+	explicit ModelResourceObserver(const QModelIndex &index, const int role)
+		: m_index(index), m_role(role)
+	{
+		qRegisterMetaType<QVector<int>>("QVector<int>");
+	}
+
+	void resourceUpdated() override
+	{
+		if (m_index.isValid())
+		{
+			// the resource changed, pretend to be the model and notify the views of the update. they will re-poll the model which will return the new resource value
+			QMetaObject::invokeMethod(const_cast<QAbstractItemModel *>(m_index.model()),
+									  "dataChanged", Qt::QueuedConnection,
+									  Q_ARG(QModelIndex, m_index), Q_ARG(QModelIndex, m_index), Q_ARG(QVector<int>, QVector<int>() << m_role));
+		}
+	}
+
+private:
+	QPersistentModelIndex m_index;
+	int m_role;
+};
+
+ResourceProxyModel::ResourceProxyModel(const int resultTypeId, QObject *parent)
+	: QIdentityProxyModel(parent), m_resultTypeId(resultTypeId)
+{
+}
+
+QVariant ResourceProxyModel::data(const QModelIndex &proxyIndex, int role) const
+{
+	const QModelIndex mapped = mapToSource(proxyIndex);
+	// valid cell that's a Qt::DecorationRole and that contains a non-empty string
+	if (mapped.isValid() && role == Qt::DecorationRole && !mapToSource(proxyIndex).data(role).toString().isEmpty())
+	{
+		// do we already have a resource for this index?
+		if (!m_resources.contains(mapped))
+		{
+			Resource::Ptr placeholder;
+			const QVariant placeholderIdentifier = mapped.data(PlaceholderRole);
+			if (!placeholderIdentifier.isNull() && placeholderIdentifier.type() == QVariant::String)
+			{
+				placeholder = Resource::create(placeholderIdentifier.toString());
+			}
+
+			// create the Resource and apply the observer for models
+			Resource::Ptr res = Resource::create(mapToSource(proxyIndex).data(role).toString(), placeholder)
+					->applyTo(new ModelResourceObserver(proxyIndex, role));
+
+			m_resources.insert(mapped, res);
+		}
+
+		return m_resources.value(mapped)->getResourceInternal(m_resultTypeId);
+	}
+	// otherwise fall back to the source model
+	return mapped.data(role);
+}
+
+void ResourceProxyModel::setSourceModel(QAbstractItemModel *model)
+{
+	if (sourceModel())
+	{
+		disconnect(sourceModel(), 0, this, 0);
+	}
+	if (model)
+	{
+		connect(model, &QAbstractItemModel::dataChanged, this, [this](const QModelIndex &tl, const QModelIndex &br, const QVector<int> &roles)
+		{
+			// invalidate resources so that they will be re-created
+			if (roles.contains(Qt::DecorationRole) || roles.contains(PlaceholderRole) || roles.isEmpty())
+			{
+				const QItemSelectionRange range(tl, br);
+				for (const QModelIndex &index : range.indexes())
+				{
+					m_resources.remove(index);
+				}
+			}
+		});
+	}
+	QIdentityProxyModel::setSourceModel(model);
+}
diff --git a/api/logic/resources/ResourceProxyModel.h b/api/logic/resources/ResourceProxyModel.h
new file mode 100644
index 00000000..98a3dbd1
--- /dev/null
+++ b/api/logic/resources/ResourceProxyModel.h
@@ -0,0 +1,39 @@
+#pragma once
+
+#include <QIdentityProxyModel>
+#include <memory>
+
+#include "multimc_logic_export.h"
+
+/// Convenience proxy model that transforms resource identifiers (strings) for Qt::DecorationRole into other types.
+class MULTIMC_LOGIC_EXPORT ResourceProxyModel : public QIdentityProxyModel
+{
+	Q_OBJECT
+public:
+	// resultTypeId is found using qMetaTypeId<T>()
+	explicit ResourceProxyModel(const int resultTypeId, QObject *parent = nullptr);
+
+	enum
+	{
+		// provide this role from your model if you want to show a placeholder
+		PlaceholderRole = Qt::UserRole + 0xabc // some random offset to not collide with other stuff
+	};
+
+	QVariant data(const QModelIndex &proxyIndex, int role) const override;
+	void setSourceModel(QAbstractItemModel *model) override;
+
+	/// Helper function, usage: m_view->setModel(ResourceProxyModel::mixin<QIcon>(m_model));
+	template <typename T>
+	static QAbstractItemModel *mixin(QAbstractItemModel *model)
+	{
+		ResourceProxyModel *proxy = new ResourceProxyModel(qMetaTypeId<T>(), model);
+		proxy->setSourceModel(model);
+		return proxy;
+	}
+
+private:
+	// mutable because it needs to be available from the const data()
+	mutable QMap<QPersistentModelIndex, std::shared_ptr<class Resource>> m_resources;
+
+	const int m_resultTypeId;
+};