From 3722a239bf1502606a3ef4f025021f23ac3fcb88 Mon Sep 17 00:00:00 2001
From: Mattes D <github@xoft.cz>
Date: Wed, 23 Jan 2019 20:54:29 +0100
Subject: BlockTypeRegistry: Initial skeleton

---
 src/BlockTypeRegistry.h | 158 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 158 insertions(+)
 create mode 100644 src/BlockTypeRegistry.h

(limited to 'src/BlockTypeRegistry.h')

diff --git a/src/BlockTypeRegistry.h b/src/BlockTypeRegistry.h
new file mode 100644
index 000000000..6a24445c5
--- /dev/null
+++ b/src/BlockTypeRegistry.h
@@ -0,0 +1,158 @@
+#pragma once
+
+
+
+
+
+#include <map>
+
+
+
+
+
+// fwd:
+class BlockState;
+
+
+
+
+
+/** Complete information about a single block type.
+The BlockTypeRegistry uses this structure to store the registered information. */
+class BlockInfo
+{
+public:
+
+	/** Callback is used to query block hints dynamically, based on the current BlockState.
+	Useful for example for redstone lamps that can be turned on or off. */
+	using HintCallback = std::function<AString(const AString & aTypeName, const BlockState & aBlockState)>;
+
+
+	/** Creates a new instance with the specified BlockTypeName and handler / hints / callbacks.
+	aPluginName specifies the name of the plugin to associate with the block type (to allow unload / reload). */
+	BlockInfo(
+		const AString & aPluginName,
+		const AString & aBlockTypeName,
+		std::shared_ptr<cBlockHandler> aHandler,
+		const std::map<AString, AString> & aHints = std::map<AString, AString>(),
+		const std::map<AString, HintCallback> & aHintCallbacks = std::map<AString, HintCallback>()
+	);
+
+
+	/** Retrieves the value associated with the specified hint for this specific BlockTypeName and BlockState.
+	Queries callbacks first, then hints if a callback doesn't exist.
+	Returns an empty string if hint not found at all. */
+	AString hintValue(
+		const AString & aHintName,
+		const BlockState & aBlockState
+	);
+
+	// Simple getters:
+	const AString & pluginName() const { return mPluginName; }
+	const AString & blockTypeName() const { return mBlockTypeName; }
+	std::shared_ptr<cBlockHandler> handler() const { return mHandler; }
+
+
+private:
+
+	/** The name of the plugin that registered the block. */
+	AString mPluginName;
+
+	/** The name of the block type, such as "minecraft:redstone_lamp" */
+	AString mBlockTypeName;
+
+	/** The callbacks to call for various interaction. */
+	std::shared_ptr<cBlockHandler> mHandler;
+
+	/** Optional hints for any subsystem to use, such as "IsSnowable" -> "1". */
+	std::map<AString, AString> mHints;
+
+	/** The callbacks for dynamic evaluation of hints, such as "LightValue" -> function(BlockTypeName, BlockState). */
+	std::map<AString, HintCallback> mHintCallbacks;
+};
+
+
+
+
+
+/** Stores information on all known block types.
+Can dynamically add and remove block types.
+Block types are identified using BlockTypeName.
+Supports unregistering and re-registering the same type by the same plugin.
+Stores the name of the plugin that registered the type, for better plugin error messages ("already registered in X")
+and so that we can unload and reload plugins. */
+class BlockTypeRegistry
+{
+public:
+	// fwd:
+	class AlreadyRegisteredException;
+
+
+	/** Creates an empty new instance of the block type registry */
+	BlockTypeRegistry() = default;
+
+	/** Registers the specified block type.
+	If the block type already exists and the plugin is the same, updates the registration.
+	If the block type already exists and the plugin is different, throws an AlreadyRegisteredException. */
+	void registerBlockType(
+		const AString & aPluginName,
+		const AString & aBlockTypeName,
+		std::shared_ptr<cBlockHandler> aHandler,
+		const std::map<AString, AString> & aHints = std::map<AString, AString>(),
+		const std::map<AString, BlockInfo::HintCallback> & aHintCallbacks = std::map<AString, BlockInfo::HintCallback>()
+	);
+
+	/** Returns the registration information for the specified BlockTypeName.
+	Returns nullptr if BlockTypeName not found. */
+	std::shared_ptr<BlockInfo> blockInfo(const AString & aBlockTypeName);
+
+	/** Removes all registrations done by the specified plugin. */
+	void removeAllByPlugin(const AString & aPluginName);
+
+
+private:
+
+	/** The actual block type registry.
+	Maps the BlockTypeName to the BlockInfo instance. */
+	std::map<AString, std::shared_ptr<BlockInfo>> mRegistry;
+
+	/** The CS that protects mRegistry against multithreaded access. */
+	cCriticalSection mCSRegistry;
+};
+
+
+
+
+
+/** The exception thrown from BlockTypeRegistry::registerBlockType() if the same block type is being registered from a different plugin. */
+class BlockTypeRegistry::AlreadyRegisteredException: public std::runtime_error
+{
+	using Super = std::runtime_error;
+
+public:
+
+	/** Creates a new instance of the exception that provides info on both the original registration and the newly attempted
+	registration that caused the failure. */
+	AlreadyRegisteredException(
+		std::shared_ptr<BlockInfo> aPreviousRegistration,
+		std::shared_ptr<BlockInfo> aNewRegistration
+	);
+
+	// Simple getters:
+	std::shared_ptr<BlockInfo> previousRegistration() const { return mPreviousRegistration; }
+	std::shared_ptr<BlockInfo> newRegistration()      const { return mNewRegistration; }
+
+
+private:
+
+	std::shared_ptr<BlockInfo> mPreviousRegistration;
+	std::shared_ptr<BlockInfo> mNewRegistration;
+
+
+	/** Returns the general exception message formatted by the two registrations.
+	The output is used when logging. */
+	static AString message(
+		std::shared_ptr<BlockInfo> aPreviousRegistration,
+		std::shared_ptr<BlockInfo> aNewRegistration
+	);
+};
-- 
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