content: package com.comphenix.tinyprotocol;
  
  import java.lang.reflect.Constructor;
  import java.lang.reflect.Field;
  import java.lang.reflect.Method;
  import java.lang.reflect.ParameterizedType;
  import java.lang.reflect.Type;
  import java.util.Arrays;
  import java.util.regex.Matcher;
  import java.util.regex.Pattern;
  
  import org.bukkit.Bukkit;
  
  /**
   * An utility class that simplifies reflection in Bukkit plugins.
   * 
   * @author Kristian
   */
  public final class Reflection {
  	/**
  	 * An interface for invoking a specific constructor.
  	 */
  	public interface ConstructorInvoker {
  		/**
  		 * Invoke a constructor for a specific class.
  		 * 
  		 * @param arguments - the arguments to pass to the constructor.
  		 * @return The constructed object.
  		 */
  		public Object invoke(Object... arguments);
  	}
  
  	/**
  	 * An interface for invoking a specific method.
  	 */
  	public interface MethodInvoker {
  		/**
  		 * Invoke a method on a specific target object.
  		 * 
  		 * @param target - the target object, or NULL for a static method.
  		 * @param arguments - the arguments to pass to the method.
  		 * @return The return value, or NULL if is void.
  		 */
  		public Object invoke(Object target, Object... arguments);
  	}
  
  	/**
  	 * An interface for retrieving the field content.
  	 * 
  	 * @param <T> - field type.
  	 */
  	public interface FieldAccessor<T> {
  		/**
  		 * Retrieve the content of a field.
  		 * 
  		 * @param target - the target object, or NULL for a static field.
  		 * @return The value of the field.
  		 */
  		public T get(Object target);
  
  		/**
  		 * Set the content of a field.
  		 * 
  		 * @param target - the target object, or NULL for a static field.
  		 * @param value - the new value of the field.
  		 */
  		public void set(Object target, Object value);
  
  		/**
  		 * Determine if the given object has this field.
  		 * 
  		 * @param target - the object to test.
  		 * @return TRUE if it does, FALSE otherwise.
  		 */
  		public boolean hasField(Object target);
  	}
  
  	// Deduce the net.minecraft.server.v* package
  	private static String OBC_PREFIX = Bukkit.getServer().getClass().getPackage().getName();
  	private static String NMS_PREFIX = OBC_PREFIX.replace("org.bukkit.craftbukkit", "net.minecraft.server");
  	private static String VERSION = OBC_PREFIX.replace("org.bukkit.craftbukkit", "").replace(".", "");
  
  	// Variable replacement
  	private static Pattern MATCH_VARIABLE = Pattern.compile("\\{([^\\}]+)\\}");
  
  	private Reflection() {
  		// Seal class
  	}
  
  	/**
  	 * Retrieve a field accessor for a specific field type and name.
  	 * 
  	 * @param target - the target type.
  	 * @param name - the name of the field, or NULL to ignore.
  	 * @param fieldType - a compatible field type.
  	 * @return The field accessor.
  	 */
  	public static <T> FieldAccessor<T> getField(Class<?> target, String name, Class<T> fieldType) {
  		return getField(target, name, fieldType, 0);
  	}
  
  	/**
  	 * Retrieve a field accessor for a specific field type and name.
  	 * 
  	 * @param className - lookup name of the class, see {@link #getClass(String)}.
  	 * @param name - the name of the field, or NULL to ignore.
  	 * @param fieldType - a compatible field type.
  	 * @return The field accessor.
  	 */
  	public static <T> FieldAccessor<T> getField(String className, String name, Class<T> fieldType) {
  		return getField(getClass(className), name, fieldType, 0);
  	}
  
  	/**
  	 * Retrieve a field accessor for a specific field type and name.
  	 * 
  	 * @param target - the target type.
  	 * @param fieldType - a compatible field type.
  	 * @param index - the number of compatible fields to skip.
  	 * @return The field accessor.
  	 */
  	public static <T> FieldAccessor<T> getField(Class<?> target, Class<T> fieldType, int index) {
  		return getField(target, null, fieldType, index);
  	}
  
  	/**
  	 * Retrieve a field accessor for a specific field type and name.
  	 * 
  	 * @param className - lookup name of the class, see {@link #getClass(String)}.
  	 * @param fieldType - a compatible field type.
  	 * @param index - the number of compatible fields to skip.
  	 * @return The field accessor.
  	 */
  	public static <T> FieldAccessor<T> getField(String className, Class<T> fieldType, int index) {
  		return getField(getClass(className), fieldType, index);
  	}
  
  	// Common method
  	private static <T> FieldAccessor<T> getField(Class<?> target, String name, Class<T> fieldType, int index) {
  		for (final Field field : target.getDeclaredFields()) {
  			if ((name == null || field.getName().equals(name)) && fieldType.isAssignableFrom(field.getType()) && index-- <= 0) {
  				field.setAccessible(true);
  
  				// A function for retrieving a specific field value
  				return new FieldAccessor<T>() {
  
  					@Override
  					@SuppressWarnings("unchecked")
  					public T get(Object target) {
  						try {
  							return (T) field.get(target);
  						} catch (IllegalAccessException e) {
  							throw new RuntimeException("Cannot access reflection.", e);
  						}
  					}
  
  					@Override
  					public void set(Object target, Object value) {
  						try {
  							field.set(target, value);
  						} catch (IllegalAccessException e) {
  							throw new RuntimeException("Cannot access reflection.", e);
  						}
  					}
  
  					@Override
  					public boolean hasField(Object target) {
  						// target instanceof DeclaringClass
  						return field.getDeclaringClass().isAssignableFrom(target.getClass());
  					}
  				};
  			}
  		}
  
  		// Search in parent classes
  		if (target.getSuperclass() != null)
  			return getField(target.getSuperclass(), name, fieldType, index);
  
  		throw new IllegalArgumentException("Cannot find field with type " + fieldType);
  	}
  
  	/**
  	 * Retrieves a field with a given type and parameters. This is most useful
  	 * when dealing with Collections.
  	 *
  	 * @param target the target class.
  	 * @param fieldType Type of the field
  	 * @param params Variable length array of type parameters
  	 * @return The field
  	 *
  	 * @throws IllegalArgumentException If the field cannot be found
  	 */
  	public static Field getParameterizedField(Class<?> target, Class<?> fieldType, Class<?>... params) {
  		for (Field field : target.getDeclaredFields()) {
  			if (field.getType().equals(fieldType)) {
  				Type type = field.getGenericType();
  				if (type instanceof ParameterizedType) {
  					if (Arrays.equals(((ParameterizedType) type).getActualTypeArguments(), params))
  						return field;
  				}
  			}
  		}
  
  		throw new IllegalArgumentException("Unable to find a field with type " + fieldType + " and params " + Arrays.toString(params));
  	}
  
  	/**
  	 * Search for the first publicly and privately defined method of the given name and parameter count.
  	 * 
  	 * @param className - lookup name of the class, see {@link #getClass(String)}.
  	 * @param methodName - the method name, or NULL to skip.
  	 * @param params - the expected parameters.
  	 * @return An object that invokes this specific method.
  	 * @throws IllegalStateException If we cannot find this method.
  	 */
  	public static MethodInvoker getMethod(String className, String methodName, Class<?>... params) {
  		return getTypedMethod(getClass(className), methodName, null, params);
  	}
  
  	/**
  	 * Search for the first publicly and privately defined method of the given name and parameter count.
  	 * 
  	 * @param clazz - a class to start with.
  	 * @param methodName - the method name, or NULL to skip.
  	 * @param params - the expected parameters.
  	 * @return An object that invokes this specific method.
  	 * @throws IllegalStateException If we cannot find this method.
  	 */
  	public static MethodInvoker getMethod(Class<?> clazz, String methodName, Class<?>... params) {
  		return getTypedMethod(clazz, methodName, null, params);
  	}
  
  	/**
  	 * Search for the first publicly and privately defined method of the given name and parameter count.
  	 * 
  	 * @param clazz - a class to start with.
  	 * @param methodName - the method name, or NULL to skip.
  	 * @param returnType - the expected return type, or NULL to ignore.
  	 * @param params - the expected parameters.
  	 * @return An object that invokes this specific method.
  	 * @throws IllegalStateException If we cannot find this method.
  	 */
  	public static MethodInvoker getTypedMethod(Class<?> clazz, String methodName, Class<?> returnType, Class<?>... params) {
  		for (final Method method : clazz.getDeclaredMethods()) {
  			if ((methodName == null || method.getName().equals(methodName))
  					&& (returnType == null || method.getReturnType().equals(returnType))
  					&& Arrays.equals(method.getParameterTypes(), params)) {
  				method.setAccessible(true);
  
  				return new MethodInvoker() {
  
  					@Override
  					public Object invoke(Object target, Object... arguments) {
  						try {
  							return method.invoke(target, arguments);
  						} catch (Exception e) {
  							throw new RuntimeException("Cannot invoke method " + method, e);
  						}
  					}
  
  				};
  			}
  		}
  
  		// Search in every superclass
  		if (clazz.getSuperclass() != null)
  			return getMethod(clazz.getSuperclass(), methodName, params);
  
  		throw new IllegalStateException(String.format("Unable to find method %s (%s).", methodName, Arrays.asList(params)));
  	}
  
  	/**
  	 * Search for the first publically and privately defined constructor of the given name and parameter count.
  	 * 
  	 * @param className - lookup name of the class, see {@link #getClass(String)}.
  	 * @param params - the expected parameters.
  	 * @return An object that invokes this constructor.
  	 * @throws IllegalStateException If we cannot find this method.
  	 */
  	public static ConstructorInvoker getConstructor(String className, Class<?>... params) {
  		return getConstructor(getClass(className), params);
  	}
  
  	/**
  	 * Search for the first publically and privately defined constructor of the given name and parameter count.
  	 * 
  	 * @param clazz - a class to start with.
  	 * @param params - the expected parameters.
  	 * @return An object that invokes this constructor.
  	 * @throws IllegalStateException If we cannot find this method.
  	 */
  	public static ConstructorInvoker getConstructor(Class<?> clazz, Class<?>... params) {
  		for (final Constructor<?> constructor : clazz.getDeclaredConstructors()) {
  			if (Arrays.equals(constructor.getParameterTypes(), params)) {
  				constructor.setAccessible(true);
  
  				return new ConstructorInvoker() {
  
  					@Override
  					public Object invoke(Object... arguments) {
  						try {
  							return constructor.newInstance(arguments);
  						} catch (Exception e) {
  							throw new RuntimeException("Cannot invoke constructor " + constructor, e);
  						}
  					}
  
  				};
  			}
  		}
  
  		throw new IllegalStateException(String.format("Unable to find constructor for %s (%s).", clazz, Arrays.asList(params)));
  	}
  
  	/**
  	 * Retrieve a class from its full name, without knowing its type on compile time.
  	 * <p>
  	 * This is useful when looking up fields by a NMS or OBC type.
  	 * <p>
  	 * 
  	 * @see {@link #getClass()} for more information.
  	 * @param lookupName - the class name with variables.
  	 * @return The class.
  	 */
  	public static Class<Object> getUntypedClass(String lookupName) {
  		@SuppressWarnings({ "rawtypes", "unchecked" })
  		Class<Object> clazz = (Class) getClass(lookupName);
  		return clazz;
  	}
  
  	/**
  	 * Retrieve a class from its full name with alternatives, without knowing its type on compile time.
  	 * <p>
  	 * This is useful when looking up fields by a NMS or OBC type.
  	 * <p>
  	 * 
  	 * @see {@link #getClass()} for more information.
  	 * @param lookupName - the class name with variables.
  	 * @param aliases - alternative names for this class.
  	 * @return The class.
  	 */
  	public static Class<Object> getUntypedClass(String lookupName, String... aliases) {
  		@SuppressWarnings({ "rawtypes", "unchecked" })
  		Class<Object> clazz = (Class) getClass(lookupName, aliases);
  		return clazz;
  	}
  
  	/**
  	 * Retrieve a class from its full name.
  	 * <p>
  	 * Strings enclosed with curly brackets - such as {TEXT} - will be replaced according to the following table:
  	 * <p>
  	 * <table border="1">
  	 * <tr>
  	 * <th>Variable</th>
  	 * <th>Content</th>
  	 * </tr>
  	 * <tr>
  	 * <td>{nms}</td>
  	 * <td>Actual package name of net.minecraft.server.VERSION</td>
  	 * </tr>
  	 * <tr>
  	 * <td>{obc}</td>
  	 * <td>Actual pacakge name of org.bukkit.craftbukkit.VERSION</td>
  	 * </tr>
  	 * <tr>
  	 * <td>{version}</td>
  	 * <td>The current Minecraft package VERSION, if any.</td>
  	 * </tr>
  	 * </table>
  	 * 
  	 * @param lookupName - the class name with variables.
  	 * @return The looked up class.
  	 * @throws IllegalArgumentException If a variable or class could not be found.
  	 */
  	public static Class<?> getClass(String lookupName) {
  		return getCanonicalClass(expandVariables(lookupName));
  	}
  
  	/**
  	 * Retrieve the first class that matches the full class name.
  	 * <p>
  	 * Strings enclosed with curly brackets - such as {TEXT} - will be replaced according to the following table:
  	 * <p>
  	 * <table border="1">
  	 * <tr>
  	 * <th>Variable</th>
  	 * <th>Content</th>
  	 * </tr>
  	 * <tr>
  	 * <td>{nms}</td>
  	 * <td>Actual package name of net.minecraft.server.VERSION</td>
  	 * </tr>
  	 * <tr>
  	 * <td>{obc}</td>
  	 * <td>Actual pacakge name of org.bukkit.craftbukkit.VERSION</td>
  	 * </tr>
  	 * <tr>
  	 * <td>{version}</td>
  	 * <td>The current Minecraft package VERSION, if any.</td>
  	 * </tr>
  	 * </table>
  	 * 
  	 * @param lookupName - the class name with variables.
  	 * @param aliases - alternative names for this class.
  	 * @return Class object.
  	 * @throws RuntimeException If we are unable to find any of the given classes.
  	 */
  	public static Class<?> getClass(String lookupName, String... aliases) {
  		try {
  			// Try the main class first
  			return getClass(lookupName);
  		} catch (RuntimeException e) {
  			Class<?> success = null;
  
  			// Try every alias too
  			for (String alias : aliases) {
  				try {
  					success = getClass(alias);
  					break;
  				} catch (RuntimeException e1) {
  					// e1.printStackTrace();
  				}
  			}
  
  			if (success != null) {
  				return success;
  			} else {
  				// Hack failed
  				throw new RuntimeException(String.format("Unable to find %s (%s)", lookupName, String.join(",", aliases)));
  			}
  		}
  	}
  
  	/**
  	 * Retrieve a class in the net.minecraft.server.VERSION.* package.
  	 * 
  	 * @param name - the name of the class, excluding the package.
  	 * @throws IllegalArgumentException If the class doesn't exist.
  	 */
  	public static Class<?> getMinecraftClass(String name) {
  		return getCanonicalClass(NMS_PREFIX + "." + name);
  	}
  
  	/**
  	 * Retrieve a class in the org.bukkit.craftbukkit.VERSION.* package.
  	 * 
  	 * @param name - the name of the class, excluding the package.
  	 * @throws IllegalArgumentException If the class doesn't exist.
  	 */
  	public static Class<?> getCraftBukkitClass(String name) {
  		return getCanonicalClass(OBC_PREFIX + "." + name);
  	}
  
  	/**
  	 * Retrieve a class by its canonical name.
  	 * 
  	 * @param canonicalName - the canonical name.
  	 * @return The class.
  	 */
  	private static Class<?> getCanonicalClass(String canonicalName) {
  		try {
  			return Class.forName(canonicalName);
  		} catch (ClassNotFoundException e) {
  			throw new IllegalArgumentException("Cannot find " + canonicalName, e);
  		}
  	}
  
  	/**
  	 * Expand variables such as "{nms}" and "{obc}" to their corresponding packages.
  	 * 
  	 * @param name - the full name of the class.
  	 * @return The expanded string.
  	 */
  	private static String expandVariables(String name) {
  		StringBuffer output = new StringBuffer();
  		Matcher matcher = MATCH_VARIABLE.matcher(name);
  
  		while (matcher.find()) {
  			String variable = matcher.group(1);
  			String replacement = "";
  
  			// Expand all detected variables
  			if ("nms".equalsIgnoreCase(variable))
  				replacement = NMS_PREFIX;
  			else if ("obc".equalsIgnoreCase(variable))
  				replacement = OBC_PREFIX;
  			else if ("version".equalsIgnoreCase(variable))
  				replacement = VERSION;
  			else
  				throw new IllegalArgumentException("Unknown variable: " + variable);
  
  			// Assume the expanded variables are all packages, and append a dot
  			if (replacement.length() > 0 && matcher.end() < name.length() && name.charAt(matcher.end()) != '.')
  				replacement += ".";
  			matcher.appendReplacement(output, Matcher.quoteReplacement(replacement));
  		}
  
  		matcher.appendTail(output);
  		return output.toString();
  	}
  }
  