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package io.lettuce.core.internal;

import java.util.IdentityHashMap;
import java.util.Map;

/**
 * Miscellaneous class utility methods. Mainly for internal use within the framework.
 *
 * @author Mark Paluch
 * @since 4.2
 */
public class LettuceClassUtils {

    /** The CGLIB class separator character "$$" */
    public static final String CGLIB_CLASS_SEPARATOR = "$$";

    /**
     * Map with primitive wrapper type as key and corresponding primitive type as value, for example: Integer.class ->
     * int.class.
     */
    private static final Map, Class> primitiveWrapperTypeMap = new IdentityHashMap, Class>(9);

    /**
     * Map with primitive type as key and corresponding wrapper type as value, for example: int.class -> Integer.class.
     */
    private static final Map, Class> primitiveTypeToWrapperMap = new IdentityHashMap, Class>(9);

    static {
        primitiveWrapperTypeMap.put(Boolean.class, boolean.class);
        primitiveWrapperTypeMap.put(Byte.class, byte.class);
        primitiveWrapperTypeMap.put(Character.class, char.class);
        primitiveWrapperTypeMap.put(Double.class, double.class);
        primitiveWrapperTypeMap.put(Float.class, float.class);
        primitiveWrapperTypeMap.put(Integer.class, int.class);
        primitiveWrapperTypeMap.put(Long.class, long.class);
        primitiveWrapperTypeMap.put(Short.class, short.class);
        primitiveWrapperTypeMap.put(Void.class, void.class);
    }

    /**
     * Determine whether the {@link Class} identified by the supplied name is present and can be loaded. Will return
     * {@code false} if either the class or one of its dependencies is not present or cannot be loaded.
     *
     * @param className the name of the class to check
     * @return whether the specified class is present
     */
    public static boolean isPresent(String className) {
        try {
            forName(className);
            return true;
        } catch (Throwable ex) {
            // Class or one of its dependencies is not present...
            return false;
        }
    }

    /**
     * Loads a class using the {@link #getDefaultClassLoader()}.
     *
     * @param className
     * @return
     */
    public static Class findClass(String className) {
        try {
            return forName(className, getDefaultClassLoader());
        } catch (ClassNotFoundException e) {
            return null;
        }
    }

    /**
     * Loads a class using the {@link #getDefaultClassLoader()}.
     *
     * @param className
     * @return
     * @throws ClassNotFoundException
     */
    public static Class forName(String className) throws ClassNotFoundException {
        return forName(className, getDefaultClassLoader());
    }

    private static Class forName(String className, ClassLoader classLoader) throws ClassNotFoundException {
        try {
            return classLoader.loadClass(className);
        } catch (ClassNotFoundException ex) {
            int lastDotIndex = className.lastIndexOf('.');
            if (lastDotIndex != -1) {
                String innerClassName = className.substring(0, lastDotIndex) + '$' + className.substring(lastDotIndex + 1);
                try {
                    return classLoader.loadClass(innerClassName);
                } catch (ClassNotFoundException ex2) {
                    // swallow - let original exception get through
                }
            }
            throw ex;
        }
    }

    /**
     * Return the default ClassLoader to use: typically the thread context ClassLoader, if available; the ClassLoader that
     * loaded the ClassUtils class will be used as fallback.
     *
     * @return the default ClassLoader (never null)
     * @see java.lang.Thread#getContextClassLoader()
     */
    private static ClassLoader getDefaultClassLoader() {
        ClassLoader cl = null;
        try {
            cl = Thread.currentThread().getContextClassLoader();
        } catch (Throwable ex) {
            // Cannot access thread context ClassLoader - falling back to system class loader...
        }
        if (cl == null) {
            // No thread context class loader -> use class loader of this class.
            cl = LettuceClassUtils.class.getClassLoader();
        }
        return cl;
    }

    /**
     * Check if the right-hand side type may be assigned to the left-hand side type, assuming setting by reflection. Considers
     * primitive wrapper classes as assignable to the corresponding primitive types.
     *
     * @param lhsType the target type
     * @param rhsType the value type that should be assigned to the target type
     * @return if the target type is assignable from the value type
     */
    public static boolean isAssignable(Class lhsType, Class rhsType) {

        LettuceAssert.notNull(lhsType, "Left-hand side type must not be null");
        LettuceAssert.notNull(rhsType, "Right-hand side type must not be null");

        if (lhsType.isAssignableFrom(rhsType)) {
            return true;
        }

        if (lhsType.isPrimitive()) {
            Class resolvedPrimitive = primitiveWrapperTypeMap.get(rhsType);
            if (lhsType == resolvedPrimitive) {
                return true;
            }
        } else {
            Class resolvedWrapper = primitiveTypeToWrapperMap.get(rhsType);
            if (resolvedWrapper != null && lhsType.isAssignableFrom(resolvedWrapper)) {
                return true;
            }
        }
        return false;
    }

}