/*
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.gbif.ws.util.spring;

import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.Arrays;
import java.util.LinkedList;
import java.util.List;

/**
 * Simple utility class for working with the reflection API and handling
 * reflection exceptions.
 * <p>Only intended for internal use.
 *
 * @author Juergen Hoeller
 * @author Rob Harrop
 * @author Rod Johnson
 * @author Costin Leau
 * @author Sam Brannen
 * @since 1.2.2
 */
public abstract class ReflectionUtils {

  /**
   * Attempt to find a {@link Field field} on the supplied {@link Class} with
   * the supplied <code>name</code> and {@link Class type}. Searches all
   * superclasses up to {@link Object}.
   *
   * @param clazz the class to introspect
   * @param name  the name of the field
   * @param type  the type of the field
   *
   * @return the corresponding Field object, or <code>null</code> if not found
   *
   * @throws IllegalArgumentException if the class or field type is
   *                                  <code>null</code> or if the field name is <em>empty</em>
   */
  public static Field findField(final Class clazz, final String name, final Class type) {
    Assert.notNull(clazz, "The 'class to introspect' supplied to findField() can not be null.");
    Assert.hasText(name, "The field name supplied to findField() can not be empty.");
    Assert.notNull(type, "The field type supplied to findField() can not be null.");
    Class searchType = clazz;
    while (!Object.class.equals(searchType) && searchType != null) {
      final Field[] fields = searchType.getDeclaredFields();
      for (int i = 0; i < fields.length; i++) {
        Field field = fields[i];
        if (name.equals(field.getName()) && type.equals(field.getType())) {
          return field;
        }
      }
      searchType = searchType.getSuperclass();
    }
    return null;
  }

  /**
   * Set the field represented by the supplied {@link Field field object} on
   * the specified {@link Object target object} to the specified
   * <code>value</code>. In accordance with
   * {@link Field#set(Object, Object)} semantics, the new value is
   * automatically unwrapped if the underlying field has a primitive type.
   * <p>Thrown exceptions are handled via a call to
   * {@link #handleReflectionException(Exception)}.
   *
   * @param field  the field to set
   * @param target the target object on which to set the field
   * @param value  the value to set; may be <code>null</code>
   */
  public static void setField(Field field, Object target, Object value) {
    try {
      field.set(target, value);
    } catch (IllegalAccessException ex) {
      handleReflectionException(ex);
      throw new IllegalStateException(
          "Unexpected reflection exception - " + ex.getClass().getName() + ": " + ex.getMessage());
    }
  }

  /**
   * Attempt to find a {@link Method} on the supplied class with the supplied name
   * and no parameters. Searches all superclasses up to <code>Object</code>.
   * <p>Returns <code>null</code> if no {@link Method} can be found.
   *
   * @param clazz the class to introspect
   * @param name  the name of the method
   *
   * @return the Method object, or <code>null</code> if none found
   */
  public static Method findMethod(Class clazz, String name) {
    return findMethod(clazz, name, new Class[0]);
  }

  /**
   * Attempt to find a {@link Method} on the supplied class with the supplied name
   * and parameter types. Searches all superclasses up to <code>Object</code>.
   * <p>Returns <code>null</code> if no {@link Method} can be found.
   *
   * @param clazz      the class to introspect
   * @param name       the name of the method
   * @param paramTypes the parameter types of the method
   *
   * @return the Method object, or <code>null</code> if none found
   */
  public static Method findMethod(Class clazz, String name, Class[] paramTypes) {
    Assert.notNull(clazz, "Class must not be null");
    Assert.notNull(name, "Method name must not be null");
    Class searchType = clazz;
    while (!Object.class.equals(searchType) && searchType != null) {
      Method[] methods =
          (searchType.isInterface() ? searchType.getMethods() : searchType.getDeclaredMethods());
      for (int i = 0; i < methods.length; i++) {
        Method method = methods[i];
        if (name.equals(method.getName())
            && Arrays.equals(paramTypes, method.getParameterTypes())) {
          return method;
        }
      }
      searchType = searchType.getSuperclass();
    }
    return null;
  }

  /**
   * Invoke the specified {@link Method} against the supplied target object
   * with no arguments. The target object can be <code>null</code> when
   * invoking a static {@link Method}.
   * <p>Thrown exceptions are handled via a call to {@link #handleReflectionException}.
   *
   * @param method the method to invoke
   * @param target the target object to invoke the method on
   *
   * @return the invocation result, if any
   *
   * @see #invokeMethod(java.lang.reflect.Method, Object, Object[])
   */
  public static Object invokeMethod(Method method, Object target) {
    return invokeMethod(method, target, null);
  }

  /**
   * Invoke the specified {@link Method} against the supplied target object
   * with the supplied arguments. The target object can be <code>null</code>
   * when invoking a static {@link Method}.
   * <p>Thrown exceptions are handled via a call to {@link #handleReflectionException}.
   *
   * @param method the method to invoke
   * @param target the target object to invoke the method on
   * @param args   the invocation arguments (may be <code>null</code>)
   *
   * @return the invocation result, if any
   *
   * @see #invokeMethod(java.lang.reflect.Method, Object, Object[])
   */
  public static Object invokeMethod(Method method, Object target, Object[] args) {
    try {
      return method.invoke(target, args);
    } catch (IllegalAccessException ex) {
      handleReflectionException(ex);
      throw new IllegalStateException(
          "Unexpected reflection exception - " + ex.getClass().getName() + ": " + ex.getMessage());
    } catch (InvocationTargetException ex) {
      handleReflectionException(ex);
      throw new IllegalStateException(
          "Unexpected reflection exception - " + ex.getClass().getName() + ": " + ex.getMessage());
    }
  }

  /**
   * Handle the given reflection exception. Should only be called if
   * no checked exception is expected to be thrown by the target method.
   * <p>Throws the underlying RuntimeException or Error in case of an
   * InvocationTargetException with such a root cause. Throws an
   * IllegalStateException with an appropriate message else.
   *
   * @param ex the reflection exception to handle
   */
  public static void handleReflectionException(Exception ex) {
    if (ex instanceof NoSuchMethodException) {
      throw new IllegalStateException("Method not found: " + ex.getMessage());
    }
    if (ex instanceof IllegalAccessException) {
      throw new IllegalStateException("Could not access method: " + ex.getMessage());
    }
    if (ex instanceof InvocationTargetException) {
      handleInvocationTargetException((InvocationTargetException) ex);
    }
    throw new IllegalStateException(
        "Unexpected reflection exception - " + ex.getClass().getName() + ": " + ex.getMessage());
  }

  /**
   * Handle the given invocation target exception. Should only be called if
   * no checked exception is expected to be thrown by the target method.
   * <p>Throws the underlying RuntimeException or Error in case of such
   * a root cause. Throws an IllegalStateException else.
   *
   * @param ex the invocation target exception to handle
   */
  public static void handleInvocationTargetException(InvocationTargetException ex) {
    if (ex.getTargetException() instanceof RuntimeException) {
      throw (RuntimeException) ex.getTargetException();
    }
    if (ex.getTargetException() instanceof Error) {
      throw (Error) ex.getTargetException();
    }
    throw new IllegalStateException(
        "Unexpected exception thrown by method - "
            + ex.getTargetException().getClass().getName()
            + ": "
            + ex.getTargetException().getMessage());
  }

  /**
   * Rethrow the given {@link Throwable exception}, which is presumably the
   * <em>target exception</em> of an {@link InvocationTargetException}.
   * Should only be called if no checked exception is expected to be thrown by
   * the target method.
   * <p> Rethrows the underlying exception cast to an {@link Exception} or
   * {@link Error} if appropriate; otherwise, throws an
   * {@link IllegalStateException}.
   *
   * @param ex the exception to rethrow
   *
   * @throws Exception the rethrown exception (in case of a checked exception)
   */
  public static void rethrowException(Throwable ex) throws Exception {
    if (ex instanceof Exception) {
      throw (Exception) ex;
    }
    if (ex instanceof Error) {
      throw (Error) ex;
    }
    throw new IllegalStateException(
        "Unexpected exception thrown by method - "
            + ex.getClass().getName()
            + ": "
            + ex.getMessage());
  }

  /**
   * Determine whether the given method explicitly declares the given exception
   * or one of its superclasses, which means that an exception of that type
   * can be propagated as-is within a reflective invocation.
   *
   * @param method        the declaring method
   * @param exceptionType the exception to throw
   *
   * @return <code>true</code> if the exception can be thrown as-is;
   *         <code>false</code> if it needs to be wrapped
   */
  public static boolean declaresException(Method method, Class exceptionType) {
    Assert.notNull(method, "Method must not be null");
    Class[] declaredExceptions = method.getExceptionTypes();
    for (int i = 0; i < declaredExceptions.length; i++) {
      Class declaredException = declaredExceptions[i];
      if (declaredException.isAssignableFrom(exceptionType)) {
        return true;
      }
    }
    return false;
  }

  /**
   * Determine whether the given field is a "public static final" constant.
   *
   * @param field the field to check
   */
  public static boolean isPublicStaticFinal(Field field) {
    int modifiers = field.getModifiers();
    return (Modifier.isPublic(modifiers)
        && Modifier.isStatic(modifiers)
        && Modifier.isFinal(modifiers));
  }

  /**
   * Make the given field accessible, explicitly setting it accessible if necessary.
   * The <code>setAccessible(true)</code> method is only called when actually necessary,
   * to avoid unnecessary conflicts with a JVM SecurityManager (if active).
   *
   * @param field the field to make accessible
   *
   * @see java.lang.reflect.Field#setAccessible
   */
  public static void makeAccessible(Field field) {
    if (!Modifier.isPublic(field.getModifiers())
        || !Modifier.isPublic(field.getDeclaringClass().getModifiers())) {
      field.setAccessible(true);
    }
  }

  /**
   * Make the given method accessible, explicitly setting it accessible if necessary.
   * The <code>setAccessible(true)</code> method is only called when actually necessary,
   * to avoid unnecessary conflicts with a JVM SecurityManager (if active).
   *
   * @param method the method to make accessible
   *
   * @see java.lang.reflect.Method#setAccessible
   */
  public static void makeAccessible(Method method) {
    if (!Modifier.isPublic(method.getModifiers())
        || !Modifier.isPublic(method.getDeclaringClass().getModifiers())) {
      method.setAccessible(true);
    }
  }

  /**
   * Make the given constructor accessible, explicitly setting it accessible if necessary.
   * The <code>setAccessible(true)</code> method is only called when actually necessary,
   * to avoid unnecessary conflicts with a JVM SecurityManager (if active).
   *
   * @param ctor the constructor to make accessible
   *
   * @see java.lang.reflect.Constructor#setAccessible
   */
  public static void makeAccessible(Constructor ctor) {
    if (!Modifier.isPublic(ctor.getModifiers())
        || !Modifier.isPublic(ctor.getDeclaringClass().getModifiers())) {
      ctor.setAccessible(true);
    }
  }

  /**
   * Perform the given callback operation on all matching methods of the
   * given class and superclasses.
   * <p>The same named method occurring on subclass and superclass will
   * appear twice, unless excluded by a {@link MethodFilter}.
   *
   * @param targetClass class to start looking at
   * @param mc          the callback to invoke for each method
   *
   * @see #doWithMethods(Class, MethodCallback, MethodFilter)
   */
  public static void doWithMethods(Class targetClass, MethodCallback mc)
      throws IllegalArgumentException {
    doWithMethods(targetClass, mc, null);
  }

  /**
   * Perform the given callback operation on all matching methods of the
   * given class and superclasses.
   * <p>The same named method occurring on subclass and superclass will
   * appear twice, unless excluded by the specified {@link MethodFilter}.
   *
   * @param targetClass class to start looking at
   * @param mc          the callback to invoke for each method
   * @param mf          the filter that determines the methods to apply the callback to
   */
  public static void doWithMethods(Class targetClass, MethodCallback mc, MethodFilter mf)
      throws IllegalArgumentException {

    // Keep backing up the inheritance hierarchy.
    do {
      Method[] methods = targetClass.getDeclaredMethods();
      for (int i = 0; i < methods.length; i++) {
        if (mf != null && !mf.matches(methods[i])) {
          continue;
        }
        try {
          mc.doWith(methods[i]);
        } catch (IllegalAccessException ex) {
          throw new IllegalStateException(
              "Shouldn't be illegal to access method '" + methods[i].getName() + "': " + ex);
        }
      }
      targetClass = targetClass.getSuperclass();
    } while (targetClass != null);
  }

  /**
   * Get all declared methods on the leaf class and all superclasses.
   * Leaf class methods are included first.
   */
  public static Method[] getAllDeclaredMethods(Class leafClass) throws IllegalArgumentException {
    final List list = new LinkedList();
    doWithMethods(
        leafClass,
        new MethodCallback() {
          @Override
          public void doWith(Method m) {
            list.add(m);
          }
        });
    return (Method[]) list.toArray(new Method[list.size()]);
  }

  /**
   * Invoke the given callback on all fields in the target class,
   * going up the class hierarchy to get all declared fields.
   *
   * @param targetClass the target class to analyze
   * @param fc          the callback to invoke for each field
   */
  public static void doWithFields(Class targetClass, FieldCallback fc)
      throws IllegalArgumentException {
    doWithFields(targetClass, fc, null);
  }

  /**
   * Invoke the given callback on all fields in the target class,
   * going up the class hierarchy to get all declared fields.
   *
   * @param targetClass the target class to analyze
   * @param fc          the callback to invoke for each field
   * @param ff          the filter that determines the fields to apply the callback to
   */
  public static void doWithFields(Class targetClass, FieldCallback fc, FieldFilter ff)
      throws IllegalArgumentException {

    // Keep backing up the inheritance hierarchy.
    do {
      // Copy each field declared on this class unless it's static or file.
      Field[] fields = targetClass.getDeclaredFields();
      for (int i = 0; i < fields.length; i++) {
        // Skip static and final fields.
        if (ff != null && !ff.matches(fields[i])) {
          continue;
        }
        try {
          fc.doWith(fields[i]);
        } catch (IllegalAccessException ex) {
          throw new IllegalStateException(
              "Shouldn't be illegal to access field '" + fields[i].getName() + "': " + ex);
        }
      }
      targetClass = targetClass.getSuperclass();
    } while (targetClass != null && targetClass != Object.class);
  }

  /**
   * Given the source object and the destination, which must be the same class
   * or a subclass, copy all fields, including inherited fields. Designed to
   * work on objects with public no-arg constructors.
   *
   * @throws IllegalArgumentException if the arguments are incompatible
   */
  public static void shallowCopyFieldState(final Object src, final Object dest)
      throws IllegalArgumentException {
    if (src == null) {
      throw new IllegalArgumentException("Source for field copy cannot be null");
    }
    if (dest == null) {
      throw new IllegalArgumentException("Destination for field copy cannot be null");
    }
    if (!src.getClass().isAssignableFrom(dest.getClass())) {
      throw new IllegalArgumentException(
          "Destination class ["
              + dest.getClass().getName()
              + "] must be same or subclass as source class ["
              + src.getClass().getName()
              + "]");
    }
    doWithFields(
        src.getClass(),
        new ReflectionUtils.FieldCallback() {
          @Override
          public void doWith(Field field) throws IllegalArgumentException, IllegalAccessException {
            makeAccessible(field);
            Object srcValue = field.get(src);
            field.set(dest, srcValue);
          }
        },
        ReflectionUtils.COPYABLE_FIELDS);
  }

  /**
   * Action to take on each method.
   */
  public static interface MethodCallback {

    /**
     * Perform an operation using the given method.
     *
     * @param method the method to operate on
     */
    void doWith(Method method) throws IllegalArgumentException, IllegalAccessException;
  }

  /**
   * Callback optionally used to method fields to be operated on by a method callback.
   */
  public static interface MethodFilter {

    /**
     * Determine whether the given method matches.
     *
     * @param method the method to check
     */
    boolean matches(Method method);
  }

  /**
   * Callback interface invoked on each field in the hierarchy.
   */
  public static interface FieldCallback {

    /**
     * Perform an operation using the given field.
     *
     * @param field the field to operate on
     */
    void doWith(Field field) throws IllegalArgumentException, IllegalAccessException;
  }

  /**
   * Callback optionally used to filter fields to be operated on by a field callback.
   */
  public static interface FieldFilter {

    /**
     * Determine whether the given field matches.
     *
     * @param field the field to check
     */
    boolean matches(Field field);
  }

  /**
   * Pre-built FieldFilter that matches all non-static, non-final fields.
   */
  public static FieldFilter COPYABLE_FIELDS =
      new FieldFilter() {
        @Override
        public boolean matches(Field field) {
          return !(Modifier.isStatic(field.getModifiers())
              || Modifier.isFinal(field.getModifiers()));
        }
      };
}