/*
    *  Copyright 2010, 2011 Chris Pheby
    *
    *  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
   *  distringibuted under the License is distringibuted 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.jadira.bindings.core.general.unmarshaller;
  
  import java.lang.invoke.MethodHandle;
  import java.lang.invoke.MethodHandles;
  import java.lang.reflect.Method;
  import java.lang.reflect.Modifier;
  
  import org.jadira.bindings.core.api.BindingException;
  import org.jadira.bindings.core.api.FromUnmarshaller;
  
  /**
   * Binding that supports an unmarshal method. The
   * unmarshal method must be statically scoped. It must accept a single parameter
   * of type S and return a type of T. For example:
   * <p>
   * {@code public static BoundType unmarshal(String string)}
   * </p>
   * @param <S> Source type for the conversion
   * @param <T> Target type
   */
  public final class MethodFromUnmarshaller<S, T> implements FromUnmarshaller<S, T> {
  
  	private static final MethodHandles.Lookup LOOKUP = MethodHandles.lookup();
  	
      private final MethodHandle unmarshalHandle;
  
      private final Class<S> boundClass;
  
      private final Class<T> targetClass;
      
      /**
       * Create a new instance
       * @param boundClass Bound class
       * @param unmarshal Unmarshal method on the target class
       */
      public MethodFromUnmarshaller(Class<S> boundClass, Method unmarshal) {
  
          this.boundClass = boundClass;
          
          if (unmarshal.getParameterTypes().length != 1) {
              throw new IllegalStateException("unmarshal method must define a single parameter");
          }
          if (!Modifier.isStatic(unmarshal.getModifiers())) {
              throw new IllegalStateException("unmarshal method must be defined as static");
          }
          if (!boundClass.isAssignableFrom(unmarshal.getReturnType())) {
              throw new IllegalStateException("unmarshal method must return " + boundClass.getSimpleName());
          }
  
          try {
  			this.unmarshalHandle = LOOKUP.unreflect(unmarshal);
  		} catch (IllegalAccessException e) {
  			throw new IllegalStateException("Method is not accessible" + unmarshal);
  		}
          
          @SuppressWarnings("unchecked")
          Class<T> myTarget = (Class<T>)unmarshal.getParameterTypes()[0];
          this.targetClass = myTarget;
      }
  
  	/**
  	 * {@inheritDoc}
  	 */
  	/* @Override */
      public S unmarshal(T object) {
  
      	if (object != null && !targetClass.isAssignableFrom(object.getClass())) {
      		throw new IllegalArgumentException("Supplied object was not instance of target class");
      	}
      	
          try {
              return getBoundClass().cast(unmarshalHandle.invoke(object));
          } catch (Throwable ex) {
          	if (ex.getCause() instanceof RuntimeException) {
                  throw (RuntimeException) ex.getCause();
              }
              throw new BindingException(ex.getMessage(), ex.getCause());
          }
      }
      
  	/**
  	 * {@inheritDoc}
  	 */
  	/* @Override */
     public Class<S> getBoundClass() {
         return boundClass;
     }
     
 	/**
 	 * {@inheritDoc}
 	 */
 	/* @Override */
     public Class<T> getTargetClass() {
         return targetClass;
     }
 }