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/* 
 * Copyright (c) 2017 Georgi Pavlov ([email protected]).
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the MIT license which accompanies 
 * this distribution, and is available at 
 * https://github.com/tengia/oauth-2/blob/master/LICENSE
 */

package net.oauth2;

import java.beans.BeanInfo;
import java.beans.IntrospectionException;
import java.beans.Introspector;
import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.Map;

/**
 * Utility class for operations on bean-like classes.  
 *
 */
public class BeanUtils {

	/**
	 * The method transforms a oauth payload object properties (grant or token) to a 
	 * properties map by introspection. The introspection will cascade through several 
	 * options to find out the key for a property value in the resulting map. This allows
	 * properties such as accessToken to be presented by keys such as "acces_tokens".
	 * The options to instruct that are 1. to supply a second argument that supplies this
	 * mapping 2. annotate properties or getters with OAuthPayloadProperty and supply 
	 * the desired key name as value of the annotation 3. stick to the same naming convention
	 * both for property names and keys.  
	 * 
	 * @param grantRequest
	 * @param propertyMap
	 * @return
	 * @throws IntrospectionException
	 * @throws IllegalAccessException
	 * @throws IllegalArgumentException
	 * @throws InvocationTargetException
	 */
	public static  Map asMap(T grantRequest, Map propertyMap) throws IntrospectionException, IllegalAccessException, IllegalArgumentException, InvocationTargetException {
		Map values = new HashMap();
		BeanInfo info = Introspector.getBeanInfo(grantRequest.getClass(), Object.class);
		for (PropertyDescriptor pd : info.getPropertyDescriptors()) {
			// This will access public properties through getters
			String name = null;
			Method getter = pd.getReadMethod();
			// first try an explicit property map if any is provided.
			if (propertyMap != null && !propertyMap.isEmpty()) {
				name = propertyMap.get(pd.getName());
			}
			// try annotations if map didn't help
			if (name == null) {
				if (getter != null) {
					// first inspect the getter for this property for annotation
					OAuthPayloadProperty propertyAnnotation = getter.getAnnotation(OAuthPayloadProperty.class);
					if (propertyAnnotation != null) {
						name = propertyAnnotation.value();
					}
				}
			}
			// next, inspect the corresponding field for annotation.
			// This algorithm assumes that the field name equals the
			// bean property descriptor's name
			if (name == null) {
				String fieldName = pd.getName();
				try {
					Field field = grantRequest.getClass().getDeclaredField(fieldName);
					field.setAccessible(true);
					OAuthPayloadProperty annotation = field.getDeclaredAnnotation(OAuthPayloadProperty.class);
					if (annotation != null) {
						name = annotation.value();
					}
				} catch (NoSuchFieldException nsfe) {
					// silently ignore
				}
			}
			// finally, try using the name of the property field assuming it
			// follows a correct naming convention for payload
			// de-/serialization to work properly
			if (name == null) {
				name = pd.getName();
			}
			if (name != null) {
				Object value = null;
				if(getter != null) {
					value = getter.invoke(grantRequest);
				} else {
					try {
						Field field = grantRequest.getClass().getDeclaredField(name);
						field.setAccessible(true);
						value = field.get(grantRequest);
					} catch (NoSuchFieldException | IllegalAccessException e) {
						// silently ignore
					}
				}
				if (value != null)
					values.put(name, value);
			}
		}
		return values;
	}


}