/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You 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.apache.bval;

import java.lang.annotation.Annotation;
import java.lang.reflect.Method;
import java.util.Collection;

import org.apache.bval.model.Features;
import org.apache.bval.model.MetaBean;
import org.apache.bval.model.MetaProperty;
import org.apache.bval.model.ValidationContext;
import org.apache.bval.model.ValidationListener;
import org.apache.bval.util.AccessStrategy;
import org.apache.bval.util.PropertyAccess;
import org.apache.bval.util.ValidationHelper;

// TODO: centralize treatMapsLikeBeans

/**
 * Description: Top-Level API-class to validate objects or object-trees. You can
 * invoke, extend or utilize this class if you need other ways to integrate
 * validation in your application.
 * <p/>
 * This class supports cyclic object graphs by keeping track of validated
 * instances in the validation context.<br/>
 */
public class BeanValidator<T extends ValidationListener> {
    private final MetaBeanFinder metaBeanFinder;

    /**
     * Create a new BeanValidator instance. Convenience constructor. Use the
     * global instance of MetaBeanManagerFactory.getFinder().
     */
    public BeanValidator() {
        this(MetaBeanManagerFactory.getFinder());
    }

    /**
     * Create a new BeanValidator instance.
     * 
     * @param metaBeanFinder
     */
    public BeanValidator(MetaBeanFinder metaBeanFinder) {
        this.metaBeanFinder = metaBeanFinder;
    }

    /**
     * Convenience API. validate a root object with all related objects with its
     * default metaBean definition.
     * 
     * @param bean
     * @return results - validation results found
     */
    public T validate(Object bean) {
        MetaBean metaBean = getMetaBeanFinder().findForClass(bean.getClass());
        return validate(bean, metaBean);
    }

    /**
     * Convenience API. validate a root object with all related objects
     * according to the metaBean.
     * 
     * @param bean
     *            - a single bean or a collection of beans (that share the same
     *            metaBean!)
     * @param metaBean
     * @return results - validation results found
     */
    public T validate(Object bean, MetaBean metaBean) {
        ValidationContext<T> context = createContext();
        context.setBean(bean, metaBean);
        ValidationHelper.validateContext(context, new BeanValidatorCallback(context), treatMapsLikeBeans);
        return context.getListener();
    }

    /**
     * Validate the method parameters based on @Validate annotations.
     * Requirements: Parameter, that are to be validated must be annotated with @Validate
     * 
     * @param method
     *            - a method
     * @param parameters
     *            - the parameters suitable to the method
     * @return a validation result or null when there was nothing to validate
     * @see Validate
     */
    public T validateCall(Method method, Object[] parameters) {
        if (parameters.length > 0) {
            // shortcut (for performance!)
            Annotation[][] annotations = method.getParameterAnnotations();
            ValidationContext<T> context = null;
            for (int i = 0; i < parameters.length; i++) {
                for (Annotation anno : annotations[i]) {
                    if (anno instanceof Validate) {
                        if (context == null)
                            context = createContext();
                        if (determineMetaBean((Validate) anno, parameters[i], context)) {
                            ValidationHelper.validateContext(context, new BeanValidatorCallback(context),
                                treatMapsLikeBeans);
                            break; // next parameter
                        }
                    }
                }
            }
            return context != null ? context.getListener() : null;
        }
        return null;
    }

    /**
     * Determine the metabean for the given object.
     * 
     * @param <VL>
     * @param validate
     * @param parameter
     * @param context
     * @return true when validation should happen, false to skip it
     */
    protected <VL extends ValidationListener> boolean determineMetaBean(Validate validate, Object parameter,
        ValidationContext<VL> context) {
        if (validate.value().length() == 0) {
            if (parameter == null)
                return false;
            Class<?> beanClass;
            if (parameter instanceof Collection<?>) { // do not validate empty
                                                      // collection
                Collection<?> coll = ((Collection<?>) parameter);
                if (coll.isEmpty())
                    return false;
                beanClass = coll.iterator().next().getClass(); // get first
                                                               // object
            } else if (parameter.getClass().isArray()) {
                beanClass = parameter.getClass().getComponentType();
            } else {
                beanClass = parameter.getClass();
            }
            context.setBean(parameter, getMetaBeanFinder().findForClass(beanClass));
        } else {
            context.setBean(parameter, getMetaBeanFinder().findForId(validate.value()));
        }
        return true;
    }

    /**
     * factory method - overwrite in subclasses
     * 
     * @return ValidationListener of the proper type
     */
    @SuppressWarnings("unchecked")
    protected T createResults() {
        return (T) new ValidationResults();
    }

    /**
     * factory method - overwrite in subclasses
     * 
     * @return ValidationContext parameterized with our listener type
     */
    protected ValidationContext<T> createContext() {
        return new BeanValidationContext<T>(createResults());
    }

    /**
     * Convenience API. validate a single property.
     * 
     * @param bean
     *            - the root object
     * @param metaProperty
     *            - metadata for the property
     * @return validation results
     */
    public T validateProperty(Object bean, MetaProperty metaProperty) {
        ValidationContext<T> context = createContext();
        context.setBean(bean);
        context.setMetaProperty(metaProperty);
        ValidationHelper.validateProperty(context);
        return context.getListener();
    }

    /**
     * {@inheritDoc} internal validate a bean (=not a collection of beans) and
     * its related beans
     */
    protected <VL extends ValidationListener> void validateBeanNet(ValidationContext<VL> context) {
        if (context.collectValidated()) {
            ValidationHelper.validateBean(context);
            for (MetaProperty prop : context.getMetaBean().getProperties()) {
                validateRelatedBean(context, prop);
            }
        }
    }

    /**
     * Validate a property of a graph.
     * 
     * @param <VL>
     * @param context
     * @param prop
     */
    protected <VL extends ValidationListener> void validateRelatedBean(ValidationContext<VL> context, MetaProperty prop) {
        AccessStrategy[] access = prop.getFeature(Features.Property.REF_CASCADE);
        if (access == null && prop.getMetaBean() != null) { // single property
                                                            // access strategy
            // save old values from context
            final Object bean = context.getBean();
            final MetaBean mbean = context.getMetaBean();
            // modify context state for relationship-target bean
            context.moveDown(prop, new PropertyAccess(bean.getClass(), prop.getName()));
            ValidationHelper.validateContext(context, new BeanValidatorCallback(context), treatMapsLikeBeans);
            // restore old values in context
            context.moveUp(bean, mbean);
        } else if (access != null) { // different accesses to relation
            // save old values from context
            final Object bean = context.getBean();
            final MetaBean mbean = context.getMetaBean();
            for (AccessStrategy each : access) {
                // modify context state for relationship-target bean
                context.moveDown(prop, each);
                ValidationHelper.validateContext(context, new BeanValidatorCallback(context), treatMapsLikeBeans);
                // restore old values in context
                context.moveUp(bean, mbean);
            }
        }
    }

    private boolean treatMapsLikeBeans = false;

    public boolean isTreatMapsLikeBeans() {
        return treatMapsLikeBeans;
    }

    public void setTreatMapsLikeBeans(boolean treatMapsLikeBeans) {
        this.treatMapsLikeBeans = treatMapsLikeBeans;
    }

    /**
     * Get the metabean finder associated with this validator.
     * 
     * @return a MetaBeanFinder
     * @see org.apache.bval.MetaBeanManagerFactory#getFinder()
     */
    public MetaBeanFinder getMetaBeanFinder() {
        return metaBeanFinder;
    }

    /**
     * Dispatches a call from {@link #validate()} to
     * {@link BeanValidator#validateBeanNet(ValidationContext)} with the current
     * context set.
     */
    private class BeanValidatorCallback implements ValidationHelper.ValidateCallback {

        private final ValidationContext<?> context;

        public BeanValidatorCallback(ValidationContext<?> context) {
            this.context = context;
        }

        public void validate() {
            validateBeanNet(context);
        }

    }

}