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Grails Web Application Framework
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/*
 * Copyright 2012 the original author or authors.
 *
 * 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 grails.beans.util

import groovy.transform.CompileStatic
import org.grails.core.util.ClassPropertyFetcher

import java.beans.PropertyDescriptor

/**
 * A map that backs onto a bean. The map is not initialized from the beans property values on creation, but instead lazily reads the values on demand.
 * No caching is applied, so each read results in a reflective call to retrieve the property. Users of this API should apply their own caching strategy if necessary.
 * 
 * 
 * Note that the {@link Map#values()} and {@link Map#entrySet()} implementations are expensive operations as they will read all properties of the target bean and should be used with caution.
 * 
 * 
 * Additionally the {@link Map#remove(java.lang.Object)} and {@link Map#clear()} methods are not implemented and will throw {@link UnsupportedOperationException}.
 * 
 * @since 2.4
 * @author Graeme Rocher
 */
@CompileStatic
class LazyBeanMap implements Map{
    final private ClassPropertyFetcher cpf
    final Object target

    /**
     * Creates a bean map
     *
     * @param target The target bean
     */
    LazyBeanMap(Object target) {
        this.target = target
        if(target != null) {
            this.cpf = ClassPropertyFetcher.forClass(target.getClass())
        }
    }

    @Override
    int size() {
        return cpf ? cpf.getPropertyDescriptors().size() : 0
    }

    @Override
    boolean isEmpty() { cpf ? false : true}

    @Override
    boolean containsKey(Object key) {
        cpf != null && cpf.getPropertyType(key.toString(), true) != null
    }

    @Override
    boolean containsValue(Object value) {
        cpf != null && values().contains(value)
    }

    @Override
    def get(Object key) {
        if(!cpf) return null
        def property = key.toString()
        if(cpf.isReadableProperty(property))
            cpf.getPropertyValue target, property
        else
            return null
    }

    @Override
    def put(String key, def value) {
        if(!cpf) return null
        def old = get(key)
        def mc = GroovySystem.metaClassRegistry.getMetaClass(target.getClass())
        mc.setProperty(target, key, value)
        return old
    }

    @Override
    Object remove(Object key) {
        throw new UnsupportedOperationException("Method remove(key) not implemented")
    }

    @Override
    void putAll(Map m) {
        if(!cpf) return
        for(String property in m.keySet()) {
            put(property, m.get(property))
        }
    }

    @Override
    void clear() {
        throw new UnsupportedOperationException("Method clear() not implemented")
    }

    @Override
    Set keySet() {
        if(!cpf) return [] as Set
        else {
            return new HashSet( cpf.getPropertyDescriptors().collect { PropertyDescriptor pd -> pd.name} )
        }
    }

    @Override
    Collection