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package com.cedarsoftware.io.reflect;

import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.MethodType;
import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.lang.reflect.Type;

import com.cedarsoftware.io.MetaUtils;

/**
 * @author Kenny Partlow ([email protected])
 *         

 *         Copyright (c) Cedar Software LLC
 *         


 *         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
 *         


 *         License
 *         


 *         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.
 */
public class Accessor {
    private final String uniqueFieldName;

    /**
     * The field we are trying to access with this method handle
     */
    private final Field field;
    private final boolean isMethod;
    private final String fieldOrMethodName;
    private final MethodHandle methodHandle;
    private final boolean isPublic;

    private Accessor(Field field, MethodHandle methodHandle, String uniqueFieldName, String fieldOrMethodName, boolean isPublic, boolean isMethod) {
        this.field = field;
        this.methodHandle = methodHandle;
        this.uniqueFieldName = uniqueFieldName;
        this.fieldOrMethodName = fieldOrMethodName;
        this.isPublic = isPublic;
        this.isMethod = isMethod;
    }

    public static Accessor createFieldAccessor(Field field, String uniqueFieldName) {
        if (!(Modifier.isPublic(field.getModifiers()) && Modifier.isPublic(field.getDeclaringClass().getModifiers()))) {
            MetaUtils.trySetAccessible(field);
        }

        try {
            MethodHandle handle = MethodHandles.lookup().unreflectGetter(field);
            return new Accessor(field, handle, uniqueFieldName, field.getName(), Modifier.isPublic(field.getModifiers()), false);
        } catch (IllegalAccessException ex) {
            return null;
        }
    }

    public static Accessor createMethodAccessor(Field field, String methodName, String uniqueFieldName) {
        try {
            MethodType type = MethodType.methodType(field.getType());
            MethodHandle handle = MethodHandles.publicLookup().findVirtual(field.getDeclaringClass(), methodName, type);
            return new Accessor(field, handle, uniqueFieldName, methodName, true, true);
        } catch (Exception ignore) {
            return null;
        }
    }

    public Object retrieve(Object o) {
        try {
            if (methodHandle == null) {
                return field.get(o);
            } else {
                return methodHandle.invoke(o);
            }
        } catch (ThreadDeath td) {
            throw td;
        } catch (Throwable t) {
            return null;
        }
    }

    /**
     * @return MethodHandle or null if there is none.
     */
    public MethodHandle getMethodHandle() {
         return methodHandle;
    }

    public boolean isMethod() {
        return isMethod;
    }

    public Class getFieldType() {
        return this.field.getType();
    }

    public Class getDeclaringClass() {
        return this.field.getDeclaringClass();
    }

    public Type getGenericType() {
        return this.field.getGenericType();
    }

    public String getActualFieldName() {
        return field.getName();
    }

    /**
     * The unique field name if two fields have the same name in the same class structure,
     * the more parent field will be qualified with the ShortName of the Declaring class
     */
    public String getUniqueFieldName() {
        return uniqueFieldName;
    }

    /**
     * The display name will be either the underlying field name or the underlying
     * method name from which the method handle was created.
     */
    public String getFieldOrMethodName() {
        return fieldOrMethodName;
    }

    /**
     * This will be the modifiers of the field or method that defines this MethodHandle
     * (or Field) itself if we had to fall back to field access.
     */
    public boolean isPublic() {
        return isPublic;
    }
}