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MetaObjects for Model-driven development - MetaData Libraries
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package com.draagon.meta.object;

import com.draagon.meta.*;
import com.draagon.meta.attr.MetaAttribute;
import com.draagon.meta.field.MetaField;
import com.draagon.meta.field.MetaFieldNotFoundException;
import com.draagon.meta.key.ForeignKey;
import com.draagon.meta.key.MetaKey;
import com.draagon.meta.key.PrimaryKey;
import com.draagon.meta.key.SecondaryKey;
import com.draagon.meta.loader.MetaDataRegistry;

import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.util.ArrayList;
import java.util.Collection;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

@SuppressWarnings("serial")
public abstract class MetaObject extends MetaData {

    private static Log log = LogFactory.getLog(MetaObject.class);

    /** Object TYPE */
    public final static String TYPE_OBJECT = "object";

    /** Object class name attribute */
    public final static String ATTR_OBJECT = "object";

    // TODO:  Should we deprecate this one and force ObjectField and ObjectArrayField to be used only?
    public final static String ATTR_OBJECT_REF = "objectRef";

    /**
     * Legacy constructor used in unit tests
     * @param name Name of the MetaObject
     * @deprecated Use MetaObject( subtype, name )
     */
    public MetaObject( String name ) {
        this( "deprecated", name );
    }

    /**
     * Constructs the MetaObject
     */
    public MetaObject(String subtype, String name ) {
        super( TYPE_OBJECT, subtype, name );
    }

    /**
     * Gets the primary MetaData class
     */
    public final Class getMetaDataClass() {
        return MetaObject.class;
    }

    /** Add Child to the MetaObject */
    public MetaObject addChild(MetaData data) throws InvalidMetaDataException {
        return super.addChild( data );
    }

    /** Wrap the MetaObject */
    public MetaObject overload() {
        return super.overload();
    }

    /**
     * Returns the MetaObject for the specified Meta Object name
     *
     * @deprecated Use MetaDataRegistry.findMetaObjectByName(), if enabled in MetaDataLoader
     */
    public static MetaObject forName(String name) {
        return MetaDataRegistry.findMetaObjectByName(name);
    }

    /**
     * Returns the MetaObject for the specified Object
     *
     * @deprecated Use MetaDataRegistry.findMetaObject(), if registry enabled in MetaDataLoader
     */
    public static MetaObject forObject(Object o) {
        return MetaDataRegistry.findMetaObject( o );
    }

    /**
     * Sets the Super Class
     */
    public MetaObject setSuperObject(MetaObject superObject) {
        setSuperData(superObject);
        return this;
    }

    /**
     * Gets the Super Object
     */
    public MetaObject getSuperObject() {
        return (MetaObject) getSuperData();
    }

    ////////////////////////////////////////////////////
    // FIELD METHODS
    /**
     * Return the MetaField count
     */
    public Collection getMetaFields() {
        return getMetaFields(true);
    }

    /**
     * Return the MetaField count
     */
    public Collection getMetaFields( boolean includeParentData ) {
        return getChildren(MetaField.class, includeParentData);
    }

    /**
     * Add a field to the MetaObject
     */
    public MetaObject addMetaField(MetaField f) {
        addChild(f);
        return this;
    }

    /**
     * Whether the named MetaField exists
     */
    public boolean hasMetaField(String name) {
        try {
            getMetaField(name);
            return true;
        } catch (MetaFieldNotFoundException e) {
            return false;
        }
    }

    /**
     * Return the specified MetaField of the MetaObject
     */
    public MetaField getMetaField(String name) {

        final String KEY = "getMetaField(" + name + ")";

        MetaField f = (MetaField) getCacheValue(KEY);

        if (f == null) {
            try {
                f = (MetaField) getChild(name, MetaField.class);
            } catch (MetaDataNotFoundException e) {
                if (getSuperObject() != null) {
                    try {
                        f = getSuperObject().getMetaField(name);
                    } catch (MetaFieldNotFoundException ex) {
                    }
                }

                throw new MetaFieldNotFoundException("MetaField [" + name + "] does not exist in MetaObject [" + toString() + "]", name);
            }

            setCacheValue(KEY, f);
        }

        return f;
    }

    /**
     * Whether the object is aware of its own state. This is false by default,
     * which means all state methods will throw an
     * UnsupportedOperationException.
     */
    public boolean isStateAware() {
        return false;
    }


    ////////////////////////////////////////////////////
    // OBJECT METHODS

    protected boolean hasObjectAttr() {
        return ( hasMetaAttr(ATTR_OBJECT, true ));
    }

    protected Class getObjectClassFromAttr() throws ClassNotFoundException {
        Class c = null;
        MetaAttribute attr = null;
        if (hasMetaAttr(ATTR_OBJECT)) {
            attr = getMetaAttr(ATTR_OBJECT);
        }
        if ( attr != null ) {
            c = loadClass( attr.getValueAsString() );
        }
        return c;
    }

    /**
     * Retrieves the object class of an object, or null if one is not specified
     */
    public Class getObjectClass() throws ClassNotFoundException {

        Class c = null;

        if ( hasObjectAttr())
            c = getObjectClassFromAttr();

        if (c == null)
            c = createClassFromMetaDataName( true );

        return c;
    }

    protected Class createClassFromMetaDataName( boolean throwError ) {

        String ostr = getName().replaceAll(PKG_SEPARATOR, ".");
        try {
            return loadClass(ostr,throwError);
        }
        catch (ClassNotFoundException e) {
            if ( throwError ) {
                throw new InvalidMetaDataException( this, "Derived Object Class [" + ostr + "] was not found");
            }
        }

        return null;
    }

    /**
     * Whether the MetaObject produces the object specified
     */
    public abstract boolean produces(Object obj);

    /**
     * Attaches a MetaObject to an Object
     *
     * @param o Object to attach
     */
    public void attachMetaObject(Object o) {
        if (o instanceof MetaObjectAware) {
            ((MetaObjectAware) o).setMetaData(this);
        }
    }

    /**
     * Sets the default values on an object
     *
     * @param o Object to set the default values on
     */
    public void setDefaultValues(Object o) {

        getMetaFields().stream()
                .filter( f -> f.getDefaultValue()!=null)
                .forEach( f -> f.setObject( o, f.getDefaultValue() ));
    }

    /**
     * Return a new MetaObject instance from the MetaObject
     */
    public Object newInstance()  {

        final String KEY = "ObjectClass";

        // See if we have this cached already
        Class oc = (Class) getCacheValue( KEY );
        if ( oc == null ) {

            try {
                oc = getObjectClass();
                if (oc == null) {
                    throw new MetaDataException("No Object Class was found on MetaObject [" + getName() + "]");
                }
            } catch (ClassNotFoundException e) {
                throw new MetaDataException("Could not find Object Class for MetaObject [" + getName() + "]: " + e.getMessage(), e);
            }

            // Store the resulting Class in the cache
            setCacheValue( KEY, oc );
        }

        try {
            if (oc.isInterface()) {
                throw new IllegalArgumentException("Could not instantiate an Interface for MetaObject [" + getName() + "]");
            }

            Object o = null;

            try {
                // Construct the object and pass the MetaObject into the constructor
                Constructor c = oc.getConstructor( MetaObject.class );
                o = c.newInstance(this);
            }
            catch (NoSuchMethodException e) {
                // Construct with no arguments && attach the metaobject
                for( Constructor c : oc.getDeclaredConstructors() ) {
                    if ( c.getParameterCount() == 0 ) {
                        try {
                            c.setAccessible(true);
                            o = c.newInstance();
                        } catch (InvocationTargetException ex) {
                            throw new RuntimeException("Could not instantiate a new Object of Class [" + oc + "] for MetaObject [" + getName() + "]: " + e.getMessage(), e);
                        }
                        attachMetaObject(o);
                        break;
                    }
                }
                if ( o == null ) throw new RuntimeException("Could not instantiate a new Object of Class [" + oc + "] for MetaObject [" + getName() + "]: No empty constructor existed" );
            }
            catch (InvocationTargetException e) {
                throw new RuntimeException("Could not instantiate a new Object of Class [" + oc + "] for MetaObject [" + getName() + "]: " + e, e);
            }

            // Set the Default Values
            setDefaultValues(o);

            return o;
        } catch (InstantiationException e) {
            throw new RuntimeException("Could not instantiate a new Object of Class [" + oc.getName() + "] for MetaObject [" + getName() + "]: " + e, e);
        } catch (IllegalAccessException e) {
            throw new RuntimeException("Illegal Access Exception instantiating a new Object for MetaObject [" + getName() + "]: " + e, e);
        }
    }

    ////////////////////////////////////////////////////
    // KEY METHODS

    public PrimaryKey getPrimaryKey() {
        return getKeyByName(PrimaryKey.NAME, PrimaryKey.class );
    }

    protected  T getKeyByName(String keyName, Class clazz ) {
        return getChild( keyName, clazz );
    }

    public SecondaryKey getSecondaryKeyByName(String keyName) {
        return getKeyByName( keyName, SecondaryKey.class );
    }

    public Collection getSecondaryKeys() {
        return getKeysOfSubType(SecondaryKey.SUBTYPE, SecondaryKey.class);
    }

    public ForeignKey getForeignKeyByName(String keyName) {
        return getKeyByName( keyName, ForeignKey.class );
    }

    public Collection getForeignKeys() {
        return getKeysOfSubType(ForeignKey.SUBTYPE, ForeignKey.class);
    }

    //public  Collection getKeysOfSubType( String subType ) {
    //    return (Collection) getKeysOfSubType( subType, MetaKey.class );
    //}

    /** Null for clazz means just look by subtype */
    protected  Collection getKeysOfSubType( String subType, Class clazz ) {
        final String CACHE_KEY = "getKeysOfSubType("+subType+","+clazz+")";
        Collection keys = (Collection) getCacheValue(CACHE_KEY);
        if ( keys == null ) {
            keys = new ArrayList<>();
            for (T key : getChildren( clazz )) {
                if ( key.getSubTypeName().equals( subType )) keys.add(key);
            }
            setCacheValue(CACHE_KEY, keys);
        }
        return keys;
    }

    public Collection getAllKeys() {
        return getChildren( MetaKey.class );
    }


    ////////////////////////////////////////////////////
    // ABSTRACT METHODS

    /**
     * Retrieves the value from the object
     */
    public abstract Object getValue(MetaField f, Object obj);

    /**
     * Sets the value on the object
     */
    public abstract void setValue(MetaField f, Object obj, Object val);

    ////////////////////////////////////////////////////
    // Validation Methods

    @Override
    public void validate() {
        super.validate();
    }

    ////////////////////////////////////////////////////
    // MISC METHODS

    public Object clone() {
        MetaObject mc = (MetaObject) super.clone();
        return mc;
    }
}