// --- BEGIN COPYRIGHT BLOCK ---
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; version 2 of the License.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License along
// with this program; if not, write to the Free Software Foundation, Inc.,
// 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
//
// (C) 2007 Red Hat, Inc.
// All rights reserved.
// --- END COPYRIGHT BLOCK ---
package com.netscape.certsrv.base;

import java.util.Enumeration;
import java.util.Hashtable;

import netscape.security.util.ObjectIdentifier;

/**
 * A class representing a meta attribute defintion.
 * <P>
 * 
 * @version $Revision$, $Date$
 */
public class MetaAttributeDef {

    private String mName;
    private ObjectIdentifier mOid;
    private Class<?> mValueClass;
    private static Hashtable<String, MetaAttributeDef> mNameToAttrDef = new Hashtable<String, MetaAttributeDef>();
    private static Hashtable<ObjectIdentifier, MetaAttributeDef> mOidToAttrDef =
            new Hashtable<ObjectIdentifier, MetaAttributeDef>();

    private MetaAttributeDef() {
    }

    /**
     * Constructs a MetaAttribute defintion
     * <P>
     * 
     * @param name attribute name
     * @param valueClass attribute value class
     * @param oid attribute object identifier
     */
    private MetaAttributeDef(String name, Class<?> valueClass,
            ObjectIdentifier oid) {
        mName = name;
        mValueClass = valueClass;
        mOid = oid;
    }

    /**
     * Gets an attribute OID.
     * <P>
     * 
     * @return returns attribute OID or null if not defined.
     */
    public ObjectIdentifier getOID() {
        return mOid;
    }

    /**
     * Gets an Java class for the attribute values
     * <P>
     * 
     * @return returns Java class for the attribute values
     */
    public Class<?> getValueClass() {
        return mValueClass;
    }

    /**
     * Gets attribute name
     * <P>
     * 
     * @return returns attribute name
     */
    public String getName() {
        return mName;
    }

    /**
     * Registers new MetaAttribute defintion
     * Attribute is defined by name, Java class for attribute values and
     * optional object identifier
     * <P>
     * 
     * @param name attribute name
     * @param valueClass attribute value class
     * @param oid attribute object identifier
     * @exception IllegalArgumentException if name or valueClass are null, or
     *                conflicting attribute definition already exists
     */
    public static MetaAttributeDef register(String name, Class<?> valueClass,
            ObjectIdentifier oid) {
        if (name == null) {
            throw new IllegalArgumentException(
                    "Attribute name must not be null");
        }
        if (valueClass == null) {
            throw new IllegalArgumentException(
                    "Attribute value class must not be null");
        }

        MetaAttributeDef newDef = new MetaAttributeDef(name, valueClass, oid);
        MetaAttributeDef oldDef;

        if ((oldDef = (MetaAttributeDef) mNameToAttrDef.get(name)) != null &&
                !oldDef.equals(newDef)) {
            throw new IllegalArgumentException(
                    "Attribute \'" + name + "\' is already defined");
        }
        if (oid != null &&
                (oldDef = (MetaAttributeDef) mOidToAttrDef.get(oid)) != null &&
                !oldDef.equals(newDef)) {
            throw new IllegalArgumentException(
                    "OID \'" + oid + "\' is already in use");
        }
        mNameToAttrDef.put(name, newDef);
        if (oid != null) {
            mOidToAttrDef.put(oid, newDef);
        }
        return newDef;
    }

    /**
     * Compares this attribute definition with another, for equality.
     * <P>
     * 
     * @return true iff names, valueClasses and object identifiers
     *         are identical.
     */
    public boolean equals(Object other) {
        if (other == this)
            return true;

        if (other instanceof MetaAttributeDef) {
            MetaAttributeDef otherDef = (MetaAttributeDef) other;

            if ((mOid != null && otherDef.mOid != null &&
                    !mOid.equals(otherDef.mOid)) ||
                    (mOid == null && otherDef.mOid != null) ||
                    !mName.equals(otherDef.mName) ||
                    !mValueClass.equals(otherDef.mValueClass)) {
                return false;
            }
        }
        return false;
    }

    /**
     * Retrieves attribute definition by name
     * <P>
     * 
     * @param name attribute name
     * @return attribute definition or null if not found
     */
    public static MetaAttributeDef forName(String name) {
        return (MetaAttributeDef) mNameToAttrDef.get(name);
    }

    /**
     * Retrieves attribute definition by object identifier
     * <P>
     * 
     * @param oid attribute object identifier
     * @return attribute definition or null if not found
     */
    public static MetaAttributeDef forOID(ObjectIdentifier oid) {
        return (MetaAttributeDef) mOidToAttrDef.get(oid);
    }

    /**
     * Returns enumeration of the registered attribute names
     * <P>
     * 
     * @return returns enumeration of the registered attribute names
     */
    public static Enumeration<String> getAttributeNames() {
        return mNameToAttrDef.keys();
    }

    /**
     * Returns enumeration of the registered attribute object identifiers
     * <P>
     * 
     * @return returns enumeration of the attribute object identifiers
     */
    public static Enumeration<ObjectIdentifier> getAttributeNameOids() {
        return mOidToAttrDef.keys();
    }
}