/*
 * 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.catalina.realm;

import java.io.ObjectStreamException;
import java.security.Principal;
import java.util.Arrays;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;

import javax.naming.Context;

import org.apache.catalina.Group;
import org.apache.catalina.LifecycleException;
import org.apache.catalina.Role;
import org.apache.catalina.Server;
import org.apache.catalina.User;
import org.apache.catalina.UserDatabase;
import org.apache.naming.ContextBindings;
import org.apache.tomcat.util.ExceptionUtils;

/**
 * Implementation of {@link org.apache.catalina.Realm} that is based on an implementation of {@link UserDatabase} made
 * available through the JNDI resources configured for this instance of Catalina. Set the <code>resourceName</code>
 * parameter to the JNDI resources name for the configured instance of <code>UserDatabase</code> that we should consult.
 *
 * @since 4.1
 */
public class UserDatabaseRealm extends RealmBase {

    // ----------------------------------------------------- Instance Variables

    /**
     * The <code>UserDatabase</code> we will use to authenticate users and identify associated roles.
     */
    protected volatile UserDatabase database = null;
    private final Object databaseLock = new Object();

    /**
     * The global JNDI name of the <code>UserDatabase</code> resource we will be utilizing.
     */
    protected String resourceName = "UserDatabase";

    /**
     * Obtain the UserDatabase from the context (rather than global) JNDI.
     */
    private boolean localJndiResource = false;

    /**
     * Use a static principal disconnected from the database. This prevents live updates to users and roles having an
     * effect on authenticated principals, but reduces use of the database.
     */
    private boolean useStaticPrincipal = false;


    // ------------------------------------------------------------- Properties

    /**
     * @return the global JNDI name of the <code>UserDatabase</code> resource we will be using.
     */
    public String getResourceName() {
        return resourceName;
    }


    /**
     * Set the global JNDI name of the <code>UserDatabase</code> resource we will be using.
     *
     * @param resourceName The new global JNDI name
     */
    public void setResourceName(String resourceName) {
        this.resourceName = resourceName;
    }


    /**
     * @return the useStaticPrincipal flag
     */
    public boolean getUseStaticPrincipal() {
        return this.useStaticPrincipal;
    }


    /**
     * Allows using a static principal disconnected from the user database.
     *
     * @param useStaticPrincipal the new value
     */
    public void setUseStaticPrincipal(boolean useStaticPrincipal) {
        this.useStaticPrincipal = useStaticPrincipal;
    }


    /**
     * Determines whether this Realm is configured to obtain the associated {@link UserDatabase} from the global JNDI
     * context or a local (web application) JNDI context.
     *
     * @return {@code true} if a local JNDI context will be used, {@code false} if the global JNDI context will be used
     */
    public boolean getLocalJndiResource() {
        return localJndiResource;
    }


    /**
     * Configure whether this Realm obtains the associated {@link UserDatabase} from the global JNDI context or a local
     * (web application) JNDI context.
     *
     * @param localJndiResource {@code true} to use a local JNDI context, {@code false} to use the global JNDI context
     */
    public void setLocalJndiResource(boolean localJndiResource) {
        this.localJndiResource = localJndiResource;
    }


    // ------------------------------------------------------ Protected Methods

    /**
     * Calls {@link UserDatabase#backgroundProcess()}.
     */
    @Override
    public void backgroundProcess() {
        UserDatabase database = getUserDatabase();
        if (database != null) {
            database.backgroundProcess();
        }
    }


    @Override
    protected String getPassword(String username) {
        UserDatabase database = getUserDatabase();
        if (database == null) {
            return null;
        }

        User user = database.findUser(username);

        if (user == null) {
            return null;
        }

        return user.getPassword();
    }


    public static String[] getRoles(User user) {
        Set<String> roles = new HashSet<>();
        Iterator<Role> uroles = user.getRoles();
        while (uroles.hasNext()) {
            Role role = uroles.next();
            roles.add(role.getName());
        }
        Iterator<Group> groups = user.getGroups();
        while (groups.hasNext()) {
            Group group = groups.next();
            uroles = group.getRoles();
            while (uroles.hasNext()) {
                Role role = uroles.next();
                roles.add(role.getName());
            }
        }
        return roles.toArray(new String[0]);
    }


    @Override
    protected Principal getPrincipal(String username) {
        UserDatabase database = getUserDatabase();
        if (database == null) {
            return null;
        }
        User user = database.findUser(username);
        if (user == null) {
            return null;
        } else {
            if (useStaticPrincipal) {
                return new GenericPrincipal(username, Arrays.asList(getRoles(user)));
            } else {
                return new UserDatabasePrincipal(user, database);
            }
        }
    }


    /*
     * Can't do this in startInternal() with local JNDI as the local JNDI context won't be initialised at this point.
     */
    private UserDatabase getUserDatabase() {
        // DCL so database MUST be volatile
        if (database == null) {
            synchronized (databaseLock) {
                if (database == null) {
                    try {
                        Context context;
                        if (localJndiResource) {
                            context = ContextBindings.getClassLoader();
                            context = (Context) context.lookup("comp/env");
                        } else {
                            Server server = getServer();
                            if (server == null) {
                                containerLog.error(sm.getString("userDatabaseRealm.noNamingContext"));
                                return null;
                            }
                            context = server.getGlobalNamingContext();
                        }
                        database = (UserDatabase) context.lookup(resourceName);
                    } catch (Throwable t) {
                        ExceptionUtils.handleThrowable(t);
                        if (containerLog != null) {
                            containerLog.error(sm.getString("userDatabaseRealm.lookup", resourceName), t);
                        }
                        database = null;
                    }
                }
            }
        }
        return database;
    }


    // ------------------------------------------------------ Lifecycle Methods

    @Override
    protected void startInternal() throws LifecycleException {
        // If the JNDI resource is global, check it here and fail the context
        // start if it is not valid. Local JNDI resources can't be validated
        // this way because the JNDI context isn't available at Realm start.
        if (!localJndiResource) {
            UserDatabase database = getUserDatabase();
            if (database == null) {
                throw new LifecycleException(sm.getString("userDatabaseRealm.noDatabase", resourceName));
            }
        }

        super.startInternal();
    }


    @Override
    protected void stopInternal() throws LifecycleException {

        // Perform normal superclass finalization
        super.stopInternal();

        // Release reference to our user database
        database = null;
    }


    @Override
    public boolean isAvailable() {
        return database != null && database.isAvailable();
    }


    public static final class UserDatabasePrincipal extends GenericPrincipal {
        private static final long serialVersionUID = 1L;
        private final transient UserDatabase database;

        public UserDatabasePrincipal(User user, UserDatabase database) {
            super(user.getName());
            this.database = database;
        }

        @Override
        public String[] getRoles() {
            if (database == null) {
                return new String[0];
            }
            User user = database.findUser(name);
            if (user == null) {
                return new String[0];
            }
            Set<String> roles = new HashSet<>();
            Iterator<Role> uroles = user.getRoles();
            while (uroles.hasNext()) {
                Role role = uroles.next();
                roles.add(role.getName());
            }
            Iterator<Group> groups = user.getGroups();
            while (groups.hasNext()) {
                Group group = groups.next();
                uroles = group.getRoles();
                while (uroles.hasNext()) {
                    Role role = uroles.next();
                    roles.add(role.getName());
                }
            }
            return roles.toArray(new String[0]);
        }

        @Override
        public boolean hasRole(String role) {
            if ("*".equals(role)) {
                return true;
            } else if (role == null) {
                return false;
            }
            if (database == null) {
                return super.hasRole(role);
            }
            Role dbrole = database.findRole(role);
            if (dbrole == null) {
                return false;
            }
            User user = database.findUser(name);
            if (user == null) {
                return false;
            }
            if (user.isInRole(dbrole)) {
                return true;
            }
            Iterator<Group> groups = user.getGroups();
            while (groups.hasNext()) {
                Group group = groups.next();
                if (group.isInRole(dbrole)) {
                    return true;
                }
            }
            return false;
        }

        /**
         * Magic method from {@link java.io.Serializable}.
         *
         * @return The object to serialize instead of this object
         *
         * @throws ObjectStreamException Not thrown by this implementation
         */
        private Object writeReplace() throws ObjectStreamException {
            // Replace with a static principal disconnected from the database
            return new GenericPrincipal(getName(), Arrays.asList(getRoles()));
        }
    }
}