/**
 *    Copyright (C) 2018-present MongoDB, Inc.
 *
 *    This program is free software: you can redistribute it and/or modify
 *    it under the terms of the Server Side Public License, version 1,
 *    as published by MongoDB, Inc.
 *
 *    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
 *    Server Side Public License for more details.
 *
 *    You should have received a copy of the Server Side Public License
 *    along with this program. If not, see
 *    <http://www.mongodb.com/licensing/server-side-public-license>.
 *
 *    As a special exception, the copyright holders give permission to link the
 *    code of portions of this program with the OpenSSL library under certain
 *    conditions as described in each individual source file and distribute
 *    linked combinations including the program with the OpenSSL library. You
 *    must comply with the Server Side Public License in all respects for
 *    all of the code used other than as permitted herein. If you modify file(s)
 *    with this exception, you may extend this exception to your version of the
 *    file(s), but you are not obligated to do so. If you do not wish to do so,
 *    delete this exception statement from your version. If you delete this
 *    exception statement from all source files in the program, then also delete
 *    it in the license file.
 */

#pragma once

#include <list>

#include "mongo/db/auth/user.h"

namespace mongo {

/**
 * A collection of authenticated users.
 * This class does not do any locking/synchronization, the consumer will be responsible for
 * synchronizing access.
 */
class UserSet {
public:
    using iterator = std::list<UserHandle>::iterator;
    using const_iterator = std::list<UserHandle>::const_iterator;

    UserSet();
    UserSet(const UserSet&) = default;
    UserSet& operator=(const UserSet&) = default;

    /**
     * Adds a User to the UserSet.
     *
     * As there can only be one user per database in the UserSet, if a User already exists for
     * the new User's database, the old user will be removed from the set and returned.  It is
     * the caller's responsibility to then release that user.  If no user already exists for the
     * new user's database, returns NULL.
     *
     * Invalidates any outstanding iterators or NameIterators.
     */
    void add(UserHandle user);

    /**
     * Replaces the user at "it" with "replacement."  Does not take ownership of the User.
     * Returns a pointer to the old user referenced by "it".  Does _not_ invalidate "iterator"
     * instances.
     */
    void replaceAt(iterator it, UserHandle replacement);

    /**
     * Removes the user at "it", and returns a pointer to it.  After this call, "it" remains
     * valid.  It will either equal "end()", or refer to some user between the values of "it"
     * and "end()" before this call was made.
     */
    void removeAt(iterator it);

    /**
     * Removes the User whose authentication credentials came from dbname, and returns that
     * user.  It is the caller's responsibility to then release that user back to the
     * authorizationManger.  If no user exists for the given database, returns NULL;
     */
    void removeByDBName(StringData dbname);

    // Returns the User with the given name, or NULL if not found.
    // Ownership of the returned User remains with the UserSet.  The pointer
    // returned is only guaranteed to remain valid until the next non-const method is called
    // on the UserSet.
    UserHandle lookup(const UserName& name) const;

    // Gets the user whose authentication credentials came from dbname, or NULL if none
    // exist.  There should be at most one such user.
    UserHandle lookupByDBName(StringData dbname) const;

    // Gets an iterator over the names of the users stored in the set.  The iterator is
    // valid until the next non-const method is called on the UserSet.
    UserNameIterator getNames() const;

    iterator begin() {
        return _users.begin();
    }

    iterator end() {
        return _users.end();
    }

    // Returns the number of users stored in the set.
    std::size_t count() const {
        return _users.size();
    }

    // Generates a BSONArray representation of the UserSet.
    BSONArray toBSON() const {
        BSONArrayBuilder userNamesArray;
        for (const auto& userHandle : _users) {
            userHandle->getName().serializeToBSON(&userNamesArray);
        }
        return userNamesArray.arr();
    }

private:
    // The UserSet maintains ownership of the Users in it, and is responsible for
    // returning them to the AuthorizationManager when done with them.
    std::list<UserHandle> _users;
};

}  // namespace mongo