/**
     * Represents the default name for an entity, i.e. the entity that's matched
     * when an exact match isn't found.
     */
    public final static String QUOTA_ENTITY_DEFAULT = // implementation defined

    /**
     * Describes an entity type.
     */
    public enum QuotaEntityType {
        USER,        // The user principal.
        CLIENT_ID,   // The client ID.

        // Note others may be added in the future.
    }

    /**
     * Describes a fully-qualified entity.
     */
    public class QuotaEntity {
        /**
         * `entries` describes the fully-qualified entity. The key is a QuotaEntityType string, however
         * there may also exist keys that are not enumerated by QuotaEntityType that still apply, e.g.
         * the server may internally associate another type. It's necessary to return all quota types
         * because quota values for these types may influence the effective quota value. However,
         * altering a quota, any types that aren't specified should be able to be inferred by the
         * server, otherwise an error is returned.
         *
         * For example, {("CLIENT_ID" -> "test-client"),
         *               ("USER" -> "test-user"),
         *               ("GROUP" -> "internal-group")}.
         */
        public QuotaEntity(Map<String, String> entries);

        public Map<String, String> entries();
    }

    /**
     * The quota types.
     */
    public enum QuotaType {
        CONSUMER_BYTE_RATE,
        PRODUCER_BYTE_RATE,
        REQUEST_PERCENTAGE,

        // Note others may be added in the future.
    }

    /**
     * The units for a quota value. Note there may be multiple units for a given quota type
     * that influences quota behavior.
     */
    public enum QuotaUnits {
        RATE_BPS,

        // Note others may be added in the future, e.g. RATE_BPS_PER_BROKER, SHARES.
    }

    /**
     * Describes a quota key.
     */
    public class QuotaKey {
        /**
         * @param type the quota type
         * @param units the units for the quota type
         */
       public QuotaKey(QuotaType type, QuotaUnits units);

       public QuotaType type();
       public QuotaUnits units();
    }

    public class QuotaFilter {
        public enum Rule {
            EXACT,    // exact name match
            NOT,      // matches all non-matching names
            PREFIX,   // matches all names with the given prefix

            // Note others may be added in the future.
        }

       /**
        * A filtering rule to be applied.
        *
        * @param entity the entity the rule applies to
        * @param rule the rule to apply
        * @param match the non-null string that's applied by the rule
        */
       public QuotaFilter(QuotaEntity entity, Rule rule, String match);

       public QuotaEntity entity();
       public Rule rule();
       public String match();
    }

    public class DescribeQuotasOptions {
        // Default.
    }

    public class DescribeQuotasResult {
        /**
         * Maps an entity to its configured quota value(s). Note if no value is defined for a quota
         * type for that entity's config, then it is not included in the resulting value map.
         *
         * @return the collection of entities that matched the filter
         */
        KafkaFuture<Map<QuotaEntity, Map<QuotaKey, Double>>> entities();
    }

    public interface Admin extends AutoCloseable {
        /**
         * Describes all entities matching all provided filters (logical AND) that have at least one
         * quota value defined.
         *
         * @param filters filtering rules to apply to matching entities
         * @param options the options to use
         * @return result containing all matching entities
         */
        DescribeQuotasResult describeQuotas(Collection<QuotaFilter> filters, DescribeQuotasOptions options);
    }

    public class AlterQuotasEntry {
        public class Op {
            /**
             * @param key the quota type and units to alter
             * @param value if set then the existing value is updated,
             *              otherwise if null, the existing value is cleared
             */
            public Op(QuotaKey key, Double value);

            public QuotaKey key();
            public Double value();
        }

        /**
         * @param entity the entity whose config will be modified
         * @param ops the alteration to perform - if value is set, then the existing value is updated,
         *            otherwise if null, the existing value is cleared
         */
        public AlterQuotasEntry(QuotaEntity entity, Collection<Op> ops);

        public QuotaEntity entity();
        public Collection<Ops> ops();
    }

    public class AlterQuotasOptions {
        // Default.
    }

    public class AlterQuotasResult {
        /**
         * @return map of a quota entity update to its future
         */
        public Map<QuotaEntity, KafkaFuture<Void>> futures();
    }

    public interface Admin extends AutoCloseable {
        /**
         * Alters the quotas as specified for the entries.
         *
         * @param alterations the alterations to perform
         * @return the result of the alterations
         */
        AlterQuotasResult alterQuotas(Collection<AlterQuotasEntry> entries, AlterQuotasOptions options);
    }