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/*
 * 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.sshd.common;

import java.nio.charset.Charset;
import java.util.Collections;
import java.util.Map;

import org.apache.sshd.common.util.MapEntryUtils;

/**
 * Indicates an entity that can be configured using properties. The properties are simple name-value pairs where the
 * actual value type depends on the property. Some automatic conversions may be available - e.g., from a string to a
 * numeric or {@code boolean} value, or from {@code int} to {@code long}, etc.. Note: implementations may decide
 * to use case insensitive property names, therefore it is highly discouraged to use names that
 * differ from each other only in case sensitivity. Also, implementations may choose to trim whitespaces, thus such are
 * also highly discouraged.
 *
 * @author Apache MINA SSHD Project
 */
public interface PropertyResolver {
    /**
     * An "empty" resolver with no properties and no parent
     */
    PropertyResolver EMPTY = new PropertyResolver() {
        @Override
        public PropertyResolver getParentPropertyResolver() {
            return null;
        }

        @Override
        public Map getProperties() {
            return Collections.emptyMap();
        }

        @Override
        public boolean isEmpty() {
            return true;
        }

        @Override
        public String toString() {
            return "EMPTY";
        }
    };

    /**
     * @return The parent resolver that can be used to query for missing properties - {@code null} if no parent
     */
    PropertyResolver getParentPropertyResolver();

    /**
     * 
     * A map of properties that can be used to configure the SSH server or client. This map will never be changed by
     * either the server or client and is not supposed to be changed at runtime (changes are not bound to have any
     * effect on a running client or server), though it may affect the creation of sessions later as these values are
     * usually not cached.
     * 
     *
     * 
     * Note: the type of the mapped property should match the expected configuration value type -
     * {@code Long, Integer, Boolean,
     * String}, etc.... If it doesn't, the {@code toString()} result of the mapped value is used to convert it to the
     * required type. E.g., if the mapped value is the string "1234" and the expected value is a
     * {@code long} then it will be parsed into one. Also, if the mapped value is an {@code Integer} but a {@code long}
     * is expected, then it will be converted into one.
     * 
     *
     * @return a valid Map containing configuration values, never {@code null}. Note: may be
     *         immutable.
     */
    Map getProperties();

    default boolean isEmpty() {
        return MapEntryUtils.isEmpty(getProperties());
    }

    default long getLongProperty(String name, long def) {
        return PropertyResolverUtils.getLongProperty(this, name, def);
    }

    default Long getLong(String name) {
        return PropertyResolverUtils.getLong(this, name);
    }

    default int getIntProperty(String name, int def) {
        return PropertyResolverUtils.getIntProperty(this, name, def);
    }

    default Integer getInteger(String name) {
        return PropertyResolverUtils.getInteger(this, name);
    }

    default boolean getBooleanProperty(String name, boolean def) {
        return PropertyResolverUtils.getBooleanProperty(this, name, def);
    }

    default Boolean getBoolean(String name) {
        return PropertyResolverUtils.getBoolean(this, name);
    }

    default String getStringProperty(String name, String def) {
        return PropertyResolverUtils.getStringProperty(this, name, def);
    }

    default String getString(String name) {
        return PropertyResolverUtils.getString(this, name);
    }

    default Object getObject(String name) {
        return PropertyResolverUtils.getObject(this, name);
    }

    default Charset getCharset(String name, Charset defaultValue) {
        Object value = getObject(name);
        return (value == null) ? defaultValue : PropertyResolverUtils.toCharset(value);
    }

    static boolean isEmpty(PropertyResolver resolver) {
        return (resolver == null) || resolver.isEmpty();
    }
}