/*
 * Copyright 2002-2020 the original author or authors.
 *
 * Licensed 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
 *
 *      https://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.springframework.core.io.support;

import java.io.FileNotFoundException;
import java.io.IOException;
import java.net.SocketException;
import java.net.UnknownHostException;
import java.util.Properties;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.core.io.Resource;
import org.springframework.lang.Nullable;
import org.springframework.util.CollectionUtils;
import org.springframework.util.DefaultPropertiesPersister;
import org.springframework.util.PropertiesPersister;

/**
 * Base class for JavaBean-style components that need to load properties
 * from one or more resources. Supports local properties as well, with
 * configurable overriding.
 *
 * @author Juergen Hoeller
 * @since 1.2.2
 */
public abstract class PropertiesLoaderSupport {

        /** Logger available to subclasses. */
        protected final Log logger = LogFactory.getLog(getClass());

        @Nullable
        protected Properties[] localProperties;

        protected boolean localOverride = false;

        @Nullable
        private Resource[] locations;

        private boolean ignoreResourceNotFound = false;

        @Nullable
        private String fileEncoding;

        private PropertiesPersister propertiesPersister = new DefaultPropertiesPersister();


        /**
         * Set local properties, e.g. via the "props" tag in XML bean definitions.
         * These can be considered defaults, to be overridden by properties
         * loaded from files.
         */
        public void setProperties(Properties properties) {
                this.localProperties = new Properties[] {properties};
        }

        /**
         * Set local properties, e.g. via the "props" tag in XML bean definitions,
         * allowing for merging multiple properties sets into one.
         */
        public void setPropertiesArray(Properties... propertiesArray) {
                this.localProperties = propertiesArray;
        }

        /**
         * Set a location of a properties file to be loaded.
         * <p>Can point to a classic properties file or to an XML file
         * that follows JDK 1.5's properties XML format.
         */
        public void setLocation(Resource location) {
                this.locations = new Resource[] {location};
        }

        /**
         * Set locations of properties files to be loaded.
         * <p>Can point to classic properties files or to XML files
         * that follow JDK 1.5's properties XML format.
         * <p>Note: Properties defined in later files will override
         * properties defined earlier files, in case of overlapping keys.
         * Hence, make sure that the most specific files are the last
         * ones in the given list of locations.
         */
        public void setLocations(Resource... locations) {
                this.locations = locations;
        }

        /**
         * Set whether local properties override properties from files.
         * <p>Default is "false": Properties from files override local defaults.
         * Can be switched to "true" to let local properties override defaults
         * from files.
         */
        public void setLocalOverride(boolean localOverride) {
                this.localOverride = localOverride;
        }

        /**
         * Set if failure to find the property resource should be ignored.
         * <p>"true" is appropriate if the properties file is completely optional.
         * Default is "false".
         */
        public void setIgnoreResourceNotFound(boolean ignoreResourceNotFound) {
                this.ignoreResourceNotFound = ignoreResourceNotFound;
        }

        /**
         * Set the encoding to use for parsing properties files.
         * <p>Default is none, using the {@code java.util.Properties}
         * default encoding.
         * <p>Only applies to classic properties files, not to XML files.
         * @see org.springframework.util.PropertiesPersister#load
         */
        public void setFileEncoding(String encoding) {
                this.fileEncoding = encoding;
        }

        /**
         * Set the PropertiesPersister to use for parsing properties files.
         * The default is DefaultPropertiesPersister.
         * @see org.springframework.util.DefaultPropertiesPersister
         */
        public void setPropertiesPersister(@Nullable PropertiesPersister propertiesPersister) {
                this.propertiesPersister =
                                (propertiesPersister != null ? propertiesPersister : new DefaultPropertiesPersister());
        }


        /**
         * Return a merged Properties instance containing both the
         * loaded properties and properties set on this FactoryBean.
         */
        protected Properties mergeProperties() throws IOException {
                Properties result = new Properties();

                if (this.localOverride) {
                        // Load properties from file upfront, to let local properties override.
                        loadProperties(result);
                }

                if (this.localProperties != null) {
                        for (Properties localProp : this.localProperties) {
                                CollectionUtils.mergePropertiesIntoMap(localProp, result);
                        }
                }

                if (!this.localOverride) {
                        // Load properties from file afterwards, to let those properties override.
                        loadProperties(result);
                }

                return result;
        }

        /**
         * Load properties into the given instance.
         * @param props the Properties instance to load into
         * @throws IOException in case of I/O errors
         * @see #setLocations
         */
        protected void loadProperties(Properties props) throws IOException {
                if (this.locations != null) {
                        for (Resource location : this.locations) {
                                if (logger.isTraceEnabled()) {
                                        logger.trace("Loading properties file from " + location);
                                }
                                try {
                                        PropertiesLoaderUtils.fillProperties(
                                                        props, new EncodedResource(location, this.fileEncoding), this.propertiesPersister);
                                }
                                catch (FileNotFoundException | UnknownHostException | SocketException ex) {
                                        if (this.ignoreResourceNotFound) {
                                                if (logger.isDebugEnabled()) {
                                                        logger.debug("Properties resource not found: " + ex.getMessage());
                                                }
                                        }
                                        else {
                                                throw ex;
                                        }
                                }
                        }
                }
        }

}