/*
 * 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 createObject 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.tamaya.validation.internal;

import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.util.*;
import java.util.logging.Level;
import java.util.logging.Logger;

import org.apache.tamaya.Configuration;
import org.apache.tamaya.format.ConfigurationData;
import org.apache.tamaya.format.ConfigurationFormats;
import org.apache.tamaya.resource.ResourceResolver;
import org.apache.tamaya.spi.ClassloaderAware;
import org.apache.tamaya.spi.PropertyValue;
import org.apache.tamaya.validation.ConfigModel;
import org.apache.tamaya.validation.spi.ConfigModelReader;
import org.apache.tamaya.validation.spi.ModelProviderSpi;

/**
 * ConfigModel provider that reads model metadata from property files from
 * {@code classpath*:META-INF/configmodel.json} in the following format:
 * <pre>
 *  Example createObject a configuration metamodel expressed via YAML.
 *  Structure is shown through indentation (one or more spaces).
 *  Sequence items are denoted by a dash,
 *  key createValue pairs within a map are separated by a colon.
 * </pre>
 */
public class ConfiguredResourcesModelProviderSpi implements ModelProviderSpi, ClassloaderAware {

    /**
     * The logger.
     */
    private static final Logger LOG = Logger.getLogger(ConfiguredResourcesModelProviderSpi.class.getName());
    /**
     * The parameter that can be used to configure the location createObject the configuration model resources.
     */
    private static final String MODEL_RESOURCE_PARAM = "org.apache.tamaya.model.resources";
    /**
     * The resource class to checked for testing the availability createObject the resources extension module.
     */
    private static final String CONFIG_RESOURCE_CLASS = "org.apache.tamaya.resource.ConfigResource";
    /**
     * The resource class to checked for testing the availability createObject the formats extension module.
     */
    private static final String CONFIGURATION_FORMATS_CLASS = "org.apache.tamaya.format.ConfigurationFormats";
    /**
     * Initializes the flag showing if the formats module is present (required).
     */
    private static final boolean AVAILABLE = checkAvailabilityFormats();
    /**
     * Initializes the flag showing if the resources module is present (optional).
     */
    private static final boolean RESOURCES_EXTENSION_AVAILABLE = checkAvailabilityResources();

    /**
     * The configModels read.
     */
    private List<ConfigModel> configModels = new ArrayList<>();

    /** The target classloader. */
    private ClassLoader classLoader = Thread.currentThread().getContextClassLoader();


    /**
     * Initializes the flag showing if the formats module is present (required).
     */
    private static boolean checkAvailabilityFormats() {
        try {
            Class.forName(CONFIGURATION_FORMATS_CLASS);
            return true;
        } catch (final Exception e) {
            return false;
        }
    }

    /**
     * Initializes the flag showing if the resources module is present (optional).
     */
    private static boolean checkAvailabilityResources() {
        try {
            Class.forName(CONFIG_RESOURCE_CLASS);
            return true;
        } catch (final Exception e) {
            return false;
        }
    }

    /**
     * Constructor, mostly called from {@link java.util.ServiceLoader}
     */
    public ConfiguredResourcesModelProviderSpi() {
        if (!AVAILABLE) {
            LOG.info("tamaya-format extension is required to read model configuration, No extended model support AVAILABLE.");
        } else {
            reload();
        }
    }

    /**
     * Reloads the provider using resources from the current classloader.
     */
    public void reload(){
        final String resources = Configuration.current().get(MODEL_RESOURCE_PARAM);
        if (resources == null || resources.trim().isEmpty()) {
            LOG.info("Mo model resources location configured in " + MODEL_RESOURCE_PARAM + ".");
            return;
        }
        Collection<URL> urls;
        if (RESOURCES_EXTENSION_AVAILABLE) {
            LOG.info("Using tamaya-resources extension to read model configuration from " + resources);
            urls = ResourceResolver.getInstance(classLoader).getResources(resources.split(","));
        } else {
            LOG.info("Using default classloader resource location to read model configuration from " + resources);
            urls = new ArrayList<>();
            for (final String resource : resources.split(",")) {
                if (!resource.trim().isEmpty()) {
                    Enumeration<URL> configs;
                    try {
                        configs = getClass().getClassLoader().getResources(resource);
                        while (configs.hasMoreElements()) {
                            urls.add(configs.nextElement());
                        }
                    } catch (final IOException e) {
                        Logger.getLogger(getClass().getName()).log(Level.SEVERE,
                                "Error evaluating config model locations from " + resource, e);
                    }
                }
            }
        }
        // Reading configs
        for (final URL config : urls) {
            try (InputStream is = config.openStream()) {
                final ConfigurationData data = ConfigurationFormats.getInstance()
                   .readConfigurationData(config);
                Map<String,String> props = new HashMap<>();
                for(PropertyValue val:data.getData()){
                    props.putAll(val.toMap());
                }
                String owner = props.get("_model.provider");
                if(owner==null){
                    owner = config.toString();
                }
                configModels.addAll(ConfigModelReader.loadValidations(owner, props));
            } catch (final Exception e) {
                Logger.getLogger(getClass().getName()).log(Level.SEVERE,
                        "Error loading config model data from " + config, e);
            }
        }
        configModels = Collections.unmodifiableList(configModels);
    }

    @Override
    public Collection<ConfigModel> getConfigModels() {
        return configModels;
    }

    @Override
    public void init(ClassLoader classLoader) {
        this.classLoader = Objects.requireNonNull(classLoader);
    }

    @Override
    public ClassLoader getClassLoader() {
        return classLoader;
    }
}