package co.codewizards.cloudstore.core.config;

import static co.codewizards.cloudstore.core.util.StringUtil.*;

import java.io.File;

import co.codewizards.cloudstore.core.util.IOUtil;

/**
 * {@code ConfigDir} represents the central configuration directory.
 * <p>
 * Besides the configuration, this directory holds all global (non-repository-related)
 * files, including log files.
 * @author Marco หงุ่ยตระกูล-Schulze - marco at codewizards dot co
 */
public class ConfigDir {

        /**
         * System property controlling the location of the central configuration directory.
         * <p>
         * If this system property is not set, it defaults to: <code>/home/tomcat/.cloudstore</code>
         * <p>
         * Note that this property is always set during runtime. If it is not set by the caller (via a <code>-D</code> JVM argument)
         * from the outside, then it is set by the code inside the running application. Therefore, this property
         * can be referenced in all configuration files where system properties are resolved (e.g. in the logback configuration).
         * @see #getValue()
         * @see #getFile()
         */
        public static final String SYSTEM_PROPERTY_CONFIG_DIR = "cloudstore.configDir";

        /**
         * System property controlling the location of the log directory.
         * <p>
         * If this system property is not set, it defaults to:
         * <code>/home/tomcat/.cloudstore/log</code>
         * <p>
         * Note that this property is always set during runtime. If it is not set by the caller (via a <code>-D</code> JVM argument)
         * from the outside, then it is set by the code inside the running application. Therefore, this property
         * can be referenced in all configuration files where system properties are resolved (e.g. in the logback configuration).
         * @see #getLogDir()
         */
        public static final String SYSTEM_PROPERTY_LOG_DIR = "cloudstore.logDir";

        private static final class ConfigDirHolder {
                public static ConfigDir instance = new ConfigDir();
        }

        private String value;
        private File file;
        private File logDir;

        /**
         * Creates an instance of {@code ConfigDir}.
         * <p>
         * This method cannot and should not be called directly. Instead, {@link #getInstance()} should be
         * used to obtain the singleton.
         */
        private ConfigDir() {
                value = System.getProperty(SYSTEM_PROPERTY_CONFIG_DIR, "/home/tomcat/.cloudstore");
                System.setProperty(SYSTEM_PROPERTY_CONFIG_DIR, value);
                String resolvedValue = IOUtil.replaceTemplateVariables(value, System.getProperties());
                file = new File(resolvedValue).getAbsoluteFile();
                if (!file.isDirectory())
                        file.mkdirs();

                if (!file.isDirectory())
                        throw new IllegalStateException("Could not create directory (permissions?!): " + file);
        }

        /**
         * Gets the singleton instance of {@code ConfigDir}.
         * @return the singleton instance of {@code ConfigDir}. Never <code>null</code>.
         */
        public static ConfigDir getInstance() {
                return ConfigDirHolder.instance;
        }

        /**
         * Gets the central configuration directory as {@code String}.
         * <p>
         * This is the <i>non-resolved</i> (as is) value of the system property {@link #SYSTEM_PROPERTY_CONFIG_DIR}.
         * Even if this property was not set (from the outside), it is initialised by default to:
         * <code>/home/tomcat/.cloudstore</code>
         * @return the central configuration directory as {@code String}. Never <code>null</code>.
         * @see #SYSTEM_PROPERTY_CONFIG_DIR
         * @see #getFile()
         */
        public String getValue() {
                return value;
        }

        /**
         * Gets the central configuration directory as <i>absolute</i> {@code File}.
         * <p>
         * In contrast to {@link #getValue()}, this file's path is <i>resolved</i>; i.e. all system properties
         * occurring in it (e.g. "/home/tomcat") were replaced by their actual values.
         * @return the central configuration directory as <i>absolute</i> {@code File}. Never <code>null</code>.
         * @see #SYSTEM_PROPERTY_CONFIG_DIR
         * @see #getValue()
         */
        public File getFile() {
                return file;
        }

        /**
         * Gets the log directory (the directory where the log files are written to).
         * <p>
         * This directory can be configured or referenced (e.g. in a logback configuation file) via
         * {@link #SYSTEM_PROPERTY_LOG_DIR}.
         * @return the log directory. Never <code>null</code>.
         * @see #SYSTEM_PROPERTY_LOG_DIR
         */
        public File getLogDir() {
                if (logDir == null) {
                        String sysPropVal = System.getProperty(SYSTEM_PROPERTY_LOG_DIR);
                        if (isEmpty(sysPropVal))
                                logDir = new File(getFile(), "log");
                        else {
                                String resolvedSysPropVal = IOUtil.replaceTemplateVariables(sysPropVal, System.getProperties());
                                logDir = new File(resolvedSysPropVal).getAbsoluteFile();
                        }

                        System.setProperty(SYSTEM_PROPERTY_LOG_DIR, logDir.getPath());
                        if (!logDir.isDirectory())
                                logDir.mkdirs();

                        if (!logDir.isDirectory())
                                throw new IllegalStateException("Could not create directory (permissions?!): " + logDir);
                }
                return logDir;
        }
}