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/**
 * Creative commons Attribution-NonCommercial license.
 *
 * http://creativecommons.org/licenses/by-nc/2.5/au/deed.en_GB
 *
 * NO WARRANTY IS GIVEN OR IMPLIED, USE AT YOUR OWN RISK.
 */
package base.jee.api;

import base.KeyValue;

import java.io.IOException;
import java.util.Date;
import java.util.Hashtable;
import java.util.Iterator;
import java.util.Map;

/**
 * Standard mechanism for getting and setting configuration settings.
 */
public class Settings {

	/** Cached version of the configuration settings */
	private Map setting = new Hashtable<>();

	private API api;

	/** Indicates at what time the cached setting data will expire */
	private long expires = (new Date()).getTime()-60*1000;

	public Settings(API api) throws IOException {
		if(api == null) {
			throw new IllegalArgumentException("Valid data source parameter is required.");
		}

		this.api = api;
		loadSettings();
	}

	/**
	 * Retrieve a configuration setting. First checks if the configuration setting
	 * is cached in memory, otherwise the configuration setting is loaded from
	 * the database.
	 *
	 * @param name
	 * @return
	 * @throws java.io.IOException Throws an IOException when there is a problem with the database
	 *     or if the name parameter does not correspond to a valid database entry
	 */
	public String get(String name) throws IOException {
		if(expires < (new Date()).getTime()) {
			loadSettings();
		}
		String value = setting.get(name);
		if(value == null) {
			throw new IOException("Required configuration parameter not specified: " + name);
		}
		return value;
	}

	/**
	 * Retrieve a configuration setting. First checks if the configuration setting
	 * is cached in memory, otherwise the configuration setting is loaded from
	 * the database.
	 *
	 * @param name
	 * @return
	 * @throws java.io.IOException
	 */
	public String get(String name, String defaultValue) throws IOException {
		if(expires < (new Date()).getTime()) {
			loadSettings();
		}
		String value = setting.get(name);
		if(value != null) {
			return value;
		}
		return defaultValue;
	}

	/**
	 * Returns a map of all the current setting key value pairs. The settings returned by
	 * this method are cached and hence at times may be inconsistent with the database.
	 *
	 * @return All current settings.
	 * @throws java.io.IOException
	 */
	public Map getAll() throws IOException {
		Map all = new Hashtable<>();
		if(expires < (new Date()).getTime()) {
			loadSettings();
		}

		Iterator i = setting.keySet().iterator();
		while(i.hasNext()) {
			String key = (String)i.next();
			all.put(key, setting.get(key));
		}

		return all;
	}

	/**
	 * Force clear the cache of setting information to ensure the next read of a setting
	 * returns the most up to date settings.
	 *
	 * @throws java.io.IOException
	 */
	public void refresh() throws IOException {
		expires = 0;
	}

	/**
	 * Update a configuration setting in memory and in the database itself. If there
	 * is a problem writing to the database, the value for this setting will not be
	 * changed in memory or in the database.
	 *
	 * @param name
	 * @param value
	 * @throws java.io.IOException Thrown when there is a problem writing to the database
	 */
	public void set(String name, String value) throws IOException {
		if(expires < (new Date()).getTime()) {
			loadSettings();
		}
		if(setting.get(name) != null && setting.get(name).equals(value)) {
			return;
		}

		api.upsertSetting(null, name, value);

		setting.put(name, value);
	}

	public void remove(String name) throws IOException {
		api.deleteSetting(null, name);
		setting.remove(name);
	}

	/**
	 * Reload the configuration settings from the database. If any problems occur
	 * while the settings are being loaded, the previous set of cached settings
	 * are retained.
	 *
	 * @throws java.io.IOException Thrown when there is a problem reading from the database.
	 */
	private void loadSettings() throws IOException {
		Map newSettings = new Hashtable<>();

		for(KeyValue r : api.getSettings(null)) {
			if(r.getValue() == null) {
				newSettings.put(r.getKey(), "");
			} else {
				newSettings.put(r.getKey(), r.getValue());
			}
		}

		// Reset the data expire time
		try {
			expires = (new Date()).getTime() + Long.parseLong(newSettings.get("setting.cache.timeout"))*1000;
		} catch(Exception e) {
			// Set a default time to expire in 60 seconds
			expires = (new Date()).getTime() + 60*1000;
		}
		setting = newSettings;

	}

	public void deleteAll() throws IOException {
		api.deleteAllSettings(null);
		setting = new Hashtable<>();

	}

}