package de.rwu.easydrop.util;

import java.io.FileInputStream;
import java.io.IOException;
import java.util.NoSuchElementException;
import java.util.Properties;

import javax.naming.ConfigurationException;

/**
 * Allows access to the config.
 *
 * @since 0.1.0
 */
public final class Config {
    /**
     * Config file location.
     */
    private String configLocation = "config/config.properties";

    /**
     * @return the configLocation
     */
    public String getConfigLocation() {
        return configLocation;
    }

    /**
     * @param newConfigLocation the configLocation to set
     */
    public void setConfigLocation(final String newConfigLocation) {
        configLocation = newConfigLocation;
    }

    /**
     * Holds the config values.
     */
    private Properties properties = null;
    /**
     * Singleton instance.
     */
    private static Config instance = null;

    /**
     * Private constructor to prevent external instantiation.
     */
    private Config() {
        // Do Nothing
    }

    /**
     * Returns current config instance.
     *
     * @return Config instance
     */
    public static Config getInstance() {
        if (instance == null) {
            instance = new Config();
        }

        return instance;
    }

    /**
     * Loads config file values into the instance.
     *
     * @throws ConfigurationException
     */
    public void loadConfig() throws ConfigurationException {
        Properties newProps = new Properties();
        try (FileInputStream input = new FileInputStream(configLocation)) {
            newProps.load(input);
            properties = newProps;
        } catch (IOException e) {
            throw new ConfigurationException("Couldn't load required config file");
        }
    }

    /**
     * Returns a config property by specified key.
     *
     * @param key Config Key, like "API_KEY"
     * @return Config value
     * @throws NoSuchElementException Required key missing
     */
    public String getProperty(final String key) throws NoSuchElementException {
        String value = null;

        try {
            value = properties.getProperty(key);
        } catch (NullPointerException e) {
            throw new NoSuchElementException("Config has not been loaded");
        }

        if (value == null) {
            throw new NoSuchElementException("Requested config value does not exist");
        }

        return value;
    }

    /**
     * Overrides a config property loaded from file for current instance.
     *
     * @param key   Config Key
     * @param value Property Value
     */
    public void setProperty(final String key, final String value) {
        properties.setProperty(key, value);
    }

    /**
     * Resets the config's properties.
     */
    public void reset() {
        properties = null;
    }
}