BelegScanner/src/main/java/de/srsoftware/belegscanner/Configuration.java

package de.srsoftware.belegscanner;

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.nio.charset.StandardCharsets;

import org.json.JSONArray;
import org.json.JSONObject;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * 
 * JSON-based Configuration manager for the Application.
 * 
 * @author Stephan Richter <s.richter@srsoftware.de>
 *
 */
public class Configuration {

	private static final Logger LOG = LoggerFactory.getLogger(Configuration.class);
	private File file;
	private JSONObject json = new JSONObject();

	/**
	 * Create/Load configuration for the application.
	 * @param appName
	 * @throws IOException
	 */
	public Configuration(String appName) throws IOException {
		String home = System.getProperty("user.home");
		String fileName = new StringBuilder().append(home).append(File.separator).append(".config").append(File.separator).append(appName).append(File.separator).append("config.json").toString();
		file = new File(fileName);
		if (file.exists()) {
			LOG.info("{} found, loading…",file);
			FileReader in = new FileReader(file);
			ByteArrayOutputStream buffer = new ByteArrayOutputStream();
			OutputStreamWriter writer = new OutputStreamWriter(buffer);
			in.transferTo(writer);
			writer.close();
			String jsonString = buffer.toString(StandardCharsets.UTF_8);
			LOG.debug("Loaded json: {}",jsonString);			
			json = jsonString.startsWith("{") ? new JSONObject(jsonString) : new JSONObject();
			in.close();
		} else {
			LOG.info("{} not found, creating new config.",file);
			json = new JSONObject();			
		}
	}
	
	/**
	 * Write contents of the configuration object to the underlying file.
	 * @throws IOException
	 */
	public void save() throws IOException {
		LOG.debug("Trying to save config…");
		File dir = file.getParentFile();
		if (!dir.exists()) dir.mkdirs();
		FileWriter out = new FileWriter(file);
		json.write(out, 2, 0);
		out.close();
	}

	/**
	 * Load an JSON array from the configuration
	 * @param key Search path in the form path.to.array
	 * @return
	 */
	public JSONArray getOrCreateArray(String key) {
		LOG.debug("requesting {} from config.",key);
		String[] parts = key.split("\\.");
		JSONObject localJson = json;
		boolean update = false;
		JSONArray result = null; 
		for (int i=0; i<parts.length; i++) {
			String localKey = parts[i];
			LOG.debug("localKey = {}",localKey);
			boolean lastPart = i == parts.length-1;
			if (!localJson.has(localKey)) {
				LOG.debug("{} not present in {}, creating…",localKey,localJson);
				localJson.put(localKey, lastPart ? new JSONArray() : new JSONObject());
				update = true;
			}
			if (lastPart) {
				result = localJson.getJSONArray(localKey);
			} else localJson = localJson.getJSONObject(localKey);
		}
		if (update) try {
			save();
		} catch (IOException ex) {
			LOG.warn("Was not able to write config to {}!",file);
		}
		return result;
	}
	
	/**
	 * Load an Object from the configuration
	 * @param <T>
	 * @param key Search path in the form path.to.array
	 * @return null, if no such path is found
	 */
	@SuppressWarnings("unchecked")
	public <T> T get(String key) {
		LOG.debug("requesting {} from config.",key);
		String[] parts = key.split("\\.");
		JSONObject localJson = json;
		for (int i=0; i<parts.length; i++) {
			String localKey = parts[i];
			LOG.debug("localKey = {}",localKey);
			boolean lastPart = i == parts.length-1;
			if (!localJson.has(localKey)) return null;
			if (lastPart) return (T) localJson.get(localKey);
			localJson = localJson.getJSONObject(localKey);
		}
		return null;
	}
	
	/**
	 * Load an Object from the configuration, create it, if it is not present
	 * @param <T>
	 * @param key Search path in the form path.to.array
	 * @param preset Content for the path, if it does not exist
	 * @return preset, if no such path is found
	 */
	@SuppressWarnings("unchecked")
	public <T> T getOrCreate(String key, T preset) {
		LOG.debug("requesting {} from config.",key);
		String[] parts = key.split("\\.");
		JSONObject localJson = json;
		boolean update = false;
		Object result = preset; 
		for (int i=0; i<parts.length; i++) {
			String localKey = parts[i];
			LOG.debug("localKey = {}",localKey);
			boolean lastPart = i == parts.length-1;
			if (!localJson.has(localKey)) {
				LOG.debug("{} not present in {}, creating…",localKey,localJson);
				localJson.put(localKey, lastPart ? preset : new JSONObject());
				update = true;
			}
			if (lastPart) {				
				result = localJson.get(localKey);
			} else localJson = localJson.getJSONObject(localKey);
		}
		if (update) try {
			save();
		} catch (IOException ex) {
			LOG.warn("Was not able to write config to {}!",file);
		}		
		return (T) result;
	}
	
	/**
	 * Add a new value to the configuration or replace an existing value
	 * @param key Search path in the form path.to.array
	 * @param value the value to add/replace
	 */
	public void set(String key, Object value) {
		LOG.debug("setting {} to {}",key,value);
		String[] parts = key.split("\\.");
		JSONObject localJson = json;
		for (int i=0; i<parts.length; i++) {
			String localKey = parts[i];
			LOG.debug("localKey = {}",localKey);
			boolean lastPart = i == parts.length-1;
			if (!lastPart && !localJson.has(localKey)) {
				localJson.put(localKey, new JSONObject());
			}
			if (lastPart) {
				localJson.put(localKey, value);
				break;
			}
			localJson = localJson.getJSONObject(localKey);
		}
		LOG.debug("altered json: {}",json);
	}
}