import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Properties;



/**
 * JSONPropertiesConverter convert a {@link Properties} file to a JSON object 
 * that can be used to access properties values with a dot separated path style.
 * <br />
 * <u>E.g.:</u> <br />
 * In properties : <em>person.name.first = "Firstname"</em><br/>
 * In JavaScript : <em>var firstname = person.name.first;</em><br/>
 *
 * 
 * @see http://www.json.org/
 */
public class JSONPropertiesConverter {

	public static void main(String[] args) {
		Properties properties = new Properties();
		properties.put("mail.format.invalid", "Format invalide");
		properties.put("format.date", "dd/mm/yy");
		
		System.out.println(new JSONPropertiesConverter().convert(properties));
	}
	
	private final HashMap<String, JSONEntry> parents = new HashMap<String, JSONEntry>();
	
	/**
	 * Convert the given {@link Properties} to a JSON Object to allow you
	 * accessing the properties values with a dot separated path.
	 *
	 * @param properties - The properties to convert.
	 * @return A string that represent the JSON Object.
	 */
	public String convert(final Properties properties) {
		parents.clear();
		for (Object objKey : properties.keySet()) {
			String key = objKey.toString();
			String parts[] = key.split("\\.");
			JSONEntry parent = null;
			for (int i=0; i<parts.length; i++) {
				if ( (i==parts.length-1) || (parts.length==1) ) { // Last key part (value)
					JSONEntry entry = new JSONEntry(parts[i], properties.getProperty(key));
					parent = getParent(parts[i-1]);
					parent.addChild(entry);
					entry.setParent(parent);
				} else if ( i==0 ) { // Root key
					//parent = getParent(parts[i]);
					parent = new JSONEntry(parts[i]);
					if ( parts.length==1 ) {
						parent.setValue(properties.getProperty(key));
					}
				} else { // First or intermediate key part
					JSONEntry entry = getParent(parts[i]);
					parent = getParent(parts[i-1]);
					parent.addChild(entry);
					entry.setParent(parent);
				}
			}
		}

		StringBuffer buffer = new StringBuffer();
		for (String key : parents.keySet()) {
			JSONEntry entry = parents.get(key);
			if ( entry.getParent()!=null ) {
				continue;
			}
			buffer.append(entry.toJSON()).append(",\n");
		}
		if ( buffer.length()>0 ) {
			buffer.replace(buffer.length()-(",\n".length()), buffer.length(), "");
		}
		return buffer.toString();
	}


	// ~ Private methods -------------------------------------------------------

	private JSONEntry getParent(final String name) {
		JSONEntry parent = null;
		if ( parents.containsKey(name) ) {
			parent = parents.get(name);
		} else {
			parent = new JSONEntry(name);
			parents.put(name, parent);
		}
		return parent;
	}

	// ~ Internal classes ------------------------------------------------------

	private class JSONEntry {

		private final String key;
		private String value;
		private JSONEntry parent;
		private List<JSONEntry> childs;

		public JSONEntry(final String key) {
			this(key, null);
		}

		public JSONEntry(final String key, final String value) {
			this.key = key;
			this.value = value;
		}

		public void setParent(final JSONEntry parent) {
			this.parent = parent;
		}

		public JSONEntry getParent() {
			return parent;
		}

		public void addChild(final JSONEntry child) {
			if ( childs == null ) {
				childs = new ArrayList<JSONEntry>(1);
			}
			if ( childs.contains(child) ) {
				childs.remove(child);
			}
			childs.add(child);
		}

		public void setValue(final String value) {
			if ( (childs!=null) && (childs.size()>0) ) {
				throw new IllegalStateException("A final entry cannot hold childs. "+toString());
			}

			this.value = value;
		}

		public String getKey() {
			return key;
		}

		public String getParentKey() {
			if ( key.indexOf('.')<=0 ) {
				return null;
			}
			String name = key.substring(key.lastIndexOf('.')+1);
			return key.substring(0, key.length()-name.length()+1);
		}

		public String toJSON() {
			/* Use double quotes for string. With using double quotes, special
			 * chars are ignored with JavaScript and only the '"' character
			 * must be escaped. */
			StringBuilder buff = new StringBuilder("\"").append(key).append("\"");
			if ( value!=null) {
				String jsValue = value
					.replaceAll("''","'")			// Remove double quotes
					.replaceAll("\\\"", "\\\\\"")	// Escape " because they are used in json
					/*.replaceAll("\\'", "\\\\'")					// Escape single quotes
					.replaceAll("\\{", "\\\\{")
					.replaceAll("\\}", "\\\\}")
					.replaceAll("\\[", "\\\\[")
					.replaceAll("\\]", "\\\\]")*/
					.replaceAll("[ \\t\\n\\x0B\\f\\r]{2,}", " "); // Remove redundant white spaces
				buff.append(" : \"").append(jsValue).append("\"");
			} else {
				buff.append(" : {");
				if ( childs!=null ) {
					for (JSONEntry child : childs) {
						buff.append(child.toJSON()).append(", ");
					}
					// Remove the last ", "
					buff.replace(buff.length()-2, buff.length(), " ");
				}
				buff.append("}");
			}
			return buff.toString();
		}
	}
}