Add yml properties manager (#134)

---------
Co-authored-by: Matthias Meyer <matthias.meyer@msg.group>

pom.xml

@@ -124,6 +124,11 @@
       <artifactId>maven-plugin-annotations</artifactId>
       <scope>provided</scope>
     </dependency>
+    <dependency>
+      <groupId>org.yaml</groupId>
+      <artifactId>snakeyaml</artifactId>
+      <version>2.3</version>
+    </dependency>
   </dependencies>
 
   <build>

src/main/java/org/codehaus/mojo/properties/managers/YmlPropertiesManager.java

@@ -0,0 +1,108 @@
+package org.codehaus.mojo.properties.managers;
+
+import javax.inject.Named;
+import javax.inject.Singleton;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.io.OutputStreamWriter;
+import java.io.PrintWriter;
+import java.io.StringReader;
+import java.io.StringWriter;
+import java.nio.charset.StandardCharsets;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Properties;
+
+import org.yaml.snakeyaml.Yaml;
+
+/**
+ * Properties manager using YAML as backand.
+ */
+@Named
+@Singleton
+public class YmlPropertiesManager implements PropertiesManager {
+
+    private static final String SUPPORTED_EXTENSION_YML = "yml";
+    private static final String SUPPORTED_EXTENSION_YAML = "yaml";
+
+    @Override
+    public boolean isExtensionSupport(final String extension) {
+        return SUPPORTED_EXTENSION_YML.equals(extension) || SUPPORTED_EXTENSION_YAML.equals(extension);
+    }
+
+    @Override
+    public Properties load(final InputStream in) throws IOException {
+        final Properties properties = new Properties();
+        final Map<String, Object> map = flattenYamlToMap("", new Yaml().load(in));
+        properties.putAll(map);
+        return properties;
+    }
+
+    public Map<String, Object> flattenYamlToMap(String parentKey, final Map<String, Object> yamlMap) {
+        if (parentKey != null && !parentKey.trim().isEmpty()) {
+            parentKey = parentKey.trim() + ".";
+        }
+        final Map<String, Object> result = new HashMap<>();
+
+        for (final Map.Entry<String, Object> entry : yamlMap.entrySet()) {
+            final String key = String.format("%s%s", parentKey, entry.getKey().trim());
+            final Object value = entry.getValue();
+            if (value instanceof Map) {
+                final Map<String, Object> stringObjectMap = flattenYamlToMap(key, (Map<String, Object>) value);
+                result.putAll(stringObjectMap);
+            } else if (value instanceof Collection) {
+                final Object[] values = ((Collection<?>) value).toArray();
+                for (int i = 0; i < values.length; i++) {
+                    if (values[i] instanceof Map) {
+                        result.putAll(flattenYamlToMap(
+                                String.format("%s%s[%d]", parentKey, entry.getKey(), i), (Map) values[i]));
+                    } else {
+                        result.put(String.format("%s%s[%d]", parentKey, entry.getKey(), i), String.valueOf(values[i]));
+                    }
+                }
+            } else {
+                result.put(key, value);
+            }
+        }
+        return result;
+    }
+
+    @Override
+    public void save(final Properties properties, final OutputStream out, String comments) throws IOException {
+
+        final OutputStreamWriter outputStreamWriter = new OutputStreamWriter(out, StandardCharsets.ISO_8859_1);
+
+        try (PrintWriter pw = new PrintWriter(outputStreamWriter);
+                StringWriter sw = new StringWriter()) {
+            properties.store(sw, comments);
+            comments = '#' + comments;
+
+            final List<String> lines = new ArrayList<>();
+            try (BufferedReader r = new BufferedReader(new StringReader(sw.toString()))) {
+                String line;
+                while ((line = r.readLine()) != null) {
+                    if (!line.startsWith("#") || line.equals(comments)) {
+                        lines.add(line);
+                    }
+                }
+            }
+
+            Collections.sort(lines);
+            for (final String l : lines) {
+                pw.println(l);
+            }
+        }
+    }
+
+    @Override
+    public String toString() {
+        return String.format("%s [extension=%s]", getClass().getSimpleName(), SUPPORTED_EXTENSION_YML);
+    }
+}

src/test/java/org/codehaus/mojo/properties/managers/YmlPropertiesManagerTest.java

@@ -0,0 +1,55 @@
+package org.codehaus.mojo.properties.managers;
+
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.util.Properties;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class YmlPropertiesManagerTest {
+
+    private static final String NL = System.lineSeparator();
+
+    private final YmlPropertiesManager manager = new YmlPropertiesManager();
+
+    @Test
+    public void testLoad() throws IOException {
+
+        // given
+        final String props = "# comments" + NL + NL + "key1:" + NL + "  key2: value1" + NL + "key3: value2" + NL
+                + "key4: " + NL + "  - A" + NL + "  - B" + NL + "  - C" + NL;
+
+        final ByteArrayInputStream inputStream = new ByteArrayInputStream(props.getBytes());
+
+        // when
+        final Properties properties = manager.load(inputStream);
+
+        // then
+        assertEquals(5, properties.size());
+        assertEquals("value1", properties.getProperty("key1.key2"));
+        assertEquals("value2", properties.getProperty("key3"));
+        assertEquals("A", properties.getProperty("key4[0]"));
+    }
+
+    @Test
+    public void testSave() throws IOException {
+
+        // given
+        final Properties properties = new Properties();
+        properties.setProperty("key1", "value1");
+        properties.setProperty("key2", "value2");
+
+        final ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
+
+        // when
+        manager.save(properties, outputStream, "Test comments");
+
+        // then
+        final String expected = "#Test comments" + NL + "key1=value1" + NL + "key2=value2" + NL;
+
+        assertEquals(expected, outputStream.toString());
+    }
+}