Implement writeYaml

Author: YangSiJun528

initializr-generator-spring/src/main/java/io/spring/initializr/generator/spring/properties/ApplicationProperties.java

@@ -29,6 +29,8 @@
  */
 public class ApplicationProperties {
 
+	private static final String YAML_SPACE = "  ";
+
 	private final Map<String, Object> properties = new HashMap<>();
 
 	/**
@@ -73,8 +75,50 @@ void writeTo(PrintWriter writer) {
 		}
 	}
 
-	void writeToYaml(PrintWriter writer) {
-		// TODO: Impl
+	void writeYaml(PrintWriter writer) {
+		Map<String, Object> nested = flattenToNestedMap(this.properties);
+		writeYamlRecursive(nested, writer, 0);
+	}
+
+	private static Map<String, Object> flattenToNestedMap(Map<String, Object> flatMap) {
+		Map<String, Object> nested = new HashMap<>();
+		flatMap.forEach((key, value) -> {
+			String[] path = parseKeyPath(key);
+			insertValueAtPath(nested, path, value);
+		});
+		return nested;
+	}
+
+	private static String[] parseKeyPath(String key) {
+		return key.split("\\.");
+	}
+
+	@SuppressWarnings("unchecked")
+	private static void insertValueAtPath(Map<String, Object> map, String[] path, Object value) {
+		Map<String, Object> current = map;
+		for (int i = 0; i < path.length - 1; i++) {
+			String segment = path[i];
+			current = (Map<String, Object>) current.computeIfAbsent(segment, (k) -> new HashMap<>());
+		}
+		current.put(path[path.length - 1], value);
+	}
+
+	private static void writeYamlRecursive(Map<String, Object> map, PrintWriter writer, int indent) {
+		map.entrySet().forEach((entry) -> writeEntry(entry, writer, indent));
+	}
+
+	@SuppressWarnings("unchecked")
+	private static void writeEntry(Map.Entry<String, Object> entry, PrintWriter writer, int indent) {
+		String indentStr = YAML_SPACE.repeat(indent);
+		Object value = entry.getValue();
+
+		if (value instanceof Map<?, ?> nestedMap) {
+			writer.printf("%s%s:%n", indentStr, entry.getKey());
+			writeYamlRecursive((Map<String, Object>) nestedMap, writer, indent + 1);
+		}
+		else {
+			writer.printf("%s%s: %s%n", indentStr, entry.getKey(), value);
+		}
 	}
 
 	private void add(String key, Object value) {

initializr-generator-spring/src/main/java/io/spring/initializr/generator/spring/properties/ApplicationYamlPropertiesContributor.java

@@ -50,7 +50,7 @@ public void contribute(Path projectRoot) throws IOException {
 		}
 		try (PrintWriter writer = new PrintWriter(Files.newOutputStream(output, StandardOpenOption.APPEND), false,
 				StandardCharsets.UTF_8)) {
-			this.properties.writeToYaml(writer);
+			this.properties.writeYaml(writer);
 		}
 	}
 

initializr-generator-spring/src/test/java/io/spring/initializr/generator/spring/properties/ApplicationPropertiesTests.java

@@ -71,6 +71,20 @@ void shouldFailOnExistingProperty() {
 			.withMessage("Property 'test' already exists");
 	}
 
+	@Test
+	void writeYaml() {
+		ApplicationProperties properties = new ApplicationProperties();
+		properties.add("name", "testapp");
+		properties.add("port", 8080);
+		properties.add("app.version", "1.0");
+		properties.add("db.host", "localhost");
+		properties.add("app.config.debug", true);
+		properties.add("db.connection.timeout", 30);
+		String written = writeYaml(properties);
+		assertThat(written).contains("name: testapp", "port: 8080", "app:\n  config:\n    debug: true\n  version: 1.0",
+				"db:\n  host: localhost\n  connection:\n    timeout: 30");
+	}
+
 	private String write(ApplicationProperties properties) {
 		StringWriter stringWriter = new StringWriter();
 		try (PrintWriter writer = new PrintWriter(stringWriter)) {
@@ -79,4 +93,12 @@ private String write(ApplicationProperties properties) {
 		return stringWriter.toString();
 	}
 
+	private String writeYaml(ApplicationProperties properties) {
+		StringWriter stringWriter = new StringWriter();
+		try (PrintWriter writer = new PrintWriter(stringWriter)) {
+			properties.writeYaml(writer);
+		}
+		return stringWriter.toString();
+	}
+
 }