Extract some common utils

Author: ppkarwasz

log4j-converter-config/pom.xml

@@ -25,7 +25,7 @@
   </parent>
 
   <artifactId>log4j-converter-config</artifactId>
-  <name>Apache Log4j Configuration converter</name>
+  <name>Apache Log4j Configuration Converter</name>
   <description>Converts various logging configuration formats to the Log4j Core 2.x format.</description>
 
   <properties>

log4j-converter-config/src/main/java/org/apache/logging/converter/config/internal/ComponentUtils.java

@@ -0,0 +1,156 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to you under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.logging.converter.config.internal;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+import java.util.TreeMap;
+import java.util.function.Supplier;
+import org.apache.logging.converter.config.ConfigurationConverterException;
+import org.apache.logging.converter.config.spi.ConfigurationNode;
+import org.jspecify.annotations.Nullable;
+
+public final class ComponentUtils {
+
+    public static ConfigurationNodeBuilder newNodeBuilder() {
+        return new ConfigurationNodeBuilder();
+    }
+
+    public static ConfigurationNode createThresholdFilter(String level) {
+        return newNodeBuilder()
+                .setPluginName("ThresholdFilter")
+                .addAttribute("level", level)
+                .build();
+    }
+
+    public static ConfigurationNode createCompositeFilter(Iterable<? extends ConfigurationNode> filters) {
+        ConfigurationNodeBuilder builder = newNodeBuilder().setPluginName("Filters");
+        filters.forEach(builder::addChild);
+        return builder.build();
+    }
+
+    private ComponentUtils() {}
+
+    public static class ConfigurationNodeBuilder implements Supplier<ConfigurationNode> {
+
+        private @Nullable String pluginName;
+        private final Map<String, String> attributes = new TreeMap<>();
+        private final List<ConfigurationNode> children = new ArrayList<>();
+
+        protected ConfigurationNodeBuilder() {}
+
+        public ConfigurationNodeBuilder setPluginName(String pluginName) {
+            this.pluginName = pluginName;
+            return this;
+        }
+
+        public ConfigurationNodeBuilder addAttribute(String key, @Nullable String value) {
+            if (value != null) {
+                attributes.put(key, value);
+            }
+            return this;
+        }
+
+        public ConfigurationNodeBuilder addAttribute(String key, boolean value) {
+            attributes.put(key, String.valueOf(value));
+            return this;
+        }
+
+        public ConfigurationNodeBuilder addChild(ConfigurationNode child) {
+            children.add(child);
+            return this;
+        }
+
+        public ConfigurationNode build() {
+            if (pluginName == null) {
+                throw new ConfigurationConverterException("No plugin name specified");
+            }
+            return new ConfigurationNodeImpl(pluginName, attributes, children);
+        }
+
+        @Override
+        public ConfigurationNode get() {
+            return build();
+        }
+    }
+
+    private static final class ConfigurationNodeImpl implements ConfigurationNode {
+
+        private final String pluginName;
+        private final Map<String, String> attributes;
+        private final List<ConfigurationNode> children;
+
+        private ConfigurationNodeImpl(
+                final String pluginName,
+                final Map<String, String> attributes,
+                final Collection<ConfigurationNode> children) {
+            this.pluginName = pluginName;
+            this.attributes = Collections.unmodifiableMap(new TreeMap<>(attributes));
+            this.children = Collections.unmodifiableList(new ArrayList<>(children));
+        }
+
+        @Override
+        public String getPluginName() {
+            return pluginName;
+        }
+
+        @Override
+        public Map<String, String> getAttributes() {
+            return attributes;
+        }
+
+        @Override
+        public List<? extends ConfigurationNode> getChildren() {
+            return children;
+        }
+
+        private static void formatTo(ConfigurationNode node, StringBuilder builder, int indent) {
+            String indentation = getIndentation(indent);
+            builder.append(indentation).append("<").append(node.getPluginName());
+            for (final Map.Entry<String, String> entry : node.getAttributes().entrySet()) {
+                builder.append(" ")
+                        .append(entry.getKey())
+                        .append("=\"")
+                        .append(entry.getValue())
+                        .append("\"");
+            }
+            builder.append(">\n");
+            for (ConfigurationNode child : node.getChildren()) {
+                formatTo(child, builder, indent + 1);
+                builder.append('\n');
+            }
+            builder.append(indentation)
+                    .append("</")
+                    .append(node.getPluginName())
+                    .append(">");
+        }
+
+        private static String getIndentation(int indent) {
+            return String.join("", Collections.nCopies(indent, "  "));
+        }
+
+        @Override
+        public String toString() {
+            StringBuilder builder = new StringBuilder();
+            formatTo(this, builder, 0);
+            return builder.toString();
+        }
+    }
+}