Add concat() function (#20)

Author: joschi

src/main/java/org/graylog/plugins/pipelineprocessor/functions/strings/Concat.java

@@ -0,0 +1,54 @@
+/**
+ * This file is part of Graylog Pipeline Processor.
+ *
+ * Graylog Pipeline Processor is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Graylog Pipeline Processor is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Graylog Pipeline Processor.  If not, see <http://www.gnu.org/licenses/>.
+ */
+package org.graylog.plugins.pipelineprocessor.functions.strings;
+
+import com.google.common.base.Strings;
+import org.graylog.plugins.pipelineprocessor.EvaluationContext;
+import org.graylog.plugins.pipelineprocessor.ast.functions.AbstractFunction;
+import org.graylog.plugins.pipelineprocessor.ast.functions.FunctionArgs;
+import org.graylog.plugins.pipelineprocessor.ast.functions.FunctionDescriptor;
+import org.graylog.plugins.pipelineprocessor.ast.functions.ParameterDescriptor;
+
+import static com.google.common.collect.ImmutableList.of;
+
+public class Concat extends AbstractFunction<String> {
+    public static final String NAME = "concat";
+    private final ParameterDescriptor<String, String> firstParam;
+    private final ParameterDescriptor<String, String> secondParam;
+
+    public Concat() {
+        firstParam = ParameterDescriptor.string("first").build();
+        secondParam = ParameterDescriptor.string("second").build();
+    }
+
+    @Override
+    public String evaluate(FunctionArgs args, EvaluationContext context) {
+        final String first = Strings.nullToEmpty(firstParam.required(args, context));
+        final String second = Strings.nullToEmpty(secondParam.required(args, context));
+
+        return first.concat(second);
+    }
+
+    @Override
+    public FunctionDescriptor<String> descriptor() {
+        return FunctionDescriptor.<String>builder()
+                .name(NAME)
+                .returnType(String.class)
+                .params(of(firstParam, secondParam))
+                .build();
+    }
+}

src/test/java/org/graylog/plugins/pipelineprocessor/functions/FunctionsSnippetsTest.java

@@ -54,6 +54,7 @@
 import org.graylog.plugins.pipelineprocessor.functions.messages.SetFields;
 import org.graylog.plugins.pipelineprocessor.functions.strings.Abbreviate;
 import org.graylog.plugins.pipelineprocessor.functions.strings.Capitalize;
+import org.graylog.plugins.pipelineprocessor.functions.strings.Concat;
 import org.graylog.plugins.pipelineprocessor.functions.strings.Contains;
 import org.graylog.plugins.pipelineprocessor.functions.strings.GrokMatch;
 import org.graylog.plugins.pipelineprocessor.functions.strings.Lowercase;
@@ -137,6 +138,7 @@ public static void registerFunctions() {
         // string functions
         functions.put(Abbreviate.NAME, new Abbreviate());
         functions.put(Capitalize.NAME, new Capitalize());
+        functions.put(Concat.NAME, new Concat());
         functions.put(Contains.NAME, new Contains());
         functions.put(Lowercase.NAME, new Lowercase());
         functions.put(Substring.NAME, new Substring());

src/test/resources/org/graylog/plugins/pipelineprocessor/functions/strings.txt

@@ -13,7 +13,8 @@ when
     abbreviate("abcdefg", 6) == "abc..." &&
     abbreviate("abcdefg", 7) == "abcdefg" &&
     abbreviate("abcdefg", 8) == "abcdefg" &&
-    abbreviate("abcdefg", 4) == "a..."
+    abbreviate("abcdefg", 4) == "a..." &&
+    concat("foo", "bar") == "foobar"
 then
     set_field("has_xyz", contains("abcdef", "xyz"));
     trigger_test();