added cpp executor and cpp searcher (#143)

* added cpp executor and cpp searcher

* improved regular expression for cpp_searcher.java

* Update CppExecutor.java

reformat compilation command

src/main/java/org/hyperskill/hstest/stage/StageTest.java

@@ -15,10 +15,7 @@
 import org.hyperskill.hstest.testcase.TestCase;
 import org.hyperskill.hstest.testing.TestRun;
 import org.hyperskill.hstest.testing.execution.MainMethodExecutor;
-import org.hyperskill.hstest.testing.execution.process.GoExecutor;
-import org.hyperskill.hstest.testing.execution.process.JavascriptExecutor;
-import org.hyperskill.hstest.testing.execution.process.PythonExecutor;
-import org.hyperskill.hstest.testing.execution.process.ShellExecutor;
+import org.hyperskill.hstest.testing.execution.process.*;
 import org.hyperskill.hstest.testing.runner.AsyncDynamicTestingRunner;
 import org.hyperskill.hstest.testing.runner.TestRunner;
 import org.junit.Test;
@@ -85,6 +82,9 @@ private TestRunner initRunner() {
 
         for (var folder : walkUserFiles(FileUtils.cwd())) {
             for (var file : folder.getFiles()) {
+                if (file.getName().endsWith(".cpp")) {
+                    return new AsyncDynamicTestingRunner(CppExecutor.class);
+                }
                 if (file.getName().endsWith(".go")) {
                     return new AsyncDynamicTestingRunner(GoExecutor.class);
                 }

src/main/java/org/hyperskill/hstest/testing/execution/process/CppExecutor.java

@@ -0,0 +1,70 @@
+package org.hyperskill.hstest.testing.execution.process;
+
+import org.hyperskill.hstest.testing.execution.ProcessExecutor;
+import org.hyperskill.hstest.testing.execution.searcher.CppSearcher;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.stream.Collectors;
+
+import static org.hyperskill.hstest.common.FileUtils.abspath;
+import static org.hyperskill.hstest.common.OsUtils.isWindows;
+
+/**
+ * Executes C++ runnable files
+ * (files with main function)
+ * in the given directory.
+ *
+ */
+public class CppExecutor extends ProcessExecutor {
+    private final String executable;
+    private final String filename;
+
+    public CppExecutor(String sourceName) {
+        super(new CppSearcher().find(sourceName));
+
+        var fileName = runnable.getFile().getName();
+
+        var withoutCpp = fileName
+                .substring(0, fileName.length() - new CppSearcher().extension().length());
+
+        if (isWindows()) {
+            executable = withoutCpp;
+            filename = executable + ".exe";
+        } else {
+            executable = "./" + withoutCpp;
+            filename = withoutCpp;
+        }
+    }
+
+    @Override
+    protected List<String> compilationCommand() {
+        return List.of("g++", "-std", "c++20", "-pipe", "-O2", "-static", "-o", filename, runnable.getFile().getName());
+    }
+
+    @Override
+    protected String filterCompilationError(String error) {
+        // Adapt error filtering if needed
+        return error;
+    }
+
+    @Override
+    protected List<String> executionCommand(List<String> args) {
+        List<String> fullArgs = new ArrayList<>();
+        fullArgs.add(executable);
+        fullArgs.addAll(args);
+
+        return fullArgs;
+    }
+
+    @Override
+    protected void cleanup() {
+        try {
+            Files.deleteIfExists(Paths.get(abspath(filename)));
+        } catch (IOException ignored) { }
+    }
+}
+

src/main/java/org/hyperskill/hstest/testing/execution/searcher/CppSearcher.java

@@ -0,0 +1,24 @@
+package org.hyperskill.hstest.testing.execution.searcher;
+
+import org.hyperskill.hstest.testing.execution.runnable.RunnableFile;
+
+/**
+ * Searches for C++ runnable files
+ * (files with main function)
+ * in the given directory
+ * and returns the first one found.
+ */
+public class CppSearcher extends BaseSearcher {
+    @Override
+    public String extension() {
+        return ".cpp";
+    }
+
+    @Override
+    public RunnableFile search(String whereToSearch) {
+        return simpleSearch(whereToSearch,
+                "int main()",
+                "(^|\\n)\\s*int\\s+main\\s*\\(.*\\)"
+        );
+    }
+}