From 93774aebe31f89c1892d3673879d1befb21ad48e Mon Sep 17 00:00:00 2001
From: Michael Hoennig <michael@hoennig.de>
Date: Thu, 4 Jul 2024 13:07:03 +0200
Subject: [PATCH] add SystemProcess as wrapper for ProcessBuilder using Strings
 for simplified input+output

---
 .../hsadminng/system/SystemProcess.java       | 57 +++++++++++++
 .../hsadminng/system/SystemProcessTest.java   | 81 +++++++++++++++++++
 2 files changed, 138 insertions(+)
 create mode 100644 src/main/java/net/hostsharing/hsadminng/system/SystemProcess.java
 create mode 100644 src/test/java/net/hostsharing/hsadminng/system/SystemProcessTest.java

diff --git a/src/main/java/net/hostsharing/hsadminng/system/SystemProcess.java b/src/main/java/net/hostsharing/hsadminng/system/SystemProcess.java
new file mode 100644
index 00000000..149c6019
--- /dev/null
+++ b/src/main/java/net/hostsharing/hsadminng/system/SystemProcess.java
@@ -0,0 +1,57 @@
+package net.hostsharing.hsadminng.system;
+
+import lombok.Getter;
+
+import java.io.BufferedReader;
+import java.io.BufferedWriter;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.io.OutputStreamWriter;
+
+public class SystemProcess {
+    private final ProcessBuilder processBuilder;
+
+    @Getter
+    private String stdOut;
+    @Getter
+    private String stdErr;
+
+    public SystemProcess(final String... command) {
+        this.processBuilder = new ProcessBuilder(command);
+    }
+
+    public int execute() throws IOException, InterruptedException {
+        final var process = processBuilder.start();
+        stdOut = fetchOutput(process.getInputStream()); // yeah, twisted ProcessBuilder API
+        stdErr = fetchOutput(process.getErrorStream());
+        return process.waitFor();
+    }
+
+    public int execute(final String input) throws IOException, InterruptedException {
+        final var process = processBuilder.start();
+        feedInput(input, process);
+        stdOut = fetchOutput(process.getInputStream()); // yeah, twisted ProcessBuilder API
+        stdErr = fetchOutput(process.getErrorStream());
+        return process.waitFor();
+    }
+
+    private static void feedInput(final String input, final Process process) throws IOException {
+        try (
+                final OutputStreamWriter stdIn = new OutputStreamWriter(process.getOutputStream()); // yeah, twisted ProcessBuilder API
+                final BufferedWriter writer = new BufferedWriter(stdIn)) {
+            writer.write(input);
+            writer.flush();
+        }
+    }
+
+    private static String fetchOutput(final InputStream inputStream) throws IOException {
+        final var output = new StringBuilder();
+        try (final BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream))) {
+            for (String line; (line = reader.readLine()) != null; ) {
+                output.append(line).append(System.lineSeparator());
+            }
+        }
+        return output.toString();
+    }
+}
diff --git a/src/test/java/net/hostsharing/hsadminng/system/SystemProcessTest.java b/src/test/java/net/hostsharing/hsadminng/system/SystemProcessTest.java
new file mode 100644
index 00000000..e1924adf
--- /dev/null
+++ b/src/test/java/net/hostsharing/hsadminng/system/SystemProcessTest.java
@@ -0,0 +1,81 @@
+package net.hostsharing.hsadminng.system;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.condition.EnabledOnOs;
+
+import java.io.IOException;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.catchThrowable;
+import static org.junit.jupiter.api.condition.OS.LINUX;
+
+class SystemProcessTest {
+
+    @Test
+    @EnabledOnOs(LINUX)
+    void shouldExecuteAndFetchOutput() throws IOException, InterruptedException {
+        // given
+        final var process = new SystemProcess("bash", "-c", "echo 'Hello, World!'; echo 'Error!' >&2");
+
+        // when
+        final var returnCode = process.execute();
+
+        // then
+        assertThat(returnCode).isEqualTo(0);
+        assertThat(process.getStdOut()).isEqualTo("Hello, World!\n");
+        assertThat(process.getStdErr()).isEqualTo("Error!\n");
+    }
+
+    @Test
+    @EnabledOnOs(LINUX)
+    void shouldReturnErrorCode() throws IOException, InterruptedException {
+        // given
+        final var process = new SystemProcess("false");
+
+        // when
+        final int returnCode = process.execute();
+
+        // then
+        assertThat(returnCode).isEqualTo(1);
+    }
+
+    @Test
+    @EnabledOnOs(LINUX)
+    void shouldExecuteAndFeedInput() throws IOException, InterruptedException {
+        // given
+        final var process = new SystemProcess("tr", "[:lower:]", "[:upper:]");
+
+        // when
+        final int returnCode = process.execute("Hallo");
+
+        // then
+        assertThat(returnCode).isEqualTo(0);
+        assertThat(process.getStdOut()).isEqualTo("HALLO\n");
+    }
+
+    @Test
+    void shouldThrowExceptionIfProgramNotFound() {
+        // given
+        final var process = new SystemProcess("non-existing program");
+
+        // when
+        final var exception = catchThrowable(process::execute);
+
+        // then
+        assertThat(exception).isInstanceOf(IOException.class)
+                .hasMessage("Cannot run program \"non-existing program\": error=2, No such file or directory");
+    }
+
+    @Test
+    void shouldBeAbleToRunMultipleTimes() throws IOException, InterruptedException {
+        // given
+        final var process = new SystemProcess("true");
+
+        // when
+        process.execute();
+        final int returnCode = process.execute();
+
+        // then
+        assertThat(returnCode).isEqualTo(0);
+    }
+}