feat(ci-server): add webhook-triggered compilation (#29)

.gitignore

@@ -0,0 +1 @@
+target/

README.md

@@ -212,6 +212,35 @@ At line:1 char:1
 
 </details>
 
+### Compilation (P1)
+
+#### Implementation
+
+When the CI server receives a GitHub push webhook on `/webhook`, it triggers compilation of the pushed branch. The `Compiler` class in `se.ciserver.build` performs the following steps:
+
+1. Creates a temporary directory
+2. Clones the specific branch using `git clone --branch <branch> --single-branch <url>`
+3. Checks out the exact commit SHA with `git checkout <sha>`
+4. Runs `mvn clean compile` in the cloned project
+5. Captures and prints the build output to the server console
+6. Cleans up the temporary directory
+
+The compilation result (success/failure) is returned in the HTTP response and printed to the server console.
+
+#### Unit testing
+
+Compilation is unit-tested in `src/test/java/MainTest.java` with the following tests:
+
+- `compilationResultStoresSuccess()` — verifies that a successful `CompilationResult` stores `success=true` and the build output.
+- `compilationResultStoresFailure()` — verifies that a failed `CompilationResult` stores `success=false` and the build output.
+- `compilerHandlesCloneFailure()` — subclasses `Compiler` to override `createProcessBuilder()` with a failing command, verifying that a clone failure returns `success=false` without throwing an exception.
+- `compilerReturnsSuccessWhenAllStepsPass()` — subclasses `Compiler` to override `createProcessBuilder()` with a succeeding command, verifying the full pipeline returns `success=true`.
+- `ciServerHandleCompilationOnPush()` — starts a local Jetty server, sends a valid push payload to `/webhook`, and verifies the response is `200` and contains the compilation result with the commit SHA.
+
+To run the tests, see [Perform unit tests](#perform-unit-tests).
+
+---
+
 ## Perform unit tests
 
 1. Build the project with **Maven**
@@ -225,10 +254,38 @@ mvn clean compile
 ```bash
 mvn test
 ```
+
+3. Verify all tests pass in the output
+
+```console
+Tests run: 9, Failures: 0, Errors: 0, Skipped: 0
+
+BUILD SUCCESS
+```
+
+### Connect the server to a webhook with ngrok
+
+1. Run the server, see [Run the server](#run-the-server).
+
+2. In a separate terminal, start ngrok to expose port `8080`:
+
+```bash
+ngrok http 8080
+```
+
+3. Copy the forwarding URL (e.g. `https://xxxx.ngrok-free.app`) from the ngrok output.
+
+4. In your GitHub repository, go to **Settings > Webhooks > Add webhook** and set:
+   - **Payload URL**: `https://xxxx.ngrok-free.app/webhook`
+   - **Content type**: `application/json`
+   - **Events**: Select "Just the push event"
+
+5. Push a commit to the repository and observe the compilation output in the server console.
 ---
 
 ## Statements of contributions
 
 | Name                       | Contribution                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
 |----------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
 | Josefine "joss2002" Nyholm | <ul><li>[x] Added initial **Maven** file-tree structure, including a basic `pom.xml` with **JDK 17** support.</li></ul><ul><li>[x] Added skeleton for CI-server in `src/main/java/se/ciserver/ContinuousIntegrationServer.java`.<ul><li>Added related dependencies, plugins; `jetty-server`, `exec-maven-plugin`</li><li>[x] Added additional documentation.</li></ul></li></ul><ul><li>[x] Added **GitHub** push event `JSON` payload component.<ul><li>[x] Added required Webhook payload object parameters and classes for `push` within `src/main/java/se/ciserver/github` including files; `PushParser.java`, `Push.java`, `Pusher.java`, `Commit.java`, `Author.java` and `Repository.java`.</li><li>[x] Added additional `Exception` extension in `InvalidPayloadException.java` specified for invalid payloads.</li><li>[x] Integrated the push parsing `JSON` payload functionality in the `ContinuousIntegrationServer.java` `handler()` to allow the CI-server to receive `JSON` payloads and present the relevant variables; `ref`, `after`, `repository.clone_url`, `pusher.name`, `head_commit.message`.</li><li>[x] Added unit tests in `src/test/java/MainTest.java` for `PushParser.java` push parsing `JSON` payload functionality and local testing of the `ContinuousIntegrationServer.java` CI-server handling of push parsing `JSON` payloads. This, as well as an additional file `src/main/java/se/ciserver/TestUtils.java` including test utilities such as reading filed. Supporting the unit tests a test `JSON` file `src/main/test/resources/githubPush.java` was added to represent a typical push event payload.</li><li>[x] Added additional dependencies in `pom.xml` for `jackson-databind` and `junit`</li><li>[x] Added additional documentation in `README.md`.</li></ul></li></ul> |
+| Avid "HotFazz" Fayaz | <ul><li>[x] Added webhook-triggered compilation (P1) in `src/main/java/se/ciserver/build/Compiler.java`.<ul><li>[x] Clones the pushed branch, checks out the exact commit, and runs `mvn clean compile`.</li><li>[x] Added `CompilationResult.java` to hold build outcome and output.</li><li>[x] Integrated compilation into `ContinuousIntegrationServer.java` webhook handler.</li><li>[x] Added unit tests in `MainTest.java` for `CompilationResult` and `Compiler` failure handling.</li><li>[x] Added documentation in `README.md` for compilation implementation and unit testing.</li></ul></li></ul> |

src/main/java/se/ciserver/ContinuousIntegrationServer.java

@@ -11,6 +11,8 @@
 import java.io.IOException;
 import java.util.stream.Collectors;
 
+import se.ciserver.build.Compiler;
+import se.ciserver.build.CompilationResult;
 import se.ciserver.github.Push;
 import se.ciserver.github.PushParser;
 import se.ciserver.github.InvalidPayloadException;
@@ -20,7 +22,8 @@
  */
 public class ContinuousIntegrationServer extends AbstractHandler
 {
-    private final PushParser parser = new PushParser();
+    private final PushParser parser   = new PushParser();
+    private final Compiler   compiler = new Compiler();
 
     /**
      * Handles incoming HTTP requests for the CI server and presents necessary information.
@@ -41,23 +44,48 @@ public void handle(String target,
     {
         if ("/webhook".equals(target) && "POST".equalsIgnoreCase(request.getMethod()))
         {
+            // Read the full JSON payload from the request body
             String json = request.getReader().lines().collect(Collectors.joining(System.lineSeparator()));
 
             try
             {
+                // Parse the GitHub push event payload into a Push object
                 Push push = parser.parse(json);
 
+                // Log the push event details to the server console
                 System.out.println("\nReceived push on branch : " + push.ref +
                                    "\nAfter SHA               : " + push.after +
                                    "\nRepository URL          : " + push.repository.clone_url +
                                    "\nPusher name             : " + push.pusher.name +
                                    "\n\nHead commit message     : " + push.head_commit.message);
 
+                // P1: Clone the pushed branch and run mvn clean compile
+                System.out.println("\nStarting compilation...");
+                CompilationResult result = compiler.compile(
+                    push.repository.clone_url,
+                    push.ref,
+                    push.after);
+
+                // Log the compilation outcome to the server console
+                if (result.success)
+                {
+                    System.out.println("\nCompilation SUCCEEDED");
+                }
+                else
+                {
+                    System.out.println("\nCompilation FAILED");
+                }
+
+                // Respond with 200 regardless of build outcome;
+                // the webhook delivery itself was successful
                 response.setStatus(HttpServletResponse.SC_OK);
-                response.getWriter().println("Push received: " + push.after);
+                response.getWriter().println(
+                    (result.success ? "Compilation succeeded" : "Compilation failed")
+                    + " for commit: " + push.after);
             }
             catch (InvalidPayloadException e)
             {
+                // Malformed or missing JSON fields
                 response.setStatus(HttpServletResponse.SC_BAD_REQUEST);
                 response.getWriter().println("Invalid payload: " + e.getMessage());
             }

src/main/java/se/ciserver/build/CompilationResult.java

@@ -0,0 +1,25 @@
+package se.ciserver.build;
+
+/**
+ * Holds the result of a compilation attempt.
+ */
+public class CompilationResult
+{
+    /** Whether the compilation succeeded (exit code 0). */
+    public final boolean success;
+
+    /** The combined stdout/stderr output from the build. */
+    public final String output;
+
+    /**
+     * Constructs a CompilationResult.
+     *
+     * @param success Whether the compilation succeeded
+     * @param output  The combined stdout/stderr output from the build
+     */
+    public CompilationResult(boolean success, String output)
+    {
+        this.success = success;
+        this.output  = output;
+    }
+}

src/main/java/se/ciserver/build/Compiler.java

@@ -0,0 +1,190 @@
+package se.ciserver.build;
+
+import java.io.BufferedReader;
+import java.io.InputStreamReader;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Comparator;
+import java.util.stream.Collectors;
+
+/**
+ * Handles cloning a repository, checking out a specific commit,
+ * and running Maven compilation.
+ */
+public class Compiler
+{
+    /**
+     * Clones the repository, checks out the specified commit, and
+     * runs {@code mvn clean compile}.
+     *
+     * @param cloneUrl  The clone URL of the repository
+     * @param branch    The branch name to clone
+     * @param commitSha The commit SHA to checkout
+     *
+     * @return A {@link CompilationResult} indicating success/failure and build output
+     */
+    public CompilationResult compile(String cloneUrl, String branch, String commitSha)
+    {
+        Path tempDir = null;
+
+        try
+        {
+            // Create an isolated temporary directory for this build
+            tempDir = Files.createTempDirectory("ci-build-");
+
+            // Step 1: Clone only the target branch (--single-branch avoids
+            // downloading the full repo history)
+            int cloneExit = runProcess(tempDir.getParent(),
+                "git", "clone", "--branch", branch, "--single-branch",
+                cloneUrl, tempDir.toString());
+
+            if (cloneExit != 0)
+            {
+                return new CompilationResult(false,
+                    "Git clone failed with exit code " + cloneExit);
+            }
+
+            // Step 2: Checkout the exact commit SHA that triggered the webhook
+            int checkoutExit = runProcess(tempDir,
+                "git", "checkout", commitSha);
+
+            if (checkoutExit != 0)
+            {
+                return new CompilationResult(false,
+                    "Git checkout failed with exit code " + checkoutExit);
+            }
+
+            // Step 3: Run Maven compilation and return the result
+            return runCompilation(tempDir);
+        }
+        catch (IOException | InterruptedException e)
+        {
+            return new CompilationResult(false,
+                "Compilation error: " + e.getMessage());
+        }
+        finally
+        {
+            // Always clean up the temporary directory to avoid disk bloat
+            if (tempDir != null)
+            {
+                cleanup(tempDir);
+            }
+        }
+    }
+
+    /**
+     * Runs a process and returns its exit code.
+     * Output is printed to System.out for server console visibility.
+     *
+     * @param workDir The working directory for the process
+     * @param command The command and its arguments
+     *
+     * @return The process exit code
+     *
+     * @throws IOException          If an I/O error occurs
+     * @throws InterruptedException If the process is interrupted
+     */
+    private int runProcess(Path workDir, String... command)
+            throws IOException, InterruptedException
+    {
+        ProcessBuilder pb = createProcessBuilder(command);
+        pb.directory(workDir.toFile());
+        pb.redirectErrorStream(true); // Merge stderr into stdout
+
+        Process process = pb.start();
+
+        // Consume output line-by-line and print to the server console
+        try (BufferedReader reader = new BufferedReader(
+                new InputStreamReader(process.getInputStream())))
+        {
+            String line;
+            while ((line = reader.readLine()) != null)
+            {
+                System.out.println(line);
+            }
+        }
+
+        // Block until the process finishes and return its exit code
+        return process.waitFor();
+    }
+
+    /**
+     * Runs {@code mvn clean compile} in the given directory and captures output.
+     *
+     * @param workDir The directory containing the Maven project
+     *
+     * @return A {@link CompilationResult} with the build outcome
+     *
+     * @throws IOException          If an I/O error occurs
+     * @throws InterruptedException If the process is interrupted
+     */
+    private CompilationResult runCompilation(Path workDir)
+            throws IOException, InterruptedException
+    {
+        ProcessBuilder pb = createProcessBuilder("mvn", "clean", "compile");
+        pb.directory(workDir.toFile());
+        pb.redirectErrorStream(true); // Merge stderr into stdout
+
+        Process process = pb.start();
+
+        // Capture all build output into a single string
+        String output;
+        try (BufferedReader reader = new BufferedReader(
+                new InputStreamReader(process.getInputStream())))
+        {
+            output = reader.lines()
+                .collect(Collectors.joining(System.lineSeparator()));
+        }
+
+        int exitCode = process.waitFor();
+
+        // Print Maven output to server console so grader can observe the build
+        System.out.println(output);
+
+        // Exit code 0 means compilation succeeded
+        return new CompilationResult(exitCode == 0, output);
+    }
+
+    /**
+     * Creates a ProcessBuilder for the given command.
+     * Protected so tests can override to avoid spawning real processes.
+     *
+     * @param command The command and its arguments
+     *
+     * @return A new ProcessBuilder configured for the command
+     */
+    protected ProcessBuilder createProcessBuilder(String... command)
+    {
+        return new ProcessBuilder(command);
+    }
+
+    /**
+     * Recursively deletes the temporary build directory.
+     *
+     * @param directory The directory to delete
+     */
+    private void cleanup(Path directory)
+    {
+        try
+        {
+            Files.walk(directory)
+                 .sorted(Comparator.reverseOrder())
+                 .forEach(path ->
+                 {
+                     try
+                     {
+                         Files.delete(path);
+                     }
+                     catch (IOException e)
+                     {
+                         /* best effort cleanup */
+                     }
+                 });
+        }
+        catch (IOException e)
+        {
+            System.err.println("Warning: Failed to clean up " + directory);
+        }
+    }
+}