Skip running example if example is unchanged

1 files changed, 108 insertions, 6 deletions

diff --git a/src/test/java/org/zwobble/hobgoblin/compiler/ExampleTests.java b/src/test/java/org/zwobble/hobgoblin/compiler/ExampleTests.java
index fd38a84..999ae83 100644
--- a/src/test/java/org/zwobble/hobgoblin/compiler/ExampleTests.java
+++ b/src/test/java/org/zwobble/hobgoblin/compiler/ExampleTests.java
@@ -5,7 +5,12 @@ import org.junit.jupiter.api.TestFactory;
 import org.zwobble.hobgoblin.compiler.testing.TestProcessRunner;
 
 import java.io.IOException;
-import java.util.List;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.*;
+import java.nio.file.attribute.BasicFileAttributes;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+import java.util.*;
 import java.util.stream.Stream;
 
 public class ExampleTests {
@@ -18,14 +23,111 @@ public class ExampleTests {
             ));
     }
 
-    private void runTest(ExampleSet exampleSet) throws IOException, InterruptedException {
+    private void runTest(ExampleSet exampleSet) throws IOException, InterruptedException, NoSuchAlgorithmException {
         var javaProjectPath = exampleSet.path().resolve("output/java");
 
         HobgoblinCompiler.compile(exampleSet.path());
 
-        TestProcessRunner.command(List.of("mvn", "compile"))
-            .cwd(javaProjectPath)
-            .runCaptureOutput()
-            .throwOnError();
+        var currentHash = hashJavaProject(javaProjectPath);
+
+        var lastTestRunPath = javaProjectPath.resolve("last-test-run.properties");
+        var lastTestRun = readLastTestRun(lastTestRunPath);
+
+        if (lastTestRun.isPresent() && lastTestRun.get().pass && lastTestRun.get().hash.equals(currentHash)) {
+            return;
+        }
+
+        try {
+            TestProcessRunner.command(List.of("mvn", "compile"))
+                .cwd(javaProjectPath)
+                .runCaptureOutput()
+                .throwOnError();
+            writeLastTestRun(lastTestRunPath, new LastTestRun(currentHash, true));
+        } catch (Throwable exception) {
+            writeLastTestRun(lastTestRunPath, new LastTestRun(currentHash, false));
+            throw exception;
+        }
+    }
+
+    private record LastTestRun(String hash, boolean pass) {}
+
+    private Optional<LastTestRun> readLastTestRun(Path path) throws IOException {
+        var properties = new Properties();
+        try (var reader = Files.newBufferedReader(path)) {
+            properties.load(reader);
+            var hash = properties.getProperty("hash");
+            var pass = properties.getProperty("result").equals("PASS");
+            return Optional.of(new LastTestRun(hash, pass));
+        } catch (NoSuchFileException exception) {
+            return Optional.empty();
+        }
+    }
+
+    private void writeLastTestRun(Path path, LastTestRun lastTestRun) throws IOException {
+        var properties = new Properties();
+        properties.setProperty("hash", lastTestRun.hash);
+        properties.setProperty("result", lastTestRun.pass ? "PASS" : "FAIL");
+        try (var writer = Files.newBufferedWriter(path)) {
+            properties.store(writer, null);
+        }
+    }
+
+    private String hashJavaProject(Path javaProjectPath) throws NoSuchAlgorithmException, IOException {
+        var paths = collectJavaProjectSourcePaths(javaProjectPath);
+
+        var digest = MessageDigest.getInstance("sha256");
+
+        for (var path : paths) {
+            digest.update(path.toString().getBytes(StandardCharsets.UTF_8));
+            digest.update(new byte[]{0});
+            var contents = Files.readAllBytes(path);
+            digest.update(contents);
+            digest.update(new byte[]{0});
+        }
+
+        return bytesToHex(digest.digest());
+    }
+
+    private static String bytesToHex(byte[] bytes) {
+        var hexString = new StringBuilder(2 * bytes.length);
+        for (var b : bytes) {
+            var hex = Integer.toHexString(0xff & b);
+            if (hex.length() == 1) {
+                hexString.append('0');
+            }
+            hexString.append(hex);
+        }
+        return hexString.toString();
+    }
+
+    private static List<Path> collectJavaProjectSourcePaths(Path javaProjectPath) throws IOException {
+        var paths = new ArrayList<Path>();
+
+        Files.walkFileTree(
+            javaProjectPath, new SimpleFileVisitor<>() {
+            @Override
+            public FileVisitResult visitFile(
+                Path file,
+                BasicFileAttributes attrs
+            ) {
+                if (!javaProjectPath.relativize(file).toString().equals("last-test-run.properties")) {
+                    paths.add(file);
+                }
+                return FileVisitResult.CONTINUE;
+            }
+
+            @Override
+            public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) throws IOException {
+                if (javaProjectPath.relativize(dir).startsWith("target")) {
+                    return FileVisitResult.SKIP_SUBTREE;
+                } else {
+                    return FileVisitResult.CONTINUE;
+                }
+            }
+        });
+
+        paths.sort(Comparator.naturalOrder());
+
+        return paths;
     }
 }