fix: disconnect desktop download on session cancel

app/src/main/java/com/droiddeck/launcher/SessionActivity.kt

@@ -1436,9 +1436,15 @@ class SessionActivity : ComponentActivity(), SurfaceHolder.Callback {
     private fun installDesktop(): String? {
         uiHandler.post { loading.percent = -1; loading.say(getString(DESKTOP_LINES.downloading), DESKTOP_LINES.topic, readable = true) }
         val entry = com.droiddeck.launcher.runtime.DesktopCatalog.desktopEntry(this)
-        val problem = com.droiddeck.launcher.runtime.DesktopCatalog.install(this, entry, { SessionState.stopRequested },
-            progressFor(DESKTOP_LINES, entry.size / 1_000_000))
-        return problem?.let { getString(R.string.session_desktop_install_failed, it) }
+        val cancellation = com.droiddeck.launcher.core.Downloader.Cancellation { SessionState.stopRequested }
+        SessionState.installCancellation = cancellation
+        return try {
+            val problem = com.droiddeck.launcher.runtime.DesktopCatalog.install(this, entry, cancellation,
+                progressFor(DESKTOP_LINES, entry.size / 1_000_000))
+            problem?.let { getString(R.string.session_desktop_install_failed, it) }
+        } finally {
+            if (SessionState.installCancellation === cancellation) SessionState.installCancellation = null
+        }
     }
 
     private fun installProton(): String? {

app/src/main/java/com/droiddeck/launcher/core/Downloader.java

@@ -15,6 +15,8 @@ import java.net.URL;
 import java.nio.charset.StandardCharsets;
 import java.util.List;
 import java.util.Properties;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicReference;
 
 public final class Downloader {
     private static final String TAG = "Downloader";
@@ -24,6 +26,32 @@ public final class Downloader {
 
     private Downloader() {}
 
+    public static final class Cancellation implements java.util.function.BooleanSupplier {
+        private final AtomicBoolean cancelled = new AtomicBoolean();
+        private final AtomicReference<HttpURLConnection> connection = new AtomicReference<>();
+        private final java.util.function.BooleanSupplier external;
+
+        public Cancellation() { this(null); }
+        public Cancellation(java.util.function.BooleanSupplier external) { this.external = external; }
+
+        public void cancel() {
+            cancelled.set(true);
+            HttpURLConnection active = connection.get();
+            if (active != null) active.disconnect();
+        }
+
+        @Override public boolean getAsBoolean() {
+            return cancelled.get() || (external != null && external.getAsBoolean());
+        }
+
+        private void attach(HttpURLConnection active) {
+            connection.set(active);
+            if (getAsBoolean()) active.disconnect();
+        }
+
+        private void detach(HttpURLConnection active) { connection.compareAndSet(active, null); }
+    }
+
     public static String downloadString(String url) {
         List<String> sources = DownloadSource.INSTANCE.candidates(url);
         for (int i = 0; i < sources.size(); i++) {
@@ -182,6 +210,7 @@ public final class Downloader {
                 have = 0;
             }
             connection = open(url, STALL_TIMEOUT_MS);
+            if (cancelled instanceof Cancellation) ((Cancellation) cancelled).attach(connection);
             if (have > 0) {
                 connection.setRequestProperty("Range", "bytes=" + have + "-");
                 connection.setRequestProperty("If-Range", identity.etag);
@@ -245,7 +274,10 @@ public final class Downloader {
             Log.w(TAG, "download " + url, e);
             return Outcome.RETRY;
         } finally {
-            if (connection != null) connection.disconnect();
+            if (connection != null) {
+                if (cancelled instanceof Cancellation) ((Cancellation) cancelled).detach(connection);
+                connection.disconnect();
+            }
         }
     }
 

app/src/main/java/com/droiddeck/launcher/runtime/DesktopCatalog.kt

@@ -86,7 +86,10 @@ object DesktopCatalog {
         install(context, entry, { false }, listener)
 
     /** A cancel stops the download and is checked once more before anything on disk changes; extraction itself runs to the end. */
-    fun install(context: Context, entry: Entry, cancelled: () -> Boolean, listener: LinuxRuntimeInstaller.ProgressListener?): String? {
+    fun install(context: Context, entry: Entry, cancelled: () -> Boolean, listener: LinuxRuntimeInstaller.ProgressListener?): String? =
+        install(context, entry, Downloader.Cancellation(cancelled), listener)
+
+    fun install(context: Context, entry: Entry, cancelled: Downloader.Cancellation, listener: LinuxRuntimeInstaller.ProgressListener?): String? {
         val root = LinuxRuntime.rootDir(context)
         if (!root.isDirectory) return context.getString(R.string.deskpkg_runtime_missing)
         if (entry.sha256.isEmpty()) return context.getString(R.string.deskpkg_no_checksum, entry.name)

app/src/main/java/com/droiddeck/launcher/session/SessionService.kt

@@ -1733,6 +1733,7 @@ class SessionService : Service() {
         fun stop(context: Context) {
             if (!SessionState.running) {
                 SessionState.stopRequested = true
+                SessionState.installCancellation?.cancel()
                 return
             }
             context.startService(Intent(context, SessionService::class.java).setAction(ACTION_STOP))

app/src/main/java/com/droiddeck/launcher/session/SessionState.kt

@@ -36,6 +36,9 @@ object SessionState {
     @Volatile
     var installing: String? = null
 
+    @Volatile
+    var installCancellation: com.droiddeck.launcher.core.Downloader.Cancellation? = null
+
     @Volatile
     var stopRequested = false
 

app/src/test/java/com/droiddeck/launcher/core/DownloaderResumeTest.kt

@@ -6,6 +6,9 @@ import java.net.Socket
 import java.nio.file.Files
 import java.security.MessageDigest
 import java.util.concurrent.CopyOnWriteArrayList
+import java.util.concurrent.CountDownLatch
+import java.util.concurrent.Executors
+import java.util.concurrent.TimeUnit
 import org.junit.After
 import org.junit.Assert.assertArrayEquals
 import org.junit.Assert.assertEquals
@@ -29,6 +32,9 @@ class DownloaderResumeTest {
     @Volatile private var misbehave = false
     @Volatile private var etag: String? = "\"v1\""
     @Volatile private var corrupt = false
+    @Volatile private var holdAfterFirstChunk = false
+    private var bodyStarted = CountDownLatch(1)
+    private var continueBody = CountDownLatch(1)
 
     @Before fun setUp() {
         dir = Files.createTempDirectory("downloader-resume").toFile()
@@ -70,8 +76,15 @@ class DownloaderResumeTest {
             val start = if (from == null) "200 OK" else "206 Partial Content"
             val extra = if (from == null) "" else "Content-Range: bytes 0-${data.size - 1}/${data.size}\r\n"
             out.write("HTTP/1.1 $start\r\n${extra}${validator}Content-Length: ${data.size}\r\nConnection: close\r\n\r\n".toByteArray())
-            out.write(content)
-            out.flush()
+            if (holdAfterFirstChunk) {
+                out.write(content, 0, 1024)
+                out.flush()
+                bodyStarted.countDown()
+                continueBody.await(5, TimeUnit.SECONDS)
+            } else {
+                out.write(content)
+                out.flush()
+            }
         } else if (from == null) {
             out.write("HTTP/1.1 200 OK\r\n${validator}Content-Length: ${data.size}\r\nConnection: close\r\n\r\n".toByteArray())
             out.write(content, 0, cutAt)
@@ -181,6 +194,25 @@ class DownloaderResumeTest {
         assertTrue("the transfer stopped early (kept=${target.length()})", target.length() in 1 until data.size)
     }
 
+    @Test fun cancellationDisconnectsAStalledTransfer() {
+        val url = "http://127.0.0.1:${server.localPort}/first"
+        val target = File(dir, "runtime.tar.zst")
+        misbehave = true
+        holdAfterFirstChunk = true
+        val cancellation = Downloader.Cancellation()
+        val executor = Executors.newSingleThreadExecutor()
+        try {
+            val result = executor.submit<Boolean> { Downloader.downloadFile(url, target, true, null, cancellation, null) }
+            assertTrue("server sent the first chunk", bodyStarted.await(2, TimeUnit.SECONDS))
+            cancellation.cancel()
+            assertFalse("cancelled download", result.get(2, TimeUnit.SECONDS))
+            assertEquals(listOf<String?>(null), requests.toList())
+        } finally {
+            continueBody.countDown()
+            executor.shutdownNow()
+        }
+    }
+
     @Test fun aCancelBeforeTheFirstRequestSendsNothing() {
         val url = "http://127.0.0.1:${server.localPort}/runtime.tar.zst"
         val target = File(dir, "runtime.tar.zst")