Preserve Epic game files when storage checks reject updates

app/src/main/java/com/droiddeck/launcher/stores/epic/EpicDownloadManager.java

@@ -205,15 +205,11 @@ public final class EpicDownloadManager {
             if (!chunkCacheDir.isDirectory() && !chunkCacheDir.mkdirs()) throw new InstallException("Could not create Epic chunk cache");
             Map<String, Long> cachedChunkBytes = prepareBoundedCache(chunkCacheDir, needed);
             long pendingBytes = 0;
+            long reclaimableBytes = 0;
             for (FileInfo f : pending) {
                 pendingBytes += f.fileSize();
                 File output = new File(installDir, f.filename.replace("\\", "/"));
-                File parent = output.getParentFile();
-                if (parent != null) parent.mkdirs();
-                // This file failed the delta check, so it cannot be resumed as a valid install.
-                // Remove it before estimating/writing its replacement to avoid requiring space
-                // for both the corrupt file and its verified replacement.
-                if (output.isFile() && !output.delete() && output.exists()) throw new InstallException("Could not replace incomplete file " + output.getName());
+                if (output.isFile()) reclaimableBytes += output.length();
             }
             boolean cacheOnInstallVolume = cachePath.isEmpty();
             long peakGameAdditional = cacheOnInstallVolume
@@ -221,13 +217,23 @@ public final class EpicDownloadManager {
                     : pendingBytes;
             long peakCacheAdditional = cacheOnInstallVolume
                     ? 0 : estimatePeakAdditionalBytes(pending, chunksByGuid, cachedChunkBytes, false);
+            peakGameAdditional = Math.max(0, peakGameAdditional - reclaimableBytes);
             long freeGame = installDir.getUsableSpace();
             if (cacheOnInstallVolume) {
                 if (freeGame > 0 && peakGameAdditional > freeGame) throw new InstallException("Not enough free space for the bounded Epic install: need up to " + fmt(peakGameAdditional) + " additional, only " + fmt(freeGame) + " free");
             } else {
                 long freeCache = chunkCacheDir.getUsableSpace();
                 if (freeCache > 0 && peakCacheAdditional > freeCache) throw new InstallException("Not enough internal space for the bounded Epic download cache: need up to " + fmt(peakCacheAdditional) + " additional, only " + fmt(freeCache) + " free");
-                if (freeGame > 0 && pendingBytes > freeGame) throw new InstallException("Not enough free space: need " + fmt(pendingBytes) + ", only " + fmt(freeGame) + " free");
+                if (freeGame > 0 && peakGameAdditional > freeGame) throw new InstallException("Not enough free space: need " + fmt(peakGameAdditional) + ", only " + fmt(freeGame) + " free");
+            }
+            if (cancel.get()) return null;
+            // Reclaim invalid/old outputs only after both volume checks accept the update.
+            // The peak estimate assumes these bytes are released before replacement writes.
+            for (FileInfo f : pending) {
+                File output = new File(installDir, f.filename.replace("\\", "/"));
+                File parent = output.getParentFile();
+                if (parent != null) parent.mkdirs();
+                if (output.isFile() && !output.delete() && output.exists()) throw new InstallException("Could not replace incomplete file " + output.getName());
             }
             cb.onLog("epic: cache " + (cacheOnInstallVolume ? "beside the game" : "scratch") + ", peak game additional=" + fmt(peakGameAdditional) + (cacheOnInstallVolume ? "" : ", peak cache additional=" + fmt(peakCacheAdditional)) + " for " + fmt(pendingBytes) + " of files");
             final long fTotalBytes = pendingBytes;

app/src/test/java/com/droiddeck/launcher/stores/epic/EpicBoundedInstallTest.kt

@@ -101,6 +101,43 @@ class EpicBoundedInstallTest {
         assertEquals("Verified files must not be downloaded again", 1, requests.get())
     }
 
+    private fun oversizedUpdate() {
+        val file = manifest.files[0]
+        val part = file.parts[0]
+        file.parts.clear()
+        repeat(100_000) {
+            file.parts.add(EpicDownloadManager.ChunkPart().apply {
+                guid = part.guid
+                size = Int.MAX_VALUE
+            })
+        }
+    }
+
+    @Test fun insufficientInstallSpacePreservesExistingFilesOnBothCacheLayouts() {
+        val oldGame = byteArrayOf(9, 8, 7)
+        val oldPart = byteArrayOf(6, 5, 4)
+        File(root, "game.bin").writeBytes(oldGame)
+        File(root, "game.bin.part").writeBytes(oldPart)
+        oversizedUpdate()
+        assertTrue(manifest.files[0].fileSize() > root.usableSpace)
+
+        for (cache in listOf("", temp.newFolder("scratch-rejected").path)) {
+            val error = assertThrows(EpicDownloadManager.InstallException::class.java) { install(cache = cache) }
+            assertTrue(error.message.orEmpty().contains("Not enough free space"))
+            assertArrayEquals(oldGame, File(root, "game.bin").readBytes())
+            assertArrayEquals(oldPart, File(root, "game.bin.part").readBytes())
+        }
+        assertEquals(0, requests.get())
+    }
+
+    @Test fun acceptedUpdateReplacesOutdatedFilesWithVerifiedOutputs() {
+        File(root, "game.bin").writeBytes(byteArrayOf(9, 8, 7))
+        File(root, "game.bin.part").writeBytes(byteArrayOf(6, 5, 4))
+        assertNotNull(install())
+        assertArrayEquals(bytes.copyOfRange(0, bytes.size / 2), File(root, "game.bin").readBytes())
+        assertArrayEquals(bytes.copyOfRange(bytes.size / 2, bytes.size), File(root, "game.bin.part").readBytes())
+    }
+
     @Test fun pauseKeepsCompletedFilesAndResumeReusesSharedCache() {
         val cancel = AtomicBoolean()
         val callback = object : EpicDownloadManager.Callback {

docs/development/stores.md

@@ -51,7 +51,9 @@ Streaming stays in the Download stage until all files are written and verified,
 Install for registration; it does not bounce between stages for each file.
 
 The space check follows the manifest delta pass and simulates file writes, chunk fetches,
-and evictions, rather than adding the entire cache to the entire game. Completed files and
+and evictions, rather than adding the entire cache to the entire game. It accounts for space
+reclaimable from outdated outputs without deleting them until both game and cache volume
+checks pass. An insufficient-space rejection preserves existing game files. Completed files and
 verified cached chunks are accounted for on resume. On a card, game and cache requirements
 are checked separately. File SHA-1 hashes are checked where supplied by the manifest; failed
 or cancelled output files are removed, and an interrupted process is repaired by the next