feat(pipeline): improve file processing with resource management and temp file handling (#5488)

# Description of Changes

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Please provide a summary of the changes, including:

- What was changed
- Why the change was made
- Any challenges encountered

Closes #(issue_number)
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---

## Checklist

### General

- [ ] I have read the [Contribution
Guidelines](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/CONTRIBUTING.md)
- [ ] I have read the [Stirling-PDF Developer
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/DeveloperGuide.md)
(if applicable)
- [ ] I have read the [How to add new languages to
Stirling-PDF](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md)
(if applicable)
- [ ] I have performed a self-review of my own code
- [ ] My changes generate no new warnings

### Documentation

- [ ] I have updated relevant docs on [Stirling-PDF's doc
repo](https://github.com/Stirling-Tools/Stirling-Tools.github.io/blob/main/docs/)
(if functionality has heavily changed)
- [ ] I have read the section [Add New Translation
Tags](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md#add-new-translation-tags)
(for new translation tags only)

### Translations (if applicable)

- [ ] I ran
[`scripts/counter_translation.py`](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/docs/counter_translation.md)

### UI Changes (if applicable)

- [ ] Screenshots or videos demonstrating the UI changes are attached
(e.g., as comments or direct attachments in the PR)

### Testing (if applicable)

- [ ] I have tested my changes locally. Refer to the [Testing
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/DeveloperGuide.md#6-testing)
for more details.

Signed-off-by: Balázs Szücs <[email protected]>

app/core/src/test/java/stirling/software/SPDF/controller/api/pipeline/PipelineProcessorTest.java

@@ -4,6 +4,8 @@ import static org.junit.jupiter.api.Assertions.*;
 import static org.mockito.ArgumentMatchers.*;
 import static org.mockito.Mockito.*;
 
+import java.nio.file.Files;
+import java.nio.file.Path;
 import java.util.List;
 import java.util.Map;
 
@@ -13,6 +15,7 @@ import org.junit.jupiter.api.extension.ExtendWith;
 import org.mockito.Mock;
 import org.mockito.junit.jupiter.MockitoExtension;
 import org.springframework.core.io.ByteArrayResource;
+import org.springframework.core.io.FileSystemResource;
 import org.springframework.core.io.Resource;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.ResponseEntity;
@@ -24,6 +27,7 @@ import stirling.software.SPDF.model.PipelineOperation;
 import stirling.software.SPDF.model.PipelineResult;
 import stirling.software.SPDF.service.ApiDocService;
 import stirling.software.common.service.UserServiceInterface;
+import stirling.software.common.util.TempFileManager;
 
 @ExtendWith(MockitoExtension.class)
 class PipelineProcessorTest {
@@ -34,11 +38,16 @@ class PipelineProcessorTest {
 
     @Mock ServletContext servletContext;
 
+    @Mock TempFileManager tempFileManager;
+
     PipelineProcessor pipelineProcessor;
 
     @BeforeEach
     void setUp() {
-        pipelineProcessor = spy(new PipelineProcessor(apiDocService, userService, servletContext));
+        pipelineProcessor =
+                spy(
+                        new PipelineProcessor(
+                                apiDocService, userService, servletContext, tempFileManager));
     }
 
     @Test
@@ -59,12 +68,18 @@ class PipelineProcessorTest {
         when(apiDocService.isValidOperation(eq("/api/v1/filter/filter-page-count"), anyMap()))
                 .thenReturn(true);
 
-        doReturn(new ResponseEntity<>(new byte[0], HttpStatus.OK))
+        // Use a FileSystemResource backed by a temp file to avoid FileNotFoundException
+        Path emptyTemp = Files.createTempFile("empty", ".tmp");
+        Resource emptyResource = new FileSystemResource(emptyTemp.toFile());
+
+        doReturn(new ResponseEntity<>(emptyResource, HttpStatus.OK))
                 .when(pipelineProcessor)
                 .sendWebRequest(anyString(), any());
 
         PipelineResult result = pipelineProcessor.runPipelineAgainstFiles(files, config);
 
+        Files.deleteIfExists(emptyTemp);
+
         assertTrue(
                 result.isFiltersApplied(),
                 "Filter flag should be true when operation filters file");
@@ -72,6 +87,45 @@ class PipelineProcessorTest {
         assertTrue(result.getOutputFiles().isEmpty(), "Filtered file list should be empty");
     }
 
+    @Test
+    void testPipelineSuccessWithResource() throws Exception {
+        PipelineOperation op = new PipelineOperation();
+        op.setOperation("/api/v1/misc/compress");
+        op.setParameters(Map.of());
+        PipelineConfig config = new PipelineConfig();
+        config.setOperations(List.of(op));
+
+        Resource inputFile = new MyFileByteArrayResource();
+        List<Resource> files = List.of(inputFile);
+
+        Path tempPath = Files.createTempFile("test-output", ".pdf");
+        Files.write(tempPath, "processed_data".getBytes());
+        Resource outputResource =
+                new FileSystemResource(tempPath.toFile()) {
+                    @Override
+                    public String getFilename() {
+                        return "processed.pdf";
+                    }
+                };
+
+        when(apiDocService.isMultiInput(anyString())).thenReturn(false);
+        when(apiDocService.getExtensionTypes(anyBoolean(), anyString())).thenReturn(List.of("pdf"));
+        when(apiDocService.isValidOperation(anyString(), anyMap())).thenReturn(true);
+
+        doReturn(new ResponseEntity<>(outputResource, HttpStatus.OK))
+                .when(pipelineProcessor)
+                .sendWebRequest(anyString(), any());
+
+        PipelineResult result = pipelineProcessor.runPipelineAgainstFiles(files, config);
+
+        verify(pipelineProcessor).sendWebRequest(anyString(), any());
+
+        assertFalse(result.isHasErrors());
+
+        // Clean up
+        Files.deleteIfExists(tempPath);
+    }
+
     private static class MyFileByteArrayResource extends ByteArrayResource {
         public MyFileByteArrayResource() {
             super("data".getBytes());