fix edge case where first segment is longer than offset

src/test/java/com/ddf/vodsystem/services/media/StreamActionsServiceTest.java

@@ -1,5 +1,6 @@
 package com.ddf.vodsystem.services.media;
 
+import com.ddf.vodsystem.dto.ClipOptions;
 import com.ddf.vodsystem.dto.CommandOutput;
 import com.ddf.vodsystem.dto.ProgressTracker;
 import org.junit.jupiter.api.BeforeEach;
@@ -17,6 +18,7 @@ import java.nio.file.NoSuchFileException;
 import java.nio.file.Path;
 import java.time.Instant;
 import java.util.List;
+import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.ExecutionException;
 
 import static org.assertj.core.api.Assertions.assertThat;
@@ -31,6 +33,9 @@ class StreamActionsServiceTest {
     @Mock
     private CommandRunner commandRunner;
 
+    @Mock
+    private MetadataService metadataService;
+
     private StreamActionsService service;
 
     @TempDir
@@ -38,13 +43,20 @@ class StreamActionsServiceTest {
 
     @BeforeEach
     void setUp() {
-        service = new StreamActionsService(commandRunner);
+        service = new StreamActionsService(commandRunner, metadataService);
     }
 
     private void createSegment(String name) throws IOException {
         Files.createFile(tempDir.resolve(name));
     }
 
+    /** Stubs the (async) metadata probe so {@code segments.getFirst()} reports {@code seconds}. */
+    private void stubHeadDuration(float seconds) {
+        ClipOptions meta = new ClipOptions();
+        meta.setDuration(seconds);
+        when(metadataService.getVideoMetadata(any())).thenReturn(CompletableFuture.completedFuture(meta));
+    }
+
     /**
      * Stubs the two-arg {@link CommandRunner#run} so the head re-encode pass
      * actually writes a non-empty file at its output path — {@code encodeHead}
@@ -56,7 +68,7 @@ class StreamActionsServiceTest {
         when(commandRunner.run(anyList(), any())).thenAnswer(inv -> {
             List<String> cmd = inv.getArgument(0);
             if (cmd.contains("mpegts")) {
-                Files.writeString(Path.of(cmd.get(cmd.size() - 1)), "x");
+                Files.writeString(Path.of(cmd.getLast()), "x");
             }
             return output;
         });
@@ -240,6 +252,67 @@ class StreamActionsServiceTest {
                 .containsExactly("30.ts", "100.ts", "110.ts");
     }
 
+    // ---------------------------------------------------------------
+    // selectSegments: head selection and trim-offset
+    // ---------------------------------------------------------------
+
+    @Test
+    void selectSegments_startWithinFirstSegment_keepsItAndComputesOffset() throws IOException {
+        createSegment("30.ts");
+        createSegment("33.ts");
+        stubHeadDuration(3f); // 30.ts spans [30s, 33s)
+
+        var selection = service.selectSegments(tempDir, Instant.ofEpochMilli(31_500), Instant.ofEpochMilli(40_000));
+
+        assertThat(selection.segments()).extracting(p -> p.getFileName().toString())
+                .containsExactly("30.ts", "33.ts");
+        assertThat(selection.trimOffset()).isEqualTo(1.5f);
+    }
+
+    @Test
+    void selectSegments_startInGapAfterFirstSegment_dropsItAndStartsAtNext() throws IOException {
+        createSegment("30.ts");
+        // user stops streaming; a gap follows 30.ts
+        createSegment("100.ts");
+        createSegment("110.ts");
+        stubHeadDuration(3f); // 30.ts only holds [30s, 33s); requested start 70s is past it
+
+        var selection = service.selectSegments(tempDir, Instant.ofEpochMilli(70_000), Instant.ofEpochMilli(111_000));
+
+        assertThat(selection.segments()).extracting(p -> p.getFileName().toString())
+                .containsExactly("100.ts", "110.ts");
+        assertThat(selection.trimOffset()).isZero();
+    }
+
+    @Test
+    void selectSegments_startPastOnlySegment_throwsIllegalArgument() throws IOException {
+        createSegment("0.ts");
+        stubHeadDuration(3f); // 0.ts holds [0s, 3s); requested start 50s has no footage
+
+        assertThatThrownBy(() ->
+                service.selectSegments(tempDir, Instant.ofEpochMilli(50_000), Instant.ofEpochMilli(60_000)))
+                .isInstanceOf(IllegalArgumentException.class);
+    }
+
+    @Test
+    void selectSegments_noSegmentsInRange_throwsIllegalArgument() {
+        assertThatThrownBy(() ->
+                service.selectSegments(tempDir, Instant.ofEpochMilli(0), Instant.ofEpochMilli(10_000)))
+                .isInstanceOf(IllegalArgumentException.class);
+    }
+
+    @Test
+    void selectSegments_probeFailure_surfacesAsIOException() throws IOException {
+        createSegment("30.ts");
+        createSegment("100.ts");
+        when(metadataService.getVideoMetadata(any()))
+                .thenReturn(CompletableFuture.failedFuture(new IOException("ffprobe boom")));
+
+        assertThatThrownBy(() ->
+                service.selectSegments(tempDir, Instant.ofEpochMilli(70_000), Instant.ofEpochMilli(111_000)))
+                .isInstanceOf(IOException.class);
+    }
+
     // ---------------------------------------------------------------
     // parseTimestampMs: unit-based conversion
     // ---------------------------------------------------------------
@@ -334,7 +407,7 @@ class StreamActionsServiceTest {
     }
 
     @Test
-    void saveSection_emptySegmentList_completesExceptionallyWithIllegalArgumentException() throws IOException {
+    void saveSection_emptySegmentList_completesExceptionallyWithIllegalArgumentException() {
         Path output = Path.of("/tmp/out/clip.mp4");
         ProgressTracker progress = new ProgressTracker();