fix(core): Fix MediaUtils parse path extension (#981)

## AgentScope-Java Version

1.0.11

## Description

* Closes: #977 
* Fix MediaUtils parse path extension

## Checklist

Please check the following items before code is ready to be reviewed.

- [x]  Code has been formatted with `mvn spotless:apply`
- [x]  All tests are passing (`mvn test`)
- [x]  Javadoc comments are complete and follow project conventions
- [x] Related documentation has been updated (e.g. links, examples,
etc.)
- [x]  Code is ready for review

Author: guanxuc

agentscope-core/src/main/java/io/agentscope/core/formatter/MediaUtils.java

@@ -27,6 +27,7 @@
 import java.nio.file.Files;
 import java.nio.file.InvalidPathException;
 import java.nio.file.Path;
+import java.nio.file.Paths;
 import java.util.Base64;
 import java.util.List;
 import javax.imageio.ImageIO;
@@ -58,7 +59,7 @@ private MediaUtils() {
 
     /**
      * Check if a URL is a local file path (not a URL with protocol scheme).
-     * Returns true for paths without http://, https://, ftp://, or file:// prefixes.
+     * Returns true for paths without http://, https://, ftp://, file:// or oss:// prefixes.
      * Used to distinguish local files from remote URLs for different processing paths.
      *
      * @param url The URL or file path to check
@@ -349,14 +350,34 @@ public static String inferAudioFormatFromMediaType(String mediaType) {
      * Extract file extension from path or URL.
      */
     public static String getExtension(String path) {
-        if (path == null) {
+        if (path == null || path.isBlank()) {
             return "";
         }
-        int dotIndex = path.lastIndexOf('.');
-        int slashIndex = Math.max(path.lastIndexOf('/'), path.lastIndexOf('\\'));
-        // Ensure the dot is after the last slash (not part of directory name)
-        if (dotIndex > slashIndex && dotIndex < path.length() - 1) {
-            return path.substring(dotIndex + 1);
+
+        Path fileNamePath;
+        try {
+            if (isLocalFile(path)) {
+                // treat as file
+                fileNamePath = Paths.get(path).normalize().getFileName();
+            } else {
+                // treat as url
+                URI uri = URI.create(path).normalize();
+                fileNamePath = Paths.get(uri.getPath()).getFileName();
+            }
+        } catch (Exception e) {
+            log.warn("Invalid path: {}", path, e);
+            return "";
+        }
+
+        if (fileNamePath == null) {
+            return "";
+        }
+
+        String fileName = fileNamePath.toString();
+        int dotIndex = fileName.lastIndexOf('.');
+        // Ensure the dot exists and is not the last character
+        if (dotIndex != -1 && dotIndex < fileName.length() - 1) {
+            return fileName.substring(dotIndex + 1);
         }
         return "";
     }

agentscope-core/src/test/java/io/agentscope/core/formatter/MediaUtilsTest.java

@@ -329,4 +329,77 @@ void testUrlToRgbaImageInputStreamWithFile() throws IOException {
         assertNotNull(is);
         is.close();
     }
+
+    @Test
+    @DisplayName("Should return empty string when path is invalid")
+    void testGetExtensionWithInvalidPath() {
+        assertEquals("", MediaUtils.getExtension(null));
+        assertEquals("", MediaUtils.getExtension(""));
+        assertEquals("", MediaUtils.getExtension("  "));
+        assertEquals("", MediaUtils.getExtension("/"));
+        assertEquals("", MediaUtils.getExtension("\\"));
+        assertEquals("", MediaUtils.getExtension("/home/user"));
+        assertEquals("", MediaUtils.getExtension("C:\\Users\\Administrator"));
+        assertEquals("", MediaUtils.getExtension("https://abc"));
+        assertEquals("", MediaUtils.getExtension("https://abc[@]123"));
+        assertEquals("", MediaUtils.getExtension("https://example.com/abc"));
+        assertEquals("", MediaUtils.getExtension("https://example.com/abc/"));
+        assertEquals("", MediaUtils.getExtension("https://example.com/img.png."));
+    }
+
+    @Test
+    @DisplayName("Should get extension with all types")
+    void testGetExtensionWithAllTypes() {
+        assertEquals("png", MediaUtils.getExtension("https://example.com/img.png"));
+        assertEquals("wav", MediaUtils.getExtension("https://example.com/audio.wav"));
+        assertEquals("mp3", MediaUtils.getExtension("https://example.com/audio.mp3"));
+        assertEquals("mp4", MediaUtils.getExtension("https://example.com/video.mp4"));
+        assertEquals("xxx", MediaUtils.getExtension("https://example.com/xxx.xxx"));
+    }
+
+    @Test
+    @DisplayName("Should get last extension when have nested types")
+    void testGetExtensionWithNestedTypes() {
+        assertEquals("gz", MediaUtils.getExtension("https://example.com/img.png.tar.gz"));
+        assertEquals("zip", MediaUtils.getExtension("https://example.com/img.png.zip"));
+    }
+
+    @Test
+    @DisplayName("Should get extension with masks")
+    void testGetExtensionWithMasks() {
+        assertEquals("png", MediaUtils.getExtension("https://example.com/img.png?id=1&type=png"));
+        assertEquals("png", MediaUtils.getExtension("https://example.com/img.png#section1.1"));
+        assertEquals(
+                "png",
+                MediaUtils.getExtension("https://example.com/img.png?id=1&type=png#section1.1"));
+        assertEquals("png", MediaUtils.getExtension("https://example.com/img.png?v=2.0.0"));
+        assertEquals(
+                "png", MediaUtils.getExtension("https://example.com/img-123&type=png&v=2.0.0.png"));
+
+        // verify the file name include special masks
+        assertEquals("png", MediaUtils.getExtension("/home/user/img-123&type=png&v=2.0.0.png"));
+        assertEquals(
+                "png",
+                MediaUtils.getExtension("C:\\Users\\Administrator\\img_123&type=png&v=2.0.0.png"));
+    }
+
+    @Test
+    @DisplayName("Should get extension with all supported protocol")
+    void testGetExtensionWithSupportedProtocol() {
+        assertEquals(
+                "png",
+                MediaUtils.getExtension("http://example.com/img.png?id=1&type=png#section1.1"));
+        assertEquals(
+                "png",
+                MediaUtils.getExtension("https://example.com/img.png?id=1&type=png#section1.1"));
+        assertEquals(
+                "png",
+                MediaUtils.getExtension("oss://example.com/img.png?id=1&type=png#section1.1"));
+        assertEquals(
+                "png",
+                MediaUtils.getExtension("file://example.com/img.png?id=1&type=png#section1.1"));
+        assertEquals(
+                "png",
+                MediaUtils.getExtension("ftp://example.com/img.png?id=1&type=png#section1.1"));
+    }
 }