fix: correct MIME type detection for file uploads

src/main/java/com/razorpay/ApiUtils.java

@@ -236,13 +236,22 @@ private static X509TrustManager createDefaultTrustManager() throws NoSuchAlgorit
     return trustManager;
   }
 
-  private static String getMediaType(String fileName){
+  static String getMediaType(String fileName) {
     int extensionIndex = fileName.lastIndexOf('.');
-    String extenionName = fileName.substring(extensionIndex + 1);
-    if(extenionName == "jpg" | extenionName == "jpeg" | extenionName == "png" | extenionName == "jfif"){
-      return "image/jpg";
+    if (extensionIndex < 0 || extensionIndex == fileName.length() - 1) {
+      return "application/octet-stream";
     }
-      return "image/pdf";
+    String extensionName = fileName.substring(extensionIndex + 1).toLowerCase();
+    if ("jpg".equals(extensionName) || "jpeg".equals(extensionName) || "jfif".equals(extensionName)) {
+      return "image/jpeg";
+    }
+    if ("png".equals(extensionName)) {
+      return "image/png";
+    }
+    if ("pdf".equals(extensionName)) {
+      return "application/pdf";
+    }
+    return "application/octet-stream";
   }
 
   private static RequestBody fileRequestBody(JSONObject requestObject){

src/test/java/com/razorpay/ApiUtilsTest.java

@@ -0,0 +1,53 @@
+package com.razorpay;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class ApiUtilsTest {
+
+  @Test
+  public void getMediaType_Jpg_ReturnsImageJpeg() {
+    assertEquals("image/jpeg", ApiUtils.getMediaType("document.jpg"));
+    assertEquals("image/jpeg", ApiUtils.getMediaType("doc.JPG"));
+  }
+
+  @Test
+  public void getMediaType_Jpeg_ReturnsImageJpeg() {
+    assertEquals("image/jpeg", ApiUtils.getMediaType("photo.jpeg"));
+    assertEquals("image/jpeg", ApiUtils.getMediaType("photo.JPEG"));
+  }
+
+  @Test
+  public void getMediaType_Png_ReturnsImagePng() {
+    assertEquals("image/png", ApiUtils.getMediaType("image.png"));
+    assertEquals("image/png", ApiUtils.getMediaType("image.PNG"));
+  }
+
+  @Test
+  public void getMediaType_Jfif_ReturnsImageJpeg() {
+    assertEquals("image/jpeg", ApiUtils.getMediaType("photo.jfif"));
+  }
+
+  @Test
+  public void getMediaType_Pdf_ReturnsApplicationPdf() {
+    assertEquals("application/pdf", ApiUtils.getMediaType("invoice.pdf"));
+    assertEquals("application/pdf", ApiUtils.getMediaType("report.PDF"));
+  }
+
+  @Test
+  public void getMediaType_UnknownExtension_ReturnsOctetStream() {
+    assertEquals("application/octet-stream", ApiUtils.getMediaType("file.xyz"));
+    assertEquals("application/octet-stream", ApiUtils.getMediaType("data.json"));
+  }
+
+  @Test
+  public void getMediaType_NoExtension_ReturnsOctetStream() {
+    assertEquals("application/octet-stream", ApiUtils.getMediaType("README"));
+  }
+
+  @Test
+  public void getMediaType_TrailingDot_ReturnsOctetStream() {
+    assertEquals("application/octet-stream", ApiUtils.getMediaType("file."));
+  }
+}