[Java] Add reason(s) to UnsupportedProvider/UnsupportedOperationExceptions

java/cuvs-java/src/main/java/com/nvidia/cuvs/spi/CuVSServiceProvider.java

@@ -17,6 +17,8 @@
 
 import java.lang.invoke.MethodHandles;
 import java.lang.invoke.MethodType;
+import java.util.ArrayList;
+import java.util.List;
 import java.util.ServiceLoader;
 
 /**
@@ -43,7 +45,10 @@ private static CuVSProvider loadProvider() {
     }
 
     static CuVSProvider builtinProvider() {
-      if (Runtime.version().feature() > 21 && isLinuxAmd64()) {
+      var supportedJavaRuntime = Runtime.version().feature() > 21;
+      var supportedOs = System.getProperty("os.name").startsWith("Linux");
+      var supportedArchitecture = System.getProperty("os.arch").equals("amd64");
+      if (supportedJavaRuntime && supportedOs && supportedArchitecture) {
         try {
           var cls = Class.forName("com.nvidia.cuvs.spi.JDKProvider");
           var ctr = MethodHandles.lookup().findConstructor(cls, MethodType.methodType(void.class));
@@ -52,16 +57,18 @@ static CuVSProvider builtinProvider() {
           throw new AssertionError(e);
         }
       }
-      return new UnsupportedProvider();
-    }
+      List<String> unsupportedReasons = new ArrayList<>();
+      if (!supportedJavaRuntime) {
+        unsupportedReasons.add("cuvs-java requires Java Runtime version 22 or greater");
+      }
+      if (!supportedOs) {
+        unsupportedReasons.add("cuvs-java supports only Linux");
+      }
+      if (!supportedArchitecture) {
+        unsupportedReasons.add("cuvs-java supports only x86");
+      }
 
-    /**
-     * Returns true iff the architecture is x64 (amd64) and the OS Linux
-     * (the * OS we currently support for the native lib).
-     */
-    static boolean isLinuxAmd64() {
-      String name = System.getProperty("os.name");
-      return (name.startsWith("Linux")) && System.getProperty("os.arch").equals("amd64");
+      return new UnsupportedProvider(String.join("; ", unsupportedReasons));
     }
   }
 }

java/cuvs-java/src/main/java/com/nvidia/cuvs/spi/UnsupportedProvider.java

@@ -24,51 +24,57 @@
  */
 final class UnsupportedProvider implements CuVSProvider {
 
+  private final String reasons;
+
+  public UnsupportedProvider(String reasons) {
+    this.reasons = reasons;
+  }
+
   @Override
   public CuVSResources newCuVSResources(Path tempDirectory) {
-    throw new UnsupportedOperationException();
+    throw new UnsupportedOperationException(reasons);
   }
 
   @Override
   public BruteForceIndex.Builder newBruteForceIndexBuilder(CuVSResources cuVSResources) {
-    throw new UnsupportedOperationException();
+    throw new UnsupportedOperationException(reasons);
   }
 
   @Override
   public CagraIndex.Builder newCagraIndexBuilder(CuVSResources cuVSResources) {
-    throw new UnsupportedOperationException();
+    throw new UnsupportedOperationException(reasons);
   }
 
   @Override
   public HnswIndex.Builder newHnswIndexBuilder(CuVSResources cuVSResources) {
-    throw new UnsupportedOperationException();
+    throw new UnsupportedOperationException(reasons);
   }
 
   @Override
   public TieredIndex.Builder newTieredIndexBuilder(CuVSResources cuVSResources) {
-    throw new UnsupportedOperationException();
+    throw new UnsupportedOperationException(reasons);
   }
 
   @Override
   public CagraIndex mergeCagraIndexes(CagraIndex[] indexes) {
-    throw new UnsupportedOperationException();
+    throw new UnsupportedOperationException(reasons);
   }
 
   @Override
   public CuVSMatrix.Builder<CuVSHostMatrix> newHostMatrixBuilder(
       long size, long dimensions, CuVSMatrix.DataType dataType) {
-    throw new UnsupportedOperationException();
+    throw new UnsupportedOperationException(reasons);
   }
 
   @Override
   public CuVSMatrix.Builder<CuVSDeviceMatrix> newDeviceMatrixBuilder(
       CuVSResources cuVSResources, long size, long dimensions, CuVSMatrix.DataType dataType) {
-    throw new UnsupportedOperationException();
+    throw new UnsupportedOperationException(reasons);
   }
 
   @Override
   public GPUInfoProvider gpuInfoProvider() {
-    throw new UnsupportedOperationException();
+    throw new UnsupportedOperationException(reasons);
   }
 
   @Override
@@ -79,26 +85,26 @@ public CuVSMatrix.Builder<CuVSDeviceMatrix> newDeviceMatrixBuilder(
       int rowStride,
       int columnStride,
       CuVSMatrix.DataType dataType) {
-    throw new UnsupportedOperationException();
+    throw new UnsupportedOperationException(reasons);
   }
 
   @Override
   public MethodHandle newNativeMatrixBuilder() {
-    throw new UnsupportedOperationException();
+    throw new UnsupportedOperationException(reasons);
   }
 
   @Override
   public CuVSMatrix newMatrixFromArray(float[][] vectors) {
-    throw new UnsupportedOperationException();
+    throw new UnsupportedOperationException(reasons);
   }
 
   @Override
   public CuVSMatrix newMatrixFromArray(int[][] vectors) {
-    throw new UnsupportedOperationException();
+    throw new UnsupportedOperationException(reasons);
   }
 
   @Override
   public CuVSMatrix newMatrixFromArray(byte[][] vectors) {
-    throw new UnsupportedOperationException();
+    throw new UnsupportedOperationException(reasons);
   }
 }