adds schema conversion APIs

CedarJava/src/main/java/com/cedarpolicy/model/schema/Schema.java

@@ -16,13 +16,15 @@
 
 package com.cedarpolicy.model.schema;
 
+import java.util.Optional;
+
 import com.cedarpolicy.loader.LibraryLoader;
 import com.cedarpolicy.model.exception.InternalException;
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.JsonMappingException;
 import com.fasterxml.jackson.databind.JsonNode;
 import com.fasterxml.jackson.databind.ObjectMapper;
 
-import java.util.Optional;
-
 /** Represents a schema. */
 public final class Schema {
     private static final ObjectMapper OBJECT_MAPPER = new ObjectMapper();
@@ -122,21 +124,55 @@ public static Schema parse(JsonOrCedar type, String str) throws InternalExceptio
 
     }
 
+    public String toCedarFormat() throws InternalException {
+        if (type == JsonOrCedar.Cedar && schemaText.isPresent()) {
+            return schemaText.get();
+        } else if (type == JsonOrCedar.Json && schemaJson.isPresent()) {
+            return jsonToCedarJni(schemaJson.get().toString());
+        } else {
+            throw new InternalException("Schema content is missing");
+        }
+    }
+
+    /**
+     * Converts a Cedar format schema to JSON format
+     *
+     * @return JsonNode representing the schema in JSON format
+     * @throws InternalException       If schema is not in Cedar format
+     * @throws JsonMappingException    If JSON mapping fails
+     * @throws JsonProcessingException If JSON processing fails
+     * @throws NullPointerException    If schema text is null
+     */
+    public JsonNode toJsonFormat()
+            throws InternalException, JsonMappingException, JsonProcessingException, NullPointerException {
+        if (type != JsonOrCedar.Cedar || schemaText.isEmpty()) {
+            throw new InternalException("Schema is not in cedar format");
+        }
+        return OBJECT_MAPPER.readTree(cedarToJsonJni(schemaText.get()));
+
+    }
+
     /** Specifies the schema format used. */
     public enum JsonOrCedar {
         /**
-         * Cedar JSON schema format. See <a href="https://docs.cedarpolicy.com/schema/json-schema.html">
-         *     https://docs.cedarpolicy.com/schema/json-schema.html</a>
+         * Cedar JSON schema format. See
+         * <a href="https://docs.cedarpolicy.com/schema/json-schema.html">
+         * https://docs.cedarpolicy.com/schema/json-schema.html</a>
          */
         Json,
         /**
-         * Cedar schema format. See <a href="https://docs.cedarpolicy.com/schema/human-readable-schema.html">
-         *     https://docs.cedarpolicy.com/schema/human-readable-schema.html</a>
+         * Cedar schema format. See
+         * <a href="https://docs.cedarpolicy.com/schema/human-readable-schema.html">
+         * https://docs.cedarpolicy.com/schema/human-readable-schema.html</a>
          */
         Cedar
     }
 
     private static native String parseJsonSchemaJni(String schemaJson) throws InternalException, NullPointerException;
 
     private static native String parseCedarSchemaJni(String schemaText) throws InternalException, NullPointerException;
+
+    private static native String jsonToCedarJni(String json) throws InternalException, NullPointerException;
+
+    private static native String cedarToJsonJni(String cedar) throws InternalException, NullPointerException;
 }

CedarJava/src/test/java/com/cedarpolicy/SchemaTests.java

@@ -16,13 +16,17 @@
 
 package com.cedarpolicy;
 
-import com.cedarpolicy.model.schema.Schema;
-import com.cedarpolicy.model.schema.Schema.JsonOrCedar;
-
-import org.junit.jupiter.api.Test;
-
 import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
 import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+import org.junit.jupiter.api.Test;
+
+import com.cedarpolicy.model.exception.InternalException;
+import com.cedarpolicy.model.schema.Schema;
+import com.cedarpolicy.model.schema.Schema.JsonOrCedar;
+import com.fasterxml.jackson.databind.JsonNode;
 
 public class SchemaTests {
     @Test
@@ -107,4 +111,65 @@ public void parseCedarSchema() {
             Schema.parse(JsonOrCedar.Cedar, "namspace Foo::Bar;");
         });
     }
+
+    @Test
+    public void testToCedarFormat() throws InternalException {
+        String cedarSchema = "entity User;";
+        Schema cedarSchemaObj = new Schema(cedarSchema);
+        String result = cedarSchemaObj.toCedarFormat();
+        assertNotNull(result);
+        assertEquals(cedarSchema, result);
+
+        String jsonSchema = """
+                {
+                    "": {
+                        "entityTypes": {
+                            "User": {}
+                        },
+                        "actions": {}
+                    }
+                }
+                """;
+        Schema jsonSchemaObj = Schema.parse(JsonOrCedar.Json, jsonSchema);
+        String convertedCedar = jsonSchemaObj.toCedarFormat();
+        assertNotNull(convertedCedar);
+        assertTrue(convertedCedar.contains("entity User"));
+
+        Schema invalidSchema = new Schema(JsonOrCedar.Cedar, java.util.Optional.empty(), java.util.Optional.empty());
+        assertThrows(InternalException.class, () -> {
+            invalidSchema.toCedarFormat();
+        });
+    }
+
+    @Test
+    public void testToJsonFormat() throws Exception {
+        String cedarSchema = "entity User;";
+        Schema cedarSchemaObj = new Schema(cedarSchema);
+        JsonNode jsonResult = cedarSchemaObj.toJsonFormat();
+        assertNotNull(jsonResult);
+        assertTrue(jsonResult.has(""));
+        assertTrue(jsonResult.get("").has("entityTypes"));
+        assertTrue(jsonResult.get("").get("entityTypes").has("User"));
+
+        String jsonSchema = """
+                {
+                    "": {
+                        "entityTypes": {
+                            "User": {}
+                        },
+                        "actions": {}
+                    }
+                }
+                """;
+        Schema jsonSchemaObj = Schema.parse(JsonOrCedar.Json, jsonSchema);
+        assertThrows(InternalException.class, () -> {
+            jsonSchemaObj.toJsonFormat();
+        });
+
+        Schema invalidSchema = new Schema(JsonOrCedar.Cedar, java.util.Optional.empty(), java.util.Optional.empty());
+        assertThrows(InternalException.class, () -> {
+            invalidSchema.toJsonFormat();
+        });
+    }
+
 }