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 +124,57 @@ 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 IllegalStateException("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.Json && schemaJson.isPresent()) {
+            return schemaJson.get();
+        } else if (type == JsonOrCedar.Cedar && schemaText.isPresent()) {
+            return OBJECT_MAPPER.readTree(cedarToJsonJni(schemaText.get()));
+        } else {
+            throw new IllegalStateException("Schema content is missing");
+        }
+    }
+
     /** 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 +16,22 @@
 
 package com.cedarpolicy;
 
-import com.cedarpolicy.model.schema.Schema;
-import com.cedarpolicy.model.schema.Schema.JsonOrCedar;
-
-import org.junit.jupiter.api.Test;
+import java.util.Optional;
 
 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.DisplayName;
+import org.junit.jupiter.api.Nested;
+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;
+import com.fasterxml.jackson.databind.ObjectMapper;
 
 public class SchemaTests {
     @Test
@@ -107,4 +116,122 @@ public void parseCedarSchema() {
             Schema.parse(JsonOrCedar.Cedar, "namspace Foo::Bar;");
         });
     }
+
+    @Nested
+    @DisplayName("toCedarFormat Tests")
+    class ToCedarFormatTests {
+
+        @Test
+        @DisplayName("Should return the same Cedar schema text")
+        void testFromCedar() throws InternalException {
+            String cedarSchema = "entity User;";
+            Schema cedarSchemaObj = new Schema(cedarSchema);
+            String result = cedarSchemaObj.toCedarFormat();
+            assertNotNull(result, "Result should not be null");
+            assertEquals(cedarSchema, result, "Should return the original Cedar schema");
+        }
+
+        @Test
+        @DisplayName("Should convert JSON schema to Cedar format")
+        void testFromJson() throws InternalException {
+            String jsonSchema = """
+                    {
+                        "": {
+                            "entityTypes": {
+                                "User": {}
+                            },
+                            "actions": {}
+                        }
+                    }
+                    """;
+            Schema jsonSchemaObj = Schema.parse(JsonOrCedar.Json, jsonSchema);
+            String result = jsonSchemaObj.toCedarFormat();
+
+            assertNotNull(result, "Result should not be null");
+            assertTrue(result.contains("entity User"), "Converted Cedar should contain the User entity");
+        }
+
+        @Test
+        @DisplayName("Should throw IllegalStateException for empty schema")
+        void testEmptySchema() {
+            Schema emptySchema = new Schema(JsonOrCedar.Cedar, Optional.empty(), Optional.empty());
+            Exception exception = assertThrows(IllegalStateException.class, emptySchema::toCedarFormat);
+            assertEquals("Schema content is missing", exception.getMessage());
+        }
+
+        @Test
+        @DisplayName("Should throw exception for malformed JSON schema")
+        void testMalformedSchema() {
+            // Missing closing brace in the JSON structure
+            String malformedJson = """
+                    {
+                        "": {
+                            "entityTypes": {
+                                "User": {}
+                            },
+                            "actions": {
+                        }
+                    """; 
+            Schema malformedSchema = new Schema(JsonOrCedar.Json, Optional.of(malformedJson), Optional.empty());
+            assertThrows(IllegalStateException.class, malformedSchema::toCedarFormat);
+        }
+    }
+
+    @Nested
+    @DisplayName("toJsonFormat Tests")
+    class ToJsonFormatTests {
+
+        @Test
+        @DisplayName("Should convert Cedar schema to JSON format")
+        void testFromCedar() throws Exception {
+            String cedarSchema = "entity User;";
+            Schema cedarSchemaObj = new Schema(cedarSchema);
+            JsonNode result = cedarSchemaObj.toJsonFormat();
+
+            String expectedJson = "{\"\":{\"entityTypes\":{\"User\":{}},\"actions\":{}}}";
+            JsonNode expectedNode = new ObjectMapper().readTree(expectedJson);
+
+            assertNotNull(result, "Result should not be null");
+            assertEquals(expectedNode, result, "JSON should match expected structure");
+        }
+
+        @Test
+        @DisplayName("Should return the same JSON schema object")
+        void testFromJson() throws Exception {
+            String jsonSchema = """
+                    {
+                        "": {
+                            "entityTypes": {
+                                "User": {}
+                            },
+                            "actions": {}
+                        }
+                    }
+                    """;
+            Schema jsonSchemaObj = Schema.parse(JsonOrCedar.Json, jsonSchema);
+            JsonNode result = jsonSchemaObj.toJsonFormat();
+
+            ObjectMapper mapper = new ObjectMapper();
+            JsonNode expectedNode = mapper.readTree(jsonSchema);
+
+            assertNotNull(result, "Result should not be null");
+            assertEquals(expectedNode, result, "JSON should match the original schema");
+        }
+
+        @Test
+        @DisplayName("Should throw IllegalStateException for empty schema")
+        void testEmptySchema() {
+            Schema emptySchema = new Schema(JsonOrCedar.Cedar, Optional.empty(), Optional.empty());
+            Exception exception = assertThrows(IllegalStateException.class, emptySchema::toJsonFormat);
+            assertEquals("Schema content is missing", exception.getMessage());
+        }
+
+        @Test
+        @DisplayName("Should throw exception for malformed Cedar schema")
+        void testMalformedSchema() {
+            String malformedCedar = "entty User";
+            Schema malformedSchema = new Schema(JsonOrCedar.Cedar, Optional.empty(), Optional.of(malformedCedar));
+            assertThrows(InternalException.class, malformedSchema::toJsonFormat);
+        }
+    }
 }