feature: base implementation

Author: csviri

core/pom.xml

@@ -104,5 +104,9 @@
       <artifactId>awaitility</artifactId>
       <scope>test</scope>
     </dependency>
+    <dependency>
+      <groupId>com.github.java-json-tools</groupId>
+      <artifactId>json-patch</artifactId>
+    </dependency>
   </dependencies>
 </project>

core/src/main/java/io/javaoperatorsdk/admissioncontroller/AdmissionController.java

@@ -0,0 +1,33 @@
+package io.javaoperatorsdk.admissioncontroller;
+
+import io.fabric8.kubernetes.api.model.KubernetesResource;
+import io.fabric8.kubernetes.api.model.admission.v1.AdmissionReview;
+import io.javaoperatorsdk.admissioncontroller.mutation.DefaultRequestMutator;
+import io.javaoperatorsdk.admissioncontroller.mutation.Mutator;
+import io.javaoperatorsdk.admissioncontroller.validation.DefaultRequestValidator;
+import io.javaoperatorsdk.admissioncontroller.validation.Validator;
+
+public class AdmissionController<T extends KubernetesResource> {
+
+  private final RequestHandler requestHandler;
+
+  public AdmissionController(Mutator<T> mutator) {
+    this(new DefaultRequestMutator<>(mutator));
+  }
+
+  public AdmissionController(Validator<T> mutator) {
+    this(new DefaultRequestValidator<>(mutator));
+  }
+
+  public AdmissionController(RequestHandler requestHandler) {
+    this.requestHandler = requestHandler;
+  }
+
+  public AdmissionReview handle(AdmissionReview admissionReview) {
+    var response = requestHandler.handle(admissionReview.getRequest());
+    AdmissionReview responseAdmissionReview = new AdmissionReview();
+    responseAdmissionReview.setResponse(response);
+    response.setUid(admissionReview.getRequest().getUid());
+    return responseAdmissionReview;
+  }
+}

core/src/main/java/io/javaoperatorsdk/admissioncontroller/AdmissionControllerException.java

@@ -0,0 +1,23 @@
+package io.javaoperatorsdk.admissioncontroller;
+
+public class AdmissionControllerException extends RuntimeException {
+
+  public AdmissionControllerException() {}
+
+  public AdmissionControllerException(String message) {
+    super(message);
+  }
+
+  public AdmissionControllerException(String message, Throwable cause) {
+    super(message, cause);
+  }
+
+  public AdmissionControllerException(Throwable cause) {
+    super(cause);
+  }
+
+  public AdmissionControllerException(String message, Throwable cause, boolean enableSuppression,
+      boolean writableStackTrace) {
+    super(message, cause, enableSuppression, writableStackTrace);
+  }
+}

core/src/main/java/io/javaoperatorsdk/admissioncontroller/AdmissionUtils.java

@@ -0,0 +1,26 @@
+package io.javaoperatorsdk.admissioncontroller;
+
+import io.fabric8.kubernetes.api.model.KubernetesResource;
+import io.fabric8.kubernetes.api.model.Status;
+import io.fabric8.kubernetes.api.model.admission.v1.AdmissionRequest;
+import io.fabric8.kubernetes.api.model.admission.v1.AdmissionResponse;
+
+public class AdmissionUtils {
+
+  public static AdmissionResponse notAllowedExceptionToAdmissionResponse(
+      NotAllowedException notAllowedException) {
+    AdmissionResponse admissionResponse = new AdmissionResponse();
+    admissionResponse.setAllowed(false);
+    Status status = new Status();
+    status.setCode(notAllowedException.getCode());
+    status.setMessage(notAllowedException.getMessage());
+    admissionResponse.setStatus(status);
+    return admissionResponse;
+  }
+
+  public static KubernetesResource getTargetResource(AdmissionRequest admissionRequest,
+      Operation operation) {
+    return operation == Operation.DELETE ? admissionRequest.getOldObject()
+        : admissionRequest.getObject();
+  }
+}

core/src/main/java/io/javaoperatorsdk/admissioncontroller/NotAllowedException.java

@@ -0,0 +1,38 @@
+package io.javaoperatorsdk.admissioncontroller;
+
+public class NotAllowedException extends AdmissionControllerException {
+
+  private int code;
+
+  public NotAllowedException() {}
+
+  public NotAllowedException(int code) {
+    this.code = code;
+  }
+
+  public NotAllowedException(String message, int code) {
+    super(message);
+    this.code = code;
+  }
+
+  public NotAllowedException(String message, Throwable cause, int code) {
+    super(message, cause);
+    this.code = code;
+  }
+
+  public NotAllowedException(Throwable cause, int code) {
+    super(cause);
+    this.code = code;
+  }
+
+  public NotAllowedException(String message, Throwable cause, boolean enableSuppression,
+      boolean writableStackTrace, int code) {
+    super(message, cause, enableSuppression, writableStackTrace);
+    this.code = code;
+  }
+
+  public int getCode() {
+    return code;
+  }
+
+}

core/src/main/java/io/javaoperatorsdk/admissioncontroller/Operation.java

@@ -0,0 +1,5 @@
+package io.javaoperatorsdk.admissioncontroller;
+
+public enum Operation {
+  CREATE, UPDATE, DELETE, CONNECT
+}

core/src/main/java/io/javaoperatorsdk/admissioncontroller/RequestHandler.java

@@ -0,0 +1,10 @@
+package io.javaoperatorsdk.admissioncontroller;
+
+import io.fabric8.kubernetes.api.model.admission.v1.AdmissionRequest;
+import io.fabric8.kubernetes.api.model.admission.v1.AdmissionResponse;
+
+public interface RequestHandler {
+
+  AdmissionResponse handle(AdmissionRequest admissionRequest);
+
+}