statefun-flink/statefun-flink-core/src/main/java/org/apache/flink/statefun/flink/core/jsonmodule/FunctionEndpointSpec.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.flink.statefun.flink.core.jsonmodule;

import java.io.Serializable;
import java.net.URI;
import java.util.Objects;
import org.apache.flink.statefun.sdk.FunctionType;
import org.apache.flink.statefun.sdk.FunctionTypeNamespaceMatcher;

public interface FunctionEndpointSpec {

  Target target();

  Kind kind();

  UrlPathTemplate urlPathTemplate();

  enum Kind {
    HTTP,
    GRPC
  }

  abstract class Target implements Serializable {

    public static Target namespace(String namespace) {
      return new NamespaceTarget(FunctionTypeNamespaceMatcher.targetNamespace(namespace));
    }

    public static Target functionType(FunctionType functionType) {
      return new FunctionTypeTarget(functionType);
    }

    public boolean isSpecificFunctionType() {
      return this.getClass() == FunctionTypeTarget.class;
    }

    public boolean isNamespace() {
      return this.getClass() == NamespaceTarget.class;
    }

    public abstract FunctionTypeNamespaceMatcher asNamespace();

    public abstract FunctionType asSpecificFunctionType();

    private static class NamespaceTarget extends Target {
      private static final long serialVersionUID = 1;

      private final FunctionTypeNamespaceMatcher namespaceMatcher;

      private NamespaceTarget(FunctionTypeNamespaceMatcher namespaceMatcher) {
        this.namespaceMatcher = Objects.requireNonNull(namespaceMatcher);
      }

      @Override
      public FunctionTypeNamespaceMatcher asNamespace() {
        return namespaceMatcher;
      }

      @Override
      public FunctionType asSpecificFunctionType() {
        throw new IllegalStateException("This target is not a specific function type");
      }
    }

    private static class FunctionTypeTarget extends Target {
      private static final long serialVersionUID = 1;

      private final FunctionType functionType;

      private FunctionTypeTarget(FunctionType functionType) {
        this.functionType = Objects.requireNonNull(functionType);
      }

      @Override
      public FunctionTypeNamespaceMatcher asNamespace() {
        throw new IllegalStateException("This target is not a namespace.");
      }

      @Override
      public FunctionType asSpecificFunctionType() {
        return functionType;
      }
    }
  }

  class UrlPathTemplate implements Serializable {
    private static final long serialVersionUID = 1;

    private static final String FUNCTION_NAME_HOLDER = "{function.name}";

    private final String template;

    public UrlPathTemplate(String template) {
      this.template = Objects.requireNonNull(template);
    }

    public URI apply(FunctionType functionType) {
      return URI.create(template.replace(FUNCTION_NAME_HOLDER, functionType.name()));
    }
  }
}