/*
    * Copyright 2022 the original author or authors.
    *
    * Licensed 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.bremersee.apiclient.webflux.contract.spring;
  
  import static org.springframework.core.annotation.AnnotationUtils.findAnnotation;
  
  import java.lang.reflect.Method;
  import java.util.Optional;
  import java.util.function.Function;
  import org.bremersee.apiclient.webflux.Invocation;
  import org.bremersee.apiclient.webflux.contract.HttpRequestMethod;
  import org.springframework.util.Assert;
  import org.springframework.web.bind.annotation.DeleteMapping;
  import org.springframework.web.bind.annotation.GetMapping;
  import org.springframework.web.bind.annotation.PatchMapping;
  import org.springframework.web.bind.annotation.PostMapping;
  import org.springframework.web.bind.annotation.PutMapping;
  import org.springframework.web.bind.annotation.RequestMapping;
  
  /**
   * The http method resolver.
   *
   * @author Christian Bremer
   */
  public class HttpMethodResolver implements Function<Invocation, HttpRequestMethod> {
  
    @Override
    public HttpRequestMethod apply(Invocation invocation) {
  
      Assert.notNull(invocation, "Invocation must be present.");
      Method method = invocation.getMethod();
      return Optional.ofNullable(findAnnotation(method, RequestMapping.class))
          .filter(requestMapping -> requestMapping.method().length > 0)
          .flatMap(requestMapping -> HttpRequestMethod.resolve(requestMapping.method()[0].name()))
          .or(() -> Optional.ofNullable(findAnnotation(method, GetMapping.class))
              .map(a -> HttpRequestMethod.GET))
          .or(() -> Optional.ofNullable(findAnnotation(method, PostMapping.class))
              .map(a -> HttpRequestMethod.POST))
          .or(() -> Optional.ofNullable(findAnnotation(method, PutMapping.class))
              .map(a -> HttpRequestMethod.PUT))
          .or(() -> Optional.ofNullable(findAnnotation(method, PatchMapping.class))
              .map(a -> HttpRequestMethod.PATCH))
          .or(() -> Optional.ofNullable(findAnnotation(method, DeleteMapping.class))
              .map(a -> HttpRequestMethod.DELETE))
          .orElseThrow(() -> new IllegalStateException(
              String.format("Cannot find request method on method '%s'.", method.getName())));
    }
  }