/*
 * Copyright (C) 2012 Square, Inc.
 *
 * 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 retrofit2;

import java.lang.annotation.Annotation;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.lang.reflect.Type;
import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.concurrent.Executor;
import okhttp3.HttpUrl;
import okhttp3.OkHttpClient;
import okhttp3.RequestBody;
import okhttp3.ResponseBody;
import retrofit2.http.GET;
import retrofit2.http.HTTP;
import retrofit2.http.Header;
import retrofit2.http.Url;

import static java.util.Collections.unmodifiableList;
import static retrofit2.Utils.checkNotNull;

/**
 * Retrofit adapts a Java interface to HTTP calls by using annotations on the declared methods to
 * define how requests are made. Create instances using {@linkplain Builder
 * the builder} and pass your interface to {@link #create} to generate an implementation.
 * <p>
 * For example,
 * <pre><code>
 * Retrofit retrofit = new Retrofit.Builder()
 *     .baseUrl("https://api.example.com/")
 *     .addConverterFactory(GsonConverterFactory.create())
 *     .build();
 *
 * MyApi api = retrofit.create(MyApi.class);
 * Response&lt;User&gt; user = api.getUser().execute();
 * </code></pre>
 *
 * @author Bob Lee (
 
[email protected])
 * @author Jake Wharton ([email protected]p.com)
 */




public final class Retrofit {



  private final Map<Method, ServiceMethod> serviceMethodCache = new LinkedHashMap<>();

  private final okhttp3.Call.Factory callFactory;
  private final HttpUrl baseUrl;//url地址 這個在平時工作中是必須要設定的，必不可少
  private final List<Converter.Factory> converterFactories;//轉換工廠？
  private final List<CallAdapter.Factory> adapterFactories;//適配工廠
  private final Executor callbackExecutor;
  private final boolean validateEagerly;


//帶引數構造器
  Retrofit(okhttp3.Call.Factory callFactory, HttpUrl baseUrl,
      List<Converter.Factory> converterFactories, List<CallAdapter.Factory> adapterFactories,
      Executor callbackExecutor, boolean validateEagerly) {

    this.callFactory = callFactory;
    this.baseUrl = baseUrl;
    this.converterFactories = unmodifiableList(converterFactories); // Defensive copy at call site.
    this.adapterFactories = unmodifiableList(adapterFactories); // Defensive copy at call site.
    this.callbackExecutor = callbackExecutor;
    this.validateEagerly = validateEagerly;
  }





  /**
   * Create an implementation of the API endpoints defined by the {@code service} interface.
   * <p>
   * The relative path for a given method is obtained from an annotation on the method describing
   * the request type. The built-in methods are {@link GET GET},
   * {@link retrofit2.http.PUT PUT}, {@link retrofit2.http.POST POST}, {@link retrofit2.http.PATCH
   * PATCH}, {@link retrofit2.http.HEAD HEAD}, {@link retrofit2.http.DELETE DELETE} and
   * {@link retrofit2.http.OPTIONS OPTIONS}. You can use a custom HTTP method with
   * {@link HTTP @HTTP}. For a dynamic URL, omit the path on the annotation and annotate the first
   * parameter with {@link Url @Url}.
   * <p>
   * Method parameters can be used to replace parts of the URL by annotating them with
   * {@link retrofit2.http.Path @Path}. Replacement sections are denoted by an identifier
   * surrounded by curly braces (e.g., "{foo}"). To add items to the query string of a URL use
   * {@link retrofit2.http.Query @Query}.
   * <p>
   * The body of a request is denoted by the {@link retrofit2.http.Body @Body} annotation. The
   * object will be converted to request representation by one of the {@link Converter.Factory}
   * instances. A {@link RequestBody} can also be used for a raw representation.
   * <p>
   * Alternative request body formats are supported by method annotations and corresponding
   * parameter annotations:
   * <ul>
   * <li>{@link retrofit2.http.FormUrlEncoded @FormUrlEncoded} - Form-encoded data with key-value
   * pairs specified by the {@link retrofit2.http.Field @Field} parameter annotation.
   * <li>{@link retrofit2.http.Multipart @Multipart} - RFC 2388-compliant multipart data with
   * parts specified by the {@link retrofit2.http.Part @Part} parameter annotation.
   * </ul>
   * <p>
   * Additional static headers can be added for an endpoint using the
   * {@link retrofit2.http.Headers @Headers} method annotation. For per-request control over a
   * header annotate a parameter with {@link Header @Header}.
   * <p>
   * By default, methods return a {@link Call} which represents the HTTP request. The generic
   * parameter of the call is the response body type and will be converted by one of the
   * {@link Converter.Factory} instances. {@link ResponseBody} can also be used for a raw
   * representation. {@link Void} can be used if you do not care about the body contents.
   * <p>
   * For example:
   * <pre>
   * public interface CategoryService {
   *   &#64;POST("category/{cat}/")
   *   Call&lt;List&lt;Item&gt;&gt; categoryList(@Path("cat") String a, @Query("page") int b);
   * }
   * </pre>
   */




  @SuppressWarnings("unchecked") // Single-interface proxy creation guarded by parameter safety.
  public <T> T create(final Class<T> service) {
    Utils.validateServiceInterface(service);
    if (validateEagerly) {
      eagerlyValidateMethods(service);
    }
    return (T) Proxy.newProxyInstance(service.getClassLoader(), new Class<?>[] { service },
        new InvocationHandler() {
          private final Platform platform = Platform.get();

          @Override public Object invoke(Object proxy, Method method, Object... args)
              throws Throwable {
            // If the method is a method from Object then defer to normal invocation.
            if (method.getDeclaringClass() == Object.class) {
              return method.invoke(this, args);
            }
            if (platform.isDefaultMethod(method)) {
              return platform.invokeDefaultMethod(method, service, proxy, args);
            }
            ServiceMethod serviceMethod = loadServiceMethod(method);
            OkHttpCall okHttpCall = new OkHttpCall<>(serviceMethod, args);
            return serviceMethod.callAdapter.adapt(okHttpCall);
          }
        });
  }

  private void eagerlyValidateMethods(Class<?> service) {
    Platform platform = Platform.get();
    for (Method method : service.getDeclaredMethods()) {
      if (!platform.isDefaultMethod(method)) {
        loadServiceMethod(method);
      }
    }
  }

  ServiceMethod loadServiceMethod(Method method) {
    ServiceMethod result;
    //同步鎖？同步程式碼塊，一次只能有一個執行緒進入
    synchronized (serviceMethodCache) {
      result = serviceMethodCache.get(method);
      if (result == null) {
        result = new ServiceMethod.Builder(this, method).build();
        serviceMethodCache.put(method, result);
      }
    }
    return result;
  }




  /**
   * The factory used to create {@linkplain okhttp3.Call OkHttp calls} for sending a HTTP requests.
   * Typically an instance of {@link OkHttpClient}.
   */
  public okhttp3.Call.Factory callFactory() {
    return callFactory;
  }



  /** The API base URL. */
//返回伺服器地址
  public HttpUrl baseUrl() {
    return baseUrl;
  }




  /**
   * Returns a list of the factories tried when creating a
   * {@linkplain #callAdapter(Type, Annotation[])} call adapter}.
   */
  public List<CallAdapter.Factory> callAdapterFactories() {
    return adapterFactories;
  }




  /**
   * Returns the {@link CallAdapter} for {@code returnType} from the available {@linkplain
   * #callAdapterFactories() factories}.
   *
   * @throws IllegalArgumentException if no call adapter available for {@code type}.
   */
  public CallAdapter<?> callAdapter(Type returnType, Annotation[] annotations) {
    return nextCallAdapter(null, returnType, annotations);
  }




  /**
   * Returns the {@link CallAdapter} for {@code returnType} from the available {@linkplain
   * #callAdapterFactories() factories} except {@code skipPast}.
   *
   * @throws IllegalArgumentException if no call adapter available for {@code type}.
   */
  public CallAdapter<?> nextCallAdapter(CallAdapter.Factory skipPast, Type returnType,
      Annotation[] annotations) {
    checkNotNull(returnType, "returnType == null");
    checkNotNull(annotations, "annotations == null");

    int start = adapterFactories.indexOf(skipPast) + 1;
    for (int i = start, count = adapterFactories.size(); i < count; i++) {
      CallAdapter<?> adapter = adapterFactories.get(i).get(returnType, annotations, this);
      if (adapter != null) {
        return adapter;
      }
    }

    StringBuilder builder = new StringBuilder("Could not locate call adapter for ")
        .append(returnType)
        .append(".\n");
    if (skipPast != null) {
      builder.append("  Skipped:");
      for (int i = 0; i < start; i++) {
        builder.append("\n   * ").append(adapterFactories.get(i).getClass().getName());
      }
      builder.append('\n');
    }
    builder.append("  Tried:");
    for (int i = start, count = adapterFactories.size(); i < count; i++) {
      builder.append("\n   * ").append(adapterFactories.get(i).getClass().getName());
    }
    throw new IllegalArgumentException(builder.toString());
  }





  /**
   * Returns a list of the factories tried when creating a
   * {@linkplain #requestBodyConverter(Type, Annotation[], Annotation[]) request body converter}, a
   * {@linkplain #responseBodyConverter(Type, Annotation[]) response body converter}, or a
   * {@linkplain #stringConverter(Type, Annotation[]) string converter}.
   */
//返回轉換工廠列表？
  public List<Converter.Factory> converterFactories() {
    return converterFactories;
  }





  /**
   * Returns a {@link Converter} for {@code type} to {@link RequestBody} from the available
   * {@linkplain #converterFactories() factories}.
   *
   * @throws IllegalArgumentException if no converter available for {@code type}.
   */
  public <T> Converter<T, RequestBody> requestBodyConverter(Type type,
      Annotation[] parameterAnnotations, Annotation[] methodAnnotations) {
    return nextRequestBodyConverter(null, type, parameterAnnotations, methodAnnotations);
  }




  /**
   * Returns a {@link Converter} for {@code type} to {@link RequestBody} from the available
   * {@linkplain #converterFactories() factories} except {@code skipPast}.
   *
   * @throws IllegalArgumentException if no converter available for {@code type}.
   */
  public <T> Converter<T, RequestBody> nextRequestBodyConverter(Converter.Factory skipPast,
      Type type, Annotation[] parameterAnnotations, Annotation[] methodAnnotations) {
    checkNotNull(type, "type == null");//非空判斷
    checkNotNull(parameterAnnotations, "parameterAnnotations == null");
    checkNotNull(methodAnnotations, "methodAnnotations == null");

    int start = converterFactories.indexOf(skipPast) + 1;
    for (int i = start, count = converterFactories.size(); i < count; i++) {
      Converter.Factory factory = converterFactories.get(i);
      Converter<?, RequestBody> converter =
          factory.requestBodyConverter(type, parameterAnnotations, methodAnnotations, this);
      if (converter != null) {
        //noinspection unchecked
        return (Converter<T, RequestBody>) converter;
      }
    }

    StringBuilder builder = new StringBuilder("Could not locate RequestBody converter for ")
        .append(type)
        .append(".\n");
    if (skipPast != null) {
      builder.append("  Skipped:");
      for (int i = 0; i < start; i++) {
        builder.append("\n   * ").append(converterFactories.get(i).getClass().getName());
      }
      builder.append('\n');
    }
    builder.append("  Tried:");
    for (int i = start, count = converterFactories.size(); i < count; i++) {
      builder.append("\n   * ").append(converterFactories.get(i).getClass().getName());
    }
    throw new IllegalArgumentException(builder.toString());
  }




  /**
   * Returns a {@link Converter} for {@link ResponseBody} to {@code type} from the available
   * {@linkplain #converterFactories() factories}.
   *
   * @throws IllegalArgumentException if no converter available for {@code type}.
   */
  public <T> Converter<ResponseBody, T> responseBodyConverter(Type type, Annotation[] annotations) {
    return nextResponseBodyConverter(null, type, annotations);
  }

  /**
   * Returns a {@link Converter} for {@link ResponseBody} to {@code type} from the available
   * {@linkplain #converterFactories() factories} except {@code skipPast}.
   *
   * @throws IllegalArgumentException if no converter available for {@code type}.
   */
  public <T> Converter<ResponseBody, T> nextResponseBodyConverter(Converter.Factory skipPast,
      Type type, Annotation[] annotations) {
    checkNotNull(type, "type == null");//非空判斷
    checkNotNull(annotations, "annotations == null");

    int start = converterFactories.indexOf(skipPast) + 1;
    for (int i = start, count = converterFactories.size(); i < count; i++) {
      Converter<ResponseBody, ?> converter =
          converterFactories.get(i).responseBodyConverter(type, annotations, this);
      if (converter != null) {
        //noinspection unchecked
        return (Converter<ResponseBody, T>) converter;
      }
    }

    StringBuilder builder = new StringBuilder("Could not locate ResponseBody converter for ")
        .append(type)
        .append(".\n");
    if (skipPast != null) {
      builder.append("  Skipped:");
      for (int i = 0; i < start; i++) {
        builder.append("\n   * ").append(converterFactories.get(i).getClass().getName());
      }
      builder.append('\n');
    }
    builder.append("  Tried:");
    for (int i = start, count = converterFactories.size(); i < count; i++) {
      builder.append("\n   * ").append(converterFactories.get(i).getClass().getName());
    }
    throw new IllegalArgumentException(builder.toString());
  }




  /**
   * Returns a {@link Converter} for {@code type} to {@link String} from the available
   * {@linkplain #converterFactories() factories}.
   */
  public <T> Converter<T, String> stringConverter(Type type, Annotation[] annotations) {
    checkNotNull(type, "type == null");//非空判斷
    checkNotNull(annotations, "annotations == null");

    for (int i = 0, count = converterFactories.size(); i < count; i++) {
      Converter<?, String> converter =
          converterFactories.get(i).stringConverter(type, annotations, this);
      if (converter != null) {
        //noinspection unchecked
        return (Converter<T, String>) converter;
      }
    }

    // Nothing matched. Resort to default converter which just calls toString().
    //noinspection unchecked
    return (Converter<T, String>) BuiltInConverters.ToStringConverter.INSTANCE;
  }




  /**
   * The executor used for {@link Callback} methods on a {@link Call}. This may be {@code null},
   * in which case callbacks should be made synchronously on the background thread.
   */
  public Executor callbackExecutor() {
    return callbackExecutor;
  }












  /**
    //這裡又是構建者模式的運用？
   * Build a new {@link Retrofit}.
   * <p>
   * Calling {@link #baseUrl} is required before calling {@link #build()}. All other methods
   * are optional.
   */
  public static final class Builder {
    private Platform platform;
    private okhttp3.Call.Factory callFactory;
    private HttpUrl baseUrl;
    private List<Converter.Factory> converterFactories = new ArrayList<>();
    private List<CallAdapter.Factory> adapterFactories = new ArrayList<>();
    private Executor callbackExecutor;
    private boolean validateEagerly;


    Builder(Platform platform) {
      this.platform = platform;
      // Add the built-in converter factory first. This prevents overriding its behavior but also
      // ensures correct behavior when using converters that consume all types.
      converterFactories.add(new BuiltInConverters());
    }



    public Builder() {
      this(Platform.get());
    }



    /**
     * The HTTP client used for requests.
     * <p>
     * This is a convenience method for calling {@link #callFactory}.
     * <p>
     * Note: This method <b>does not</b> make a defensive copy of {@code client}. Changes to its
     * settings will affect subsequent requests. Pass in a {@linkplain OkHttpClient#clone() cloned}
     * instance to prevent this if desired.
     */
    ////設定使用OkHttp網路請求，okhttp是高效能的http庫，擁有佇列執行緒池，輕鬆解決併發，自動維護socket連線池
    public Builder client(OkHttpClient client) {
      return callFactory(checkNotNull(client, "client == null"));
    }




    /**
     * Specify a custom call factory for creating {@link Call} instances.
     * <p>
     * Note: Calling {@link #client} automatically sets this value.
     */
    public Builder callFactory(okhttp3.Call.Factory factory) {
      this.callFactory = checkNotNull(factory, "factory == null");
      return this;
    }




    /**
     * Set the API base URL.
     *
     * @see #baseUrl(HttpUrl)
     */
//設定伺服器訪問地址
    public Builder baseUrl(String baseUrl) {
      checkNotNull(baseUrl, "baseUrl == null");//非空判斷
      HttpUrl httpUrl = HttpUrl.parse(baseUrl);
      if (httpUrl == null) {
        throw new IllegalArgumentException("Illegal URL: " + baseUrl);
      }
      return baseUrl(httpUrl);
    }





    /**
     * Set the API base URL.
     * <p>
     * The specified endpoint values (such as with {@link GET @GET}) are resolved against this
     * value using {@link HttpUrl#resolve(String)}. The behavior of this matches that of an
     * {@code <a href="">} link on a website resolving on the current URL.
     * <p>
     * <b>Base URLs should always end in {@code /}.</b>
     * <p>
     * A trailing {@code /} ensures that endpoints values which are relative paths will correctly
     * append themselves to a base which has path components.
     * <p>

     * <b>Correct:正確的伺服器地址格式如下</b><br>
     * Base URL: http://example.com/api/<br>
     * Endpoint: foo/bar/<br>
     * Result: http://example.com/api/foo/bar/

     * <p>
     * <b>Incorrect:錯誤的伺服器地址格式如下</b><br>
     * Base URL: http://example.com/api<br>
     * Endpoint: foo/bar/<br>
     * Result: http://example.com/foo/bar/

     * <p>
     * This method enforces that {@code baseUrl} has a trailing {@code /}.
     * <p>
     * <b>Endpoint values which contain a leading {@code /} are absolute.</b>
     * <p>
     * Absolute values retain only the host from {@code baseUrl} and ignore any specified path
     * components.
     * <p>
     * Base URL: http://example.com/api/<br>
     * Endpoint: /foo/bar/<br>
     * Result: http://example.com/foo/bar/
     * <p>
     * Base URL: http://example.com/<br>
     * Endpoint: /foo/bar/<br>
     * Result: http://example.com/foo/bar/
     * <p>
     * <b>Endpoint values may be a full URL.</b>
     * <p>
     * Values which have a host replace the host of {@code baseUrl} and values also with a scheme
     * replace the scheme of {@code baseUrl}.
     * <p>
     * Base URL: http://example.com/<br>
     * Endpoint: https://github.com/square/retrofit/<br>
     * Result: https://github.com/square/retrofit/
     * <p>
     * Base URL: http://example.com<br>
     * Endpoint: //github.com/square/retrofit/<br>
     * Result: http://github.com/square/retrofit/ (note the scheme stays 'http')
     */
//設定伺服器訪問地址
    public Builder baseUrl(HttpUrl baseUrl) {
      checkNotNull(baseUrl, "baseUrl == null");
      List<String> pathSegments = baseUrl.pathSegments();
      if (!"".equals(pathSegments.get(pathSegments.size() - 1))) {
        throw new IllegalArgumentException("baseUrl must end in /: " + baseUrl);
      }
      this.baseUrl = baseUrl;
      return this;
    }







    /** Add converter factory for serialization and deserialization of objects. */
////新增轉化庫，預設是Gson? 例如：GsonConverterFactory.create()
    public Builder addConverterFactory(Converter.Factory factory) {
      converterFactories.add(checkNotNull(factory, "factory == null"));
      return this;
    }







    /**
     * Add a call adapter factory for supporting service method return types other than {@link
     * Call}.
     */

    ////添加回調庫，可以採用RxJava 例如：RxJavaCallAdapterFactory.create()

    public Builder addCallAdapterFactory(CallAdapter.Factory factory) {
      adapterFactories.add(checkNotNull(factory, "factory == null"));
      return this;
    }





    /**
     * The executor on which {@link Callback} methods are invoked when returning {@link Call} from
     * your service method.
     * <p>
     * Note: {@code executor} is not used for {@linkplain #addCallAdapterFactory custom method
     * return types}.
     */
    public Builder callbackExecutor(Executor executor) {
      this.callbackExecutor = checkNotNull(executor, "executor == null");
      return this;
    }



    /**
     * When calling {@link #create} on the resulting {@link Retrofit} instance, eagerly validate
     * the configuration of all methods in the supplied interface.
     */
    public Builder validateEagerly(boolean validateEagerly) {
      this.validateEagerly = validateEagerly;
      return this;
    }








    /**
     * Create the {@link Retrofit} instance using the configured values.
     * <p>
     * Note: If neither {@link #client} nor {@link #callFactory} is called a default {@link
     * OkHttpClient} will be created and used.
     */
    //最後一步，建立例項
    public Retrofit build() {
      if (baseUrl == null) {//伺服器地址不能為空
        throw new IllegalStateException("Base URL required.");
      }

      okhttp3.Call.Factory callFactory = this.callFactory;
      if (callFactory == null) {
        callFactory = new OkHttpClient();//初始化例項
      }

      Executor callbackExecutor = this.callbackExecutor;
      if (callbackExecutor == null) {
        callbackExecutor = platform.defaultCallbackExecutor();
      }

      // Make a defensive copy of the adapters and add the default Call adapter.
      List<CallAdapter.Factory> adapterFactories = new ArrayList<>(this.adapterFactories);
      adapterFactories.add(platform.defaultCallAdapterFactory(callbackExecutor));

      // Make a defensive copy of the converters.
      List<Converter.Factory> converterFactories = new ArrayList<>(this.converterFactories);


      return new Retrofit(callFactory, baseUrl, converterFactories, adapterFactories,
          callbackExecutor, validateEagerly);//返回結果
    }








  }//構建者類結束



}//game over