package com.atlassian.marketplace.client.impl;
   
   import java.io.ByteArrayInputStream;
   import java.io.ByteArrayOutputStream;
   import java.io.InputStream;
   import java.net.URI;
   
   import com.atlassian.marketplace.client.MpacException;
   import com.atlassian.marketplace.client.api.Page;
  import com.atlassian.marketplace.client.api.PageReader;
  import com.atlassian.marketplace.client.api.PageReference;
  import com.atlassian.marketplace.client.http.SimpleHttpResponse;
  import com.atlassian.marketplace.client.model.Links;
  import com.atlassian.marketplace.client.model.TestModelBuilders;
  import com.atlassian.marketplace.client.util.UriBuilder;
  
  import com.google.common.base.Function;
  import com.google.common.base.Functions;
  
  import static com.atlassian.marketplace.client.impl.ApiHelper.JSON;
  import static com.atlassian.marketplace.client.impl.ApiHelper.closeQuietly;
  
  abstract class ApiImplBase
  {
      protected final ApiHelper apiHelper;
      protected final InternalModel.MinimalLinks root;
      protected final URI apiRoot;
      
      protected ApiImplBase(ApiHelper apiHelper, InternalModel.MinimalLinks root, String rootLinkRel) throws MpacException
      {
          this.apiHelper = apiHelper;
          this.root = root;
          this.apiRoot = apiHelper.requireLinkUri(root.getLinks(), rootLinkRel, root.getClass());
      }
      
      protected URI getApiRoot()
      {
          return apiRoot;
      }
      
      protected UriBuilder fromApiRoot()
      {
          return UriBuilder.fromUri(apiRoot);
      }
      
      protected Links getLinksOnly(URI uri) throws MpacException
      {
          InternalModel.MinimalLinks rep = apiHelper.getEntity(uri, InternalModel.MinimalLinks.class);
          return rep.getLinks();
      }
  
      protected <T> T genericCreate(URI collectionUri, T entity) throws MpacException
      {
          return genericCreate(collectionUri, entity, Functions.<URI>identity());
      }
      
      protected <T> T genericCreate(URI collectionUri, T entity, Function<URI, URI> resultUriTransform) throws MpacException
      {
          ByteArrayOutputStream bos = new ByteArrayOutputStream();
          apiHelper.getEncoding().encode(bos, entity, false);
          byte[] bytes = bos.toByteArray();
          return createdOrUpdatedEntityResult(apiHelper.getHttp().post(apiHelper.resolveLink(collectionUri),
              new ByteArrayInputStream(bytes), bytes.length, JSON, JSON),
              entity.getClass(),
              resultUriTransform);
      }
  
      protected <T> T genericUpdate(URI uri, T original, T updated) throws MpacException
      {
          if (uri == TestModelBuilders.DEFAULT_URI)
          {
              // If the entity's self URI is DEFAULT_URI, then it's not a real, updatable entity that was obtained
              // from the server - it's something the caller built.  In that case there's no point in trying to
              // send a PATCH request to this fake URI; return a more informative error instead.
              throw new MpacException.CannotUpdateNonServerSideEntity();
          }
          ByteArrayOutputStream bos = new ByteArrayOutputStream();
          apiHelper.getEncoding().encodeChanges(bos, original, updated);
          byte[] bytes = bos.toByteArray();
          return createdOrUpdatedEntityResult(apiHelper.getHttp().patch(apiHelper.resolveLink(uri), bytes),
              original.getClass(), Functions.<URI>identity());
      }
      
      @SuppressWarnings("unchecked")
      private <T> T createdOrUpdatedEntityResult(SimpleHttpResponse response, Class<?> entityClass,
          Function<URI, URI> resultUriTransform) throws MpacException
      {
          try
          {
              int status = response.getStatus();
              if (status == 200 || status == 201 || status == 204)
              {
                  for (String location: response.getHeader("Location"))
                  {
                      return apiHelper.getEntityUncached(resultUriTransform.apply(URI.create(location)), (Class<T>) entityClass);
                  }
                  throw new MpacException("Server did not return expected Location header");
              }
              throw apiHelper.responseException(response);
         }
         finally
         {
             closeQuietly(response);
         }
     }
 
     protected <T, U extends InternalModel.EntityCollection<T>> PageReader<T> pageReader(final Class<U> collectionRepClass)
     {
         return new PageReader<T>()
         {
             @Override
             public Page<T> readPage(PageReference<T> ref, InputStream in) throws MpacException
             {
                 U rep = apiHelper.decode(in, collectionRepClass);
                 return new PageImpl<T>(ref, rep.getLinks(), rep.getItems(), rep.getCount(), this);
             }
         };
     }
 }