/*
 * Copyright (C) 2014 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 com.squareup.okhttp.internal.http;

import com.squareup.okhttp.OkResponseCache;
import com.squareup.okhttp.Request;
import com.squareup.okhttp.Response;
import com.squareup.okhttp.ResponseSource;
import java.io.IOException;
import java.net.CacheRequest;
import java.net.CacheResponse;
import java.net.HttpURLConnection;
import java.net.ResponseCache;
import java.net.URI;
import java.util.List;
import java.util.Map;

/**
 * An adapter from {@link ResponseCache} to {@link com.squareup.okhttp.OkResponseCache}. This class
 * enables OkHttp to continue supporting Java standard response cache implementations.
 */
public class ResponseCacheAdapter implements OkResponseCache {

  private final ResponseCache delegate;

  public ResponseCacheAdapter(ResponseCache delegate) {
    this.delegate = delegate;
  }

  public ResponseCache getDelegate() {
    return delegate;
  }

  @Override
  public Response get(Request request) throws IOException {
    CacheResponse javaResponse = getJavaCachedResponse(request);
    if (javaResponse == null) {
      return null;
    }
    return JavaApiConverter.createOkResponse(request, javaResponse);
  }

  @Override
  public CacheRequest put(Response response) throws IOException {
    URI uri = response.request().uri();
    HttpURLConnection connection = JavaApiConverter.createJavaUrlConnection(response);
    return delegate.put(uri, connection);
  }

  @Override
  public boolean maybeRemove(Request request) throws IOException {
    // This method is treated as optional and there is no obvious way of implementing it with
    // ResponseCache. Removing items from the cache due to modifications made from this client is
    // not essential given that modifications could be made from any other client. We have to assume
    // that it's ok to keep using the cached data. Otherwise the server shouldn't declare it as
    // cacheable or the client should be careful about caching it.
    return false;
  }

  @Override
  public void update(Response cached, Response network) throws IOException {
    // This method is treated as optional and there is no obvious way of implementing it with
    // ResponseCache. Updating headers is useful if the server changes the metadata for a resource
    // (e.g. max age) to extend or truncate the life of that resource in the cache. If the metadata
    // is not updated the caching behavior may not be optimal, but will obey the metadata sent
    // with the original cached response.
  }

  @Override
  public void trackConditionalCacheHit() {
    // This method is treated as optional.
  }

  @Override
  public void trackResponse(ResponseSource source) {
    // This method is treated as optional.
  }

  /**
   * Returns the {@link CacheResponse} from the delegate by converting the
   * OkHttp {@link Request} into the arguments required by the {@link ResponseCache}.
   */
  private CacheResponse getJavaCachedResponse(Request request) throws IOException {
    Map<String, List<String>> headers = JavaApiConverter.extractJavaHeaders(request);
    return delegate.get(request.uri(), request.method(), headers);
  }

}