content: /*
   * Copyright (C) 2017 The Android Open Source Project
   *
   * 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.google.android.exoplayer2.drm;
  
  import com.google.android.exoplayer2.util.Log;
  import com.google.android.exoplayer2.util.Util;
  import org.json.JSONArray;
  import org.json.JSONException;
  import org.json.JSONObject;
  
  /** Utility methods for ClearKey. */
  /* package */ final class ClearKeyUtil {
  
    private static final String TAG = "ClearKeyUtil";
  
    private ClearKeyUtil() {}
  
    /**
     * Adjusts ClearKey request data obtained from the Android ClearKey CDM to be spec compliant.
     *
     * @param request The request data.
     * @return The adjusted request data.
     */
    public static byte[] adjustRequestData(byte[] request) {
      if (Util.SDK_INT >= 27) {
        return request;
      }
      // Prior to O-MR1 the ClearKey CDM encoded the values in the "kids" array using Base64 encoding
      // rather than Base64Url encoding. See [Internal: b/64388098]. We know the exact request format
      // from the platform's InitDataParser.cpp. Since there aren't any "+" or "/" symbols elsewhere
      // in the request, it's safe to fix the encoding by replacement through the whole request.
      String requestString = Util.fromUtf8Bytes(request);
      return Util.getUtf8Bytes(base64ToBase64Url(requestString));
    }
  
    /**
     * Adjusts ClearKey response data to be suitable for providing to the Android ClearKey CDM.
     *
     * @param response The response data.
     * @return The adjusted response data.
     */
    public static byte[] adjustResponseData(byte[] response) {
      if (Util.SDK_INT >= 27) {
        return response;
      }
      // Prior to O-MR1 the ClearKey CDM expected Base64 encoding rather than Base64Url encoding for
      // the "k" and "kid" strings. See [Internal: b/64388098]. We know that the ClearKey CDM only
      // looks at the k, kid and kty parameters in each key, so can ignore the rest of the response.
      try {
        JSONObject responseJson = new JSONObject(Util.fromUtf8Bytes(response));
        StringBuilder adjustedResponseBuilder = new StringBuilder("{\"keys\":[");
        JSONArray keysArray = responseJson.getJSONArray("keys");
        for (int i = 0; i < keysArray.length(); i++) {
          if (i != 0) {
            adjustedResponseBuilder.append(",");
          }
          JSONObject key = keysArray.getJSONObject(i);
          adjustedResponseBuilder.append("{\"k\":\"");
          adjustedResponseBuilder.append(base64UrlToBase64(key.getString("k")));
          adjustedResponseBuilder.append("\",\"kid\":\"");
          adjustedResponseBuilder.append(base64UrlToBase64(key.getString("kid")));
          adjustedResponseBuilder.append("\",\"kty\":\"");
          adjustedResponseBuilder.append(key.getString("kty"));
          adjustedResponseBuilder.append("\"}");
        }
        adjustedResponseBuilder.append("]}");
        return Util.getUtf8Bytes(adjustedResponseBuilder.toString());
      } catch (JSONException e) {
        Log.e(TAG, "Failed to adjust response data: " + Util.fromUtf8Bytes(response), e);
        return response;
      }
    }
  
    private static String base64ToBase64Url(String base64) {
      return base64.replace('+', '-').replace('/', '_');
    }
  
    private static String base64UrlToBase64(String base64Url) {
      return base64Url.replace('-', '+').replace('_', '/');
    }
  }
  