// Copyright (C) 2018 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.googlesource.gerrit.plugins.oauth;

import static org.scribe.model.OAuthConstants.ACCESS_TOKEN;

import com.google.common.annotations.VisibleForTesting;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import org.scribe.exceptions.OAuthException;
import org.scribe.extractors.AccessTokenExtractor;
import org.scribe.model.Token;
import org.scribe.utils.Preconditions;

class OAuth2AccessTokenJsonExtractor implements AccessTokenExtractor {
  private static final Pattern ACCESS_TOKEN_REGEX_PATTERN =
      Pattern.compile("\"" + ACCESS_TOKEN + "\"\\s*:\\s*\"(\\S*?)\"");

  private OAuth2AccessTokenJsonExtractor() {}

  private static final AccessTokenExtractor INSTANCE = new OAuth2AccessTokenJsonExtractor();

  static AccessTokenExtractor instance() {
    return INSTANCE;
  }

  @VisibleForTesting
  @Override
  public Token extract(String response) {
    Preconditions.checkEmptyString(response, "Cannot extract a token from a null or empty String");
    Matcher matcher = ACCESS_TOKEN_REGEX_PATTERN.matcher(response);
    if (matcher.find()) {
      return new Token(matcher.group(1), "", response);
    }
    throw new OAuthException("Cannot extract an access token. Response was: " + response);
  }
}