// Copyright 2019 Google LLC. All rights reserved.
package com.google.video.widevine.jts.httpclient;

import com.google.api.client.googleapis.auth.oauth2.GoogleCredential;
import java.io.FileInputStream;
import java.io.IOException;
import java.util.Arrays;
import java.util.List;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * JTS Cloud Credentials.
 *
 * Provides Oauth2 authentication, and access/refresh tokens.
 */
public class Credentials {

  private static final List<String> SCOPES = Arrays.asList(
      "https://www.googleapis.com/auth/cloud-platform",
      "https://www.googleapis.com/auth/widevine/frontend");
  private static final int   MIN_ACCESS_TOKEN_REFRESH_SEC = 1200;
  private static final Logger logger = Logger.getLogger(Credentials.class.getName());

  private String credentialsJsonFile = null;
  private GoogleCredential googleCredential = null;
  private String accessToken = null;

  /**
   * Credentials Constructor.
   *
   * @param credentialsJsonFile The full path to a GCP service account json credentials file.
   */
  public Credentials(String credentialsJsonFile) throws IOException {
    this.credentialsJsonFile = credentialsJsonFile;
    activateGoogleCredentials();
  }

  private void activateGoogleCredentials() throws IOException {
    googleCredential = GoogleCredential
        .fromStream(new FileInputStream(credentialsJsonFile))
        .createScoped(SCOPES);
    googleCredential.refreshToken();
  }

  /** Provides an Oauth2 Access Token that can be used to make GCP service calls.*/
  public String getAccessToken() throws IOException {
    if (accessToken == null
            || googleCredential.getExpiresInSeconds() <= MIN_ACCESS_TOKEN_REFRESH_SEC) {
      googleCredential.refreshToken();
      accessToken = googleCredential.getAccessToken();
      logger.log(Level.INFO, "Getting new access token.");
    }
    return accessToken;
  }
}