//
// Copyright (C) 2019 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.

#include "credential_source.h"

#include <glog/logging.h>

namespace {

std::chrono::steady_clock::duration REFRESH_WINDOW =
    std::chrono::minutes(2);
std::string REFRESH_URL = "http://metadata.google.internal/computeMetadata/"
    "v1/instance/service-accounts/default/token";

}

GceMetadataCredentialSource::GceMetadataCredentialSource() {
  latest_credential = "";
  expiration = std::chrono::steady_clock::now();
}

std::string GceMetadataCredentialSource::Credential() {
  if (expiration - std::chrono::steady_clock::now() < REFRESH_WINDOW) {
    RefreshCredential();
  }
  return latest_credential;
}

void GceMetadataCredentialSource::RefreshCredential() {
  Json::Value credential_json =
      curl.DownloadToJson(REFRESH_URL, {"Metadata-Flavor: Google"});

  CHECK(!credential_json.isMember("error")) << "Error fetching credentials. " <<
      "Response was " << credential_json;
  bool has_access_token = credential_json.isMember("access_token");
  bool has_expires_in = credential_json.isMember("expires_in");
  if (!has_access_token || !has_expires_in) {
    LOG(FATAL) << "GCE credential was missing access_token or expires_in. "
        << "Full response was " << credential_json << "";
  }

  expiration = std::chrono::steady_clock::now()
      + std::chrono::seconds(credential_json["expires_in"].asInt());
  latest_credential = credential_json["access_token"].asString();
}

std::unique_ptr<CredentialSource> GceMetadataCredentialSource::make() {
  return std::unique_ptr<CredentialSource>(new GceMetadataCredentialSource());
}

FixedCredentialSource::FixedCredentialSource(const std::string& credential) {
  this->credential = credential;
}

std::string FixedCredentialSource::Credential() {
  return credential;
}

std::unique_ptr<CredentialSource> FixedCredentialSource::make(
    const std::string& credential) {
  return std::unique_ptr<CredentialSource>(new FixedCredentialSource(credential));
}