// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "google_apis/gaia/oauth2_access_token_fetcher.h"

#include <algorithm>
#include <string>
#include <vector>

#include "base/json/json_reader.h"
#include "base/metrics/histogram.h"
#include "base/metrics/sparse_histogram.h"
#include "base/strings/string_util.h"
#include "base/strings/stringprintf.h"
#include "base/time/time.h"
#include "base/values.h"
#include "google_apis/gaia/gaia_urls.h"
#include "google_apis/gaia/google_service_auth_error.h"
#include "net/base/escape.h"
#include "net/base/load_flags.h"
#include "net/http/http_status_code.h"
#include "net/url_request/url_fetcher.h"
#include "net/url_request/url_request_context_getter.h"
#include "net/url_request/url_request_status.h"

using net::ResponseCookies;
using net::URLFetcher;
using net::URLFetcherDelegate;
using net::URLRequestContextGetter;
using net::URLRequestStatus;

namespace {
static const char kGetAccessTokenBodyFormat[] =
    "client_id=%s&"
    "client_secret=%s&"
    "grant_type=refresh_token&"
    "refresh_token=%s";

static const char kGetAccessTokenBodyWithScopeFormat[] =
    "client_id=%s&"
    "client_secret=%s&"
    "grant_type=refresh_token&"
    "refresh_token=%s&"
    "scope=%s";

static const char kAccessTokenKey[] = "access_token";
static const char kExpiresInKey[] = "expires_in";
static const char kErrorKey[] = "error";

// Enumerated constants for logging server responses on 400 errors, matching
// RFC 6749.
enum OAuth2ErrorCodesForHistogram {
   OAUTH2_ACCESS_ERROR_INVALID_REQUEST = 0,
   OAUTH2_ACCESS_ERROR_INVALID_CLIENT,
   OAUTH2_ACCESS_ERROR_INVALID_GRANT,
   OAUTH2_ACCESS_ERROR_UNAUTHORIZED_CLIENT,
   OAUTH2_ACCESS_ERROR_UNSUPPORTED_GRANT_TYPE,
   OAUTH2_ACCESS_ERROR_INVALID_SCOPE,
   OAUTH2_ACCESS_ERROR_UNKNOWN,
   OAUTH2_ACCESS_ERROR_COUNT
};

OAuth2ErrorCodesForHistogram OAuth2ErrorToHistogramValue(
    const std::string& error) {
  if (error == "invalid_request")
    return OAUTH2_ACCESS_ERROR_INVALID_REQUEST;
  else if (error == "invalid_client")
    return OAUTH2_ACCESS_ERROR_INVALID_CLIENT;
  else if (error == "invalid_grant")
    return OAUTH2_ACCESS_ERROR_INVALID_GRANT;
  else if (error == "unauthorized_client")
    return OAUTH2_ACCESS_ERROR_UNAUTHORIZED_CLIENT;
  else if (error == "unsupported_grant_type")
    return OAUTH2_ACCESS_ERROR_UNSUPPORTED_GRANT_TYPE;
  else if (error == "invalid_scope")
    return OAUTH2_ACCESS_ERROR_INVALID_SCOPE;

  return OAUTH2_ACCESS_ERROR_UNKNOWN;
}

static GoogleServiceAuthError CreateAuthError(URLRequestStatus status) {
  CHECK(!status.is_success());
  if (status.status() == URLRequestStatus::CANCELED) {
    return GoogleServiceAuthError(GoogleServiceAuthError::REQUEST_CANCELED);
  } else {
    DLOG(WARNING) << "Could not reach Google Accounts servers: errno "
                  << status.error();
    return GoogleServiceAuthError::FromConnectionError(status.error());
  }
}

static URLFetcher* CreateFetcher(URLRequestContextGetter* getter,
                                 const GURL& url,
                                 const std::string& body,
                                 URLFetcherDelegate* delegate) {
  bool empty_body = body.empty();
  URLFetcher* result = net::URLFetcher::Create(
      0, url,
      empty_body ? URLFetcher::GET : URLFetcher::POST,
      delegate);

  result->SetRequestContext(getter);
  result->SetLoadFlags(net::LOAD_DO_NOT_SEND_COOKIES |
                       net::LOAD_DO_NOT_SAVE_COOKIES);
  // Fetchers are sometimes cancelled because a network change was detected,
  // especially at startup and after sign-in on ChromeOS. Retrying once should
  // be enough in those cases; let the fetcher retry up to 3 times just in case.
  // http://crbug.com/163710
  result->SetAutomaticallyRetryOnNetworkChanges(3);

  if (!empty_body)
    result->SetUploadData("application/x-www-form-urlencoded", body);

  return result;
}
}  // namespace

OAuth2AccessTokenFetcher::OAuth2AccessTokenFetcher(
    OAuth2AccessTokenConsumer* consumer,
    URLRequestContextGetter* getter)
    : consumer_(consumer),
      getter_(getter),
      state_(INITIAL) { }

OAuth2AccessTokenFetcher::~OAuth2AccessTokenFetcher() { }

void OAuth2AccessTokenFetcher::CancelRequest() {
  fetcher_.reset();
}

void OAuth2AccessTokenFetcher::Start(const std::string& client_id,
                                     const std::string& client_secret,
                                     const std::string& refresh_token,
                                     const std::vector<std::string>& scopes) {
  client_id_ = client_id;
  client_secret_ = client_secret;
  refresh_token_ = refresh_token;
  scopes_ = scopes;
  StartGetAccessToken();
}

void OAuth2AccessTokenFetcher::StartGetAccessToken() {
  CHECK_EQ(INITIAL, state_);
  state_ = GET_ACCESS_TOKEN_STARTED;
  fetcher_.reset(CreateFetcher(
      getter_,
      MakeGetAccessTokenUrl(),
      MakeGetAccessTokenBody(
          client_id_, client_secret_, refresh_token_, scopes_),
      this));
  fetcher_->Start();  // OnURLFetchComplete will be called.
}

void OAuth2AccessTokenFetcher::EndGetAccessToken(
    const net::URLFetcher* source) {
  CHECK_EQ(GET_ACCESS_TOKEN_STARTED, state_);
  state_ = GET_ACCESS_TOKEN_DONE;

  URLRequestStatus status = source->GetStatus();
  int histogram_value = status.is_success() ? source->GetResponseCode() :
                                              status.error();
  UMA_HISTOGRAM_SPARSE_SLOWLY("Gaia.ResponseCodesForOAuth2AccessToken",
                              histogram_value);
  if (!status.is_success()) {
    OnGetTokenFailure(CreateAuthError(status));
    return;
  }

  switch (source->GetResponseCode()) {
    case net::HTTP_OK:
      break;
    case net::HTTP_FORBIDDEN:
    case net::HTTP_INTERNAL_SERVER_ERROR:
      // HTTP_FORBIDDEN (403) is treated as temporary error, because it may be
      // '403 Rate Limit Exeeded.' 500 is always treated as transient.
      OnGetTokenFailure(GoogleServiceAuthError(
          GoogleServiceAuthError::SERVICE_UNAVAILABLE));
      return;
    case net::HTTP_BAD_REQUEST: {
      // HTTP_BAD_REQUEST (400) usually contains error as per
      // http://tools.ietf.org/html/rfc6749#section-5.2.
      std::string gaia_error;
      if (!ParseGetAccessTokenFailureResponse(source, &gaia_error)) {
        OnGetTokenFailure(GoogleServiceAuthError(
            GoogleServiceAuthError::SERVICE_ERROR));
        return;
      }

      OAuth2ErrorCodesForHistogram access_error(OAuth2ErrorToHistogramValue(
          gaia_error));
      UMA_HISTOGRAM_ENUMERATION("Gaia.BadRequestTypeForOAuth2AccessToken",
                                access_error, OAUTH2_ACCESS_ERROR_COUNT);

      OnGetTokenFailure(access_error == OAUTH2_ACCESS_ERROR_INVALID_GRANT ?
          GoogleServiceAuthError(
              GoogleServiceAuthError::INVALID_GAIA_CREDENTIALS) :
          GoogleServiceAuthError(
              GoogleServiceAuthError::SERVICE_ERROR));
      return;
    }
    default:
      // The other errors are treated as permanent error.
      OnGetTokenFailure(GoogleServiceAuthError(
          GoogleServiceAuthError::INVALID_GAIA_CREDENTIALS));
      return;
  }

  // The request was successfully fetched and it returned OK.
  // Parse out the access token and the expiration time.
  std::string access_token;
  int expires_in;
  if (!ParseGetAccessTokenSuccessResponse(
          source, &access_token, &expires_in)) {
    DLOG(WARNING) << "Response doesn't match expected format";
    OnGetTokenFailure(
        GoogleServiceAuthError(GoogleServiceAuthError::SERVICE_UNAVAILABLE));
    return;
  }
  // The token will expire in |expires_in| seconds. Take a 10% error margin to
  // prevent reusing a token too close to its expiration date.
  OnGetTokenSuccess(
      access_token,
      base::Time::Now() + base::TimeDelta::FromSeconds(9 * expires_in / 10));
}

void OAuth2AccessTokenFetcher::OnGetTokenSuccess(
    const std::string& access_token,
    const base::Time& expiration_time) {
  consumer_->OnGetTokenSuccess(access_token, expiration_time);
}

void OAuth2AccessTokenFetcher::OnGetTokenFailure(
    const GoogleServiceAuthError& error) {
  state_ = ERROR_STATE;
  consumer_->OnGetTokenFailure(error);
}

void OAuth2AccessTokenFetcher::OnURLFetchComplete(
    const net::URLFetcher* source) {
  CHECK(source);
  CHECK(state_ == GET_ACCESS_TOKEN_STARTED);
  EndGetAccessToken(source);
}

// static
GURL OAuth2AccessTokenFetcher::MakeGetAccessTokenUrl() {
  return GaiaUrls::GetInstance()->oauth2_token_url();
}

// static
std::string OAuth2AccessTokenFetcher::MakeGetAccessTokenBody(
    const std::string& client_id,
    const std::string& client_secret,
    const std::string& refresh_token,
    const std::vector<std::string>& scopes) {
  std::string enc_client_id = net::EscapeUrlEncodedData(client_id, true);
  std::string enc_client_secret =
      net::EscapeUrlEncodedData(client_secret, true);
  std::string enc_refresh_token =
      net::EscapeUrlEncodedData(refresh_token, true);
  if (scopes.empty()) {
    return base::StringPrintf(
        kGetAccessTokenBodyFormat,
        enc_client_id.c_str(),
        enc_client_secret.c_str(),
        enc_refresh_token.c_str());
  } else {
    std::string scopes_string = JoinString(scopes, ' ');
    return base::StringPrintf(
        kGetAccessTokenBodyWithScopeFormat,
        enc_client_id.c_str(),
        enc_client_secret.c_str(),
        enc_refresh_token.c_str(),
        net::EscapeUrlEncodedData(scopes_string, true).c_str());
  }
}

scoped_ptr<base::DictionaryValue> ParseGetAccessTokenResponse(
    const net::URLFetcher* source) {
  CHECK(source);

  std::string data;
  source->GetResponseAsString(&data);
  scoped_ptr<base::Value> value(base::JSONReader::Read(data));
  if (!value.get() || value->GetType() != base::Value::TYPE_DICTIONARY)
    value.reset();

  return scoped_ptr<base::DictionaryValue>(
      static_cast<base::DictionaryValue*>(value.release()));
}

// static
bool OAuth2AccessTokenFetcher::ParseGetAccessTokenSuccessResponse(
    const net::URLFetcher* source,
    std::string* access_token,
    int* expires_in) {
  CHECK(access_token);
  scoped_ptr<base::DictionaryValue> value = ParseGetAccessTokenResponse(
      source);
  if (value.get() == NULL)
    return false;

  return value->GetString(kAccessTokenKey, access_token) &&
      value->GetInteger(kExpiresInKey, expires_in);
}

// static
bool OAuth2AccessTokenFetcher::ParseGetAccessTokenFailureResponse(
    const net::URLFetcher* source,
    std::string* error) {
  CHECK(error);
  scoped_ptr<base::DictionaryValue> value = ParseGetAccessTokenResponse(
      source);
  if (value.get() == NULL)
    return false;
  return value->GetString(kErrorKey, error);
}