// Copyright 2014 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 "components/update_client/request_sender.h"

#include <algorithm>
#include <utility>

#include "base/base64.h"
#include "base/bind.h"
#include "base/location.h"
#include "base/logging.h"
#include "base/strings/stringprintf.h"
#include "base/threading/thread_task_runner_handle.h"
#include "components/client_update_protocol/ecdsa.h"
#include "components/update_client/configurator.h"
#include "components/update_client/update_client_errors.h"
#include "components/update_client/utils.h"
#include "net/http/http_response_headers.h"
#include "services/network/public/cpp/simple_url_loader.h"

namespace update_client {

namespace {

// This is an ECDSA prime256v1 named-curve key.
constexpr int kKeyVersion = 8;
const char kKeyPubBytesBase64[] =
    "MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAE+J2iCpfk8lThcuKUPzTaVcUjhNR3"
    "AYHK+tTelGdHvyGGx7RP7BphYSPmpH6P4Vr72ak0W1a0bW55O9HW2oz3rQ==";

// The ETag header carries the ECSDA signature of the protocol response, if
// signing has been used.
constexpr const char* kHeaderEtag = "ETag";

// The server uses the optional X-Retry-After header to indicate that the
// current request should not be attempted again. Any response received along
// with the X-Retry-After header should be interpreted as it would have been
// without the X-Retry-After header.
//
// In addition to the presence of the header, the value of the header is
// used as a signal for when to do future update checks, but only when the
// response is over https. Values over http are not trusted and are ignored.
//
// The value of the header is the number of seconds to wait before trying to do
// a subsequent update check. The upper bound for the number of seconds to wait
// before trying to do a subsequent update check is capped at 24 hours.
constexpr const char* kHeaderXRetryAfter = "X-Retry-After";
constexpr int64_t kMaxRetryAfterSec = 24 * 60 * 60;

}  // namespace

RequestSender::RequestSender(scoped_refptr<Configurator> config)
    : config_(config), use_signing_(false) {}

RequestSender::~RequestSender() {
  DCHECK(thread_checker_.CalledOnValidThread());
}

void RequestSender::Send(
    const std::vector<GURL>& urls,
    const base::flat_map<std::string, std::string>& request_extra_headers,
    const std::string& request_body,
    bool use_signing,
    RequestSenderCallback request_sender_callback) {
  DCHECK(thread_checker_.CalledOnValidThread());

  urls_ = urls;
  request_extra_headers_ = request_extra_headers;
  request_body_ = request_body;
  use_signing_ = use_signing;
  request_sender_callback_ = std::move(request_sender_callback);

  if (urls_.empty()) {
    return HandleSendError(static_cast<int>(ProtocolError::MISSING_URLS), 0);
  }

  cur_url_ = urls_.begin();

  if (use_signing_) {
    public_key_ = GetKey(kKeyPubBytesBase64);
    if (public_key_.empty())
      return HandleSendError(
          static_cast<int>(ProtocolError::MISSING_PUBLIC_KEY), 0);
  }

  SendInternal();
}

void RequestSender::SendInternal() {
  DCHECK(cur_url_ != urls_.end());
  DCHECK(cur_url_->is_valid());
  DCHECK(thread_checker_.CalledOnValidThread());

  GURL url(*cur_url_);

  if (use_signing_) {
    DCHECK(!public_key_.empty());
    signer_ = client_update_protocol::Ecdsa::Create(kKeyVersion, public_key_);
    std::string request_query_string;
    signer_->SignRequest(request_body_, &request_query_string);

    url = BuildUpdateUrl(url, request_query_string);
  }

  update_client::LoadCompleteCallback callback = base::BindOnce(
      &RequestSender::OnSimpleURLLoaderComplete, base::Unretained(this), url);

  url_loader_ =
      SendProtocolRequest(url, request_extra_headers_, request_body_,
                          std::move(callback), config_->URLLoaderFactory());
  if (!url_loader_)
    base::ThreadTaskRunnerHandle::Get()->PostTask(
        FROM_HERE,
        base::BindOnce(&RequestSender::SendInternalComplete,
                       base::Unretained(this),
                       static_cast<int>(ProtocolError::URL_FETCHER_FAILED),
                       std::string(), std::string(), 0));
}

void RequestSender::SendInternalComplete(int error,
                                         const std::string& response_body,
                                         const std::string& response_etag,
                                         int retry_after_sec) {
  if (!error) {
    if (!use_signing_) {
      base::ThreadTaskRunnerHandle::Get()->PostTask(
          FROM_HERE, base::BindOnce(std::move(request_sender_callback_), 0,
                                    response_body, retry_after_sec));
      return;
    }

    DCHECK(use_signing_);
    DCHECK(signer_);
    if (signer_->ValidateResponse(response_body, response_etag)) {
      base::ThreadTaskRunnerHandle::Get()->PostTask(
          FROM_HERE, base::BindOnce(std::move(request_sender_callback_), 0,
                                    response_body, retry_after_sec));
      return;
    }

    error = static_cast<int>(ProtocolError::RESPONSE_NOT_TRUSTED);
  }

  DCHECK(error);

  // A positive |retry_after_sec| is a hint from the server that the client
  // should not send further request until the cooldown has expired.
  if (retry_after_sec <= 0 && ++cur_url_ != urls_.end() &&
      base::ThreadTaskRunnerHandle::Get()->PostTask(
          FROM_HERE, base::BindOnce(&RequestSender::SendInternal,
                                    base::Unretained(this)))) {
    return;
  }

  HandleSendError(error, retry_after_sec);
}

void RequestSender::OnSimpleURLLoaderComplete(
    const GURL& original_url,
    std::unique_ptr<std::string> response_body) {
  DCHECK(thread_checker_.CalledOnValidThread());

  VLOG(1) << "request completed from url: " << original_url.spec();

  int response_code = -1;
  if (url_loader_->ResponseInfo() && url_loader_->ResponseInfo()->headers) {
    response_code = url_loader_->ResponseInfo()->headers->response_code();
  }

  int fetch_error = -1;
  if (response_body && response_code == 200) {
    fetch_error = 0;
  } else if (response_code != -1) {
    fetch_error = response_code;
  } else {
    fetch_error = url_loader_->NetError();
  }

  int64_t retry_after_sec(-1);
  if (original_url.SchemeIsCryptographic() && fetch_error > 0) {
    retry_after_sec =
        GetInt64HeaderValue(url_loader_.get(), kHeaderXRetryAfter);
    retry_after_sec = std::min(retry_after_sec, kMaxRetryAfterSec);
  }

  base::ThreadTaskRunnerHandle::Get()->PostTask(
      FROM_HERE,
      base::BindOnce(&RequestSender::SendInternalComplete,
                     base::Unretained(this), fetch_error,
                     response_body ? *response_body : std::string(),
                     GetStringHeaderValue(url_loader_.get(), kHeaderEtag),
                     static_cast<int>(retry_after_sec)));
}

void RequestSender::HandleSendError(int error, int retry_after_sec) {
  base::ThreadTaskRunnerHandle::Get()->PostTask(
      FROM_HERE, base::BindOnce(std::move(request_sender_callback_), error,
                                std::string(), retry_after_sec));
}

std::string RequestSender::GetKey(const char* key_bytes_base64) {
  std::string result;
  return base::Base64Decode(std::string(key_bytes_base64), &result)
             ? result
             : std::string();
}

GURL RequestSender::BuildUpdateUrl(const GURL& url,
                                   const std::string& query_params) {
  const std::string query_string(
      url.has_query() ? base::StringPrintf("%s&%s", url.query().c_str(),
                                           query_params.c_str())
                      : query_params);
  GURL::Replacements replacements;
  replacements.SetQueryStr(query_string);

  return url.ReplaceComponents(replacements);
}

std::string RequestSender::GetStringHeaderValue(
    const network::SimpleURLLoader* url_loader,
    const char* header_name) {
  DCHECK(url_loader);
  if (url_loader->ResponseInfo() && url_loader->ResponseInfo()->headers) {
    std::string etag;
    return url_loader->ResponseInfo()->headers->EnumerateHeader(
               nullptr, header_name, &etag)
               ? etag
               : std::string();
  }

  return std::string();
}

int64_t RequestSender::GetInt64HeaderValue(
    const network::SimpleURLLoader* url_loader,
    const char* header_name) {
  DCHECK(url_loader);
  if (url_loader->ResponseInfo() && url_loader->ResponseInfo()->headers) {
    return url_loader->ResponseInfo()->headers->GetInt64HeaderValue(
        header_name);
  }
  return -1;
}

}  // namespace update_client