// Copyright (c) 2013 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.
//
// The |FeedbackSender| object stores the user feedback to spellcheck
// suggestions in a |Feedback| object.
//
// When spelling service returns spellcheck results, these results first arrive
// in |FeedbackSender| to assign hash identifiers for each
// misspelling-suggestion pair. If the spelling service identifies the same
// misspelling as already displayed to the user, then |FeedbackSender| reuses
// the same hash identifiers to avoid duplication. It detects the duplicates by
// comparing misspelling offsets in text. Spelling service can return duplicates
// because we request spellcheck for whole paragraphs, as context around a
// misspelled word is important to the spellcheck algorithm.
//
// All feedback is initially pending. When a user acts upon a misspelling such
// that the misspelling is no longer displayed (red squiggly line goes away),
// then the feedback for this misspelling is finalized. All finalized feedback
// is erased after being sent to the spelling service. Pending feedback is kept
// around for |kSessionHours| hours and then finalized even if user did not act
// on the misspellings.
//
// |FeedbackSender| periodically requests a list of hashes of all remaining
// misspellings in renderers. When a renderer responds with a list of hashes,
// |FeedbackSender| uses the list to determine which misspellings are no longer
// displayed to the user and sends the current state of user feedback to the
// spelling service.

#include "components/spellcheck/browser/feedback_sender.h"

#include <algorithm>
#include <iterator>
#include <utility>

#include "base/command_line.h"
#include "base/hash.h"
#include "base/json/json_writer.h"
#include "base/location.h"
#include "base/metrics/field_trial.h"
#include "base/single_thread_task_runner.h"
#include "base/stl_util.h"
#include "base/strings/string_number_conversions.h"
#include "base/strings/stringprintf.h"
#include "base/threading/thread_task_runner_handle.h"
#include "base/values.h"
#include "components/data_use_measurement/core/data_use_user_data.h"
#include "components/spellcheck/browser/word_trimmer.h"
#include "components/spellcheck/common/spellcheck_common.h"
#include "components/spellcheck/common/spellcheck_marker.h"
#include "components/spellcheck/common/spellcheck_messages.h"
#include "components/spellcheck/common/spellcheck_switches.h"
#include "content/public/browser/render_process_host.h"
#include "crypto/random.h"
#include "crypto/secure_hash.h"
#include "crypto/sha2.h"
#include "google_apis/google_api_keys.h"
#include "net/base/load_flags.h"
#include "net/url_request/url_fetcher.h"
#include "net/url_request/url_request_context_getter.h"

namespace spellcheck {

namespace {

const size_t kMaxFeedbackSizeBytes = 10 * 1024 * 1024;  // 10 MB

// The default URL where feedback data is sent.
const char kFeedbackServiceURL[] = "https://www.googleapis.com/rpc";

// The minimum number of seconds between sending batches of feedback.
const int kMinIntervalSeconds = 5;

// Returns a hash of |session_start|, the current timestamp, and
// |suggestion_index|.
uint32_t BuildHash(const base::Time& session_start, size_t suggestion_index) {
  return base::Hash(
      base::StringPrintf("%" PRId64 "%" PRId64 "%" PRIuS,
                         session_start.ToInternalValue(),
                         base::Time::Now().ToInternalValue(),
                         suggestion_index));
}

uint64_t BuildAnonymousHash(const FeedbackSender::RandSalt& r,
                            const base::string16& s) {
  std::unique_ptr<crypto::SecureHash> hash(
      crypto::SecureHash::Create(crypto::SecureHash::SHA256));

  hash->Update(s.data(), s.size() * sizeof(s[0]));
  hash->Update(&r, sizeof(r));

  uint64_t result;
  hash->Finish(&result, sizeof(result));
  return result;
}

// Returns a pending feedback data structure for the spellcheck |result| and
// |text|.
Misspelling BuildFeedback(const SpellCheckResult& result,
                          const base::string16& text) {
  size_t start = result.location;
  base::string16 context = TrimWords(&start, start + result.length, text,
                                     spellcheck::kContextWordCount);
  return Misspelling(context,
                     start,
                     result.length,
                     std::vector<base::string16>(1, result.replacement),
                     result.hash);
}

// Builds suggestion info from |suggestions|.
std::unique_ptr<base::ListValue> BuildSuggestionInfo(
    const std::vector<Misspelling>& misspellings,
    bool is_first_feedback_batch,
    const FeedbackSender::RandSalt& salt) {
  std::unique_ptr<base::ListValue> list(new base::ListValue);
  for (const auto& raw_misspelling : misspellings) {
    std::unique_ptr<base::DictionaryValue> misspelling(
        SerializeMisspelling(raw_misspelling));
    misspelling->SetBoolean("isFirstInSession", is_first_feedback_batch);
    misspelling->SetBoolean("isAutoCorrection", false);
    // hash(R) fields come from red_underline_extensions.proto
    // fixed64 user_misspelling_id = ...
    misspelling->SetString(
        "userMisspellingId",
        base::Uint64ToString(BuildAnonymousHash(
            salt, raw_misspelling.context.substr(raw_misspelling.location,
                                                 raw_misspelling.length))));
    // repeated fixed64 user_suggestion_id = ...
    std::unique_ptr<base::ListValue> suggestion_list(new base::ListValue());
    for (const auto& suggestion : raw_misspelling.suggestions) {
      suggestion_list->AppendString(
          base::Uint64ToString(BuildAnonymousHash(salt, suggestion)));
    }
    misspelling->Set("userSuggestionId", suggestion_list.release());
    list->Append(std::move(misspelling));
  }
  return list;
}

// Builds feedback parameters from |suggestion_info|, |language|, and |country|.
// Takes ownership of |suggestion_list|.
std::unique_ptr<base::DictionaryValue> BuildParams(
    std::unique_ptr<base::ListValue> suggestion_info,
    const std::string& language,
    const std::string& country) {
  std::unique_ptr<base::DictionaryValue> params(new base::DictionaryValue);
  params->Set("suggestionInfo", suggestion_info.release());
  params->SetString("key", google_apis::GetAPIKey());
  params->SetString("language", language);
  params->SetString("originCountry", country);
  params->SetString("clientName", "Chrome");
  return params;
}

// Builds feedback data from |params|. Takes ownership of |params|.
std::unique_ptr<base::Value> BuildFeedbackValue(
    std::unique_ptr<base::DictionaryValue> params,
    const std::string& api_version) {
  std::unique_ptr<base::DictionaryValue> result(new base::DictionaryValue);
  result->Set("params", params.release());
  result->SetString("method", "spelling.feedback");
  result->SetString("apiVersion", api_version);
  return std::move(result);
}

// Returns true if the misspelling location is within text bounds.
bool IsInBounds(int misspelling_location,
                int misspelling_length,
                size_t text_length) {
  return misspelling_location >= 0 && misspelling_length > 0 &&
         static_cast<size_t>(misspelling_location) < text_length &&
         static_cast<size_t>(misspelling_location + misspelling_length) <=
             text_length;
}

// Returns the feedback API version.
std::string GetApiVersion() {
  // This guard is temporary.
  // TODO(rouslan): Remove the guard. http://crbug.com/247726
  if (base::FieldTrialList::FindFullName(kFeedbackFieldTrialName) ==
          kFeedbackFieldTrialEnabledGroupName &&
      base::CommandLine::ForCurrentProcess()->HasSwitch(
          spellcheck::switches::kEnableSpellingFeedbackFieldTrial)) {
    return "v2-internal";
  }
  return "v2";
}

}  // namespace

FeedbackSender::FeedbackSender(net::URLRequestContextGetter* request_context,
                               const std::string& language,
                               const std::string& country)
    : request_context_(request_context),
      api_version_(GetApiVersion()),
      language_(language),
      country_(country),
      misspelling_counter_(0),
      feedback_(kMaxFeedbackSizeBytes),
      session_start_(base::Time::Now()),
      feedback_service_url_(kFeedbackServiceURL) {
  // The command-line switch is for testing and temporary.
  // TODO(rouslan): Remove the command-line switch when testing is complete.
  // http://crbug.com/247726
  if (base::CommandLine::ForCurrentProcess()->HasSwitch(
          spellcheck::switches::kSpellingServiceFeedbackUrl)) {
    feedback_service_url_ =
        GURL(base::CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
            spellcheck::switches::kSpellingServiceFeedbackUrl));
  }
}

FeedbackSender::~FeedbackSender() {
}

void FeedbackSender::SelectedSuggestion(uint32_t hash, int suggestion_index) {
  Misspelling* misspelling = feedback_.GetMisspelling(hash);
  // GetMisspelling() returns null for flushed feedback. Feedback is flushed
  // when the session expires every |kSessionHours| hours.
  if (!misspelling)
    return;
  misspelling->action.set_type(SpellcheckAction::TYPE_SELECT);
  misspelling->action.set_index(suggestion_index);
  misspelling->timestamp = base::Time::Now();
}

void FeedbackSender::AddedToDictionary(uint32_t hash) {
  Misspelling* misspelling = feedback_.GetMisspelling(hash);
  // GetMisspelling() returns null for flushed feedback. Feedback is flushed
  // when the session expires every |kSessionHours| hours.
  if (!misspelling)
    return;
  misspelling->action.set_type(SpellcheckAction::TYPE_ADD_TO_DICT);
  misspelling->timestamp = base::Time::Now();
  const std::set<uint32_t>& hashes =
      feedback_.FindMisspellings(GetMisspelledString(*misspelling));
  for (uint32_t hash : hashes) {
    Misspelling* duplicate_misspelling = feedback_.GetMisspelling(hash);
    if (!duplicate_misspelling || duplicate_misspelling->action.IsFinal())
      continue;
    duplicate_misspelling->action.set_type(SpellcheckAction::TYPE_ADD_TO_DICT);
    duplicate_misspelling->timestamp = misspelling->timestamp;
  }
}

void FeedbackSender::RecordInDictionary(uint32_t hash) {
  Misspelling* misspelling = feedback_.GetMisspelling(hash);
  // GetMisspelling() returns null for flushed feedback. Feedback is flushed
  // when the session expires every |kSessionHours| hours.
  if (!misspelling)
    return;
  misspelling->action.set_type(SpellcheckAction::TYPE_IN_DICTIONARY);
}

void FeedbackSender::IgnoredSuggestions(uint32_t hash) {
  Misspelling* misspelling = feedback_.GetMisspelling(hash);
  // GetMisspelling() returns null for flushed feedback. Feedback is flushed
  // when the session expires every |kSessionHours| hours.
  if (!misspelling)
    return;
  misspelling->action.set_type(SpellcheckAction::TYPE_PENDING_IGNORE);
  misspelling->timestamp = base::Time::Now();
}

void FeedbackSender::ManuallyCorrected(uint32_t hash,
                                       const base::string16& correction) {
  Misspelling* misspelling = feedback_.GetMisspelling(hash);
  // GetMisspelling() returns null for flushed feedback. Feedback is flushed
  // when the session expires every |kSessionHours| hours.
  if (!misspelling)
    return;
  misspelling->action.set_type(SpellcheckAction::TYPE_MANUALLY_CORRECTED);
  misspelling->action.set_value(correction);
  misspelling->timestamp = base::Time::Now();
}

void FeedbackSender::OnReceiveDocumentMarkers(
    int renderer_process_id,
    const std::vector<uint32_t>& markers) {
  if ((base::Time::Now() - session_start_).InHours() >=
      spellcheck::kSessionHours) {
    FlushFeedback();
    return;
  }

  if (!feedback_.RendererHasMisspellings(renderer_process_id))
    return;

  feedback_.FinalizeRemovedMisspellings(renderer_process_id, markers);
  SendFeedback(feedback_.GetMisspellingsInRenderer(renderer_process_id),
               !renderers_sent_feedback_.count(renderer_process_id));
  renderers_sent_feedback_.insert(renderer_process_id);
  feedback_.EraseFinalizedMisspellings(renderer_process_id);
}

void FeedbackSender::OnSpellcheckResults(
    int renderer_process_id,
    const base::string16& text,
    const std::vector<SpellCheckMarker>& markers,
    std::vector<SpellCheckResult>* results) {
  // Don't collect feedback if not going to send it.
  if (!timer_.IsRunning())
    return;

  // Generate a map of marker offsets to marker hashes. This map helps to
  // efficiently lookup feedback data based on the position of the misspelling
  // in text.
  typedef std::map<size_t, uint32_t> MarkerMap;
  MarkerMap marker_map;
  for (size_t i = 0; i < markers.size(); ++i)
    marker_map[markers[i].offset] = markers[i].hash;

  for (auto& result : *results) {
    if (!IsInBounds(result.location, result.length, text.length()))
      continue;
    MarkerMap::const_iterator marker_it = marker_map.find(result.location);
    if (marker_it != marker_map.end() &&
        feedback_.HasMisspelling(marker_it->second)) {
      // If the renderer already has a marker for this spellcheck result, then
      // set the hash of the spellcheck result to be the same as the marker.
      result.hash = marker_it->second;
    } else {
      // If the renderer does not yet have a marker for this spellcheck result,
      // then generate a new hash for the spellcheck result.
      result.hash = BuildHash(session_start_, ++misspelling_counter_);
    }
    // Save the feedback data for the spellcheck result.
    feedback_.AddMisspelling(renderer_process_id, BuildFeedback(result, text));
  }
}

void FeedbackSender::OnLanguageCountryChange(const std::string& language,
                                             const std::string& country) {
  FlushFeedback();
  language_ = language;
  country_ = country;
}

void FeedbackSender::StartFeedbackCollection() {
  if (timer_.IsRunning())
    return;

  int interval_seconds = spellcheck::kFeedbackIntervalSeconds;
  // This command-line switch is for testing and temporary.
  // TODO(rouslan): Remove the command-line switch when testing is complete.
  // http://crbug.com/247726
  if (base::CommandLine::ForCurrentProcess()->HasSwitch(
          spellcheck::switches::kSpellingServiceFeedbackIntervalSeconds)) {
    base::StringToInt(
        base::CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
            spellcheck::switches::kSpellingServiceFeedbackIntervalSeconds),
        &interval_seconds);
    if (interval_seconds < kMinIntervalSeconds)
      interval_seconds = kMinIntervalSeconds;
    static const int kSessionSeconds = spellcheck::kSessionHours * 60 * 60;
    if (interval_seconds >  kSessionSeconds)
      interval_seconds = kSessionSeconds;
  }
  timer_.Start(FROM_HERE,
               base::TimeDelta::FromSeconds(interval_seconds),
               this,
               &FeedbackSender::RequestDocumentMarkers);
}

void FeedbackSender::StopFeedbackCollection() {
  if (!timer_.IsRunning())
    return;

  FlushFeedback();
  timer_.Stop();
}

void FeedbackSender::RandBytes(void* p, size_t len) {
  crypto::RandBytes(p, len);
}

void FeedbackSender::OnURLFetchComplete(const net::URLFetcher* source) {
  for (ScopedVector<net::URLFetcher>::iterator sender_it = senders_.begin();
       sender_it != senders_.end();
       ++sender_it) {
    if (*sender_it == source) {
      senders_.erase(sender_it);
      return;
    }
  }
  delete source;
}

void FeedbackSender::RequestDocumentMarkers() {
  // Request document markers from all the renderers that are still alive.
  std::set<int> alive_renderers;
  for (content::RenderProcessHost::iterator it(
           content::RenderProcessHost::AllHostsIterator());
       !it.IsAtEnd();
       it.Advance()) {
    alive_renderers.insert(it.GetCurrentValue()->GetID());
    it.GetCurrentValue()->Send(new SpellCheckMsg_RequestDocumentMarkers());
  }

  // Asynchronously send out the feedback for all the renderers that are no
  // longer alive.
  std::vector<int> known_renderers = feedback_.GetRendersWithMisspellings();
  std::sort(known_renderers.begin(), known_renderers.end());
  std::vector<int> dead_renderers =
      base::STLSetDifference<std::vector<int>>(known_renderers,
                                               alive_renderers);
  for (int renderer_process_id : dead_renderers) {
    base::ThreadTaskRunnerHandle::Get()->PostTask(
        FROM_HERE,
        base::Bind(&FeedbackSender::OnReceiveDocumentMarkers, AsWeakPtr(),
                   renderer_process_id, std::vector<uint32_t>()));
  }
}

void FeedbackSender::FlushFeedback() {
  if (feedback_.Empty())
    return;
  feedback_.FinalizeAllMisspellings();
  SendFeedback(feedback_.GetAllMisspellings(),
               renderers_sent_feedback_.empty());
  feedback_.Clear();
  renderers_sent_feedback_.clear();
  session_start_ = base::Time::Now();
  timer_.Reset();
}

void FeedbackSender::SendFeedback(const std::vector<Misspelling>& feedback_data,
                                  bool is_first_feedback_batch) {
  if (base::Time::Now() - last_salt_update_ > base::TimeDelta::FromHours(24)) {
    RandBytes(&salt_, sizeof(salt_));
    last_salt_update_ = base::Time::Now();
  }
  std::unique_ptr<base::Value> feedback_value(BuildFeedbackValue(
      BuildParams(
          BuildSuggestionInfo(feedback_data, is_first_feedback_batch, salt_),
          language_, country_),
      api_version_));
  std::string feedback;
  base::JSONWriter::Write(*feedback_value, &feedback);

  // The tests use this identifier to mock the URL fetcher.
  static const int kUrlFetcherId = 0;
  net::URLFetcher* sender =
      net::URLFetcher::Create(kUrlFetcherId, feedback_service_url_,
                              net::URLFetcher::POST, this).release();
  data_use_measurement::DataUseUserData::AttachToFetcher(
      sender, data_use_measurement::DataUseUserData::SPELL_CHECKER);
  sender->SetLoadFlags(net::LOAD_DO_NOT_SEND_COOKIES |
                       net::LOAD_DO_NOT_SAVE_COOKIES);
  sender->SetUploadData("application/json", feedback);
  senders_.push_back(sender);

  // Request context is nullptr in testing.
  if (request_context_.get()) {
    sender->SetRequestContext(request_context_.get());
    sender->Start();
  }
}

}  // namespace spellcheck