// 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.

// DownloadHistory manages persisting DownloadItems to the history service by
// observing a single DownloadManager and all its DownloadItems using an
// AllDownloadItemNotifier.
//
// DownloadHistory decides whether and when to add items to, remove items from,
// and update items in the database. DownloadHistory uses DownloadHistoryData to
// store per-DownloadItem data such as whether the item is persisted or being
// persisted, and the last history::DownloadRow that was passed to the database.
// When the DownloadManager and its delegate (ChromeDownloadManagerDelegate) are
// initialized, DownloadHistory is created and queries the HistoryService. When
// the HistoryService calls back from QueryDownloads() to QueryCallback(),
// DownloadHistory will then wait for DownloadManager to call
// LoadHistoryDownloads(), and uses DownloadManager::CreateDownloadItem() to
// inform DownloadManager of these persisted DownloadItems. CreateDownloadItem()
// internally calls OnDownloadCreated(), which normally adds items to the
// database, so LoadHistoryDownloads() uses |loading_id_| to disable adding
// these items to the database.  If a download is removed via
// OnDownloadRemoved() while the item is still being added to the database,
// DownloadHistory uses |removed_while_adding_| to remember to remove the item
// when its ItemAdded() callback is called.  All callbacks are bound with a weak
// pointer to DownloadHistory to prevent use-after-free bugs.
// ChromeDownloadManagerDelegate owns DownloadHistory, and deletes it in
// Shutdown(), which is called by DownloadManagerImpl::Shutdown() after all
// DownloadItems are destroyed.

#include "chrome/browser/download/download_history.h"

#include <utility>

#include "base/bind.h"
#include "base/macros.h"
#include "base/memory/ptr_util.h"
#include "base/metrics/histogram_macros.h"
#include "base/task/post_task.h"
#include "build/build_config.h"
#include "chrome/browser/download/download_crx_util.h"
#include "components/download/public/common/download_features.h"
#include "components/download/public/common/download_item.h"
#include "components/download/public/common/download_utils.h"
#include "components/history/content/browser/download_conversions.h"
#include "components/history/core/browser/download_database.h"
#include "components/history/core/browser/download_row.h"
#include "components/history/core/browser/history_service.h"
#include "content/public/browser/browser_task_traits.h"
#include "content/public/browser/browser_thread.h"
#include "content/public/browser/download_manager.h"
#include "extensions/buildflags/buildflags.h"

#if BUILDFLAG(ENABLE_EXTENSIONS)
#include "chrome/browser/extensions/api/downloads/downloads_api.h"
#endif

namespace {

// Per-DownloadItem data. This information does not belong inside DownloadItem,
// and keeping maps in DownloadHistory from DownloadItem to this information is
// error-prone and complicated. Unfortunately, DownloadHistory::removing_*_ and
// removed_while_adding_ cannot be moved into this class partly because
// DownloadHistoryData is destroyed when DownloadItems are destroyed, and we
// have no control over when DownloadItems are destroyed.
class DownloadHistoryData : public base::SupportsUserData::Data {
 public:
  enum PersistenceState {
    NOT_PERSISTED,
    PERSISTING,
    PERSISTED,
  };

  static DownloadHistoryData* Get(download::DownloadItem* item) {
    base::SupportsUserData::Data* data = item->GetUserData(kKey);
    return static_cast<DownloadHistoryData*>(data);
  }

  static const DownloadHistoryData* Get(const download::DownloadItem* item) {
    const base::SupportsUserData::Data* data = item->GetUserData(kKey);
    return static_cast<const DownloadHistoryData*>(data);
  }

  explicit DownloadHistoryData(download::DownloadItem* item) {
    item->SetUserData(kKey, base::WrapUnique(this));
  }

  ~DownloadHistoryData() override {}

  PersistenceState state() const { return state_; }
  void SetState(PersistenceState s) { state_ = s; }

  // This allows DownloadHistory::OnDownloadUpdated() to see what changed in a
  // DownloadItem if anything, in order to prevent writing to the database
  // unnecessarily.  It is nullified when the item is no longer in progress in
  // order to save memory.
  history::DownloadRow* info() { return info_.get(); }
  void set_info(const history::DownloadRow& i) {
    // TODO(qinmin): avoid creating a new copy each time.
    info_.reset(new history::DownloadRow(i));
  }
  void clear_info() {
    info_.reset();
  }

 private:
  static const char kKey[];

  PersistenceState state_ = NOT_PERSISTED;
  std::unique_ptr<history::DownloadRow> info_;

  DISALLOW_COPY_AND_ASSIGN(DownloadHistoryData);
};

const char DownloadHistoryData::kKey[] =
  "DownloadItem DownloadHistoryData";

history::DownloadRow GetDownloadRow(download::DownloadItem* item) {
  std::string by_ext_id, by_ext_name;
#if BUILDFLAG(ENABLE_EXTENSIONS)
  extensions::DownloadedByExtension* by_ext =
      extensions::DownloadedByExtension::Get(item);
  if (by_ext) {
    by_ext_id = by_ext->id();
    by_ext_name = by_ext->name();
  }
#endif

  history::DownloadRow download;
  download.current_path = item->GetFullPath();
  download.target_path = item->GetTargetFilePath();
  download.url_chain = item->GetUrlChain();
  download.referrer_url = item->GetReferrerUrl();
  download.site_url = item->GetSiteUrl();
  download.tab_url = item->GetTabUrl();
  download.tab_referrer_url = item->GetTabReferrerUrl();
  download.http_method = std::string();  // HTTP method not available yet.
  download.mime_type = item->GetMimeType();
  download.original_mime_type = item->GetOriginalMimeType();
  download.start_time = item->GetStartTime();
  download.end_time = item->GetEndTime();
  download.etag = item->GetETag();
  download.last_modified = item->GetLastModifiedTime();
  download.received_bytes = item->GetReceivedBytes();
  download.total_bytes = item->GetTotalBytes();
  download.state = history::ToHistoryDownloadState(item->GetState());
  download.danger_type =
      history::ToHistoryDownloadDangerType(item->GetDangerType());
  download.interrupt_reason =
      history::ToHistoryDownloadInterruptReason(item->GetLastReason());
  download.hash = std::string();  // Hash value not available yet.
  download.id = history::ToHistoryDownloadId(item->GetId());
  download.guid = item->GetGuid();
  download.opened = item->GetOpened();
  download.last_access_time = item->GetLastAccessTime();
  download.transient = item->IsTransient();
  download.by_ext_id = by_ext_id;
  download.by_ext_name = by_ext_name;
  download.download_slice_info = history::GetHistoryDownloadSliceInfos(*item);
  return download;
}

enum class ShouldUpdateHistoryResult {
  NO_UPDATE,
  UPDATE,
  UPDATE_IMMEDIATELY,
};

ShouldUpdateHistoryResult ShouldUpdateHistory(
    const history::DownloadRow* previous,
    const history::DownloadRow& current) {
  // When download path is determined, Chrome should commit the history
  // immediately. Otherwise the file will be left permanently on the external
  // storage if Chrome crashes right away.
  // TODO(qinmin): this doesn't solve all the issues. When download starts,
  // Chrome will write the http response data to a temporary file, and later
  // rename it. If Chrome is killed before committing the history here,
  // that temporary file will still get permanently left.
  // See http://crbug.com/664677.
  if (previous == nullptr || previous->current_path != current.current_path)
    return ShouldUpdateHistoryResult::UPDATE_IMMEDIATELY;

  // Ignore url_chain, referrer, site_url, http_method, mime_type,
  // original_mime_type, start_time, id, and guid. These fields don't change.
  if ((previous->target_path != current.target_path) ||
      (previous->end_time != current.end_time) ||
      (previous->received_bytes != current.received_bytes) ||
      (previous->total_bytes != current.total_bytes) ||
      (previous->etag != current.etag) ||
      (previous->last_modified != current.last_modified) ||
      (previous->state != current.state) ||
      (previous->danger_type != current.danger_type) ||
      (previous->interrupt_reason != current.interrupt_reason) ||
      (previous->hash != current.hash) ||
      (previous->opened != current.opened) ||
      (previous->last_access_time != current.last_access_time) ||
      (previous->transient != current.transient) ||
      (previous->by_ext_id != current.by_ext_id) ||
      (previous->by_ext_name != current.by_ext_name) ||
      (previous->download_slice_info != current.download_slice_info)) {
    return ShouldUpdateHistoryResult::UPDATE;
  }

  return ShouldUpdateHistoryResult::NO_UPDATE;
}

typedef std::vector<history::DownloadRow> InfoVector;

}  // anonymous namespace

DownloadHistory::HistoryAdapter::HistoryAdapter(
    history::HistoryService* history)
    : history_(history) {
}
DownloadHistory::HistoryAdapter::~HistoryAdapter() {}

void DownloadHistory::HistoryAdapter::QueryDownloads(
    const history::HistoryService::DownloadQueryCallback& callback) {
  history_->QueryDownloads(callback);
}

void DownloadHistory::HistoryAdapter::CreateDownload(
    const history::DownloadRow& info,
    const history::HistoryService::DownloadCreateCallback& callback) {
  history_->CreateDownload(info, callback);
}

void DownloadHistory::HistoryAdapter::UpdateDownload(
    const history::DownloadRow& data, bool should_commit_immediately) {
  history_->UpdateDownload(data, should_commit_immediately);
}

void DownloadHistory::HistoryAdapter::RemoveDownloads(
    const std::set<uint32_t>& ids) {
  history_->RemoveDownloads(ids);
}

DownloadHistory::Observer::Observer() {}
DownloadHistory::Observer::~Observer() {}

// static
bool DownloadHistory::IsPersisted(const download::DownloadItem* item) {
  const DownloadHistoryData* data = DownloadHistoryData::Get(item);
  return data && (data->state() == DownloadHistoryData::PERSISTED);
}

DownloadHistory::DownloadHistory(content::DownloadManager* manager,
                                 std::unique_ptr<HistoryAdapter> history)
    : notifier_(manager, this),
      history_(std::move(history)),
      loading_id_(download::DownloadItem::kInvalidId),
      history_size_(0),
      initial_history_query_complete_(false),
      weak_ptr_factory_(this) {
  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
  content::DownloadManager::DownloadVector items;
  notifier_.GetManager()->GetAllDownloads(&items);
  for (content::DownloadManager::DownloadVector::const_iterator
       it = items.begin(); it != items.end(); ++it) {
    OnDownloadCreated(notifier_.GetManager(), *it);
  }
  history_->QueryDownloads(base::Bind(
      &DownloadHistory::QueryCallback, weak_ptr_factory_.GetWeakPtr()));
}

DownloadHistory::~DownloadHistory() {
  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
  for (Observer& observer : observers_)
    observer.OnDownloadHistoryDestroyed();
  observers_.Clear();
}

void DownloadHistory::AddObserver(DownloadHistory::Observer* observer) {
  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
  observers_.AddObserver(observer);

  if (initial_history_query_complete_)
    observer->OnHistoryQueryComplete();
}

void DownloadHistory::RemoveObserver(DownloadHistory::Observer* observer) {
  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
  observers_.RemoveObserver(observer);
}

void DownloadHistory::QueryCallback(std::unique_ptr<InfoVector> infos) {
  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
  // ManagerGoingDown() may have happened before the history loaded.
  if (!notifier_.GetManager())
    return;

  notifier_.GetManager()->OnHistoryQueryComplete(
      base::BindOnce(&DownloadHistory::LoadHistoryDownloads,
                     weak_ptr_factory_.GetWeakPtr(), std::move(infos)));
}

void DownloadHistory::LoadHistoryDownloads(std::unique_ptr<InfoVector> infos) {
  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
  DCHECK(notifier_.GetManager());

  for (InfoVector::const_iterator it = infos->begin();
       it != infos->end(); ++it) {
    loading_id_ = history::ToContentDownloadId(it->id);
    download::DownloadItem::DownloadState history_download_state =
        history::ToContentDownloadState(it->state);
    download::DownloadInterruptReason history_reason =
        history::ToContentDownloadInterruptReason(it->interrupt_reason);
    download::DownloadItem* item = notifier_.GetManager()->CreateDownloadItem(
        it->guid, loading_id_, it->current_path, it->target_path, it->url_chain,
        it->referrer_url, it->site_url, it->tab_url, it->tab_referrer_url,
        it->mime_type, it->original_mime_type, it->start_time, it->end_time,
        it->etag, it->last_modified, it->received_bytes, it->total_bytes,
        std::string(),  // TODO(asanka): Need to persist and restore hash of
                        // partial file for an interrupted download. No need to
                        // store hash for a completed file.
        history_download_state,
        history::ToContentDownloadDangerType(it->danger_type), history_reason,
        it->opened, it->last_access_time, it->transient,
        history::ToContentReceivedSlices(it->download_slice_info));
    // DownloadManager returns a nullptr if it decides to remove the download
    // permanently.
    if (item == nullptr) {
      ScheduleRemoveDownload(it->id);
      continue;
    }
    DCHECK_EQ(download::DownloadItem::kInvalidId, loading_id_);

    // The download might have been in the terminal state without informing
    // history DB. If this is the case, populate the new state back to history
    // DB.
    if (item->IsDone() &&
        !download::IsDownloadDone(item->GetURL(), history_download_state,
                                  history_reason)) {
      OnDownloadUpdated(notifier_.GetManager(), item);
    }
#if BUILDFLAG(ENABLE_EXTENSIONS)
    if (!it->by_ext_id.empty() && !it->by_ext_name.empty()) {
      new extensions::DownloadedByExtension(
          item, it->by_ext_id, it->by_ext_name);
      item->UpdateObservers();
    }
#endif
    DCHECK_EQ(DownloadHistoryData::PERSISTED,
              DownloadHistoryData::Get(item)->state());
    ++history_size_;
  }

  // Indicate that the history db is initialized.
  notifier_.GetManager()->PostInitialization(
      content::DownloadManager::DOWNLOAD_INITIALIZATION_DEPENDENCY_HISTORY_DB);

  initial_history_query_complete_ = true;
  for (Observer& observer : observers_)
    observer.OnHistoryQueryComplete();
}

void DownloadHistory::MaybeAddToHistory(download::DownloadItem* item) {
  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);

  if (!NeedToUpdateDownloadHistory(item))
    return;

  uint32_t download_id = item->GetId();
  DownloadHistoryData* data = DownloadHistoryData::Get(item);
  bool removing = removing_ids_.find(download_id) != removing_ids_.end();

  // TODO(benjhayden): Remove IsTemporary().
  if (download_crx_util::IsExtensionDownload(*item) ||
      item->IsTemporary() ||
      (data->state() != DownloadHistoryData::NOT_PERSISTED) ||
      removing)
    return;

  data->SetState(DownloadHistoryData::PERSISTING);
  // Keep the info for in-progress download, so we can check whether history DB
  // update is needed when DownloadUpdated() is called.
  history::DownloadRow download_row = GetDownloadRow(item);
  if (item->GetState() == download::DownloadItem::IN_PROGRESS)
    data->set_info(download_row);
  history_->CreateDownload(
      download_row,
      base::BindRepeating(&DownloadHistory::ItemAdded,
                          weak_ptr_factory_.GetWeakPtr(), download_id));
}

void DownloadHistory::ItemAdded(uint32_t download_id, bool success) {
  if (removed_while_adding_.find(download_id) !=
      removed_while_adding_.end()) {
    removed_while_adding_.erase(download_id);
    if (success)
      ScheduleRemoveDownload(download_id);
    return;
  }

  if (!notifier_.GetManager())
    return;

  download::DownloadItem* item =
      notifier_.GetManager()->GetDownload(download_id);
  if (!item) {
    // This item will have called OnDownloadDestroyed().  If the item should
    // have been removed from history, then it would have also called
    // OnDownloadRemoved(), which would have put |download_id| in
    // removed_while_adding_, handled above.
    return;
  }

  DownloadHistoryData* data = DownloadHistoryData::Get(item);
  bool was_persisted = IsPersisted(item);

  // The sql INSERT statement failed. Avoid an infinite loop: don't
  // automatically retry. Retry adding the next time the item is updated by
  // resetting the state to NOT_PERSISTED.
  if (!success) {
    DVLOG(20) << __func__ << " INSERT failed id=" << download_id;
    data->SetState(DownloadHistoryData::NOT_PERSISTED);
    return;
  }
  data->SetState(DownloadHistoryData::PERSISTED);

  UMA_HISTOGRAM_CUSTOM_COUNTS("Download.HistorySize2",
                              history_size_,
                              1/*min*/,
                              (1 << 23)/*max*/,
                              (1 << 7)/*num_buckets*/);
  ++history_size_;

  // Notify the observer about the change in the persistence state.
  if (was_persisted != IsPersisted(item)) {
    for (Observer& observer : observers_)
      observer.OnDownloadStored(item, *data->info());
  }
}

void DownloadHistory::OnDownloadCreated(content::DownloadManager* manager,
                                        download::DownloadItem* item) {
  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);

  // All downloads should pass through OnDownloadCreated exactly once.
  CHECK(!DownloadHistoryData::Get(item));
  DownloadHistoryData* data = new DownloadHistoryData(item);
  if (item->GetId() == loading_id_)
    OnDownloadRestoredFromHistory(item);
  if (item->GetState() == download::DownloadItem::IN_PROGRESS)
    data->set_info(GetDownloadRow(item));
  MaybeAddToHistory(item);
}

void DownloadHistory::OnDownloadUpdated(content::DownloadManager* manager,
                                        download::DownloadItem* item) {
  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
  DownloadHistoryData* data = DownloadHistoryData::Get(item);
  if (data->state() == DownloadHistoryData::NOT_PERSISTED) {
    MaybeAddToHistory(item);
    return;
  }
  if (item->IsTemporary()) {
    OnDownloadRemoved(notifier_.GetManager(), item);
    return;
  }
  if (!NeedToUpdateDownloadHistory(item))
    return;

  history::DownloadRow current_info(GetDownloadRow(item));
  ShouldUpdateHistoryResult should_update_result =
      ShouldUpdateHistory(data->info(), current_info);
  bool should_update =
      (should_update_result != ShouldUpdateHistoryResult::NO_UPDATE);
  UMA_HISTOGRAM_ENUMERATION("Download.HistoryPropagatedUpdate",
                            should_update, 2);
  if (should_update) {
    history_->UpdateDownload(
        current_info,
        should_update_result == ShouldUpdateHistoryResult::UPDATE_IMMEDIATELY);
    for (Observer& observer : observers_)
      observer.OnDownloadStored(item, current_info);
  }
  if (item->GetState() == download::DownloadItem::IN_PROGRESS) {
    data->set_info(current_info);
  } else {
    data->clear_info();
  }
}

void DownloadHistory::OnDownloadOpened(content::DownloadManager* manager,
                                       download::DownloadItem* item) {
  OnDownloadUpdated(manager, item);
}

void DownloadHistory::OnDownloadRemoved(content::DownloadManager* manager,
                                        download::DownloadItem* item) {
  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);

  DownloadHistoryData* data = DownloadHistoryData::Get(item);
  if (data->state() != DownloadHistoryData::PERSISTED) {
    if (data->state() == DownloadHistoryData::PERSISTING) {
      // ScheduleRemoveDownload will be called when history_ calls ItemAdded().
      removed_while_adding_.insert(item->GetId());
    }
    return;
  }
  ScheduleRemoveDownload(item->GetId());
  // This is important: another OnDownloadRemoved() handler could do something
  // that synchronously fires an OnDownloadUpdated().
  data->SetState(DownloadHistoryData::NOT_PERSISTED);
  // ItemAdded increments history_size_ only if the item wasn't
  // removed_while_adding_, so the next line does not belong in
  // ScheduleRemoveDownload().
  --history_size_;
}

void DownloadHistory::ScheduleRemoveDownload(uint32_t download_id) {
  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);

  // For database efficiency, batch removals together if they happen all at
  // once.
  if (removing_ids_.empty()) {
    base::PostTaskWithTraits(
        FROM_HERE, {content::BrowserThread::UI},
        base::BindOnce(&DownloadHistory::RemoveDownloadsBatch,
                       weak_ptr_factory_.GetWeakPtr()));
  }
  removing_ids_.insert(download_id);
}

void DownloadHistory::RemoveDownloadsBatch() {
  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
  IdSet remove_ids;
  removing_ids_.swap(remove_ids);
  history_->RemoveDownloads(remove_ids);
  for (Observer& observer : observers_)
    observer.OnDownloadsRemoved(remove_ids);
}

void DownloadHistory::OnDownloadRestoredFromHistory(
    download::DownloadItem* item) {
  DownloadHistoryData* data = DownloadHistoryData::Get(item);
  data->SetState(DownloadHistoryData::PERSISTED);
  loading_id_ = download::DownloadItem::kInvalidId;
}

bool DownloadHistory::NeedToUpdateDownloadHistory(
    download::DownloadItem* item) {
#if BUILDFLAG(ENABLE_EXTENSIONS)
  // Always populate new extension downloads to history.
  DownloadHistoryData* data = DownloadHistoryData::Get(item);
  extensions::DownloadedByExtension* by_ext =
      extensions::DownloadedByExtension::Get(item);
  if (by_ext && !by_ext->id().empty() && !by_ext->name().empty() &&
      data->state() != DownloadHistoryData::NOT_PERSISTED) {
    return true;
  }
#endif

  // When download DB is enabled, only downloads that are in terminal state
  // are added to or updated in history DB. In-progress and interrupted download
  // will be stored in the in-progress DB.
  return !base::FeatureList::IsEnabled(
             download::features::kDownloadDBForNewDownloads) ||
         item->IsSavePackageDownload() || item->IsDone();
}