// 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 "components/sync_sessions/synced_session_tracker.h"

#include <utility>

#include "base/logging.h"
#include "base/memory/ptr_util.h"
#include "base/strings/utf_string_conversions.h"
#include "components/sync_sessions/sync_sessions_client.h"

namespace sync_sessions {

namespace {

// Helper for iterating through all tabs within a window, and all navigations
// within a tab, to find if there's a valid syncable url.
bool ShouldSyncSessionWindow(SyncSessionsClient* sessions_client,
                             const sessions::SessionWindow& window) {
  for (const auto& tab : window.tabs) {
    for (const sessions::SerializedNavigationEntry& navigation :
         tab->navigations) {
      if (sessions_client->ShouldSyncURL(navigation.virtual_url())) {
        return true;
      }
    }
  }
  return false;
}

// Presentable means |foreign_session| must have syncable content.
bool IsPresentable(SyncSessionsClient* sessions_client,
                   SyncedSession* foreign_session) {
  for (auto iter = foreign_session->windows.begin();
       iter != foreign_session->windows.end(); ++iter) {
    if (ShouldSyncSessionWindow(sessions_client, *(iter->second))) {
      return true;
    }
  }
  return false;
}

}  // namespace

SyncedSessionTracker::SyncedSessionTracker(SyncSessionsClient* sessions_client)
    : sessions_client_(sessions_client) {}

SyncedSessionTracker::~SyncedSessionTracker() {
  Clear();
}

void SyncedSessionTracker::SetLocalSessionTag(
    const std::string& local_session_tag) {
  local_session_tag_ = local_session_tag;
}

bool SyncedSessionTracker::LookupAllForeignSessions(
    std::vector<const SyncedSession*>* sessions,
    SessionLookup lookup) const {
  DCHECK(sessions);
  sessions->clear();
  for (const auto& session_pair : synced_session_map_) {
    SyncedSession* foreign_session = session_pair.second.get();
    if (session_pair.first != local_session_tag_ &&
        (lookup == RAW || IsPresentable(sessions_client_, foreign_session))) {
      sessions->push_back(foreign_session);
    }
  }
  return !sessions->empty();
}

bool SyncedSessionTracker::LookupSessionWindows(
    const std::string& session_tag,
    std::vector<const sessions::SessionWindow*>* windows) const {
  DCHECK(windows);
  windows->clear();

  auto iter = synced_session_map_.find(session_tag);
  if (iter == synced_session_map_.end())
    return false;
  for (const auto& window_pair : iter->second->windows)
    windows->push_back(window_pair.second.get());

  return true;
}

bool SyncedSessionTracker::LookupSessionTab(
    const std::string& tag,
    SessionID::id_type tab_id,
    const sessions::SessionTab** tab) const {
  DCHECK(tab);
  auto tab_map_iter = synced_tab_map_.find(tag);
  if (tab_map_iter == synced_tab_map_.end()) {
    // We have no record of this session.
    *tab = nullptr;
    return false;
  }
  auto tab_iter = tab_map_iter->second.find(tab_id);
  if (tab_iter == tab_map_iter->second.end()) {
    // We have no record of this tab.
    *tab = nullptr;
    return false;
  }
  *tab = tab_iter->second;
  return true;
}

void SyncedSessionTracker::LookupTabNodeIds(const std::string& session_tag,
                                            std::set<int>* tab_node_ids) {
  tab_node_ids->clear();
  auto session_iter = synced_session_map_.find(session_tag);
  if (session_iter != synced_session_map_.end()) {
    tab_node_ids->insert(session_iter->second->tab_node_ids.begin(),
                         session_iter->second->tab_node_ids.end());
  }
  // In case an invalid node id was included, remove it.
  tab_node_ids->erase(TabNodePool::kInvalidTabNodeID);
}

bool SyncedSessionTracker::LookupLocalSession(
    const SyncedSession** output) const {
  auto it = synced_session_map_.find(local_session_tag_);
  if (it != synced_session_map_.end()) {
    *output = it->second.get();
    return true;
  }
  return false;
}

SyncedSession* SyncedSessionTracker::GetSession(
    const std::string& session_tag) {
  if (synced_session_map_.find(session_tag) != synced_session_map_.end())
    return synced_session_map_[session_tag].get();

  std::unique_ptr<SyncedSession> synced_session =
      base::MakeUnique<SyncedSession>();
  DVLOG(1) << "Creating new session with tag " << session_tag << " at "
           << synced_session.get();
  synced_session->session_tag = session_tag;
  synced_session_map_[session_tag] = std::move(synced_session);

  return synced_session_map_[session_tag].get();
}

bool SyncedSessionTracker::DeleteSession(const std::string& session_tag) {
  unmapped_windows_.erase(session_tag);
  unmapped_tabs_.erase(session_tag);

  bool header_existed = false;
  auto iter = synced_session_map_.find(session_tag);
  if (iter != synced_session_map_.end()) {
    // An implicitly created session that has children tabs but no header node
    // will have never had the device_type changed from unset.
    header_existed = iter->second->device_type != SyncedSession::TYPE_UNSET;
    // SyncedSession's destructor will trigger deletion of windows which will in
    // turn trigger the deletion of tabs. This doesn't affect the convenience
    // maps.
    synced_session_map_.erase(iter);
  }

  // These two erase(...) calls only affect the convenience maps.
  synced_window_map_.erase(session_tag);
  synced_tab_map_.erase(session_tag);

  return header_existed;
}

void SyncedSessionTracker::ResetSessionTracking(
    const std::string& session_tag) {
  SyncedSession* session = GetSession(session_tag);

  for (auto& window_pair : session->windows) {
    // First unmap the tabs in the window.
    for (auto& tab : window_pair.second->tabs) {
      SessionID::id_type tab_id = tab->tab_id.id();
      unmapped_tabs_[session_tag][tab_id] = std::move(tab);
    }
    window_pair.second->tabs.clear();

    // Then unmap the window itself.
    unmapped_windows_[session_tag][window_pair.first] =
        std::move(window_pair.second);
  }
  session->windows.clear();
}

void SyncedSessionTracker::DeleteForeignTab(const std::string& session_tag,
                                            int tab_node_id) {
  auto session_iter = synced_session_map_.find(session_tag);
  if (session_iter != synced_session_map_.end()) {
    session_iter->second->tab_node_ids.erase(tab_node_id);
  }
}

void SyncedSessionTracker::CleanupSession(const std::string& session_tag) {
  for (const auto& window_pair : unmapped_windows_[session_tag])
    synced_window_map_[session_tag].erase(window_pair.first);
  unmapped_windows_[session_tag].clear();

  for (const auto& tab_pair : unmapped_tabs_[session_tag])
    synced_tab_map_[session_tag].erase(tab_pair.first);
  unmapped_tabs_[session_tag].clear();
}

void SyncedSessionTracker::PutWindowInSession(const std::string& session_tag,
                                              SessionID::id_type window_id) {
  std::unique_ptr<sessions::SessionWindow> window;

  auto iter = unmapped_windows_[session_tag].find(window_id);
  if (iter != unmapped_windows_[session_tag].end()) {
    DCHECK_EQ(synced_window_map_[session_tag][window_id], iter->second.get());
    window = std::move(iter->second);
    unmapped_windows_[session_tag].erase(iter);
    DVLOG(1) << "Putting seen window " << window_id << " at " << window.get()
             << "in " << (session_tag == local_session_tag_ ? "local session"
                                                            : session_tag);
  } else {
    // Create the window.
    window = base::MakeUnique<sessions::SessionWindow>();
    window->window_id.set_id(window_id);
    synced_window_map_[session_tag][window_id] = window.get();
    DVLOG(1) << "Putting new window " << window_id << " at " << window.get()
             << "in " << (session_tag == local_session_tag_ ? "local session"
                                                            : session_tag);
  }
  DCHECK_EQ(window->window_id.id(), window_id);
  DCHECK(GetSession(session_tag)->windows.end() ==
         GetSession(session_tag)->windows.find(window_id));
  GetSession(session_tag)->windows[window_id] = std::move(window);
}

void SyncedSessionTracker::PutTabInWindow(const std::string& session_tag,
                                          SessionID::id_type window_id,
                                          SessionID::id_type tab_id,
                                          size_t tab_index) {
  // We're called here for two reasons. 1) We've received an update to the
  // SessionWindow information of a SessionHeader node for a foreign session,
  // and 2) The SessionHeader node for our local session changed. In both cases
  // we need to update our tracking state to reflect the change.
  //
  // Because the SessionHeader nodes are separate from the individual tab nodes
  // and we don't store tab_node_ids in the header / SessionWindow specifics,
  // the tab_node_ids are not always available when processing headers.
  // We know that we will eventually process (via GetTab) every single tab node
  // in the system, so we permit ourselves to use kInvalidTabNodeID here and
  // rely on the later update to build the mapping (or a restart).
  GetTabImpl(session_tag, tab_id, TabNodePool::kInvalidTabNodeID);

  // The tab should be unmapped.
  std::unique_ptr<sessions::SessionTab> tab;
  auto it = unmapped_tabs_[session_tag].find(tab_id);
  if (it != unmapped_tabs_[session_tag].end()) {
    tab = std::move(it->second);
    unmapped_tabs_[session_tag].erase(it);
  }
  DCHECK(tab);

  tab->window_id.set_id(window_id);
  DVLOG(1) << "  - tab " << tab_id << " added to window " << window_id;
  DCHECK(GetSession(session_tag)->windows.find(window_id) !=
         GetSession(session_tag)->windows.end());
  auto& window_tabs = GetSession(session_tag)->windows[window_id]->tabs;
  if (window_tabs.size() <= tab_index) {
    window_tabs.resize(tab_index + 1);
  }
  DCHECK(!window_tabs[tab_index]);
  window_tabs[tab_index] = std::move(tab);
}

sessions::SessionTab* SyncedSessionTracker::GetTab(
    const std::string& session_tag,
    SessionID::id_type tab_id,
    int tab_node_id) {
  DCHECK_NE(TabNodePool::kInvalidTabNodeID, tab_node_id);
  return GetTabImpl(session_tag, tab_id, tab_node_id);
}

sessions::SessionTab* SyncedSessionTracker::GetTabImpl(
    const std::string& session_tag,
    SessionID::id_type tab_id,
    int tab_node_id) {
  sessions::SessionTab* tab_ptr = nullptr;
  auto iter = synced_tab_map_[session_tag].find(tab_id);
  if (iter != synced_tab_map_[session_tag].end()) {
    tab_ptr = iter->second;
    if (tab_node_id != TabNodePool::kInvalidTabNodeID &&
        tab_id != TabNodePool::kInvalidTabID) {
      // TabIDs are not stable across restarts of a client. Consider this
      // example with two tabs:
      //
      // http://a.com  TabID1 --> NodeIDA
      // http://b.com  TabID2 --> NodeIDB
      //
      // After restart, tab ids are reallocated. e.g, one possibility:
      // http://a.com TabID2 --> NodeIDA
      // http://b.com TabID1 --> NodeIDB
      //
      // If that happend on a remote client, here we will see an update to
      // TabID1 with tab_node_id changing from NodeIDA to NodeIDB, and TabID2
      // with tab_node_id changing from NodeIDB to NodeIDA.
      //
      // We can also wind up here if we created this tab as an out-of-order
      // update to the header node for this session before actually associating
      // the tab itself, so the tab node id wasn't available at the time and
      // is currently kInvalidTabNodeID.
      //
      // In both cases, we can safely throw it into the set of node ids.
      GetSession(session_tag)->tab_node_ids.insert(tab_node_id);
    }

    if (VLOG_IS_ON(1)) {
      std::string title;
      if (tab_ptr->navigations.size() > 0) {
        title =
            " (" + base::UTF16ToUTF8(tab_ptr->navigations.back().title()) + ")";
      }
      DVLOG(1) << "Getting "
               << (session_tag == local_session_tag_ ? "local session"
                                                     : session_tag)
               << "'s seen tab " << tab_id << " at " << tab_ptr << " " << title;
    }
  } else {
    std::unique_ptr<sessions::SessionTab> tab =
        base::MakeUnique<sessions::SessionTab>();
    tab_ptr = tab.get();
    tab->tab_id.set_id(tab_id);
    synced_tab_map_[session_tag][tab_id] = tab_ptr;
    unmapped_tabs_[session_tag][tab_id] = std::move(tab);
    GetSession(session_tag)->tab_node_ids.insert(tab_node_id);
    DVLOG(1) << "Getting "
             << (session_tag == local_session_tag_ ? "local session"
                                                   : session_tag)
             << "'s new tab " << tab_id << " at " << tab_ptr;
  }
  DCHECK(tab_ptr);
  DCHECK_EQ(tab_ptr->tab_id.id(), tab_id);
  return tab_ptr;
}

void SyncedSessionTracker::Clear() {
  // Cleanup unmapped tabs and windows.
  unmapped_windows_.clear();
  unmapped_tabs_.clear();

  // Delete SyncedSession objects (which also deletes all their windows/tabs).
  synced_session_map_.clear();

  // Get rid of our convenience maps (does not delete the actual Window/Tabs
  // themselves; they should have all been deleted above).
  synced_window_map_.clear();
  synced_tab_map_.clear();

  local_session_tag_.clear();
}

}  // namespace sync_sessions