gecko/toolkit/components/places/src/History.cpp

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 * vim: sw=2 ts=2 et lcs=trail\:.,tab\:>~ :
 * ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is Places code.
 *
 * The Initial Developer of the Original Code is
 * the Mozilla Foundation.
 * Portions created by the Initial Developer are Copyright (C) 2009
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *   Shawn Wilsher <me@shawnwilsher.com> (Original Author)
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either the GNU General Public License Version 2 or later (the "GPL"), or
 * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
 * of those above. If you wish to allow use of your version of this file only
 * under the terms of either the GPL or the LGPL, and not to allow others to
 * use your version of this file under the terms of the MPL, indicate your
 * decision by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL or the LGPL. If you do not delete
 * the provisions above, a recipient may use your version of this file under
 * the terms of any one of the MPL, the GPL or the LGPL.
 *
 * ***** END LICENSE BLOCK ***** */

#ifdef MOZ_IPC
#include "mozilla/dom/ContentChild.h"
#include "mozilla/dom/ContentParent.h"
#include "nsXULAppAPI.h"
#endif

#include "History.h"
#include "nsNavHistory.h"
#include "nsNavBookmarks.h"
#include "Helpers.h"

#include "mozilla/storage.h"
#include "mozilla/dom/Link.h"
#include "nsDocShellCID.h"
#include "nsIEventStateManager.h"
#include "mozilla/Services.h"
#include "nsThreadUtils.h"
#include "nsNetUtil.h"

// Initial size for the cache holding visited status observers.
#define VISIT_OBSERVERS_INITIAL_CACHE_SIZE 128

using namespace mozilla::dom;

namespace mozilla {
namespace places {

////////////////////////////////////////////////////////////////////////////////
//// Global Defines

#define URI_VISITED "visited"
#define URI_NOT_VISITED "not visited"
#define URI_VISITED_RESOLUTION_TOPIC "visited-status-resolution"
// Observer event fired after a visit has been registered in the DB.
#define URI_VISIT_SAVED "uri-visit-saved"

////////////////////////////////////////////////////////////////////////////////
//// Anonymous Helpers

namespace {

class VisitedQuery : public AsyncStatementCallback
{
public:
  static nsresult Start(nsIURI* aURI)
  {
    NS_PRECONDITION(aURI, "Null URI");

#ifdef MOZ_IPC
  // If we are a content process, always remote the request to the
  // parent process.
  if (XRE_GetProcessType() == GeckoProcessType_Content) {
    mozilla::dom::ContentChild* cpc =
      mozilla::dom::ContentChild::GetSingleton();
    NS_ASSERTION(cpc, "Content Protocol is NULL!");
    (void)cpc->SendStartVisitedQuery(aURI);
    return NS_OK;
  }
#endif

    nsNavHistory* navHistory = nsNavHistory::GetHistoryService();
    NS_ENSURE_STATE(navHistory);
    if (navHistory->hasEmbedVisit(aURI)) {
      nsRefPtr<VisitedQuery> callback = new VisitedQuery(aURI, true);
      NS_ENSURE_TRUE(callback, NS_ERROR_OUT_OF_MEMORY);
      // As per IHistory contract, we must notify asynchronously.
      nsCOMPtr<nsIRunnable> event =
        NS_NewRunnableMethod(callback, &VisitedQuery::NotifyVisitedStatus);
      NS_DispatchToMainThread(event);

      return NS_OK;
    }

    mozIStorageAsyncStatement* stmt =
      History::GetService()->GetIsVisitedStatement();
    NS_ENSURE_STATE(stmt);

    // Bind by index for performance.
    nsresult rv = URIBinder::Bind(stmt, 0, aURI);
    NS_ENSURE_SUCCESS(rv, rv);

    nsRefPtr<VisitedQuery> callback = new VisitedQuery(aURI);
    NS_ENSURE_TRUE(callback, NS_ERROR_OUT_OF_MEMORY);

    nsCOMPtr<mozIStoragePendingStatement> handle;
    return stmt->ExecuteAsync(callback, getter_AddRefs(handle));
  }

  NS_IMETHOD HandleResult(mozIStorageResultSet* aResults)
  {
    // If this method is called, we've gotten results, which means we have a
    // visit.
    mIsVisited = true;
    return NS_OK;
  }

  NS_IMETHOD HandleError(mozIStorageError* aError)
  {
    // mIsVisited is already set to false, and that's the assumption we will
    // make if an error occurred.
    return NS_OK;
  }

  NS_IMETHOD HandleCompletion(PRUint16 aReason)
  {
    if (aReason != mozIStorageStatementCallback::REASON_FINISHED) {
      return NS_OK;
    }

    nsresult rv = NotifyVisitedStatus();
    NS_ENSURE_SUCCESS(rv, rv);
    return NS_OK;
  }

  nsresult NotifyVisitedStatus()
  {
    if (mIsVisited) {
      History::GetService()->NotifyVisited(mURI);
    }

    nsCOMPtr<nsIObserverService> observerService =
      mozilla::services::GetObserverService();
    if (observerService) {
      nsAutoString status;
      if (mIsVisited) {
        status.AssignLiteral(URI_VISITED);
      }
      else {
        status.AssignLiteral(URI_NOT_VISITED);
      }
      (void)observerService->NotifyObservers(mURI,
                                             URI_VISITED_RESOLUTION_TOPIC,
                                             status.get());
    }

    return NS_OK;
  }

private:
  VisitedQuery(nsIURI* aURI, bool aIsVisited=false)
  : mURI(aURI)
  , mIsVisited(aIsVisited)
  {
  }

  nsCOMPtr<nsIURI> mURI;
  bool mIsVisited;
};

struct VisitData {
  VisitData()
  : placeId(0)
  , visitId(0)
  , sessionId(0)
  , hidden(false)
  , typed(false)
  , transitionType(-1)
  , visitTime(0)
  {
  }

  PRInt64 placeId;
  PRInt64 visitId;
  PRInt64 sessionId;
  nsCString spec;
  nsString revHost;
  bool hidden;
  bool typed;
  PRInt32 transitionType;
  PRTime visitTime;
};


/**
 * Notifies observers about a visit.
 */
class NotifyVisitObservers : public nsRunnable
{
public:
  NotifyVisitObservers(VisitData& aPlace,
                       VisitData& aReferrer)
  : mPlace(aPlace)
  , mReferrer(aReferrer)
  {
  }

  NS_IMETHOD Run()
  {
    NS_PRECONDITION(NS_IsMainThread(),
                    "This should be called on the main thread");

    nsNavHistory* navHistory = nsNavHistory::GetHistoryService();
    if (!navHistory) {
      NS_WARNING("Trying to notify about a visit but cannot get the history service!");
      return NS_OK;
    }

    nsCOMPtr<nsIURI> uri;
    (void)NS_NewURI(getter_AddRefs(uri), mPlace.spec);

    // Notify nsNavHistory observers of visit, but only for certain types of
    // visits to maintain consistency with nsNavHistory::GetQueryResults.
    if (!mPlace.hidden &&
        mPlace.transitionType != nsINavHistoryService::TRANSITION_EMBED &&
        mPlace.transitionType != nsINavHistoryService::TRANSITION_FRAMED_LINK) {
      navHistory->NotifyOnVisit(uri, mPlace.visitId, mPlace.visitTime,
                                mPlace.sessionId, mReferrer.visitId,
                                mPlace.transitionType);
    }

    nsCOMPtr<nsIObserverService> obsService =
      mozilla::services::GetObserverService();
    if (obsService) {
      nsresult rv = obsService->NotifyObservers(uri, URI_VISIT_SAVED, nsnull);
      NS_WARN_IF_FALSE(NS_SUCCEEDED(rv), "Could not notify observers");
    }

    History::GetService()->NotifyVisited(uri);

    return NS_OK;
  }
private:
  VisitData mPlace;
  VisitData mReferrer;
};

/**
 * Adds a visit to the database.
 */
class InsertVisitedURI : public nsRunnable
{
public:
  /**
   * Adds a visit to the database asynchronously.
   *
   * @param aConnection
   *        The database connection to use for these operations.
   * @param aPlace
   *        The location to record a visit.
   * @param [optional] aReferrer
   *        The page that "referred" us to aPlace.
   */
  static nsresult Start(mozIStorageConnection* aConnection,
                        VisitData& aPlace,
                        nsIURI* aReferrer = nsnull)
  {
    NS_PRECONDITION(NS_IsMainThread(),
                    "This should be called on the main thread");

    nsRefPtr<InsertVisitedURI> event =
      new InsertVisitedURI(aConnection, aPlace, aReferrer);

    // Speculatively get a new session id for our visit.  While it is true that
    // we will use the session id from the referrer if the visit was "recent"
    // enough, we cannot call this method off of the main thread, so we have to
    // consume an id now.
    nsNavHistory* navHistory = nsNavHistory::GetHistoryService();
    NS_ENSURE_TRUE(navHistory, NS_ERROR_UNEXPECTED);
    event->mPlace.sessionId = navHistory->GetNewSessionID();

    // Get the target thread, and then start the work!
    nsCOMPtr<nsIEventTarget> target = do_GetInterface(aConnection);
    NS_ENSURE_TRUE(target, NS_ERROR_UNEXPECTED);
    nsresult rv = target->Dispatch(event, NS_DISPATCH_NORMAL);
    NS_ENSURE_SUCCESS(rv, rv);

    return NS_OK;
  }

  NS_IMETHOD Run()
  {
    NS_PRECONDITION(!NS_IsMainThread(),
                    "This should not be called on the main thread");

    bool known = FetchPageInfo(mPlace);

    // If we had a referrer, we want to know about its last visit to put this
    // new visit into the same session.
    if (!mReferrer.spec.IsEmpty()) {
      bool recentVisit = FetchVisitInfo(mReferrer, mPlace.visitTime);
      // At this point, we know the referrer's session id, which this new visit
      // should also share.
      if (recentVisit) {
        mPlace.sessionId = mReferrer.sessionId;
      }
      // However, if it isn't recent enough, we don't care to log anything about
      // the referrer and we'll start a new session.
      else {
        // This is sufficient to ignore our referrer.  This behavior has test
        // coverage, so if this invariant changes, we'll know.
        mReferrer.visitId = 0;
      }
    }

    mozStorageTransaction transaction(mDBConn, PR_FALSE,
                                      mozIStorageConnection::TRANSACTION_IMMEDIATE);
    nsresult rv;
    nsCOMPtr<mozIStorageStatement> stmt;
    // If the page was in moz_places, we need to update the entry.
    if (known) {
      NS_ASSERTION(mPlace.placeId > 0, "must have a valid place id!");

      stmt = mHistory->syncStatements.GetCachedStatement(
          "UPDATE moz_places "
          "SET hidden = :hidden, typed = :typed "
          "WHERE id = :page_id "
        );
      NS_ENSURE_STATE(stmt);
      rv = stmt->BindInt64ByName(NS_LITERAL_CSTRING("page_id"), mPlace.placeId);
      NS_ENSURE_SUCCESS(rv, rv);
    }
    // Otherwise, the page was not in moz_places, so now we have to add it.
    else {
      NS_ASSERTION(mPlace.placeId == 0, "should not have a valid place id!");

      stmt = mHistory->syncStatements.GetCachedStatement(
          "INSERT INTO moz_places "
            "(url, rev_host, hidden, typed, guid) "
          "VALUES (:page_url, :rev_host, :hidden, :typed, GENERATE_GUID()) "
        );
      NS_ENSURE_STATE(stmt);

      rv = stmt->BindStringByName(NS_LITERAL_CSTRING("rev_host"),
                                  mPlace.revHost);
      NS_ENSURE_SUCCESS(rv, rv);
      rv = URIBinder::Bind(stmt, NS_LITERAL_CSTRING("page_url"), mPlace.spec);
      NS_ENSURE_SUCCESS(rv, rv);
    }
    rv = stmt->BindInt32ByName(NS_LITERAL_CSTRING("typed"), mPlace.typed);
    NS_ENSURE_SUCCESS(rv, rv);
    rv = stmt->BindInt32ByName(NS_LITERAL_CSTRING("hidden"), mPlace.hidden);
    NS_ENSURE_SUCCESS(rv, rv);

    mozStorageStatementScoper scoper(stmt);
    rv = stmt->Execute();
    NS_ENSURE_SUCCESS(rv, rv);

    rv = AddVisit(mPlace, mReferrer);
    NS_ENSURE_SUCCESS(rv, rv);

    rv = UpdateFrecency(mPlace);
    NS_ENSURE_SUCCESS(rv, rv);

    rv = transaction.Commit();
    NS_ENSURE_SUCCESS(rv, rv);

    // Finally, dispatch an event to the main thread to notify observers.
    nsCOMPtr<nsIRunnable> event = new NotifyVisitObservers(mPlace, mReferrer);
    rv = NS_DispatchToMainThread(event);
    NS_ENSURE_SUCCESS(rv, rv);

    return NS_OK;
  }
private:
  InsertVisitedURI(mozIStorageConnection* aConnection,
                   VisitData& aPlace,
                   nsIURI* aReferrer)
  : mDBConn(aConnection)
  , mPlace(aPlace)
  , mHistory(History::GetService())
  {
    if (aReferrer) {
      (void)aReferrer->GetSpec(mReferrer.spec);
    }
  }

  /**
   * Loads information about the page into _place from moz_places.
   *
   * @param _place
   *        The VisitData for the place we need to know information about.
   * @return true if the page was recorded in moz_places, false otherwise.
   */
  bool FetchPageInfo(VisitData& _place)
  {
    NS_PRECONDITION(!_place.spec.IsEmpty(), "must have a non-empty spec!");

    nsCOMPtr<mozIStorageStatement> stmt =
      mHistory->syncStatements.GetCachedStatement(
        "SELECT id, typed, hidden "
        "FROM moz_places "
        "WHERE url = :page_url "
      );
    NS_ENSURE_TRUE(stmt, false);
    mozStorageStatementScoper scoper(stmt);

    nsresult rv = URIBinder::Bind(stmt, NS_LITERAL_CSTRING("page_url"),
                                  _place.spec);
    NS_ENSURE_SUCCESS(rv, false);

    PRBool hasResult;
    rv = stmt->ExecuteStep(&hasResult);
    NS_ENSURE_SUCCESS(rv, false);
    if (!hasResult) {
      return false;
    }

    rv = stmt->GetInt64(0, &_place.placeId);
    NS_ENSURE_SUCCESS(rv, false);

    if (!_place.typed) {
      // If this transition wasn't typed, others might have been. If database
      // has location as typed, reflect that in our data structure.
      PRInt32 typed;
      rv = stmt->GetInt32(1, &typed);
      _place.typed = !!typed;
      NS_ENSURE_SUCCESS(rv, true);
    }
    if (_place.hidden) {
      // If this transition was hidden, it is possible that others were not.
      // Any one visible transition makes this location visible. If database
      // has location as visible, reflect that in our data structure.
      PRInt32 hidden;
      rv = stmt->GetInt32(2, &hidden);
      _place.hidden = !!hidden;
      NS_ENSURE_SUCCESS(rv, true);
    }

    return true;
  }

  /**
   * Loads visit information about the page into _place.
   *
   * @param _place
   *        The VisitData for the place we need to know visit information about.
   * @param [optional] aThresholdStart
   *        The timestamp of a new visit (not represented by _place) used to
   *        determine if the page was recently visited or not.
   * @return true if the page was recently (determined with aThresholdStart)
   *         visited, false otherwise.
   */
  bool FetchVisitInfo(VisitData& _place,
                      PRTime aThresholdStart = 0)
  {
    NS_PRECONDITION(!_place.spec.IsEmpty(), "must have a non-empty spec!");

    nsCOMPtr<mozIStorageStatement> stmt =
      mHistory->syncStatements.GetCachedStatement(
        "SELECT id, session, visit_date "
        "FROM moz_historyvisits "
        "WHERE place_id = (SELECT id FROM moz_places WHERE url = :page_url) "
        "ORDER BY visit_date DESC "
      );
    NS_ENSURE_TRUE(stmt, false);
    mozStorageStatementScoper scoper(stmt);

    nsresult rv = URIBinder::Bind(stmt, NS_LITERAL_CSTRING("page_url"),
                                  _place.spec);
    NS_ENSURE_SUCCESS(rv, false);

    PRBool hasResult;
    rv = stmt->ExecuteStep(&hasResult);
    NS_ENSURE_SUCCESS(rv, false);
    if (!hasResult) {
      return false;
    }

    rv = stmt->GetInt64(0, &_place.visitId);
    NS_ENSURE_SUCCESS(rv, false);
    rv = stmt->GetInt64(1, &_place.sessionId);
    NS_ENSURE_SUCCESS(rv, false);
    rv = stmt->GetInt64(2, &_place.visitTime);
    NS_ENSURE_SUCCESS(rv, false);

    // If we have been given a visit threshold start time, go ahead and
    // calculate if we have been recently visited.
    if (aThresholdStart &&
        aThresholdStart - _place.visitTime <= RECENT_EVENT_THRESHOLD) {
      return true;
    }

    return false;
  }

  /**
   * Adds a visit for _place and updates it with the right visit id.
   *
   * @param _place
   *        The VisitData for the place we need to know visit information about.
   * @param aReferrer
   *        A reference to the referrer's visit data.
   */
  nsresult AddVisit(VisitData& _place,
                    const VisitData& aReferrer)
  {
    nsresult rv;
    nsCOMPtr<mozIStorageStatement> stmt;
    if (_place.placeId) {
      stmt = mHistory->syncStatements.GetCachedStatement(
        "INSERT INTO moz_historyvisits "
          "(from_visit, place_id, visit_date, visit_type, session) "
        "VALUES (:from_visit, :page_id, :visit_date, :visit_type, :session) "
      );
      NS_ENSURE_STATE(stmt);
      rv = stmt->BindInt64ByName(NS_LITERAL_CSTRING("page_id"), mPlace.placeId);
      NS_ENSURE_SUCCESS(rv, rv);
    }
    else {
      stmt = mHistory->syncStatements.GetCachedStatement(
        "INSERT INTO moz_historyvisits "
          "(from_visit, place_id, visit_date, visit_type, session) "
        "VALUES (:from_visit, (SELECT id FROM moz_places WHERE url = :page_url), :visit_date, :visit_type, :session) "
      );
      NS_ENSURE_STATE(stmt);
      rv = URIBinder::Bind(stmt, NS_LITERAL_CSTRING("page_url"), _place.spec);
      NS_ENSURE_SUCCESS(rv, rv);
    }
    rv = stmt->BindInt64ByName(NS_LITERAL_CSTRING("from_visit"),
                               aReferrer.visitId);
    NS_ENSURE_SUCCESS(rv, rv);
    rv = stmt->BindInt64ByName(NS_LITERAL_CSTRING("visit_date"),
                               _place.visitTime);
    NS_ENSURE_SUCCESS(rv, rv);
    PRInt32 transitionType = _place.transitionType;
    NS_ASSERTION(transitionType >= nsINavHistoryService::TRANSITION_LINK &&
                 transitionType <= nsINavHistoryService::TRANSITION_FRAMED_LINK,
                 "Invalid transition type!");
    rv = stmt->BindInt32ByName(NS_LITERAL_CSTRING("visit_type"),
                               transitionType);
    NS_ENSURE_SUCCESS(rv, rv);
    rv = stmt->BindInt64ByName(NS_LITERAL_CSTRING("session"),
                               _place.sessionId);
    NS_ENSURE_SUCCESS(rv, rv);

    mozStorageStatementScoper scoper(stmt);
    rv = stmt->Execute();
    NS_ENSURE_SUCCESS(rv, rv);

    // Now that it should be in the database, we need to obtain the id of the
    // place we just added.
    bool visited = FetchVisitInfo(_place);
    if (visited) {
      NS_NOTREACHED("Not visited after adding a visit!");
    }

    return NS_OK;
  }

  /**
   * Updates the frecency, and possibly the hidden-ness of aPlace.
   *
   * @param aPlace
   *        The VisitData for the place we want to update.
   */
  nsresult UpdateFrecency(const VisitData& aPlace)
  {
    nsresult rv;
    { // First, set our frecency to the proper value.
      nsCOMPtr<mozIStorageStatement> stmt;
      if (aPlace.placeId) {
        stmt = mHistory->syncStatements.GetCachedStatement(
          "UPDATE moz_places "
          "SET frecency = CALCULATE_FRECENCY(:page_id) "
          "WHERE id = :page_id"
        );
        NS_ENSURE_STATE(stmt);
        rv = stmt->BindInt64ByName(NS_LITERAL_CSTRING("page_id"), mPlace.placeId);
        NS_ENSURE_SUCCESS(rv, rv);
      }
      else {
        stmt = mHistory->syncStatements.GetCachedStatement(
          "UPDATE moz_places "
          "SET frecency = CALCULATE_FRECENCY(id) "
          "WHERE url = :page_url"
        );
        NS_ENSURE_STATE(stmt);
        rv = URIBinder::Bind(stmt, NS_LITERAL_CSTRING("page_url"), aPlace.spec);
        NS_ENSURE_SUCCESS(rv, rv);
      }
      mozStorageStatementScoper scoper(stmt);

      rv = stmt->Execute();
      NS_ENSURE_SUCCESS(rv, rv);
    }

    { // Now, we need to mark the page as not hidden if the frecency is now
      // nonzero.
      nsCOMPtr<mozIStorageStatement> stmt;
      if (aPlace.placeId) {
        stmt = mHistory->syncStatements.GetCachedStatement(
          "UPDATE moz_places "
          "SET hidden = 0 "
          "WHERE id = :page_id AND frecency <> 0"
        );
        NS_ENSURE_STATE(stmt);
        rv = stmt->BindInt64ByName(NS_LITERAL_CSTRING("page_id"), mPlace.placeId);
        NS_ENSURE_SUCCESS(rv, rv);
      }
      else {
        stmt = mHistory->syncStatements.GetCachedStatement(
          "UPDATE moz_places "
          "SET hidden = 0 "
          "WHERE url = :page_url AND frecency <> 0"
        );
        NS_ENSURE_STATE(stmt);
        rv = URIBinder::Bind(stmt, NS_LITERAL_CSTRING("page_url"), aPlace.spec);
        NS_ENSURE_SUCCESS(rv, rv);
      }

      mozStorageStatementScoper scoper(stmt);
      rv = stmt->Execute();
      NS_ENSURE_SUCCESS(rv, rv);
    }

    return NS_OK;
  }

  mozIStorageConnection* mDBConn;

  VisitData mPlace;
  VisitData mReferrer;

  /**
   * Strong reference to the History object because we do not want it to
   * disappear out from under us.
   */
  nsRefPtr<History> mHistory;
};

/**
 * Notifies observers about a pages title changing.
 */
class NotifyTitleObservers : public nsRunnable
{
public:
  /**
   * Notifies observers on the main thread.
   *
   * @param aSpec
   *        The spec of the URI to notify about.
   * @param aTitle
   *        The new title to notify about.
   */
  NotifyTitleObservers(const nsCString& aSpec,
                       const nsString& aTitle)
  : mSpec(aSpec)
  , mTitle(aTitle)
  {
    NS_PRECONDITION(!NS_IsMainThread(),
                    "This should not be called on the main thread");
  }

  NS_IMETHOD Run()
  {
    NS_PRECONDITION(NS_IsMainThread(),
                    "This should be called on the main thread");

    nsNavHistory* navHistory = nsNavHistory::GetHistoryService();
    NS_ENSURE_TRUE(navHistory, NS_ERROR_OUT_OF_MEMORY);
    nsCOMPtr<nsIURI> uri;
    (void)NS_NewURI(getter_AddRefs(uri), mSpec);
    navHistory->NotifyTitleChange(uri, mTitle);

    return NS_OK;
  }
private:
  const nsCString mSpec;
  const nsString mTitle;
};


/**
 * Sets the page title for a page in moz_places (if necessary).
 */
class SetPageTitle : public nsRunnable
{
public:
  /**
   * Sets a pages title in the database asynchronously.
   *
   * @param aConnection
   *        The database connection to use for this operation.
   * @param aURI
   *        The URI to set the page title on.
   * @param aTitle
   *        The title to set for the page, if the page exists.
   */
  static nsresult Start(mozIStorageConnection* aConnection,
                        nsIURI* aURI,
                        const nsString& aTitle)
  {
    NS_PRECONDITION(NS_IsMainThread(),
                    "This should be called on the main thread");
    NS_PRECONDITION(aURI, "Must pass a non-null URI object!");

    nsCString spec;
    nsresult rv = aURI->GetSpec(spec);
    NS_ENSURE_SUCCESS(rv, rv);

    nsRefPtr<SetPageTitle> event = new SetPageTitle(spec, aTitle);

    // Get the target thread, and then start the work!
    nsCOMPtr<nsIEventTarget> target = do_GetInterface(aConnection);
    NS_ENSURE_TRUE(target, NS_ERROR_UNEXPECTED);
    rv = target->Dispatch(event, NS_DISPATCH_NORMAL);
    NS_ENSURE_SUCCESS(rv, rv);

    return NS_OK;
  }

  NS_IMETHOD Run()
  {
    NS_PRECONDITION(!NS_IsMainThread(),
                    "This should not be called on the main thread");

    // First, see if the page exists in the database (we'll need its id later).
    nsCOMPtr<mozIStorageStatement> stmt =
      mHistory->syncStatements.GetCachedStatement(
        "SELECT id, title "
        "FROM moz_places "
        "WHERE url = :page_url "
      );
    NS_ENSURE_STATE(stmt);

    PRInt64 placeId = 0;
    nsAutoString title;
    {
      mozStorageStatementScoper scoper(stmt);
      nsresult rv = URIBinder::Bind(stmt, NS_LITERAL_CSTRING("page_url"),
                                    mSpec);
      NS_ENSURE_SUCCESS(rv, rv);

      PRBool hasResult;
      rv = stmt->ExecuteStep(&hasResult);
      NS_ENSURE_SUCCESS(rv, rv);
      if (!hasResult) {
        // We have no record of this page, so there is no need to do any further
        // work.
        return NS_OK;
      }

      rv = stmt->GetInt64(0, &placeId);
      NS_ENSURE_SUCCESS(rv, rv);

      rv = stmt->GetString(1, title);
      NS_ENSURE_SUCCESS(rv, rv);
    }

    NS_ASSERTION(placeId > 0, "We somehow have an invalid place id here!");

    // Also, if we have the same title, there is no reason to do another write
    // or notify our observers, so bail early.
    if (mTitle.Equals(title) || (mTitle.IsVoid() && title.IsVoid())) {
      return NS_OK;
    }

    // Now we can update our database record.
    stmt = mHistory->syncStatements.GetCachedStatement(
        "UPDATE moz_places "
        "SET title = :page_title "
        "WHERE id = :page_id "
      );
    NS_ENSURE_STATE(stmt);

    {
      mozStorageStatementScoper scoper(stmt);
      nsresult rv = stmt->BindInt64ByName(NS_LITERAL_CSTRING("page_id"),
                                          placeId);
      NS_ENSURE_SUCCESS(rv, rv);
      if (mTitle.IsVoid()) {
        rv = stmt->BindNullByName(NS_LITERAL_CSTRING("page_title"));
      }
      else {
        rv = stmt->BindStringByName(NS_LITERAL_CSTRING("page_title"),
                                    StringHead(mTitle, TITLE_LENGTH_MAX));
      }
      NS_ENSURE_SUCCESS(rv, rv);
      rv = stmt->Execute();
      NS_ENSURE_SUCCESS(rv, rv);
    }

    nsCOMPtr<nsIRunnable> event = new NotifyTitleObservers(mSpec, mTitle);
    nsresult rv = NS_DispatchToMainThread(event);
    NS_ENSURE_SUCCESS(rv, rv);

    return NS_OK;
  }

private:
  SetPageTitle(const nsCString& aSpec,
               const nsString& aTitle)
  : mSpec(aSpec)
  , mTitle(aTitle)
  , mHistory(History::GetService())
  {
  }

  const nsCString mSpec;
  const nsString mTitle;

  /**
   * Strong reference to the History object because we do not want it to
   * disappear out from under us.
   */
  nsRefPtr<History> mHistory;
};

} // anonymous namespace

////////////////////////////////////////////////////////////////////////////////
//// History

History* History::gService = NULL;

History::History()
: mShuttingDown(false)
, syncStatements(mDBConn)
{
  NS_ASSERTION(!gService, "Ruh-roh!  This service has already been created!");
  gService = this;

  nsCOMPtr<nsIObserverService> os = mozilla::services::GetObserverService();
  NS_WARN_IF_FALSE(os, "Observer service was not found!");
  if (os) {
    (void)os->AddObserver(this, TOPIC_PLACES_SHUTDOWN, PR_FALSE);
  }
}

History::~History()
{
  gService = NULL;

#ifdef DEBUG
  if (mObservers.IsInitialized()) {
    NS_ASSERTION(mObservers.Count() == 0,
                 "Not all Links were removed before we disappear!");
  }
#endif
}

void
History::NotifyVisited(nsIURI* aURI)
{
  NS_ASSERTION(aURI, "Ruh-roh!  A NULL URI was passed to us!");

#ifdef MOZ_IPC
  if (XRE_GetProcessType() == GeckoProcessType_Default) {
    mozilla::dom::ContentParent* cpp = 
      mozilla::dom::ContentParent::GetSingleton(PR_FALSE);
    if (cpp)
      (void)cpp->SendNotifyVisited(aURI);
  }
#endif

  // If the hash table has not been initialized, then we have nothing to notify
  // about.
  if (!mObservers.IsInitialized()) {
    return;
  }

  // Additionally, if we have no observers for this URI, we have nothing to
  // notify about.
  KeyClass* key = mObservers.GetEntry(aURI);
  if (!key) {
    return;
  }

  // Walk through the array, and update each Link node.
  const ObserverArray& observers = key->array;
  ObserverArray::index_type len = observers.Length();
  for (ObserverArray::index_type i = 0; i < len; i++) {
    Link* link = observers[i];
    link->SetLinkState(eLinkState_Visited);
    NS_ASSERTION(len == observers.Length(),
                 "Calling SetLinkState added or removed an observer!");
  }

  // All the registered nodes can now be removed for this URI.
  mObservers.RemoveEntry(aURI);
}

mozIStorageAsyncStatement*
History::GetIsVisitedStatement()
{
  if (mIsVisitedStatement) {
    return mIsVisitedStatement;
  }

  // If we don't yet have a database connection, go ahead and clone it now.
  if (!mReadOnlyDBConn) {
    mozIStorageConnection* dbConn = GetDBConn();
    NS_ENSURE_TRUE(dbConn, nsnull);

    (void)dbConn->Clone(PR_TRUE, getter_AddRefs(mReadOnlyDBConn));
    NS_ENSURE_TRUE(mReadOnlyDBConn, nsnull);
  }

  // Now we can create our cached statement.
  nsresult rv = mReadOnlyDBConn->CreateAsyncStatement(NS_LITERAL_CSTRING(
    "SELECT h.id "
    "FROM moz_places h "
    "WHERE url = ?1 "
      "AND EXISTS(SELECT id FROM moz_historyvisits WHERE place_id = h.id LIMIT 1) "
  ),  getter_AddRefs(mIsVisitedStatement));
  NS_ENSURE_SUCCESS(rv, nsnull);
  return mIsVisitedStatement;
}

/* static */
History*
History::GetService()
{
  if (gService) {
    return gService;
  }

  nsCOMPtr<IHistory> service(do_GetService(NS_IHISTORY_CONTRACTID));
  NS_ABORT_IF_FALSE(service, "Cannot obtain IHistory service!");
  NS_ASSERTION(gService, "Our constructor was not run?!");

  return gService;
}

/* static */
History*
History::GetSingleton()
{
  if (!gService) {
    gService = new History();
    NS_ENSURE_TRUE(gService, nsnull);
  }

  NS_ADDREF(gService);
  return gService;
}

mozIStorageConnection*
History::GetDBConn()
{
  if (mDBConn) {
    return mDBConn;
  }

  nsNavHistory* navHistory = nsNavHistory::GetHistoryService();
  NS_ENSURE_TRUE(navHistory, nsnull);

  nsresult rv = navHistory->GetDBConnection(getter_AddRefs(mDBConn));
  NS_ENSURE_SUCCESS(rv, nsnull);

  return mDBConn;
}

void
History::Shutdown()
{
  NS_ASSERTION(!mShuttingDown, "Shutdown was called more than once!");

  mShuttingDown = true;

  // Clean up our statements and connection.
  nsISupports* obj = static_cast<IHistory*>(this);
  nsCOMPtr<nsIRunnable> event =
    new FinalizeStatementCacheProxy<mozIStorageStatement>(syncStatements, obj);
  nsCOMPtr<nsIEventTarget> target = do_GetInterface(mDBConn);
  if (target) {
    (void)target->Dispatch(event, NS_DISPATCH_NORMAL);
  }

  if (mReadOnlyDBConn) {
    if (mIsVisitedStatement) {
      (void)mIsVisitedStatement->Finalize();
    }
    (void)mReadOnlyDBConn->AsyncClose(nsnull);
  }
}

////////////////////////////////////////////////////////////////////////////////
//// IHistory

NS_IMETHODIMP
History::VisitURI(nsIURI* aURI,
                  nsIURI* aLastVisitedURI,
                  PRUint32 aFlags)
{
  NS_PRECONDITION(aURI, "URI should not be NULL.");
  if (mShuttingDown) {
    return NS_OK;
  }

#ifdef MOZ_IPC
  if (XRE_GetProcessType() == GeckoProcessType_Content) {
    mozilla::dom::ContentChild* cpc =
      mozilla::dom::ContentChild::GetSingleton();
    NS_ASSERTION(cpc, "Content Protocol is NULL!");
    (void)cpc->SendVisitURI(aURI, aLastVisitedURI, aFlags);
    return NS_OK;
  } 
#endif /* MOZ_IPC */

  nsNavHistory* navHistory = nsNavHistory::GetHistoryService();
  NS_ENSURE_TRUE(navHistory, NS_ERROR_OUT_OF_MEMORY);

  // Silently return if URI is something we shouldn't add to DB.
  PRBool canAdd;
  nsresult rv = navHistory->CanAddURI(aURI, &canAdd);
  NS_ENSURE_SUCCESS(rv, rv);
  if (!canAdd) {
    return NS_OK;
  }

  if (aLastVisitedURI) {
    PRBool same;
    rv = aURI->Equals(aLastVisitedURI, &same);
    NS_ENSURE_SUCCESS(rv, rv);
    if (same) {
      // Do not save refresh-page visits.
      return NS_OK;
    }
  }

  VisitData place;
  rv = aURI->GetSpec(place.spec);
  NS_ENSURE_SUCCESS(rv, rv);
  (void)GetReversedHostname(aURI, place.revHost);

  // Assigns a type to the edge in the visit linked list. Each type will be
  // considered differently when weighting the frecency of a location.
  PRUint32 recentFlags = navHistory->GetRecentFlags(aURI);
  bool redirected = false;
  bool isFollowedLink = recentFlags & nsNavHistory::RECENT_ACTIVATED;

  // Embed visits should never be added to the database, and the same is valid
  // for redirects across frames.
  // For the above reasoning non-toplevel transitions are handled at first.
  // if the visit is toplevel or a non-toplevel followed link, then it can be
  // handled as usual and stored on disk.

  if (!(aFlags & IHistory::TOP_LEVEL) && !isFollowedLink) {
    // A frame redirected to a new site without user interaction.
    place.transitionType = nsINavHistoryService::TRANSITION_EMBED;
  }
  else if (aFlags & IHistory::REDIRECT_TEMPORARY) {
    place.transitionType = nsINavHistoryService::TRANSITION_REDIRECT_TEMPORARY;
    redirected = true;
  }
  else if (aFlags & IHistory::REDIRECT_PERMANENT) {
    place.transitionType = nsINavHistoryService::TRANSITION_REDIRECT_PERMANENT;
    redirected = true;
  }
  else if (recentFlags & nsNavHistory::RECENT_TYPED) {
    place.transitionType = nsINavHistoryService::TRANSITION_TYPED;
  }
  else if (recentFlags & nsNavHistory::RECENT_BOOKMARKED) {
    place.transitionType = nsINavHistoryService::TRANSITION_BOOKMARK;
  }
  else if (!(aFlags & IHistory::TOP_LEVEL) && isFollowedLink) {
    // User activated a link in a frame.
    place.transitionType = nsINavHistoryService::TRANSITION_FRAMED_LINK;
  }
  else {
    // User was redirected or link was clicked in the main window.
    place.transitionType = nsINavHistoryService::TRANSITION_LINK;
  }

  place.typed = place.transitionType == nsINavHistoryService::TRANSITION_TYPED;
  place.hidden =
    place.transitionType == nsINavHistoryService::TRANSITION_FRAMED_LINK ||
    place.transitionType == nsINavHistoryService::TRANSITION_EMBED ||
    redirected;
  place.visitTime = PR_Now();

  // EMBED visits are session-persistent and should not go through the database.
  // They exist only to keep track of isVisited status during the session.
  if (place.transitionType == nsINavHistoryService::TRANSITION_EMBED) {
    navHistory->registerEmbedVisit(aURI, place.visitTime);
    // Finally, enqueue an event to notify observers.
    VisitData noReferrer;
    nsCOMPtr<nsIRunnable> event = new NotifyVisitObservers(place, noReferrer);
    rv = NS_DispatchToMainThread(event);
    NS_ENSURE_SUCCESS(rv, rv);
  }
  else {
    mozIStorageConnection* dbConn = GetDBConn();
    NS_ENSURE_STATE(dbConn);

    rv = InsertVisitedURI::Start(dbConn, place, aLastVisitedURI);
    NS_ENSURE_SUCCESS(rv, rv);
  }

  // Finally, notify that we've been visited.
  nsCOMPtr<nsIObserverService> obsService =
    mozilla::services::GetObserverService();
  if (obsService) {
    obsService->NotifyObservers(aURI, NS_LINK_VISITED_EVENT_TOPIC, nsnull);
  }

  return NS_OK;
}

NS_IMETHODIMP
History::RegisterVisitedCallback(nsIURI* aURI,
                                 Link* aLink)
{
  NS_ASSERTION(aURI, "Must pass a non-null URI!");
#ifdef MOZ_IPC
  if (XRE_GetProcessType() == GeckoProcessType_Content) {
    NS_PRECONDITION(aLink, "Must pass a non-null Link!");
  }
#else
  NS_PRECONDITION(aLink, "Must pass a non-null Link!");
#endif

  // First, ensure that our hash table is setup.
  if (!mObservers.IsInitialized()) {
    NS_ENSURE_TRUE(mObservers.Init(VISIT_OBSERVERS_INITIAL_CACHE_SIZE),
                   NS_ERROR_OUT_OF_MEMORY);
  }

  // Obtain our array of observers for this URI.
#ifdef DEBUG
  bool keyAlreadyExists = !!mObservers.GetEntry(aURI);
#endif
  KeyClass* key = mObservers.PutEntry(aURI);
  NS_ENSURE_TRUE(key, NS_ERROR_OUT_OF_MEMORY);
  ObserverArray& observers = key->array;

  if (observers.IsEmpty()) {
    NS_ASSERTION(!keyAlreadyExists,
                 "An empty key was kept around in our hashtable!");

    // We are the first Link node to ask about this URI, or there are no pending
    // Links wanting to know about this URI.  Therefore, we should query the
    // database now.
    nsresult rv = VisitedQuery::Start(aURI);

    // In IPC builds, we are passed a NULL Link from
    // ContentParent::RecvStartVisitedQuery.  Since we won't be adding a NULL
    // entry to our list of observers, and the code after this point assumes
    // that aLink is non-NULL, we will need to return now.
    if (NS_FAILED(rv) || !aLink) {
      // Remove our array from the hashtable so we don't keep it around.
      mObservers.RemoveEntry(aURI);
      return rv;
    }
  }
#ifdef MOZ_IPC
  // In IPC builds, we are passed a NULL Link from
  // ContentParent::RecvStartVisitedQuery.  All of our code after this point
  // assumes aLink is non-NULL, so we have to return now.
  else if (!aLink) {
    NS_ASSERTION(XRE_GetProcessType() == GeckoProcessType_Default,
                 "We should only ever get a null Link in the default process!");
    return NS_OK;
  }
#endif

  // Sanity check that Links are not registered more than once for a given URI.
  // This will not catch a case where it is registered for two different URIs.
  NS_ASSERTION(!observers.Contains(aLink),
               "Already tracking this Link object!");

  // Start tracking our Link.
  if (!observers.AppendElement(aLink)) {
    // Curses - unregister and return failure.
    (void)UnregisterVisitedCallback(aURI, aLink);
    return NS_ERROR_OUT_OF_MEMORY;
  }

  return NS_OK;
}

NS_IMETHODIMP
History::UnregisterVisitedCallback(nsIURI* aURI,
                                   Link* aLink)
{
  NS_ASSERTION(aURI, "Must pass a non-null URI!");
  NS_ASSERTION(aLink, "Must pass a non-null Link object!");

  // Get the array, and remove the item from it.
  KeyClass* key = mObservers.GetEntry(aURI);
  if (!key) {
    NS_ERROR("Trying to unregister for a URI that wasn't registered!");
    return NS_ERROR_UNEXPECTED;
  }
  ObserverArray& observers = key->array;
  if (!observers.RemoveElement(aLink)) {
    NS_ERROR("Trying to unregister a node that wasn't registered!");
    return NS_ERROR_UNEXPECTED;
  }

  // If the array is now empty, we should remove it from the hashtable.
  if (observers.IsEmpty()) {
    mObservers.RemoveEntry(aURI);
  }

  return NS_OK;
}

NS_IMETHODIMP
History::SetURITitle(nsIURI* aURI, const nsAString& aTitle)
{
  NS_PRECONDITION(aURI, "Must pass a non-null URI!");
  if (mShuttingDown) {
    return NS_OK;
  }

#ifdef MOZ_IPC
  if (XRE_GetProcessType() == GeckoProcessType_Content) {
    mozilla::dom::ContentChild * cpc = 
      mozilla::dom::ContentChild::GetSingleton();
    NS_ASSERTION(cpc, "Content Protocol is NULL!");
    (void)cpc->SendSetURITitle(aURI, nsDependentString(aTitle));
    return NS_OK;
  } 
#endif /* MOZ_IPC */

  nsNavHistory* navHistory = nsNavHistory::GetHistoryService();

  // At first, it seems like nav history should always be available here, no
  // matter what.
  //
  // nsNavHistory fails to register as a service if there is no profile in
  // place (for instance, if user is choosing a profile).
  //
  // Maybe the correct thing to do is to not register this service if no
  // profile has been selected?
  //
  NS_ENSURE_TRUE(navHistory, NS_ERROR_FAILURE);

  PRBool canAdd;
  nsresult rv = navHistory->CanAddURI(aURI, &canAdd);
  NS_ENSURE_SUCCESS(rv, rv);
  if (!canAdd) {
    return NS_OK;
  }

  // Embed visits don't have a database entry, thus don't set a title on them.
  if (navHistory->hasEmbedVisit(aURI)) {
    return NS_OK;
  }

  nsAutoString title;
  if (aTitle.IsEmpty()) {
    title.SetIsVoid(PR_TRUE);
  }
  else {
    title.Assign(aTitle);
  }

  mozIStorageConnection* dbConn = GetDBConn();
  NS_ENSURE_STATE(dbConn);

  rv = SetPageTitle::Start(dbConn, aURI, title);
  NS_ENSURE_SUCCESS(rv, rv);

  return NS_OK;
}

////////////////////////////////////////////////////////////////////////////////
//// nsIObserver

NS_IMETHODIMP
History::Observe(nsISupports* aSubject, const char* aTopic,
                 const PRUnichar* aData)
{
  if (strcmp(aTopic, TOPIC_PLACES_SHUTDOWN) == 0) {
    Shutdown();

    nsCOMPtr<nsIObserverService> os = mozilla::services::GetObserverService();
    if (os) {
      (void)os->RemoveObserver(this, TOPIC_PLACES_SHUTDOWN);
    }
  }

  return NS_OK;
}

////////////////////////////////////////////////////////////////////////////////
//// nsISupports

NS_IMPL_THREADSAFE_ISUPPORTS2(
  History
, IHistory
, nsIObserver
)

} // namespace places
} // namespace mozilla