/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 * vim: sw=2 ts=2 et lcs=trail\:.,tab\:>~ :
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "mozilla/DebugOnly.h"

#include "VacuumManager.h"

#include "mozilla/Services.h"
#include "mozilla/Preferences.h"
#include "nsIObserverService.h"
#include "nsIFile.h"
#include "nsThreadUtils.h"
#include "mozilla/Logging.h"
#include "prtime.h"

#include "mozStorageConnection.h"
#include "mozIStorageStatement.h"
#include "mozIStorageAsyncStatement.h"
#include "mozIStoragePendingStatement.h"
#include "mozIStorageError.h"
#include "mozStorageHelper.h"
#include "nsXULAppAPI.h"

#define OBSERVER_TOPIC_IDLE_DAILY "idle-daily"
#define OBSERVER_TOPIC_XPCOM_SHUTDOWN "xpcom-shutdown"

// Used to notify begin and end of a heavy IO task.
#define OBSERVER_TOPIC_HEAVY_IO "heavy-io-task"
#define OBSERVER_DATA_VACUUM_BEGIN NS_LITERAL_STRING("vacuum-begin")
#define OBSERVER_DATA_VACUUM_END NS_LITERAL_STRING("vacuum-end")

// This preferences root will contain last vacuum timestamps (in seconds) for
// each database.  The database filename is used as a key.
#define PREF_VACUUM_BRANCH "storage.vacuum.last."

// Time between subsequent vacuum calls for a certain database.
#define VACUUM_INTERVAL_SECONDS 30 * 86400 // 30 days.

extern PRLogModuleInfo *gStorageLog;

namespace mozilla {
namespace storage {

namespace {

////////////////////////////////////////////////////////////////////////////////
//// BaseCallback

class BaseCallback : public mozIStorageStatementCallback
{
public:
  NS_DECL_ISUPPORTS
  NS_DECL_MOZISTORAGESTATEMENTCALLBACK
  BaseCallback() {}
protected:
  virtual ~BaseCallback() {}
};

NS_IMETHODIMP
BaseCallback::HandleError(mozIStorageError *aError)
{
#ifdef DEBUG
  int32_t result;
  nsresult rv = aError->GetResult(&result);
  NS_ENSURE_SUCCESS(rv, rv);
  nsAutoCString message;
  rv = aError->GetMessage(message);
  NS_ENSURE_SUCCESS(rv, rv);

  nsAutoCString warnMsg;
  warnMsg.AppendLiteral("An error occured during async execution: ");
  warnMsg.AppendInt(result);
  warnMsg.Append(' ');
  warnMsg.Append(message);
  NS_WARNING(warnMsg.get());
#endif
  return NS_OK;
}

NS_IMETHODIMP
BaseCallback::HandleResult(mozIStorageResultSet *aResultSet)
{
  // We could get results from PRAGMA statements, but we don't mind them.
  return NS_OK;
}

NS_IMETHODIMP
BaseCallback::HandleCompletion(uint16_t aReason)
{
  // By default BaseCallback will just be silent on completion.
  return NS_OK;
}

NS_IMPL_ISUPPORTS(
  BaseCallback
, mozIStorageStatementCallback
)

//////////////////////////////////////////////////////////////////////////////// 
//// Vacuumer declaration.

class Vacuumer : public BaseCallback
{
public:
  NS_DECL_MOZISTORAGESTATEMENTCALLBACK

  explicit Vacuumer(mozIStorageVacuumParticipant *aParticipant);

  bool execute();
  nsresult notifyCompletion(bool aSucceeded);

private:
  nsCOMPtr<mozIStorageVacuumParticipant> mParticipant;
  nsCString mDBFilename;
  nsCOMPtr<mozIStorageConnection> mDBConn;
};

////////////////////////////////////////////////////////////////////////////////
//// Vacuumer implementation.

Vacuumer::Vacuumer(mozIStorageVacuumParticipant *aParticipant)
  : mParticipant(aParticipant)
{
}

bool
Vacuumer::execute()
{
  MOZ_ASSERT(NS_IsMainThread(), "Must be running on the main thread!");

  // Get the connection and check its validity.
  nsresult rv = mParticipant->GetDatabaseConnection(getter_AddRefs(mDBConn));
  NS_ENSURE_SUCCESS(rv, false);
  bool ready = false;
  if (!mDBConn || NS_FAILED(mDBConn->GetConnectionReady(&ready)) || !ready) {
    NS_WARNING("Unable to get a connection to vacuum database");
    return false;
  }

  // Ask for the expected page size.  Vacuum can change the page size, unless
  // the database is using WAL journaling.
  // TODO Bug 634374: figure out a strategy to fix page size with WAL.
  int32_t expectedPageSize = 0;
  rv = mParticipant->GetExpectedDatabasePageSize(&expectedPageSize);
  if (NS_FAILED(rv) || !Service::pageSizeIsValid(expectedPageSize)) {
    NS_WARNING("Invalid page size requested for database, will use default ");
    NS_WARNING(mDBFilename.get());
    expectedPageSize = Service::getDefaultPageSize();
  }

  // Get the database filename.  Last vacuum time is stored under this name
  // in PREF_VACUUM_BRANCH.
  nsCOMPtr<nsIFile> databaseFile;
  mDBConn->GetDatabaseFile(getter_AddRefs(databaseFile));
  if (!databaseFile) {
    NS_WARNING("Trying to vacuum a in-memory database!");
    return false;
  }
  nsAutoString databaseFilename;
  rv = databaseFile->GetLeafName(databaseFilename);
  NS_ENSURE_SUCCESS(rv, false);
  mDBFilename = NS_ConvertUTF16toUTF8(databaseFilename);
  MOZ_ASSERT(!mDBFilename.IsEmpty(), "Database filename cannot be empty");

  // Check interval from last vacuum.
  int32_t now = static_cast<int32_t>(PR_Now() / PR_USEC_PER_SEC);
  int32_t lastVacuum;
  nsAutoCString prefName(PREF_VACUUM_BRANCH);
  prefName += mDBFilename;
  rv = Preferences::GetInt(prefName.get(), &lastVacuum);
  if (NS_SUCCEEDED(rv) && (now - lastVacuum) < VACUUM_INTERVAL_SECONDS) {
    // This database was vacuumed recently, skip it.
    return false;
  }

  // Notify that we are about to start vacuuming.  The participant can opt-out
  // if it cannot handle a vacuum at this time, and then we'll move to the next
  // one.
  bool vacuumGranted = false;
  rv = mParticipant->OnBeginVacuum(&vacuumGranted);
  NS_ENSURE_SUCCESS(rv, false);
  if (!vacuumGranted) {
    return false;
  }

  // Notify a heavy IO task is about to start.
  nsCOMPtr<nsIObserverService> os = mozilla::services::GetObserverService();
  if (os) {
    DebugOnly<nsresult> rv =
      os->NotifyObservers(nullptr, OBSERVER_TOPIC_HEAVY_IO,
                          OBSERVER_DATA_VACUUM_BEGIN.get());
    MOZ_ASSERT(NS_SUCCEEDED(rv), "Should be able to notify");
  }

  // Execute the statements separately, since the pragma may conflict with the
  // vacuum, if they are executed in the same transaction.
  nsCOMPtr<mozIStorageAsyncStatement> pageSizeStmt;
  nsAutoCString pageSizeQuery(MOZ_STORAGE_UNIQUIFY_QUERY_STR
                              "PRAGMA page_size = ");
  pageSizeQuery.AppendInt(expectedPageSize);
  rv = mDBConn->CreateAsyncStatement(pageSizeQuery,
                                     getter_AddRefs(pageSizeStmt));
  NS_ENSURE_SUCCESS(rv, false);
  nsRefPtr<BaseCallback> callback = new BaseCallback();
  nsCOMPtr<mozIStoragePendingStatement> ps;
  rv = pageSizeStmt->ExecuteAsync(callback, getter_AddRefs(ps));
  NS_ENSURE_SUCCESS(rv, false);

  nsCOMPtr<mozIStorageAsyncStatement> stmt;
  rv = mDBConn->CreateAsyncStatement(NS_LITERAL_CSTRING(
    "VACUUM"
  ), getter_AddRefs(stmt));
  NS_ENSURE_SUCCESS(rv, false);
  rv = stmt->ExecuteAsync(this, getter_AddRefs(ps));
  NS_ENSURE_SUCCESS(rv, false);

  return true;
}

////////////////////////////////////////////////////////////////////////////////
//// mozIStorageStatementCallback

NS_IMETHODIMP
Vacuumer::HandleError(mozIStorageError *aError)
{
#ifdef DEBUG
  int32_t result;
  nsresult rv = aError->GetResult(&result);
  NS_ENSURE_SUCCESS(rv, rv);
  nsAutoCString message;
  rv = aError->GetMessage(message);
  NS_ENSURE_SUCCESS(rv, rv);

  nsAutoCString warnMsg;
  warnMsg.AppendLiteral("Unable to vacuum database: ");
  warnMsg.Append(mDBFilename);
  warnMsg.AppendLiteral(" - ");
  warnMsg.AppendInt(result);
  warnMsg.Append(' ');
  warnMsg.Append(message);
  NS_WARNING(warnMsg.get());
#endif

  if (MOZ_LOG_TEST(gStorageLog, LogLevel::Error)) {
    int32_t result;
    nsresult rv = aError->GetResult(&result);
    NS_ENSURE_SUCCESS(rv, rv);
    nsAutoCString message;
    rv = aError->GetMessage(message);
    NS_ENSURE_SUCCESS(rv, rv);
    MOZ_LOG(gStorageLog, LogLevel::Error,
           ("Vacuum failed with error: %d '%s'. Database was: '%s'",
            result, message.get(), mDBFilename.get()));
  }
  return NS_OK;
}

NS_IMETHODIMP
Vacuumer::HandleResult(mozIStorageResultSet *aResultSet)
{
  NS_NOTREACHED("Got a resultset from a vacuum?");
  return NS_OK;
}

NS_IMETHODIMP
Vacuumer::HandleCompletion(uint16_t aReason)
{
  if (aReason == REASON_FINISHED) {
    // Update last vacuum time.
    int32_t now = static_cast<int32_t>(PR_Now() / PR_USEC_PER_SEC);
    MOZ_ASSERT(!mDBFilename.IsEmpty(), "Database filename cannot be empty");
    nsAutoCString prefName(PREF_VACUUM_BRANCH);
    prefName += mDBFilename;
    DebugOnly<nsresult> rv = Preferences::SetInt(prefName.get(), now);
    MOZ_ASSERT(NS_SUCCEEDED(rv), "Should be able to set a preference"); 
  }

  notifyCompletion(aReason == REASON_FINISHED);

  return NS_OK;
}

nsresult
Vacuumer::notifyCompletion(bool aSucceeded)
{
  nsCOMPtr<nsIObserverService> os = mozilla::services::GetObserverService();
  if (os) {
    os->NotifyObservers(nullptr, OBSERVER_TOPIC_HEAVY_IO,
                        OBSERVER_DATA_VACUUM_END.get());
  }

  nsresult rv = mParticipant->OnEndVacuum(aSucceeded);
  NS_ENSURE_SUCCESS(rv, rv);

  return NS_OK;
}

} // Anonymous namespace.

////////////////////////////////////////////////////////////////////////////////
//// VacuumManager

NS_IMPL_ISUPPORTS(
  VacuumManager
, nsIObserver
)

VacuumManager *
VacuumManager::gVacuumManager = nullptr;

VacuumManager *
VacuumManager::getSingleton()
{
  //Don't allocate it in the child Process.
  if (!XRE_IsParentProcess()) {
    return nullptr;
  }

  if (gVacuumManager) {
    NS_ADDREF(gVacuumManager);
    return gVacuumManager;
  }
  gVacuumManager = new VacuumManager();
  if (gVacuumManager) {
    NS_ADDREF(gVacuumManager);
  }
  return gVacuumManager;
}

VacuumManager::VacuumManager()
  : mParticipants("vacuum-participant")
{
  MOZ_ASSERT(!gVacuumManager,
             "Attempting to create two instances of the service!");
  gVacuumManager = this;
}

VacuumManager::~VacuumManager()
{
  // Remove the static reference to the service.  Check to make sure its us
  // in case somebody creates an extra instance of the service.
  MOZ_ASSERT(gVacuumManager == this,
             "Deleting a non-singleton instance of the service");
  if (gVacuumManager == this) {
    gVacuumManager = nullptr;
  }
}

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

NS_IMETHODIMP
VacuumManager::Observe(nsISupports *aSubject,
                       const char *aTopic,
                       const char16_t *aData)
{
  if (strcmp(aTopic, OBSERVER_TOPIC_IDLE_DAILY) == 0) {
    // Try to run vacuum on all registered entries.  Will stop at the first
    // successful one.
    nsCOMArray<mozIStorageVacuumParticipant> entries;
    mParticipants.GetEntries(entries);
    // If there are more entries than what a month can contain, we could end up
    // skipping some, since we run daily.  So we use a starting index.
    static const char* kPrefName = PREF_VACUUM_BRANCH "index";
    int32_t startIndex = Preferences::GetInt(kPrefName, 0);
    if (startIndex >= entries.Count()) {
      startIndex = 0;
    }
    int32_t index;
    for (index = startIndex; index < entries.Count(); ++index) {
      nsRefPtr<Vacuumer> vacuum = new Vacuumer(entries[index]);
      // Only vacuum one database per day.
      if (vacuum->execute()) {
        break;
      }
    }
    DebugOnly<nsresult> rv = Preferences::SetInt(kPrefName, index);
    MOZ_ASSERT(NS_SUCCEEDED(rv), "Should be able to set a preference");
  }

  return NS_OK;
}

} // namespace storage
} // namespace mozilla