/*=============================================================================

  Library: CTK

  Copyright (c) German Cancer Research Center,
    Division of Medical and Biological Informatics

  Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0

  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License.

=============================================================================*/

#include "ctkCmdLineModuleManager.h"

#include "ctkCmdLineModuleBackend.h"
#include "ctkCmdLineModuleFrontend.h"
#include "ctkCmdLineModuleTimeoutException.h"
#include "ctkCmdLineModuleCache_p.h"
#include "ctkCmdLineModuleFuture.h"
#include "ctkCmdLineModuleXmlValidator.h"
#include "ctkCmdLineModuleReference.h"
#include "ctkCmdLineModuleReference_p.h"
#include "ctkCmdLineModuleRunException.h"
#include "ctkCmdLineModuleXmlException.h"
#include "ctkCmdLineModuleTimeoutException.h"

#include <ctkException.h>

#include <QFileInfo>
#include <QDir>
#include <QStringList>
#include <QBuffer>
#include <QUrl>
#include <QHash>
#include <QList>
#include <QMutex>
#include <QDebug>
#include <QFuture>

#include <algorithm>

#if (QT_VERSION < QT_VERSION_CHECK(4,7,0))
extern int qHash(const QUrl& url);
#endif

//----------------------------------------------------------------------------
struct ctkCmdLineModuleManagerPrivate
{
  ctkCmdLineModuleManagerPrivate(ctkCmdLineModuleManager::ValidationMode mode, const QString& cacheDir)
    : XmlTimeOut(30000)
    , ValidationMode(mode)
  {
    QFileInfo fileInfo(cacheDir);
    if (!fileInfo.exists())
    {
      if (!QDir().mkpath(cacheDir))
      {
        qWarning() << "Command line module cache disabled. Directory" << cacheDir << "could not be created.";
        return;
      }
    }

    if (fileInfo.isWritable())
    {
      ModuleCache.reset(new ctkCmdLineModuleCache(cacheDir));
    }
    else
    {
      qWarning() << "Command line module cache disabled. Directory" << cacheDir << "is not writable.";
    }
  }

  void checkBackends_unlocked(const QUrl& location)
  {
    if (!this->SchemeToBackend.contains(location.scheme()))
    {
      throw ctkInvalidArgumentException(QString("No suitable backend registered for module at ") + location.toString());
    }
  }

  QMutex Mutex;
  QHash<QString, ctkCmdLineModuleBackend*> SchemeToBackend;
  QHash<QUrl, ctkCmdLineModuleReference> LocationToRef;
  QScopedPointer<ctkCmdLineModuleCache> ModuleCache;
  int XmlTimeOut;

  ctkCmdLineModuleManager::ValidationMode ValidationMode;
};

//----------------------------------------------------------------------------
ctkCmdLineModuleManager::ctkCmdLineModuleManager(ValidationMode validationMode, const QString& cacheDir)
  : d(new ctkCmdLineModuleManagerPrivate(validationMode, cacheDir))
{
}

//----------------------------------------------------------------------------
ctkCmdLineModuleManager::~ctkCmdLineModuleManager()
{
}

//----------------------------------------------------------------------------
ctkCmdLineModuleManager::ValidationMode ctkCmdLineModuleManager::validationMode() const
{
  return d->ValidationMode;
}


//----------------------------------------------------------------------------
void ctkCmdLineModuleManager::setValidationMode(const ValidationMode& mode)
{
  d->ValidationMode = mode;
}


//----------------------------------------------------------------------------
void ctkCmdLineModuleManager::setTimeOutForXMLRetrieval(int xmlTimeout)
{
  d->XmlTimeOut = xmlTimeout;
}

//----------------------------------------------------------------------------
int ctkCmdLineModuleManager::timeOutForXMLRetrieval() const
{
  return d->XmlTimeOut;
}

//----------------------------------------------------------------------------
void ctkCmdLineModuleManager::registerBackend(ctkCmdLineModuleBackend *backend)
{
  QMutexLocker lock(&d->Mutex);

  QList<QString> supportedSchemes = backend->schemes();

  // Check if there is already a backend registerd for any of the
  // supported schemes. We only supported one backend per scheme.
  foreach (QString scheme, supportedSchemes)
  {
    if (d->SchemeToBackend.contains(scheme))
    {
      throw ctkInvalidArgumentException(QString("A backend for scheme %1 is already registered.").arg(scheme));
    }
  }

  // All good
  foreach (QString scheme, supportedSchemes)
  {
    d->SchemeToBackend[scheme] = backend;
  }
}

//----------------------------------------------------------------------------
ctkCmdLineModuleBackend*ctkCmdLineModuleManager::backend(const QString& scheme) const
{
  QHash<QString, ctkCmdLineModuleBackend*>::ConstIterator iter =
      d->SchemeToBackend.find(scheme);
  return iter == d->SchemeToBackend.end() ? NULL : iter.value();
}

//----------------------------------------------------------------------------
QList<ctkCmdLineModuleBackend*> ctkCmdLineModuleManager::backends() const
{
  QList<ctkCmdLineModuleBackend*> result = d->SchemeToBackend.values();
  qSort(result);
  result.erase(std::unique(result.begin(), result.end()), result.end());
  return result;
}

//----------------------------------------------------------------------------
ctkCmdLineModuleReference
ctkCmdLineModuleManager::registerModule(const QUrl &location)
{
  QByteArray xml;
  ctkCmdLineModuleBackend* backend = NULL;
  {
    QMutexLocker lock(&d->Mutex);

    d->checkBackends_unlocked(location);

    // If the module is already registered, just return the reference
    if (d->LocationToRef.contains(location))
    {
      return d->LocationToRef[location];
    }

    backend = d->SchemeToBackend[location.scheme()];
  }

  bool fromCache = false;
  qint64 newTimeStamp = 0;
  qint64 cacheTimeStamp = 0;
  int timeout = backend->timeOutForXmlRetrieval();
  if (timeout == 0)
  {
    timeout = d->XmlTimeOut;
  }

  if (d->ModuleCache)
  {
    newTimeStamp = backend->timeStamp(location);
    cacheTimeStamp = d->ModuleCache->timeStamp(location);
    if (cacheTimeStamp < 0                // i.e. timestamp is invalid
        || cacheTimeStamp < newTimeStamp) // i.e. timestamp is genuinely out of date
    {
      // newly fetch the XML description
      try
      {
        xml = backend->rawXmlDescription(location, timeout);
      }
      catch (const ctkCmdLineModuleTimeoutException&)
      {
        // in case of a time-out, do not cache it as a failed attempt
        // by recording an empty QByteArray in the cache
        throw;
      }
      catch (...)
      {
        // cache the failed attempt
        d->ModuleCache->cacheXmlDescription(location, newTimeStamp, QByteArray());
        throw;
      }
    }
    else
    {
      // use the cached XML description
      xml = d->ModuleCache->rawXmlDescription(location);
      fromCache = true;
    }
  }
  else
  {
    try
    {
      xml = backend->rawXmlDescription(location, timeout);
    }
    catch (const ctkCmdLineModuleRunException& e)
    {
      qDebug() << "Extracting XML from " << e.location().toString() << " failed with errorCode " << e.errorCode() << " and return string " << e.errorString();
      throw;
    }
    catch (const ctkException& e)
    {
      qDebug() << e.what();
      throw;
    }
  }

  if (xml.isEmpty())
  {
    if (!fromCache && d->ModuleCache)
    {
      d->ModuleCache->cacheXmlDescription(location, newTimeStamp, QByteArray());
    }
    throw ctkInvalidArgumentException(QString("No XML output available from ") + location.toString());
  }

  ctkCmdLineModuleReference ref;
  ref.d->Location = location;
  ref.d->RawXmlDescription = xml;
  ref.d->Backend = backend;

  if (d->ValidationMode != SKIP_VALIDATION)
  {
    // validate the outputted xml description
    QBuffer input(&xml);
    input.open(QIODevice::ReadOnly);

    ctkCmdLineModuleXmlValidator validator(&input);
    if (!validator.validateInput())
    {
      if (d->ModuleCache)
      {
        // validation failed, cache the description anyway
        d->ModuleCache->cacheXmlDescription(location, newTimeStamp, xml);
      }

      if (d->ValidationMode == STRICT_VALIDATION)
      {
        throw ctkInvalidArgumentException(QString("Validating module at %1 failed: %2")
                                          .arg(location.toString()).arg(validator.errorString()));
      }
      else
      {
        ref.d->XmlValidationErrorString = validator.errorString();
      }
    }
    else
    {
      if (d->ModuleCache && newTimeStamp > 0 && !fromCache)
      {
        // successfully validated the xml, cache it
        d->ModuleCache->cacheXmlDescription(location, newTimeStamp, xml);
      }
    }
  }
  else
  {
    if (!fromCache && d->ModuleCache)
    {
      // cache it
      d->ModuleCache->cacheXmlDescription(location, newTimeStamp, xml);
    }
  }

  {
    QMutexLocker lock(&d->Mutex);
    // Check that we don't have a race condition
    if (d->LocationToRef.contains(location))
    {
      // Another thread registered a module with the same location
      return d->LocationToRef[location];
    }
    d->LocationToRef[location] = ref;
  }

  emit moduleRegistered(ref);
  return ref;
}

//----------------------------------------------------------------------------
void ctkCmdLineModuleManager::unregisterModule(const ctkCmdLineModuleReference& ref)
{
  if (!ref) return;

  {
    QMutexLocker lock(&d->Mutex);
    if (!d->LocationToRef.contains(ref.location()))
    {
      return;
    }
    d->LocationToRef.remove(ref.location());
    if (d->ModuleCache)
    {
      d->ModuleCache->removeCacheEntry(ref.location());
    }
  }
  emit moduleUnregistered(ref);
}


//----------------------------------------------------------------------------
void ctkCmdLineModuleManager::clearCache()
{
  d->ModuleCache->clearCache();
}


//----------------------------------------------------------------------------
ctkCmdLineModuleReference ctkCmdLineModuleManager::moduleReference(const QUrl &location) const
{
  QMutexLocker lock(&d->Mutex);
  QHash<QUrl, ctkCmdLineModuleReference>::const_iterator iter = d->LocationToRef.find(location);
  return (iter == d->LocationToRef.end()) ? ctkCmdLineModuleReference() : iter.value();
}

//----------------------------------------------------------------------------
QList<ctkCmdLineModuleReference> ctkCmdLineModuleManager::moduleReferences() const
{
  QMutexLocker lock(&d->Mutex);
  return d->LocationToRef.values();
}

//----------------------------------------------------------------------------
ctkCmdLineModuleFuture ctkCmdLineModuleManager::run(ctkCmdLineModuleFrontend *frontend)
{
  QMutexLocker lock(&d->Mutex);
  d->checkBackends_unlocked(frontend->location());

  ctkCmdLineModuleFuture future = d->SchemeToBackend[frontend->location().scheme()]->run(frontend);
  frontend->setFuture(future);
  emit frontend->started();
  return future;
}