/**
 * Orthanc - A Lightweight, RESTful DICOM Store
 * Copyright (C) 2012-2016 Sebastien Jodogne, Medical Physics
 * Department, University Hospital of Liege, Belgium
 * Copyright (C) 2017-2023 Osimis S.A., Belgium
 * Copyright (C) 2024-2026 Orthanc Team SRL, Belgium
 * Copyright (C) 2021-2026 Sebastien Jodogne, ICTEAM UCLouvain, Belgium
 *
 * This program is free software: you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 **/


#include "../PrecompiledHeadersServer.h"
#include "ResourceModificationJob.h"

#include "../../../OrthancFramework/Sources/DicomParsing/IDicomTranscoder.h"
#include "../../../OrthancFramework/Sources/Logging.h"
#include "../../../OrthancFramework/Sources/SerializationToolbox.h"
#include "../DicomInstanceToStore.h"
#include "../ServerContext.h"
#include "../ServerTranscoder.h"

#include <dcmtk/dcmdata/dcfilefo.h>
#include <dcmtk/dcmdata/dcdeftag.h>
#include <cassert>

namespace Orthanc
{
  static void FormatResource(Json::Value& target,
                             ResourceType level,
                             const std::string& id)
  {
    target["Type"] = EnumerationToString(level);
    target["ID"] = id;
    target["Path"] = GetBasePath(level, id);
  }
  
  class ResourceModificationJob::SingleOutput : public IOutput
  {
  private:
    ResourceType  level_;
    bool          isFirst_;
    std::string   id_;
    std::string   patientId_;

  public:
    explicit SingleOutput(ResourceType level) :
      level_(level),
      isFirst_(true)
    {
      if (level_ != ResourceType_Patient &&
          level_ != ResourceType_Study &&
          level_ != ResourceType_Series)
      {
        throw OrthancException(ErrorCode_ParameterOutOfRange);
      }            
    }

    virtual void Update(DicomInstanceHasher& hasher) ORTHANC_OVERRIDE
    {
      if (isFirst_)
      {
        switch (level_)
        {
          case ResourceType_Series:
            id_ = hasher.HashSeries();
            break;

          case ResourceType_Study:
            id_ = hasher.HashStudy();
            break;

          case ResourceType_Patient:
            id_ = hasher.HashPatient();
            break;

          default:
            THROW_WITH_FILE_AND_LINE_INFO(ErrorCode_InternalError);
        }

        patientId_ = hasher.HashPatient();
        isFirst_ = false;
      }
    }

    virtual void Format(Json::Value& target) const ORTHANC_OVERRIDE
    {
      assert(target.type() == Json::objectValue);

      if (!isFirst_)
      {
        FormatResource(target, level_, id_);
        target["PatientID"] = patientId_;
      }
    }

    virtual bool IsSingleResource() const ORTHANC_OVERRIDE
    {
      return true;
    }

    ResourceType GetLevel() const
    {
      return level_;
    }
  };
    

  class ResourceModificationJob::MultipleOutputs : public IOutput
  {
  private:
    static void FormatResources(Json::Value& target,
                                ResourceType level,
                                const std::set<std::string>& resources)
    {
      assert(target.type() == Json::arrayValue);

      for (std::set<std::string>::const_iterator
             it = resources.begin(); it != resources.end(); ++it)
      {
        Json::Value item = Json::objectValue;
        FormatResource(item, level, *it);
        target.append(item);        
      }
    }
    
    std::set<std::string>  instances_;
    std::set<std::string>  series_;
    std::set<std::string>  studies_;
    std::set<std::string>  patients_;

  public:
    virtual void Update(DicomInstanceHasher& hasher) ORTHANC_OVERRIDE
    {
      instances_.insert(hasher.HashInstance());
      series_.insert(hasher.HashSeries());
      studies_.insert(hasher.HashStudy());
      patients_.insert(hasher.HashPatient());
    }

    virtual void Format(Json::Value& target) const ORTHANC_OVERRIDE
    {
      assert(target.type() == Json::objectValue);
      Json::Value resources = Json::arrayValue;
      FormatResources(resources, ResourceType_Instance, instances_);
      FormatResources(resources, ResourceType_Series, series_);
      FormatResources(resources, ResourceType_Study, studies_);
      FormatResources(resources, ResourceType_Patient, patients_);
      target["Resources"] = resources;
    }

    virtual bool IsSingleResource() const ORTHANC_OVERRIDE
    {
      return false;
    }
  };

  // Reset is called when resubmitting a failed job
  void ResourceModificationJob::Reset()
  {
    boost::recursive_mutex::scoped_lock lock(mutex_);

    // TODO: cleanup the instances that have been generated during the previous run
    modifiedSeries_.clear();
    instancesToReconstruct_.clear();

    ThreadedSetOfInstancesJob::Reset();
  }

  void ResourceModificationJob::PostProcessInstances()
  {
    boost::recursive_mutex::scoped_lock lock(mutex_);

    // reconstruct the parents MainDicomTags in case one of them has changed
    if (instancesToReconstruct_.size() > 0)
    {
      for (std::set<std::string>::const_iterator it = instancesToReconstruct_.begin(); it != instancesToReconstruct_.end(); ++it)
      {
        std::unique_ptr<DicomDataSource::Dicom> dicom(GetContext().ReadParsedDicom(*it));
        DicomDataSource::Dicom::Lock dicomLock(*dicom);

        const ParsedDicomFile& modifiedDicom = dicomLock.GetContent();

        GetContext().GetIndex().ReconstructInstance(modifiedDicom, false, ResourceType_Instance /* dummy */);
      }
    }
    
  }

  bool ResourceModificationJob::HandleInstance(const std::string& instance)
  {
    if (modification_.get() == NULL ||
        output_.get() == NULL)
    {
      throw OrthancException(ErrorCode_BadSequenceOfCalls,
                             "No modification was provided for this job");
    }

      
    LOG(INFO) << "Modifying instance in a job: " << instance;

    /**
     * Retrieve the original instance from the DICOM cache.
     **/
    
    std::unique_ptr<DicomInstanceHasher> originalHasher;
    std::unique_ptr<ParsedDicomFile> modified;
    std::set<std::string> instanceLabels;
    std::set<std::string> seriesLabels;
    std::set<std::string> studyLabels;
    std::set<std::string> patientLabels;
 
    try
    {
      std::unique_ptr<DicomDataSource::Dicom> dicom(GetContext().ReadParsedDicom(instance));
      DicomDataSource::Dicom::Lock lock(*dicom);

      const ParsedDicomFile& original = lock.GetContent();

      originalHasher.reset(new DicomInstanceHasher(original.GetHasher()));
      modified.reset(original.Clone(true));
    }
    catch (OrthancException& e)
    {
      LOG(WARNING) << "An error occurred while executing a Modification job on instance " << instance << ": " << e.GetDetails();
      throw;
    }


    /**
     * Compute the resulting DICOM instance.
     **/

    {
      boost::recursive_mutex::scoped_lock lock(mutex_);  // DicomModification object is not thread safe, we must protect it from here

      modification_->Apply(modified);

      if (modification_->AreLabelsKept())
      {
        GetContext().GetIndex().ListLabels(instanceLabels, instance, ResourceType_Instance);
        // we must also save the parent labels.  This instance might currently be the only one in the hierarchy and therefore it might be in charge of restoring all labels of the hierarchy
        GetContext().GetIndex().ListLabels(seriesLabels, originalHasher->HashSeries(), ResourceType_Series);
        GetContext().GetIndex().ListLabels(studyLabels, originalHasher->HashStudy(), ResourceType_Study);
        GetContext().GetIndex().ListLabels(patientLabels, originalHasher->HashPatient(), ResourceType_Patient);
      }
    }

    const std::string modifiedUid = IDicomTranscoder::GetSopInstanceUid(modified->GetDcmtkObject());
    
    if (transcode_)
    {
      std::set<DicomTransferSyntax> syntaxes;
      syntaxes.insert(transferSyntax_);

      IDicomTranscoder::DicomImage source;
      source.AcquireParsed(*modified);  // "modified" is invalid below this point
      
      IDicomTranscoder::DicomImage transcoded;
      if (GetContext().GetTranscoder()->Transcode(transcoded, source, syntaxes, TranscodingSopInstanceUidMode_AllowNew))
      {
        modified.reset(transcoded.ReleaseAsParsedDicomFile());

        // Fix the SOP instance UID in order the preserve the
        // references between instance UIDs in the DICOM hierarchy
        // (the UID might have changed in the case of lossy transcoding)
        if (modified.get() == NULL ||
            modified->GetDcmtkObject().getDataset() == NULL ||
            !modified->GetDcmtkObject().getDataset()->putAndInsertString(
              DCM_SOPInstanceUID, modifiedUid.c_str(), OFTrue /* replace */).good())
        {
          THROW_WITH_FILE_AND_LINE_INFO(ErrorCode_InternalError);
        }
      }
      else
      {
        LOG(WARNING) << "Cannot transcode instance, keeping original transfer syntax: " << instance;
        modified.reset(source.ReleaseAsParsedDicomFile());
      }
    }

    assert(modifiedUid == IDicomTranscoder::GetSopInstanceUid(modified->GetDcmtkObject()));

    std::unique_ptr<DicomInstanceToStore> toStore(DicomInstanceToStore::CreateFromParsedDicomFile(*modified));
    toStore->SetOrigin(origin_);
    toStore->SetSkipIngestTranscoding(transcode_); // do not apply IngestTranscoding if you have forced the transfer syntax during the modification/anonymization


    /**
     * Prepare the metadata information to associate with the
     * resulting DICOM instance (AnonymizedFrom/ModifiedFrom).
     **/

    DicomInstanceHasher modifiedHasher = modified->GetHasher();
      
    MetadataType metadataType = (isAnonymization_ ?
                                 MetadataType_AnonymizedFrom :
                                 MetadataType_ModifiedFrom);

    if (originalHasher->HashSeries() != modifiedHasher.HashSeries())
    {
      toStore->AddMetadata(ResourceType_Series, metadataType, originalHasher->HashSeries());
    }

    if (originalHasher->HashStudy() != modifiedHasher.HashStudy())
    {
      toStore->AddMetadata(ResourceType_Study, metadataType, originalHasher->HashStudy());
    }

    if (originalHasher->HashPatient() != modifiedHasher.HashPatient())
    {
      toStore->AddMetadata(ResourceType_Patient, metadataType, originalHasher->HashPatient());
    }

    assert(instance == originalHasher->HashInstance());
    toStore->AddMetadata(ResourceType_Instance, metadataType, instance);


    /**
     * Store the resulting DICOM instance into the Orthanc store.
     **/

    std::string modifiedInstance;
    ServerContext::StoreResult result = GetContext().Store(modifiedInstance, *toStore);
    if (result.GetStatus() != StoreStatus_Success && result.GetStatus() != StoreStatus_AlreadyStored) // when retrying a job, we might save the same data again
    {
      throw OrthancException(ErrorCode_CannotStoreInstance,
                             "Error while storing a modified instance " + instance);
    }

    {
      boost::recursive_mutex::scoped_lock lock(mutex_);  // DicomModification object is not thread safe, we must protect it from here

      if (modification_->AreLabelsKept())
      {
        GetContext().GetIndex().AddLabels(instance, ResourceType_Instance, instanceLabels);
        GetContext().GetIndex().AddLabels(modifiedHasher.HashSeries(), ResourceType_Series, seriesLabels);
        GetContext().GetIndex().AddLabels(modifiedHasher.HashStudy(), ResourceType_Study, studyLabels);
        GetContext().GetIndex().AddLabels(modifiedHasher.HashPatient(), ResourceType_Patient, patientLabels);
      }
    }


    /**
     * The assertion below will fail if automated transcoding to a
     * lossy transfer syntax is enabled in the Orthanc core, and if
     * the source instance is not in this transfer syntax.
     **/
    // assert(modifiedInstance == modifiedHasher.HashInstance());

    {
      boost::recursive_mutex::scoped_lock lock(outputMutex_);

      output_->Update(modifiedHasher);
      if (modifiedSeries_.find(modifiedHasher.HashSeries()) == modifiedSeries_.end())
      {
        modifiedSeries_.insert(modifiedHasher.HashSeries());
        // add an instance to reconstruct for each series
        instancesToReconstruct_.insert(modifiedHasher.HashInstance());
      }
      
    }

    return true;
  }


  ResourceModificationJob::ResourceModificationJob(ServerContext& context, unsigned int workersCount) :
    ThreadedSetOfInstancesJob(context, true /* post processing step */, true /* by default, keep source */, workersCount),
    isAnonymization_(false),
    transcode_(false),
    transferSyntax_(DicomTransferSyntax_LittleEndianExplicit)  // dummy initialization
  {
  }


  void ResourceModificationJob::SetSingleResourceModification(DicomModification* modification,
                                                              ResourceType outputLevel,
                                                              bool isAnonymization)
  {
    if (modification == NULL)
    {
      throw OrthancException(ErrorCode_NullPointer);
    }
    else if (IsStarted())
    {
      throw OrthancException(ErrorCode_BadSequenceOfCalls);
    }
    else
    {
      modification_.reset(modification);
      output_.reset(new SingleOutput(outputLevel));
      isAnonymization_ = isAnonymization;
    }
  }


  void ResourceModificationJob::SetMultipleResourcesModification(DicomModification* modification,
                                                                 bool isAnonymization)
  {
    if (modification == NULL)
    {
      throw OrthancException(ErrorCode_NullPointer);
    }
    else if (IsStarted())
    {
      throw OrthancException(ErrorCode_BadSequenceOfCalls);
    }
    else
    {
      modification_.reset(modification);
      output_.reset(new MultipleOutputs);
      isAnonymization_ = isAnonymization;
    }
  }


  void ResourceModificationJob::SetOrigin(const DicomInstanceOrigin& origin)
  {
    if (IsStarted())
    {
      throw OrthancException(ErrorCode_BadSequenceOfCalls);
    }
    else
    {
      origin_ = origin;
    }
  }

  
  void ResourceModificationJob::SetOrigin(const RestApiCall& call)
  {
    SetOrigin(DicomInstanceOrigin::FromRest(call));
  }


#if ORTHANC_BUILD_UNIT_TESTS == 1
  const DicomModification& ResourceModificationJob::GetModification() const
  {
    if (modification_.get() == NULL)
    {
      throw OrthancException(ErrorCode_BadSequenceOfCalls);
    }
    else
    {
      return *modification_;
    }
  }
#endif

  DicomTransferSyntax ResourceModificationJob::GetTransferSyntax() const
  {
    if (transcode_)
    {
      return transferSyntax_;
    }
    else
    {
      throw OrthancException(ErrorCode_BadSequenceOfCalls);
    }
  }
  

  void ResourceModificationJob::SetTranscode(DicomTransferSyntax syntax)
  {
    if (IsStarted())
    {
      throw OrthancException(ErrorCode_BadSequenceOfCalls);
    }
    else
    {
      transcode_ = true;
      transferSyntax_ = syntax;
    }    
  }


  void ResourceModificationJob::SetTranscode(const std::string& transferSyntaxUid)
  {
    DicomTransferSyntax s;
    if (LookupTransferSyntax(s, transferSyntaxUid))
    {
      SetTranscode(s);
    }
    else
    {
      throw OrthancException(ErrorCode_BadFileFormat,
                             "Unknown transfer syntax UID: " + transferSyntaxUid);
    }
  }


  void ResourceModificationJob::ClearTranscode()
  {
    if (IsStarted())
    {
      throw OrthancException(ErrorCode_BadSequenceOfCalls);
    }
    else
    {
      transcode_ = false;
    }
  }


  bool ResourceModificationJob::IsSingleResourceModification() const
  {
    if (modification_.get() == NULL)
    {
      assert(output_.get() == NULL);
      throw OrthancException(ErrorCode_BadSequenceOfCalls);
    }
    else
    {
      boost::recursive_mutex::scoped_lock lock(outputMutex_);

      assert(output_.get() != NULL);
      return output_->IsSingleResource();
    }
  }
  

  ResourceType ResourceModificationJob::GetOutputLevel() const
  {
    boost::recursive_mutex::scoped_lock lock(outputMutex_);

    if (IsSingleResourceModification())
    {
      assert(modification_.get() != NULL &&
             output_.get() != NULL);
      return dynamic_cast<const SingleOutput&>(*output_).GetLevel();
    }
    else
    {
      // Not applicable if multiple resources
      throw OrthancException(ErrorCode_BadSequenceOfCalls);
    }
  }


  void ResourceModificationJob::GetPublicContent(Json::Value& value) const
  {
    boost::recursive_mutex::scoped_lock lock(outputMutex_);

    ThreadedSetOfInstancesJob::GetPublicContent(value);

    value["IsAnonymization"] = isAnonymization_;

    if (output_.get() != NULL)
    {
      output_->Format(value);
    }

    if (transcode_)
    {
      value["Transcode"] = GetTransferSyntaxUid(transferSyntax_);
    }
  }


  static const char* MODIFICATION = "Modification";
  static const char* ORIGIN = "Origin";
  static const char* IS_ANONYMIZATION = "IsAnonymization";
  static const char* TRANSCODE = "Transcode";
  static const char* OUTPUT_LEVEL = "OutputLevel";
  static const char* IS_SINGLE_RESOURCE = "IsSingleResource";
  

  ResourceModificationJob::ResourceModificationJob(ServerContext& context,
                                                   const Json::Value& serialized) :
    ThreadedSetOfInstancesJob(context, serialized, false /* no post processing step */, true /* by default, keep source */),
    transferSyntax_(DicomTransferSyntax_LittleEndianExplicit)  // dummy initialization
  {
    assert(serialized.type() == Json::objectValue);

    origin_ = DicomInstanceOrigin(serialized[ORIGIN]);

    if (serialized.isMember(TRANSCODE))
    {
      SetTranscode(SerializationToolbox::ReadString(serialized, TRANSCODE));
    }
    else
    {
      transcode_ = false;
    }

    bool isSingleResource;
    if (serialized.isMember(IS_SINGLE_RESOURCE))
    {
      isSingleResource = SerializationToolbox::ReadBoolean(serialized, IS_SINGLE_RESOURCE);
    }
    else
    {
      isSingleResource = true;  // Backward compatibility with Orthanc <= 1.9.3
    }

    bool isAnonymization = SerializationToolbox::ReadBoolean(serialized, IS_ANONYMIZATION);
    std::unique_ptr<DicomModification> modification(new DicomModification(serialized[MODIFICATION]));

    if (isSingleResource)
    {
      ResourceType outputLevel;
      
      if (serialized.isMember(OUTPUT_LEVEL))
      {
        // New in Orthanc 1.9.4. This fixes an *incorrect* behavior in
        // Orthanc <= 1.9.3, in which "outputLevel" would be set to
        // "modification->GetLevel()"
        outputLevel = StringToResourceType(SerializationToolbox::ReadString(serialized, OUTPUT_LEVEL).c_str());
      }
      else
      {
        // Use the buggy convention from Orthanc <= 1.9.3 (which is
        // the only thing we have at hand)
        outputLevel = modification->GetLevel();

        if (outputLevel == ResourceType_Instance)
        {
          // This should never happen, but as "SingleOutput" doesn't
          // support instance-level anonymization, don't take any risk
          // and choose an arbitrary output level
          outputLevel = ResourceType_Patient;
        }
      }
      
      SetSingleResourceModification(modification.release(), outputLevel, isAnonymization);
    }
    else
    {
      // New in Orthanc 1.9.4
      SetMultipleResourcesModification(modification.release(), isAnonymization);
    }
  }
  
  bool ResourceModificationJob::Serialize(Json::Value& value) const
  {
    if (modification_.get() == NULL)
    {
      throw OrthancException(ErrorCode_BadSequenceOfCalls);
    }
    else if (!ThreadedSetOfInstancesJob::Serialize(value))
    {
      return false;
    }
    else
    {
      assert(value.type() == Json::objectValue);
      
      value[IS_ANONYMIZATION] = isAnonymization_;

      if (transcode_)
      {
        value[TRANSCODE] = GetTransferSyntaxUid(transferSyntax_);
      }

      origin_.Serialize(value[ORIGIN]);
      
      Json::Value tmp;

      {
        boost::recursive_mutex::scoped_lock lock(mutex_);  // DicomModification object is not thread safe, we must protect it from here
  
        modification_->Serialize(tmp);
      }

      value[MODIFICATION] = tmp;

      // New in Orthanc 1.9.4
      value[IS_SINGLE_RESOURCE] = IsSingleResourceModification();
      if (IsSingleResourceModification())
      {
        value[OUTPUT_LEVEL] = EnumerationToString(GetOutputLevel());
      }
      
      return true;
    }
  }

  void ResourceModificationJob::PerformSanityChecks()
  {
    boost::recursive_mutex::scoped_lock lock(mutex_);  // because we access the parentResources_

    if (modification_.get() == NULL)
    {
      throw OrthancException(ErrorCode_BadSequenceOfCalls);
    }

    bool replacePatientMainDicomTags = false;

    ResourceType modificationLevel = modification_->GetLevel();
    std::set<DicomTag> replacedTags;
    modification_->GetReplacedTags(replacedTags);

    for (std::set<DicomTag>::const_iterator it = replacedTags.begin(); it != replacedTags.end(); ++it)
    {
      replacePatientMainDicomTags |= DicomMap::IsMainDicomTag(*it, ResourceType_Patient);
    }

    if ((modificationLevel == ResourceType_Study ||
         modificationLevel == ResourceType_Patient) &&
        !modification_->IsReplaced(DICOM_TAG_PATIENT_ID) &&
        modification_->IsKept(DICOM_TAG_STUDY_INSTANCE_UID) &&
        modification_->IsKept(DICOM_TAG_SERIES_INSTANCE_UID) &&
        modification_->IsKept(DICOM_TAG_SOP_INSTANCE_UID))
    {
      // if we keep the SOPInstanceUID, it very likely means that we are modifying existing resources 'in place'

      // we must make sure we do not delete them at the end of the job
      if (!IsKeepSource()) // note: we can refine this criteria -> this is valid only if all DicomUIDs are kept identical (but this can happen through Keep or Replace options)
      {
        throw OrthancException(ErrorCode_BadRequest,
                              "When keeping StudyInstanceUID, SeriesInstanceUID and SOPInstanceUID tag, you must set KeepSource to true to avoid deleting the modified files at the end of the process");
      }

      // and we must make sure that we overwite them with the modified resources
      if (!GetContext().IsOverwriteInstances())
      {
        throw OrthancException(ErrorCode_BadRequest,
                              "When keeping StudyInstanceUID, SeriesInstanceUID and SOPInstanceUID tag, you must have the 'OverwriteInstances' Orthanc configuration set to true in order to replace the modified resources");
      }
    }

    if (GetContext().IsPatientLevelEnabled() && modificationLevel == ResourceType_Study && replacePatientMainDicomTags)
    {
      for (std::map<std::string, ResourceType>::const_iterator it = parentResources_.begin(); it != parentResources_.end(); ++it)
      {
        // When modifying a study, you may not modify patient tags as you wish.
        // - If this is the patient's only study, you may modify all patient tags. This could be performed in 2 steps (modify the patient and then, the study) but, 
        //   for many use cases, it's helpful to be able to do it one step (e.g, to modify a name in a study that has just been acquired)
        // - If the patient already has other studies, you may only 'attach' the study to an existing patient by modifying 
        //   all patient tags from the study to match those of the target patient.
        // - Otherwise, you can't modify the patient tags
        const std::string& studyId = it->first;
        
        std::string targetPatientId;
        if (modification_->IsReplaced(DICOM_TAG_PATIENT_ID))
        {
          targetPatientId = modification_->GetReplacementAsString(DICOM_TAG_PATIENT_ID);
        }
        else
        {
          FindRequest request(ResourceType_Study);
          request.SetOrthancStudyId(studyId);
          request.SetRetrieveMainDicomTags(true);

          FindResponse response;
          GetContext().GetIndex().ExecuteFind(response, request);

          if (response.GetSize() == 1)
          {
            DicomMap tags;
            response.GetResourceByIndex(0).GetMainDicomTags(tags, ResourceType_Study);
            targetPatientId = tags.GetStringValue(DICOM_TAG_PATIENT_ID, "", false);
          }
          else
          {
            throw OrthancException(ErrorCode_UnknownResource, "Study not found");
          }
        }

        // try to find the targetPatient
        std::vector<std::string> lookupPatientResult;
        GetContext().GetIndex().LookupIdentifierExact(lookupPatientResult, ResourceType_Patient, DICOM_TAG_PATIENT_ID, targetPatientId);

        // if the patient exists, check how many child studies it has.
        if (lookupPatientResult.size() >= 1)
        {
          FindRequest request(ResourceType_Patient);
          request.SetOrthancPatientId(lookupPatientResult[0]);
          request.SetRetrieveMainDicomTags(true);
          request.GetChildrenSpecification(ResourceType_Study).SetRetrieveIdentifiers(true);

          FindResponse response;
          GetContext().GetIndex().ExecuteFind(response, request);

          if (response.GetSize() == 1)
          {
            const FindResponse::Resource& targetPatient = response.GetResourceByIndex(0);

            const std::set<std::string>& childrenIds = targetPatient.GetChildrenIdentifiers(ResourceType_Study);

            bool targetPatientHasOtherStudies = childrenIds.size() > 1;
            if (childrenIds.size() == 1)
            {
              targetPatientHasOtherStudies = (childrenIds.find(studyId) == childrenIds.end());  // if the patient has one study that is not the one being modified
            }

            if (targetPatientHasOtherStudies)
            {
              DicomMap mainDicomTags;
              targetPatient.GetMainDicomTags(mainDicomTags, ResourceType_Patient);

              // this is allowed if all patient replacedTags do match the target patient tags
              DicomMap targetPatientTags;
              mainDicomTags.ExtractPatientInformation(targetPatientTags);

              std::set<DicomTag> mainPatientTags;
              DicomMap::GetMainDicomTags(mainPatientTags, ResourceType_Patient);
              
              for (std::set<DicomTag>::const_iterator mainPatientTag = mainPatientTags.begin();
                   mainPatientTag != mainPatientTags.end(); ++mainPatientTag)
              {
                // if the target patient has this tag AND
                //   if it is either missing from the Replace OR
                //   if it is in the Replace but different from the current patient tag
                if (targetPatientTags.HasTag(*mainPatientTag) &&
                    ((!modification_->IsReplaced(*mainPatientTag) && targetPatientTags.GetStringValue(*mainPatientTag, "", false).size() > 0) ||
                     (modification_->IsReplaced(*mainPatientTag) && modification_->GetReplacementAsString(*mainPatientTag) != targetPatientTags.GetStringValue(*mainPatientTag, "", false))))
                {
                  if (!modification_->IsReplaced(*mainPatientTag))
                  {
                    throw OrthancException(ErrorCode_BadRequest, std::string("Trying to change patient tags in a study.  "
                      "The Patient already exists and has other studies.  All the 'Replace' tags should match the existing patient main dicom tags "
                      "and you should specify all Patient MainDicomTags in your query.  Try using /patients/../modify instead to modify the patient. Missing tag in the 'Replace' tags: ") + mainPatientTag->Format());
                  }
                  else
                  {
                    throw OrthancException(ErrorCode_BadRequest, std::string("Trying to change patient tags in a study.  "
                      "The Patient already exists and has other studies.  All the 'Replace' tags should match the existing patient main dicom tags "
                      "and you should specify all Patient MainDicomTags in your query.  Try using /patients/../modify instead to modify the patient. Failing tag: ") + mainPatientTag->Format());
                  }
                }
                else if (!targetPatientTags.HasTag(*mainPatientTag) && modification_->IsReplaced(*mainPatientTag) )
                {
                  throw OrthancException(ErrorCode_BadRequest, std::string("Trying to change patient tags in a study.  "
                    "The Patient already exists and has other studies.  You are trying to replace a tag that is not defined yet in this patient. " 
                    "Try using /patients/../modify instead to modify the patient. Failing tag: ") + mainPatientTag->Format());
                }
              }
            }
          }
        }
      }      
    }
  }
}
