// SPDX-FileCopyrightText: Copyright (c) Kitware Inc.
// SPDX-License-Identifier: BSD-3-Clause
#include "vtkSMStateVersionController.h"

// Don't include vtkAxis. Cannot add dependency on vtkChartsCore in
// vtkPVServerManagerCore.
// #include "vtkAxis.h"
#include "vtkLogger.h"
#include "vtkMath.h"
#include "vtkNew.h"
#include "vtkObjectFactory.h"
#include "vtkPVXMLElement.h"
#include "vtkPVXMLParser.h"
#include "vtkSMPropertyHelper.h"
#include "vtkSMSession.h"
#include "vtkSMSessionProxyManager.h"
#include "vtkSelectionNode.h"
#include "vtkWeakPointer.h"

#include <algorithm>
#include <set>
#include <sstream>
#include <string>
#include <tuple>
#include <vector>
#include <vtk_pugixml.h>

using namespace pugi;
using namespace std;

namespace
{
// A helper class to keep track of "id"s used in the state file and help
// generate new unique ones.
class UniqueIdGenerator
{
  vtkTypeUInt32 LastUniqueId = 1000; // let's just start at some high number.
public:
  UniqueIdGenerator(const xml_document& document)
  {
    auto xnodes = document.select_nodes("//Proxy[@id]");
    for (const auto& xnode : xnodes)
    {
      this->LastUniqueId = std::max(
        this->LastUniqueId, static_cast<vtkTypeUInt32>(xnode.node().attribute("id").as_uint()));
    }
  }

  vtkTypeUInt32 GetNextUniqueId() { return (++this->LastUniqueId); }
};

class vtkSMVersion
{
public:
  int Major;
  int Minor;
  int Patch;

  vtkSMVersion(int major, int minor, int patch)
    : Major(major)
    , Minor(minor)
    , Patch(patch)
  {
  }

  bool operator<(const vtkSMVersion& other) const
  {
    if (this->Major == other.Major)
    {
      if (this->Minor == other.Minor)
      {
        return this->Patch < other.Patch;
      }
      else
      {
        return this->Minor < other.Minor;
      }
    }
    else
    {
      return this->Major < other.Major;
    }
  }
};

//===========================================================================
// Helper functions
//===========================================================================
void PurgeElement(const pugi::xml_node& node)
{
  node.parent().remove_child(node);
}

void PurgeElements(const pugi::xpath_node_set& elements_of_interest)
{
  for (pugi::xpath_node_set::const_iterator iter = elements_of_interest.begin();
       iter != elements_of_interest.end(); ++iter)
  {
    pugi::xml_node node = iter->node();
    PurgeElement(node);
  }
}

//===========================================================================
struct Process_4_2_to_5_1
{
  bool operator()(xml_document& document) { return RemoveCubeAxesColorLinks(document); }

  // Remove global property link state for "CubeAxesColor"
  bool RemoveCubeAxesColorLinks(xml_document& document)
  {
    pugi::xpath_node_set links =
      document.select_nodes("//GlobalPropertyLink[@property=\"CubeAxesColor\"]");
    PurgeElements(links);
    return true;
  }
};

//===========================================================================
struct Process_5_1_to_5_4
{
  bool operator()(xml_document& document) { return ScalarBarLengthToPosition2(document); }

  // Read scalar bar Position2 property and set it as the ScalarBarLength
  bool ScalarBarLengthToPosition2(xml_document& document)
  {
    pugi::xpath_node_set proxy_nodes =
      document.select_nodes("//ServerManagerState/Proxy[@group='representations' and "
                            "@type='ScalarBarWidgetRepresentation']");

    double position2[2];

    // Note: Each property is from a different ScalarBarWidgetRepresentation.
    for (pugi::xpath_node_set::const_iterator iter = proxy_nodes.begin(); iter != proxy_nodes.end();
         ++iter)
    {
      pugi::xml_node proxy_node = iter->node();
      std::string id_string(proxy_node.attribute("id").value());

      //--------------------------
      // Handle Position property
      // We don't change the Position property here as its purpose remains the
      // same (determining the lower left position of the scalar bar). However,
      // we do change the "Window Location" property from the default
      // "Lower Right" to "Any Location" so that the scalar bar will appear
      // approximately where it was. It is a new property, so we need to
      // add an XML node.
      pugi::xml_node location_node = proxy_node.append_child();
      location_node.set_name("Property");
      location_node.append_attribute("name").set_value("WindowLocation");
      location_node.append_attribute("id").set_value((id_string + ".WindowLocation").c_str());
      location_node.append_attribute("number_of_elements").set_value("1");
      pugi::xml_node element_node = location_node.append_child();
      element_node.set_name("Element");
      element_node.append_attribute("index").set_value("0");
      element_node.append_attribute("value").set_value("0");

      //--------------------------
      // Handle Position2 property
      pugi::xml_node pos2_node =
        proxy_node.find_child_by_attribute("Property", "name", "Position2");

      // Change the 'name' attribute
      pos2_node.attribute("name").set_value("ScalarBarLength");

      // Change the 'id' attribute to be safe.
      pos2_node.attribute("id").set_value((id_string + ".ScalarBarLength").c_str());

      // Should be just two Element nodes
      pugi::xml_node first_element = pos2_node.child("Element");
      position2[0] = first_element.attribute("value").as_double();
      position2[1] = first_element.next_sibling("Element").attribute("value").as_double();

      // Assume the length is the largest element and ensure its value is the
      // first Element
      double length = vtkMath::Max(position2[0], position2[1]);
      first_element.attribute("value").set_value(length);

      // Position2 had two elements, ScalarBarLength has 1, so delete the
      // second one.
      pos2_node.remove_child(first_element.next_sibling());

      // Fix up the 'id' attribute in the Domain node
      first_element.next_sibling().attribute("id").set_value(
        (id_string + ".ScalarBarLength").c_str());
    }

    return true;
  }
};

//===========================================================================
struct Process_5_4_to_5_5
{
  bool operator()(xml_document& document)
  {
    return LockScalarRange(document) && CalculatorAttributeMode(document) &&
      CGNSReaderUpdates(document) && HeadlightToAdditionalLight(document) &&
      DataBoundsInflateScaleFactor(document) && AnnotateAttributesInput(document) &&
      ClipInvert(document);
  }

  bool LockScalarRange(xml_document& document)
  {
    pugi::xpath_node_set proxy_nodes =
      document.select_nodes("//ServerManagerState/Proxy[@group='lookup_tables' and "
                            "@type='PVLookupTable']");

    for (pugi::xpath_node_set::const_iterator iter = proxy_nodes.begin(); iter != proxy_nodes.end();
         ++iter)
    {
      pugi::xml_node proxy_node = iter->node();
      std::string id_string(proxy_node.attribute("id").value());

      pugi::xml_node lock_scalar_range_node =
        proxy_node.find_child_by_attribute("Property", "name", "LockScalarRange");

      pugi::xml_node element = lock_scalar_range_node.child("Element");
      int lock_scalar_range = element.attribute("value").as_int();

      lock_scalar_range_node.attribute("name").set_value("AutomaticRescaleRangeMode");
      lock_scalar_range_node.attribute("id").set_value(
        (id_string + ".AutomaticRescaleRangeMode").c_str());
      if (lock_scalar_range)
      {
        element.attribute("value").set_value("-1");
      }
      else
      {
        element.attribute("value").set_value('0');
      }
    }

    return true;
  }

  bool AnnotateAttributesInput(xml_document& document)
  {
    pugi::xpath_node_set proxy_nodes =
      document.select_nodes("//ServerManagerState/Proxy[@group='filters' and "
                            "@type='AnnotateAttributeData']");

    for (auto iter = proxy_nodes.begin(); iter != proxy_nodes.end(); ++iter)
    {
      pugi::xml_node proxy_node = iter->node();
      pugi::xml_node association_node =
        proxy_node.find_child_by_attribute("Property", "name", "ArrayAssociation");
      pugi::xml_node arrayname_node =
        proxy_node.find_child_by_attribute("Property", "name", "ArrayName");
      if (!association_node || !arrayname_node)
      {
        continue;
      }

      pugi::xml_node newInputNode = proxy_node.append_child("Property");
      newInputNode.append_attribute("name").set_value("SelectInputArray");
      newInputNode.append_attribute("number_of_elements").set_value(5);

      pugi::xml_node childNode = newInputNode.append_child("Element");
      childNode.append_attribute("index").set_value(0);
      childNode.append_attribute("value").set_value("");

      childNode = newInputNode.append_child("Element");
      childNode.append_attribute("index").set_value(1);
      childNode.append_attribute("value").set_value("");

      childNode = newInputNode.append_child("Element");
      childNode.append_attribute("index").set_value(2);
      childNode.append_attribute("value").set_value("");

      childNode = newInputNode.append_child("Element");
      childNode.append_attribute("index").set_value(3);
      childNode.append_attribute("value").set_value(
        association_node.child("Element").attribute("value").as_int());

      childNode = newInputNode.append_child("Element");
      childNode.append_attribute("index").set_value(4);
      childNode.append_attribute("value").set_value(
        arrayname_node.child("Element").attribute("value").as_string());
    }
    return true;
  }

  bool CalculatorAttributeMode(xml_document& document)
  {
    pugi::xpath_node_set proxy_nodes =
      document.select_nodes("//ServerManagerState/Proxy[@group='filters' and "
                            "@type='Calculator']/Property[@name='AttributeMode']");

    for (auto iter = proxy_nodes.begin(); iter != proxy_nodes.end(); ++iter)
    {
      pugi::xml_node attribute_mode = iter->node();

      pugi::xml_node element = attribute_mode.child("Element");
      int attribute_mode_value = element.attribute("value").as_int();

      attribute_mode.attribute("name").set_value("AttributeType");
      element.attribute("value").set_value(attribute_mode_value - 1);

      attribute_mode.remove_child("Domain");
    }
    return true;
  }

  /**
   * Handle changes to properties on `CGNSSeriesReader`.
   * 1. `BaseStatus`, `FamilyStatus`, `LoadMesh`, and `LoadBndPatch` properties have been removed.
   * 2. a new `Blocks` property takes in block selection instead
   */
  bool CGNSReaderUpdates(xml_document& document)
  {
    pugi::xpath_node_set proxy_nodes = document.select_nodes(
      "//ServerManagerState/Proxy[@group='sources' and @type='CGNSSeriesReader']");
    for (auto xnode : proxy_nodes)
    {
      auto proxyNode = xnode.node();
      if (!proxyNode.select_nodes("//Property[@name='Blocks']").empty())
      {
        // state is already newer.
        continue;
      }

      bool loadMesh = true;
      if (!proxyNode.select_nodes("//Property[@name='LoadMesh']/Element[@index='0' and value='0']")
             .empty())
      {
        loadMesh = false;
      }

      bool loadBndPatch = false;
      if (!proxyNode
             .select_nodes("//Property[@name='LoadBndPatch']/Element[@index='0' and value='1']")
             .empty())
      {
        loadBndPatch = true;
      }

      // now collect names for selected bases and families.
      std::set<std::string> selectedPaths;
      auto xprops_set =
        proxyNode.select_nodes("//Property[@name='BaseStatus']/Element[@value='1']");
      for (auto xpropnode : xprops_set)
      {
        std::string baseName = xpropnode.node().previous_sibling().attribute("value").value();
        if (loadMesh)
        {
          std::ostringstream stream;
          stream << "/Grids/" << baseName.c_str();
          selectedPaths.insert(stream.str());
        }
        if (loadBndPatch)
        {
          std::ostringstream stream;
          stream << "/Patches/" << baseName.c_str();
          selectedPaths.insert(stream.str());
        }
      }

      xprops_set = proxyNode.select_nodes("//Property[@name='FamilyStatus']/Element[@value='1']");
      for (auto xpropnode : xprops_set)
      {
        std::string familyName = xpropnode.node().previous_sibling().attribute("value").value();
        std::ostringstream stream;
        stream << "/Families/" << familyName.c_str();
        selectedPaths.insert(stream.str());
      }

      auto blocksNode = proxyNode.append_child("Property");
      blocksNode.append_attribute("name").set_value("Blocks");
      blocksNode.append_attribute("number_of_elements")
        .set_value(static_cast<int>(selectedPaths.size() * 2));
      int index = 0;
      for (const auto& spath : selectedPaths)
      {
        auto eNode = blocksNode.append_child("Element");
        eNode.append_attribute("index").set_value(index++);
        eNode.append_attribute("value").set_value(spath.c_str());

        eNode = blocksNode.append_child("Element");
        eNode.append_attribute("index").set_value(index++);
        eNode.append_attribute("value").set_value(1);
      }
    }
    return true;
  }

  /** Translate the fixed single headlight into a configurable light with the same properties
   */
  bool HeadlightToAdditionalLight(xml_document& document)
  {
    UniqueIdGenerator generator(document);

    pugi::xpath_node_set proxy_nodes =
      document.select_nodes("//ServerManagerState/Proxy[@group='views' and @type='RenderView']");

    pugi::xml_node smstate = document.root().child("ServerManagerState");

    for (auto xnode : proxy_nodes)
    {
      auto proxyNode = xnode.node();
      std::string id_string(proxyNode.attribute("id").value());
      // Don't check for LightSwitch - it seems to find the new light's LightSwitch
      // as well as the old one in RenderView.
      if (proxyNode.select_nodes("//Property[@name='LightDiffuseColor']").empty())
      {
        // state is already newer.
        continue;
      }
      // If the property LightSwitch is on, we add a light
      auto switchNode = proxyNode.select_node("//Property[@name='LightSwitch']");
      if (switchNode.node().child("Element").attribute("value").as_int() == 1)
      {
        // add a proxy group to the SM, with one headlight, with intensity and color set
        // get the old color and intensity. Diffuse color was set by the UI.
        double diffuseR = 1, diffuseG = 1, diffuseB = 1;
        double intensity = 1;
        auto colorNode = proxyNode.select_node("//Property[@name='LightDiffuseColor']").node();
        if (colorNode)
        {
          auto colorElt = colorNode.child("Element");
          diffuseR = colorElt.attribute("value").as_double();
          colorElt = colorElt.next_sibling("Element");
          diffuseG = colorElt.attribute("value").as_double();
          colorElt = colorElt.next_sibling("Element");
          diffuseB = colorElt.attribute("value").as_double();
        }
        auto intensityNode = proxyNode.select_node("//Property[@name='LightIntensity']").node();
        if (intensityNode)
        {
          auto intensityElt = intensityNode.child("Element");
          intensity = intensityElt.attribute("value").as_double();
        }
        // Here's the full structure, we will ignore properties with default values, and domains.
        // <Proxy group="additional_lights" type="Light" id="8232" servers="21">
        //   <Property name="DiffuseColor" id="8232.DiffuseColor" number_of_elements="3">
        //     <Element index="0" value="1"/>
        //     <Element index="1" value="1"/>
        //     <Element index="2" value="1"/>
        //     <Domain name="range" id="8232.DiffuseColor.range"/>
        //   </Property>
        //   <Property name="LightIntensity" id="8232.LightIntensity" number_of_elements="1">
        //     <Element index="0" value="1"/>
        //     <Domain name="range" id="8232.LightIntensity.range"/>
        //   </Property>
        //   <Property name="LightSwitch" id="8232.LightSwitch" number_of_elements="1">
        //     <Element index="0" value="1"/>
        //     <Domain name="bool" id="8232.LightSwitch.bool"/>
        //   </Property>
        //   <Property name="LightType" id="8232.LightType" number_of_elements="1">
        //     <Element index="0" value="1"/>
        //     <Domain name="enum" id="8232.LightType.enum">
        //       <Entry value="1" text="Headlight"/>
        //       <Entry value="2" text="Camera"/>
        //       <Entry value="3" text="Scene"/>
        //       <Entry value="4" text="Ambient"/>
        //     </Domain>
        //   </Property>
        // </Proxy>
        vtkTypeUInt32 proxyId = generator.GetNextUniqueId();
        std::ostringstream stream;
        stream << "<Proxy group=\"additional_lights\" type=\"Light\" id=\"" << proxyId
               << "\" servers=\"21\" >\n";
        stream << "  <Property name=\"DiffuseColor\" id=\"" << proxyId
               << ".DiffuseColor\" number_of_elements=\"3\" >\n";
        stream << "    <Element index=\"" << 0 << "\" value=\"" << diffuseR << "\"/>\n";
        stream << "    <Element index=\"" << 1 << "\" value=\"" << diffuseG << "\"/>\n";
        stream << "    <Element index=\"" << 2 << "\" value=\"" << diffuseB << "\"/>\n";
        stream << "  </Property>\n";
        stream << "  <Property name=\"LightIntensity\" id=\"" << proxyId
               << ".LightIntensity\" number_of_elements=\"1\" >\n";
        stream << "    <Element index=\"" << 0 << "\" value=\"" << intensity << "\"/>\n";
        stream << "  </Property>\n";
        stream << "  <Property name=\"LightType\" id=\"" << proxyId
               << ".LightType\" number_of_elements=\"1\" >\n";
        stream << "    <Element index=\"" << 0 << "\" value=\"1\"/>\n";
        stream << "  </Property>\n";
        stream << "</Proxy>\n";
        // and a proxy collection to the SMS
        // <ProxyCollection name="additional_lights">
        //   <Item id="8232" name="Light1"/>
        // </ProxyCollection>
        stream << "<ProxyCollection name=\"additional_lights\" >\n";
        stream << "  <Item id=\"" << proxyId << "\" name=\"Light1\"/>\n";
        stream << "</ProxyCollection>\n";

        std::string buffer = stream.str();
        if (!smstate.append_buffer(buffer.c_str(), buffer.size()))
        {
          // vtkWarningMacro("Unable to add new light to match deprecated headlight. "
          //   "Add a light manually in the Lights Inspector.");
        }

        // add a proxy property to this view for the light
        // <Property name="AdditionalLights" id="8135.AdditionalLights" number_of_elements="1">
        //   <Proxy value="8232"/>
        // </Property>
        auto additionalLightsNode =
          proxyNode.select_node("//Property[@name='AdditionalLights']").node();
        if (!additionalLightsNode)
        {
          additionalLightsNode = proxyNode.append_child("Property");
          additionalLightsNode.append_attribute("name").set_value("AdditionalLights");
          std::ostringstream stream2;
          stream2 << id_string << ".AdditionalLights";
          additionalLightsNode.append_attribute("id").set_value(stream2.str().c_str());
        }
        additionalLightsNode.append_attribute("number_of_elements").set_value(1);
        additionalLightsNode.append_child("Proxy").append_attribute("value").set_value(proxyId);
      }
      // Remove the old fixed-light properties:
      // LightDiffuseColor, LightAmbientColor, LightSpecularColor,
      // LightIntensity, LightSwitch, LightType
      PurgeElements(proxyNode.select_nodes("//Property[@name='LightDiffuseColor' "
                                           "or @name='LightAmbientColor' "
                                           "or @name='LightSpecularColor' "
                                           "or @name='LightIntensity' "
                                           "or @name='LightSwitch' "
                                           "or @name='LightType']"));
    }
    return true;
  }

  bool DataBoundsInflateScaleFactor(xml_document& document)
  {
    pugi::xpath_node_set proxy_nodes =
      document.select_nodes("//ServerManagerState/Proxy[@group='annotations' and "
                            "@type='GridAxes3DActor']");

    for (auto xnode : proxy_nodes)
    {
      auto proxyNode = xnode.node();
      if (proxyNode.select_nodes("//Property[@name='DataBoundsInflateFactor']").empty())
      {
        // state is already newer.
        continue;
      }

      auto prop = proxyNode.select_node("//Property[@name='DataBoundsInflateFactor']").node();
      auto valueElt = prop.child("Element");
      double inflateFactor = valueElt.attribute("value").as_double();

      prop.attribute("name").set_value("DataBoundsScaleFactor");
      valueElt.attribute("value").set_value(inflateFactor + 1);
      prop.remove_child("Domain");
    }
    return true;
  }

  bool ClipInvert(xml_document& document)
  {
    pugi::xpath_node_set proxy_nodes =
      document.select_nodes("//ServerManagerState/Proxy[@group='filters' and "
                            "@type='Clip']");
    for (auto xnode : proxy_nodes)
    {
      auto proxyNode = xnode.node();
      if (proxyNode.select_nodes("//Property[@name='InsideOut']").empty())
      {
        // state is already newer.
        continue;
      }

      auto prop = proxyNode.select_node("//Property[@name='InsideOut']").node();
      auto valueElt = prop.child("Element");
      int invert = valueElt.attribute("value").as_int();

      prop.attribute("name").set_value("Invert");
      valueElt.attribute("value").set_value(invert);
      prop.remove_child("Domain");
    }
    return true;
  }

  vtkWeakPointer<vtkSMSession> Session;
};

//===========================================================================
struct Process_5_6_to_5_7
{
  bool operator()(xml_document& document)
  {
    return ConvertResampleWithDataset(document) && ConvertIdsFilter(document) &&
      ConvertOSPRayNames(document) && ConvertBox(document) &&
      ConvertExodusLegacyBlockNamesWithElementTypes(document) && RemoveColorPropertyLinks(document);
  }

  static bool ConvertResampleWithDataset(xml_document& document)
  {
    // Change InputProperty names for the inputs to be a bit clearer.
    pugi::xpath_node_set elements = document.select_nodes(
      "//ServerManagerState/Proxy[@group='filters' and @type='ResampleWithDataset']");
    for (auto iter = elements.begin(); iter != elements.end(); ++iter)
    {
      pugi::xml_node proxy_node = iter->node();
      // Rename the Input property and change the name attribute.
      pugi::xml_node input_node = proxy_node.find_child_by_attribute("Property", "name", "Input");
      input_node.attribute("name").set_value("SourceDataArrays");

      // Rename the Source property and change the name attribute.
      pugi::xml_node source_node = proxy_node.find_child_by_attribute("Property", "name", "Source");
      source_node.attribute("name").set_value("DestinationMesh");
    }

    return true;
  }

  static bool ConvertIdsFilter(xml_document& document)
  {
    // `ArrayName` property was removed, instead replaced by `CellIdsArrayName`
    // and `PointIdsArrayName`.
    pugi::xpath_node_set elements =
      document.select_nodes("//ServerManagerState/Proxy[@group='filters' and "
                            "@type='GenerateIdScalars']/Property[@name='ArrayName']");
    for (auto iter = elements.begin(); iter != elements.end(); ++iter)
    {
      auto arrayname_node = iter->node();
      auto proxy_node = arrayname_node.parent();
      std::string id = proxy_node.attribute("id").value();

      arrayname_node.attribute("name").set_value("CellIdsArrayName");
      arrayname_node.attribute("id").set_value((id + ".CellIdsArrayName").c_str());
      proxy_node.append_copy(arrayname_node);

      arrayname_node.attribute("name").set_value("PointIdsArrayName");
      arrayname_node.attribute("id").set_value((id + ".PointIdsArrayName").c_str());
    }

    return true;
  };

  static bool ConvertOSPRayNames(xml_document& document)
  {
    // The `EnableOSPray` property for the first time got a label, which is `Enable Ray Tracing`.
    // Other OSPRay label changes appear to have no effect on the state file.
    pugi::xpath_node_set elements =
      document.select_nodes("//ServerManagerState/Proxy[@group='views' "
                            "and @type='RenderView']/Property[@name='EnableOSPRay']");
    for (auto iter = elements.begin(); iter != elements.end(); ++iter)
    {
      auto property_node = iter->node();
      auto proxy_node = property_node.parent();

      property_node.attribute("name").set_value("EnableRayTracing");
      proxy_node.append_copy(property_node);
    }

    return true;
  };

  static bool ConvertBox(xml_document& document)
  {
    pugi::xpath_node_set elements = document.select_nodes(
      "//ServerManagerState/Proxy[@group='implicit_functions' and @type='Box']");
    for (auto iter = elements.begin(); iter != elements.end(); ++iter)
    {
      pugi::xml_node proxy_node = iter->node();
      std::string id_string(proxy_node.attribute("id").value());

      // add a `UseReferenceBounds=1` property to each one.
      auto node = proxy_node.append_child("Property");
      node.append_attribute("name").set_value("UseReferenceBounds");
      node.append_attribute("id").set_value((id_string + ".UseReferenceBounds").c_str());
      node.append_attribute("number_of_elements").set_value("1");

      auto elem = node.append_child("Element");
      elem.append_attribute("index").set_value("0");
      elem.append_attribute("value").set_value("1");

      // find 'Scale' property and rename it to 'Length'
      for (auto pchild = proxy_node.child("Property"); pchild;
           pchild = pchild.next_sibling("Property"))
      {
        if (strcmp(pchild.attribute("name").as_string(), "Scale") == 0)
        {
          pchild.attribute("name").set_value("Length");
        }
      }
    }

    return true;
  }

  static bool ConvertExodusLegacyBlockNamesWithElementTypes(xml_document& document)
  {
    pugi::xpath_node_set elements =
      document.select_nodes("//ServerManagerState/Proxy[@group='sources' and "
                            "(@type='ExodusIIReader' or @type='ExodusRestartReader')]");
    for (auto iter = elements.begin(); iter != elements.end(); ++iter)
    {
      pugi::xml_node proxy_node = iter->node();
      std::string id_string(proxy_node.attribute("id").value());

      // add a `UseLegacyBlockNamesWithElementTypes=1` property to each one.
      auto node = proxy_node.append_child("Property");
      node.append_attribute("name").set_value("UseLegacyBlockNamesWithElementTypes");
      node.append_attribute("id").set_value(
        (id_string + ".UseLegacyBlockNamesWithElementTypes").c_str());
      node.append_attribute("number_of_elements").set_value("1");

      auto elem = node.append_child("Element");
      elem.append_attribute("index").set_value("0");
      elem.append_attribute("value").set_value("1");
    }

    return true;
  }

  static bool RemoveColorPropertyLinks(xml_document& document)
  {
    pugi::xpath_node_set elements =
      document.select_nodes("//ServerManagerState/Links/GlobalPropertyLink"
                            "[@property='Color']");
    PurgeElements(elements);

    return true;
  }
};

//===========================================================================
struct Process_5_7_to_5_8
{
  bool operator()(xml_document& document) { return ConvertGlobalPropertyLinks(document); }

  /*
   * With 5.8, we no longer save / load "GlobalPropertyLink" which were used to
   * save links to the global ColorPalette proxy. Update that to the new way
   * this is handled.
   */
  static bool ConvertGlobalPropertyLinks(xml_document& document)
  {
    pugi::xpath_node_set elements =
      document.select_nodes("//ServerManagerState/Links/GlobalPropertyLink");
    if (elements.empty())
    {
      return true;
    }

    auto node = document.select_node("//ServerManagerState").node();
    auto settingsNode = node.append_child("Settings");
    auto colorPaletteNode = settingsNode.append_child("SettingsProxy");
    colorPaletteNode.append_attribute("group").set_value("settings");
    colorPaletteNode.append_attribute("type").set_value("ColorPalette");
    auto linksNode = colorPaletteNode.append_child("Links");
    for (auto xnode : elements)
    {
      auto gpnode = xnode.node();
      auto pnode = linksNode.append_child("Property");
      pnode.append_attribute("source_property")
        .set_value(gpnode.attribute("global_name").as_string());
      pnode.append_attribute("target_id").set_value(gpnode.attribute("proxy").as_string());
      pnode.append_attribute("target_property").set_value(gpnode.attribute("property").as_string());
      pnode.append_attribute("unlink_if_modified").set_value(1);
    }

    ::PurgeElements(elements);
    return true;
  }
};

//===========================================================================
struct Process_5_8_to_5_9
{
  bool operator()(xml_document& document) { return WarnCGNSReader(document); }

  static bool WarnCGNSReader(xml_document& document)
  {
    pugi::xpath_node_set elements =
      document.select_nodes("//ServerManagerState/Proxy[@group='sources' and "
                            "(@type='CGNSSeriesReader')]");
    if (elements.empty())
    {
      return true;
    }

    // Unfortunately, there's no easy way to convert obsolete SIL-based
    // selection to base/family selection, so we simply warn.
    vtkGenericWarningMacro(
      "Your state file uses CGNS reader. The selection mechanism "
      "in the reader was changed in ParaView 5.9 and is not compatible with older "
      "states. As a result, the visualization may be different than with earlier versions. "
      "You may have to manually adjust properties on the the CGNS reader after loading state.");
    return true;
  }
};

//===========================================================================
struct Process_5_9_to_5_10
{
  bool operator()(xml_document& document)
  {
    return HandleSpreadsheetRepresentationCompositeDataSetIndex(document) &&
      HandleExtractBlock(document) && HandleRepresentationBlockVisibility(document) &&
      HandleRepresentationBlockColor(document) && HandleRepresentationBlockOpacity(document) &&
      HandleSelectionQuerySource(document) && ConvertProbeLine(document) &&
      HandleBackgroundColor(document) && HandleCalculatorParserType(document) &&
      ConvertThreshold(document) && HandleGradient(document);
  }

  static std::string GetSelector(unsigned int cid)
  {
    return std::string("//*[@cid='") + std::to_string(cid) + "']";
    ;
  }

  static void ConvertCompositeIdsToSelectors(pugi::xml_node& node)
  {
    for (auto child : node.children("Element"))
    {
      auto value_attribute = child.attribute("value");
      value_attribute.set_value(GetSelector(value_attribute.as_uint()).c_str());
    }
  }

  static bool HandleSpreadsheetRepresentationCompositeDataSetIndex(xml_document& document)
  {
    auto xpath_set = document.select_nodes(
      "//ServerManagerState/Proxy[@group='representations' and "
      "@type='SpreadSheetRepresentation']/Property[@name='CompositeDataSetIndex']");
    for (auto xpath_node : xpath_set)
    {
      // convert CompositeDataSetIndex to "BlockVisibilities".
      auto node = xpath_node.node();
      node.attribute("name").set_value("BlockVisibilities");
      ConvertCompositeIdsToSelectors(node);
    }

    return true;
  }

  static bool HandleExtractBlock(xml_document& document)
  {
    auto xpath_set = document.select_nodes("//ServerManagerState/Proxy[@group='filters' and "
                                           "@type='ExtractBlock']/Property[@name='BlockIndices']");
    for (auto xpath_node : xpath_set)
    {
      auto node = xpath_node.node();
      node.attribute("name").set_value("Selectors");
      ConvertCompositeIdsToSelectors(node);
    }
    return true;
  }

  static bool HandleRepresentationBlockVisibility(xml_document& document)
  {
    bool warn_about_hidden_blocks = false;
    auto xpath_set = document.select_nodes("//ServerManagerState/Proxy[@group='representations']/"
                                           "Property[@name='BlockVisibility']");
    for (auto xpath_node : xpath_set)
    {
      auto node = xpath_node.node();
      const int numElements = node.attribute("number_of_elements").as_int();
      if (numElements == 0)
      {
        // if no overrides were specified, simply remove the property.
        node.parent().remove_child(node);
        continue;
      }

      node.attribute("name").set_value("BlockSelectors");

      std::vector<std::pair<unsigned int, bool>> visibilities(numElements / 2);
      for (auto child : node.children("Element"))
      {
        const int index = child.attribute("index").as_int();
        auto& pair = visibilities.at(index / 2);
        if (index % 2 == 0)
        {
          pair.first = child.attribute("value").as_uint();
        }
        else
        {
          pair.second = (child.attribute("value").as_int() == 1);
        }
      }

      while (auto child = node.child("Element"))
      {
        node.remove_child(child);
      }

      // convert to selectors.
      int index = 0;
      for (auto& pair : visibilities)
      {
        if (pair.second)
        {
          auto child = node.append_child("Element");
          child.append_attribute("index").set_value(index++);
          child.append_attribute("value").set_value(GetSelector(pair.first).c_str());
        }
        else
        {
          warn_about_hidden_blocks = true;
        }
      }
      node.attribute("number_of_elements").set_value(index);
    }

    if (warn_about_hidden_blocks)
    {
      vtkGenericWarningMacro("The state have blocks that were hidden explicitly. "
                             "Due to changes in the way block visibilities are specified, this may "
                             "not get loaded correctly.");
    }
    return true;
  }

  static bool HandleRepresentationBlockColor(xml_document& document)
  {
    auto xpath_set = document.select_nodes("//ServerManagerState/Proxy[@group='representations']/"
                                           "Property[@name='BlockColor']");
    for (auto xpath_node : xpath_set)
    {
      std::vector<std::tuple<unsigned int, double, double, double>> colors;

      auto node = xpath_node.node();
      node.attribute("name").set_value("BlockColors");
      // not is the weird map property, so the XML is strange looking.
      for (auto element : node.children("Element"))
      {
        const unsigned int id = element.attribute("index").as_uint();
        double rgb[3];
        int index = 0;
        for (auto value : element.children("Value"))
        {
          assert(index < 3);
          rgb[index++] = value.attribute("value").as_double();
        }
        colors.emplace_back(id, rgb[0], rgb[1], rgb[2]);
      }

      while (auto child = node.child("Element"))
      {
        node.remove_child(child);
      }

      int index = 0;
      for (const auto& tuple : colors)
      {
        auto child = node.append_child("Element");
        child.append_attribute("index").set_value(index++);
        child.append_attribute("value").set_value(GetSelector(std::get<0>(tuple)).c_str());

        child = node.append_child("Element");
        child.append_attribute("index").set_value(index++);
        child.append_attribute("value").set_value(std::get<1>(tuple));

        child = node.append_child("Element");
        child.append_attribute("index").set_value(index++);
        child.append_attribute("value").set_value(std::get<2>(tuple));

        child = node.append_child("Element");
        child.append_attribute("index").set_value(index++);
        child.append_attribute("value").set_value(std::get<3>(tuple));
      }
      node.attribute("number_of_elements").set_value(index);
    }
    return true;
  }

  static bool HandleRepresentationBlockOpacity(xml_document& document)
  {
    auto xpath_set = document.select_nodes("//ServerManagerState/Proxy[@group='representations']/"
                                           "Property[@name='BlockOpacity']");
    for (auto xpath_node : xpath_set)
    {
      std::vector<std::tuple<unsigned int, double>> opacities;

      auto node = xpath_node.node();
      node.attribute("name").set_value("BlockOpacities");
      // not is the weird map property, so the XML is strange looking.
      for (auto element : node.children("Element"))
      {
        const unsigned int id = element.attribute("index").as_uint();
        const double alpha = element.child("Value").attribute("value").as_double();
        opacities.emplace_back(id, alpha);
      }

      while (auto child = node.child("Element"))
      {
        node.remove_child(child);
      }

      int index = 0;
      for (const auto& tuple : opacities)
      {
        auto child = node.append_child("Element");
        child.append_attribute("index").set_value(index++);
        child.append_attribute("value").set_value(GetSelector(std::get<0>(tuple)).c_str());

        child = node.append_child("Element");
        child.append_attribute("index").set_value(index++);
        child.append_attribute("value").set_value(std::get<1>(tuple));
      }
      node.attribute("number_of_elements").set_value(index);
    }
    return true;
  }

  static bool HandleSelectionQuerySource(xml_document& document)
  {
    // convert CompositeIndex to Selectors
    auto xpath_set = document.select_nodes(
      "//ServerManagerState/Proxy[@group='sources' and @type='SelectionQuerySource']/"
      "Property[@name='CompositeIndex']");
    for (auto xpath_node : xpath_set)
    {
      auto node = xpath_node.node();
      node.attribute("name").set_value("Selectors");
      ConvertCompositeIdsToSelectors(node);
    }

    // convert FieldType to ElementType.
    xpath_set = document.select_nodes(
      "//ServerManagerState/Proxy[@group='sources' and @type='SelectionQuerySource']/"
      "Property[@name='FieldType']");
    for (auto xpath_node : xpath_set)
    {
      auto node = xpath_node.node();
      node.attribute("name").set_value("ElementType");
      auto value = node.child("Element").attribute("value");
      value.set_value(vtkSelectionNode::ConvertSelectionFieldToAttributeType(value.as_int()));
    }

    return true;
  }

  static bool ConvertProbeLine(xml_document& document)
  {
    bool warn = false;

    pugi::xpath_node_set xpath_set =
      document.select_nodes("//ServerManagerState/Proxy[@group='filters' and @type='ProbeLine']");
    for (auto& element : xpath_set)
    {
      bool downgrade = true;

      for (auto property : element.node().children("Property"))
      {
        if (strcmp(property.attribute("name").as_string(), "Point1") == 0)
        {
          downgrade = false;
          break;
        }
      }

      if (downgrade)
      {
        element.node().attribute("type").set_value("ProbeLineLegacy");
        warn = true;
      }
    }

    if (warn)
    {
      vtkGenericWarningMacro(
        "The state file uses the old 'ProbeLine' filter implementation. "
        "The implementation has changed in ParaView 5.10. "
        "Consider replacing the Probe line filter with a new Probe line filter. The old "
        "implementation "
        "is still available as 'Probe Line Legacy' and will be used for loading this state file.");
    }
    return true;
  }

  static bool HandleBackgroundColor(xml_document& document)
  {
    // We added a single BackgroundColorMode property that combined multiple
    // properties that potentially conflicted causing issues.
    auto views = document.select_nodes("//ServerManagerState/Proxy[@group='views']");
    for (const auto& item : views)
    {
      auto node = item.node();
      auto useGradienBackground =
        node.select_node("//Property[@name='UseGradientBackground']/Element[@index='0']").node();
      auto useTexturedBackground =
        node.select_node("//Property[@name='UseTexturedBackground']/Element[@index='0']").node();
      auto useSkyboxBackground =
        node.select_node("//Property[@name='UseSkyboxBackground']/Element[@index='0']").node();

      if (!useGradienBackground && !useTexturedBackground && !useSkyboxBackground)
      {
        continue;
      }

      int mode = 0; // vtkPVRenderView::DEFAULT;
      if (useSkyboxBackground.attribute("value").as_int(0) == 1)
      {
        mode = 3; // vtkPVRenderView::SKYBOX;
      }
      else if (useTexturedBackground.attribute("value").as_int(0) == 1)
      {
        mode = 2; // vtkPVRenderView::IMAGE;
      }
      else if (useGradienBackground.attribute("value").as_int(0) == 1)
      {
        mode = 1; // vtkPVRenderView::GRADIENT;
      }

      const std::string id(node.attribute("id").value());
      auto backgroundColorMode = node.append_child("Property");
      backgroundColorMode.append_attribute("name").set_value("BackgroundColorMode");
      backgroundColorMode.append_attribute("number_of_elements").set_value(1);
      backgroundColorMode.append_attribute("id").set_value((id + ".BackgroundColorMode").c_str());
      auto elementNode = backgroundColorMode.append_child("Element");
      elementNode.append_attribute("index").set_value(0);
      elementNode.append_attribute("value").set_value(mode);

      node.remove_child(useGradienBackground.parent());
      node.remove_child(useTexturedBackground.parent());
      node.remove_child(useSkyboxBackground.parent());

      // in 5.10, we added a new property that affects if background colors
      // specified on the view is respected at all. It's tricky to determine if
      // the user did override background in state file. Hence, we treat them as
      // overridden to respect background color in state.
      auto useColorPaletteForBackground = node.append_child("Property");
      useColorPaletteForBackground.append_attribute("name").set_value(
        "UseColorPaletteForBackground");
      useColorPaletteForBackground.append_attribute("number_of_elements").set_value(1);
      useColorPaletteForBackground.append_attribute("id").set_value(
        (id + ".UseColorPaletteForBackground").c_str());

      elementNode = useColorPaletteForBackground.append_child("Element");
      elementNode.append_attribute("index").set_value(0);
      elementNode.append_attribute("value").set_value(0);
    }

    return true;
  }

  static bool HandleCalculatorParserType(xml_document& document)
  {
    // ParaView 5.10's Calculator has a new function parser that differs
    // slightly in the syntax it supports that is enabled by default.
    // For pre-5.10 state files, we switch back to the old function parser.

    auto calculators = document.select_nodes("//ServerManagerState/Proxy[@group='filters'"
                                             "and @type='Calculator']");

    for (auto xnode : calculators)
    {
      auto proxyNode = xnode.node();
      std::string idString(proxyNode.attribute("id").value());

      // Insert FunctionParserTypeProperty XML
      //<Property name="FunctionParserType" id="id.FunctionParserType" number_of_elements="1">
      //  <Element index="0" value="0"/>
      //</Property>
      auto propertyNode = proxyNode.append_child("Property");
      propertyNode.append_attribute("name").set_value("FunctionParserType");
      std::string newIDString = idString + ".FunctionParserType";
      propertyNode.append_attribute("id").set_value(newIDString.c_str());
      propertyNode.append_attribute("number_of_elements").set_value("1");
      auto elementNode = propertyNode.append_child("Element");
      elementNode.append_attribute("index").set_value("0");
      elementNode.append_attribute("value").set_value("0");
    }

    return true;
  }

  static bool ConvertThreshold(xml_document& document)
  {
    // The property ThresholdBetween of the Threshold filter has been removed
    // and replaced with:
    //   - Property LowerThreshold for the lower threshold value
    //   - Property UpperThreshold for the upper threshold value
    //   - Property ThresholdMethod for the thresholding function
    auto fixup_threshold = [](pugi::xml_node node) {
      if (!node.select_nodes("./Property[@name='ThresholdBetween']").empty())
      {
        const std::string id(node.attribute("id").value());

        // Retrieve threshold values
        auto elementNode =
          node.select_node("./Property[@name='ThresholdBetween']/Element[@index='0']").node();
        double lower = elementNode.attribute("value").as_double();

        elementNode =
          node.select_node("./Property[@name='ThresholdBetween']/Element[@index='1']").node();
        double upper = elementNode.attribute("value").as_double();

        // Remove ThresholdBetween node
        node.remove_child("./Property[@name='ThresholdBetween']");

        // Append LowerThreshold node with lower value
        auto thresholdNode = node.append_child("Property");
        thresholdNode.append_attribute("name").set_value("LowerThreshold");
        thresholdNode.append_attribute("id").set_value((id + ".LowerThreshold").c_str());
        thresholdNode.append_attribute("number_of_elements").set_value(1);

        elementNode = thresholdNode.append_child("Element");
        elementNode.append_attribute("index").set_value(0);
        elementNode.append_attribute("value").set_value(lower);

        // Append UpperThreshold node with upper value
        thresholdNode = node.append_child("Property");
        thresholdNode.append_attribute("name").set_value("UpperThreshold");
        thresholdNode.append_attribute("id").set_value((id + ".UpperThreshold").c_str());
        thresholdNode.append_attribute("number_of_elements").set_value(1);

        elementNode = thresholdNode.append_child("Element");
        elementNode.append_attribute("index").set_value(0);
        elementNode.append_attribute("value").set_value(upper);

        // Append ThresholdMethod node
        thresholdNode = node.append_child("Property");
        thresholdNode.append_attribute("name").set_value("ThresholdMethod");
        thresholdNode.append_attribute("id").set_value((id + ".ThresholdMethod").c_str());
        thresholdNode.append_attribute("number_of_elements").set_value(1);

        elementNode = thresholdNode.append_child("Element");
        elementNode.append_attribute("index").set_value(0);
        elementNode.append_attribute("value").set_value(0);
      }
    };

    pugi::xpath_node_set xpath_set =
      document.select_nodes("//ServerManagerState/Proxy[@group='filters' and @type='Threshold']");
    for (auto xpath_node : xpath_set)
    {
      fixup_threshold(xpath_node.node());
    }

    pugi::xpath_node_set xpath_set_vtkm = document.select_nodes(
      "//ServerManagerState/Proxy[@group='filters' and @type='VTKmThreshold']");
    for (auto xpath_node : xpath_set_vtkm)
    {
      fixup_threshold(xpath_node.node());
    }

    return true;
  }

  static bool HandleGradient(xml_document& document)
  {
    // The filters Gradient (for vtkImageData) and Gradient Of Unstructured DataSet
    // (UnstructuredGradient) (for vtkDataSet) have been merged and replaced with a
    // unique Gradient filter (for vtkDataSet). This new filter is based on the previous
    // UnstructuredGradient, to which the functionality from the previous Gradient is added.

    // Replace UnstructuredGradient filters by Gradient
    pugi::xpath_node_set xpath_set = document.select_nodes(
      "//ServerManagerState/Proxy[@group='filters' and @type='UnstructuredGradient']");

    for (auto xpath_node : xpath_set)
    {
      auto node = xpath_node.node();
      const std::string id(node.attribute("id").value());

      // Change filter type
      node.attribute("type").set_value("Gradient");

      // Insert BoundaryMethod property
      auto propertyNode = node.append_child("Property");
      propertyNode.append_attribute("name").set_value("BoundaryMethod");
      propertyNode.append_attribute("id").set_value((id + ".BoundaryMethod").c_str());
      propertyNode.append_attribute("number_of_elements").set_value(1);

      auto elementNode = propertyNode.append_child("Element");
      elementNode.append_attribute("index").set_value(0);
      elementNode.append_attribute("value").set_value(1);

      // Insert Dimensionality property
      propertyNode = node.append_child("Property");
      propertyNode.append_attribute("name").set_value("Dimensionality");
      propertyNode.append_attribute("id").set_value((id + ".Dimensionality").c_str());
      propertyNode.append_attribute("number_of_elements").set_value(1);

      elementNode = propertyNode.append_child("Element");
      elementNode.append_attribute("index").set_value(0);
      elementNode.append_attribute("value").set_value(3);
    }

    // Update Gradient filters with new properties
    xpath_set =
      document.select_nodes("//ServerManagerState/Proxy[@group='filters' and @type='Gradient']");

    for (auto xpath_node : xpath_set)
    {
      auto node = xpath_node.node();

      if (node.select_nodes("./Property[@name='BoundaryMethod']").empty())
      {
        const std::string id(node.attribute("id").value());

        // Insert BoundaryMethod property
        auto propertyNode = node.append_child("Property");
        propertyNode.append_attribute("name").set_value("BoundaryMethod");
        propertyNode.append_attribute("id").set_value((id + ".BoundaryMethod").c_str());
        propertyNode.append_attribute("number_of_elements").set_value(1);

        auto elementNode = propertyNode.append_child("Element");
        elementNode.append_attribute("index").set_value(0);
        elementNode.append_attribute("value").set_value(0);

        // Insert ComputeGradient property
        propertyNode = node.append_child("Property");
        propertyNode.append_attribute("name").set_value("ComputeGradient");
        propertyNode.append_attribute("id").set_value((id + ".ComputeGradient").c_str());
        propertyNode.append_attribute("number_of_elements").set_value(1);

        elementNode = propertyNode.append_child("Element");
        elementNode.append_attribute("index").set_value(0);
        elementNode.append_attribute("value").set_value(1);

        // Insert ResultArrayName property
        propertyNode = node.append_child("Property");
        propertyNode.append_attribute("name").set_value("ResultArrayName");
        propertyNode.append_attribute("id").set_value((id + ".ResultArrayName").c_str());
        propertyNode.append_attribute("number_of_elements").set_value(1);

        elementNode = propertyNode.append_child("Element");
        elementNode.append_attribute("index").set_value(0);
        elementNode.append_attribute("value").set_value("Gradient");

        // Insert FasterApproximation property
        propertyNode = node.append_child("Property");
        propertyNode.append_attribute("name").set_value("FasterApproximation");
        propertyNode.append_attribute("id").set_value((id + ".FasterApproximation").c_str());
        propertyNode.append_attribute("number_of_elements").set_value(1);

        elementNode = propertyNode.append_child("Element");
        elementNode.append_attribute("index").set_value(0);
        elementNode.append_attribute("value").set_value(0);

        // Insert ComputeDivergence property
        propertyNode = node.append_child("Property");
        propertyNode.append_attribute("name").set_value("ComputeDivergence");
        propertyNode.append_attribute("id").set_value((id + ".ComputeDivergence").c_str());
        propertyNode.append_attribute("number_of_elements").set_value(1);

        elementNode = propertyNode.append_child("Element");
        elementNode.append_attribute("index").set_value(0);
        elementNode.append_attribute("value").set_value(0);

        // Insert DivergenceArrayName property
        propertyNode = node.append_child("Property");
        propertyNode.append_attribute("name").set_value("DivergenceArrayName");
        propertyNode.append_attribute("id").set_value((id + ".DivergenceArrayName").c_str());
        propertyNode.append_attribute("number_of_elements").set_value(1);

        elementNode = propertyNode.append_child("Element");
        elementNode.append_attribute("index").set_value(0);
        elementNode.append_attribute("value").set_value("Divergence");

        // Insert ComputeVorticity property
        propertyNode = node.append_child("Property");
        propertyNode.append_attribute("name").set_value("ComputeVorticity");
        propertyNode.append_attribute("id").set_value((id + ".ComputeVorticity").c_str());
        propertyNode.append_attribute("number_of_elements").set_value(1);

        elementNode = propertyNode.append_child("Element");
        elementNode.append_attribute("index").set_value(0);
        elementNode.append_attribute("value").set_value(0);

        // Insert VorticityArrayName property
        propertyNode = node.append_child("Property");
        propertyNode.append_attribute("name").set_value("VorticityArrayName");
        propertyNode.append_attribute("id").set_value((id + ".VorticityArrayName").c_str());
        propertyNode.append_attribute("number_of_elements").set_value(1);

        elementNode = propertyNode.append_child("Element");
        elementNode.append_attribute("index").set_value(0);
        elementNode.append_attribute("value").set_value("Vorticity");

        // Insert ComputeQCriterion property
        propertyNode = node.append_child("Property");
        propertyNode.append_attribute("name").set_value("ComputeQCriterion");
        propertyNode.append_attribute("id").set_value((id + ".ComputeQCriterion").c_str());
        propertyNode.append_attribute("number_of_elements").set_value(1);

        elementNode = propertyNode.append_child("Element");
        elementNode.append_attribute("index").set_value(0);
        elementNode.append_attribute("value").set_value(0);

        // Insert QCriterionArrayName property
        propertyNode = node.append_child("Property");
        propertyNode.append_attribute("name").set_value("QCriterionArrayName");
        propertyNode.append_attribute("id").set_value((id + ".QCriterionArrayName").c_str());
        propertyNode.append_attribute("number_of_elements").set_value(1);

        elementNode = propertyNode.append_child("Element");
        elementNode.append_attribute("index").set_value(0);
        elementNode.append_attribute("value").set_value("Q Criterion");

        // Insert ContributingCellOption property
        propertyNode = node.append_child("Property");
        propertyNode.append_attribute("name").set_value("ContributingCellOption");
        propertyNode.append_attribute("id").set_value((id + ".ContributingCellOption").c_str());
        propertyNode.append_attribute("number_of_elements").set_value(1);

        elementNode = propertyNode.append_child("Element");
        elementNode.append_attribute("index").set_value(0);
        elementNode.append_attribute("value").set_value(2);

        // Insert ReplacementValueOption property
        propertyNode = node.append_child("Property");
        propertyNode.append_attribute("name").set_value("ReplacementValueOption");
        propertyNode.append_attribute("id").set_value((id + ".ReplacementValueOption").c_str());
        propertyNode.append_attribute("number_of_elements").set_value(1);

        elementNode = propertyNode.append_child("Element");
        elementNode.append_attribute("index").set_value(0);
        elementNode.append_attribute("value").set_value(1);
      }
    }

    return true;
  }
};

struct Process_5_10_to_5_11
{
  bool operator()(xml_document& document) { return HandleDataSetSurfaceFilter(document); }

  static bool HandleDataSetSurfaceFilter(xml_document& document)
  {
    pugi::xpath_node_set xpath_set = document.select_nodes(
      "//ServerManagerState/Proxy[@group='filters' and @type='DataSetSurfaceFilter']");

    for (auto xpath_node : xpath_set)
    {
      auto node = xpath_node.node();
      for (auto child : node.children())
      {
        // remove UseGeometryFilter flag
        if (std::string(child.attribute("name").as_string()) == "UseGeometryFilter")
        {
          node.remove_child(child);
        }
      }
    }

    return true;
  }
};

struct Process_5_11_to_5_12
{
  bool operator()(xml_document& document)
  {
    return ConvertTableFFT(document) && HandleSlice(document) && HandlePolarAxes(document);
  }

  static bool ConvertTableFFT(xml_document& document)
  {
    pugi::xpath_node_set xpath_set =
      document.select_nodes("//ServerManagerState/Proxy[@group='filters' and @type='TableFFT']");

    for (auto xpath_node : xpath_set)
    {
      auto node = xpath_node.node();

      if (auto averageNode = node.find_child_by_attribute("name", "AverageFft"))
      {
        averageNode.attribute("name").set_value("UseWelchMethod");
      }

      if (auto optimizeNode = node.find_child_by_attribute("name", "OptimizeForRealInput"))
      {
        optimizeNode.attribute("name").set_value("OneSidedSpectrum");
      }

      if (auto nblockNode = node.find_child_by_attribute("name", "NumberOfBlock"))
      {
        node.remove_child(nblockNode);
      }
    }

    return true;
  }

  // RealTime is replaced by sequence
  static bool HandlePlayMode(xml_document& document)
  {
    pugi::xpath_node_set xpath_set = document.select_nodes(
      "//ServerManagerState/Proxy[@group='animation' and @type='AnimationScene']");

    if (xpath_set.empty())
    {
      return true;
    }

    for (auto xpath_node : xpath_set)
    {
      auto node = xpath_node.node();

      if (auto playmodeNode = node.find_child_by_attribute("name", "PlayMode"))
      {
        if (playmodeNode.child("Element").attribute("value").as_int() == 1)
        {
          playmodeNode.child("Element").attribute("value").set_value("0");
        }
      }
    }

    return true;
  }

  static bool HandleSlice(xml_document& document)
  {
    pugi::xpath_node_set xpath_set =
      document.select_nodes("//ServerManagerState/Proxy[@group='filters' and @type='Cut']");

    if (xpath_set.empty())
    {
      return true;
    }

    // generate missing proxies
    pugi::xml_node smstate = document.root().child("ServerManagerState");
    UniqueIdGenerator generator(document);

    const vtkTypeUInt32 mergeId = generator.GetNextUniqueId();
    const vtkTypeUInt32 octreeMergeId = generator.GetNextUniqueId();
    const vtkTypeUInt32 nonMergeId = generator.GetNextUniqueId();

    std::ostringstream stream;
    stream << "<Proxy group=\"incremental_point_locators\" type=\"MergePoints\" id=\"" << mergeId
           << "\" servers=\"1\" >\n";
    stream << "  <Property name=\"Divisions\" id=\"" << mergeId
           << ".Divisions\" number_of_elements=\"3\" >\n";
    stream << "    <Element index=\"0\" value=\"50\"/>\n";
    stream << "    <Element index=\"1\" value=\"50\"/>\n";
    stream << "    <Element index=\"2\" value=\"50\"/>\n";
    stream << "  </Property>\n";
    stream << "  <Property name=\"NumberOfPointsPerBucket\" id=\"" << mergeId
           << ".NumberOfPointsPerBucket\" number_of_elements=\"1\" >\n";
    stream << "    <Element index=\"0\" value=\"8\"/>\n";
    stream << "  </Property>\n";
    stream << "</Proxy>\n";

    stream
      << "<Proxy group=\"incremental_point_locators\" type=\"IncrementalOctreeMergePoints\" id=\""
      << octreeMergeId << "\" servers=\"1\" >\n";
    stream << "  <Property name=\"MaxPointsPerLeaf\" id=\"" << octreeMergeId
           << ".MaxPointsPerLeaf\" number_of_elements=\"1\" >\n";
    stream << "    <Element index=\"0\" value=\"128\"/>\n";
    stream << "    <Domain name=\"range\" id=\"" << octreeMergeId
           << ".MaxPointsPerLeaf.range\"/>\n";
    stream << "  </Property>\n";
    stream << "  <Property name=\"Tolerance\" id=\"" << octreeMergeId
           << ".Tolerance\" number_of_elements=\"1\" >\n";
    stream << "    <Element index=\"0\" value=\"0\"/>\n";
    stream << "  </Property>\n";
    stream << "</Proxy>\n";

    stream << "<Proxy group=\"incremental_point_locators\" type=\"NonMergingPointLocator\" id=\""
           << nonMergeId << "\" servers=\"1\" >\n";
    stream << "  <Property name=\"Divisions\" id=\"" << nonMergeId
           << ".Divisions\" number_of_elements=\"3\" >\n";
    stream << "    <Element index=\"0\" value=\"50\"/>\n";
    stream << "    <Element index=\"1\" value=\"50\"/>\n";
    stream << "    <Element index=\"2\" value=\"50\"/>\n";
    stream << "  </Property>\n";
    stream << "  <Property name=\"NumberOfPointsPerBucket\" id=\"" << nonMergeId
           << ".NumberOfPointsPerBucket\" number_of_elements=\"1\" >\n";
    stream << "    <Element index=\"0\" value=\"8\"/>\n";
    stream << "  </Property>\n";
    stream << "</Proxy>\n";

    std::string buffer = stream.str();
    if (!smstate.append_buffer(buffer.c_str(), buffer.size()))
    {
      vtkGenericWarningMacro("Unable to add locators to match deprecated merge points.");
    }

    // replace property
    for (auto xpath_node : xpath_set)
    {
      auto node = xpath_node.node();
      const std::string id(node.attribute("id").value());
      bool mergePoints = true;

      // remove MergePoints property
      if (auto mergeNode = node.find_child_by_attribute("name", "MergePoints"))
      {
        mergePoints = mergeNode.child("Element").attribute("value").as_int() == 1;
        node.remove_child(mergeNode);
      }

      // add Locator property
      auto locatorNode = node.append_child("Property");
      locatorNode.append_attribute("name").set_value("Locator");
      locatorNode.append_attribute("id").set_value((id + ".Locator").c_str());
      locatorNode.append_attribute("number_of_elements").set_value(1);

      locatorNode.append_child("Proxy").append_attribute("value").set_value(
        mergePoints ? mergeId : nonMergeId);

      auto domainGroupsNode = locatorNode.append_child("Domain");
      domainGroupsNode.append_attribute("name").set_value("groups");
      domainGroupsNode.append_attribute("id").set_value((id + ".Locator.groups").c_str());

      auto domainListNode = locatorNode.append_child("Domain");
      domainListNode.append_attribute("name").set_value("proxy_list");
      domainListNode.append_attribute("id").set_value((id + ".Locator.proxy_list").c_str());
      domainListNode.append_child("Proxy").append_attribute("value").set_value(mergeId);
      domainListNode.append_child("Proxy").append_attribute("value").set_value(octreeMergeId);
      domainListNode.append_child("Proxy").append_attribute("value").set_value(nonMergeId);
    }

    return true;
  }

  static bool HandlePolarAxes(xml_document& document)
  {
    pugi::xpath_node_set xpath_set = document.select_nodes(
      "//ServerManagerState/Proxy[@group='representations' and @type='PolarAxesRepresentation']");

    // replace and add properties
    // adding only properties that shouldn't have default values
    for (auto xpath_node : xpath_set)
    {
      auto node = xpath_node.node();
      const std::string id(node.attribute("id").value());

      // update and rename NumberOfPolarAxes
      if (auto nbPolarAxesNode = node.find_child_by_attribute("name", "NumberOfPolarAxis"))
      {
        auto autoNode = node.find_child_by_attribute("name", "AutoSubdividePolarAxis");
        bool isAuto = autoNode.child("Element").attribute("value").as_bool();
        if (isAuto)
        {
          nbPolarAxesNode.child("Element").attribute("value").set_value(5);
        }
        nbPolarAxesNode.attribute("name").set_value("NumberOfPolarAxes");
      }

      // add DeltaAngleRadialAxes if NumberOfRadialAxes is specified
      if (auto nbRadialAxesNode = node.find_child_by_attribute("name", "NumberOfRadialAxes"))
      {
        bool isNotAuto = nbRadialAxesNode.child("Element").attribute("value").as_int() > 0;
        if (isNotAuto)
        {
          // add DeltaAngleRadialAxes property
          auto propertyNode = node.append_child("Property");
          propertyNode.append_attribute("name").set_value("DeltaAngleRadialAxes");
          propertyNode.append_attribute("id").set_value((id + ".DeltaAngleRadialAxes").c_str());
          propertyNode.append_attribute("number_of_elements").set_value(1);

          auto elementNode = propertyNode.append_child("Element");
          elementNode.append_attribute("index").set_value(0);
          elementNode.append_attribute("value").set_value(0.0);

          auto domainNode = propertyNode.append_child("Domain");
          domainNode.append_attribute("name").set_value("range");
          domainNode.append_attribute("id").set_value((id + ".DeltaAngleRadialAxes.range").c_str());
        }
      }

      // add ArcTickMatchesRadialAxes property
      auto propertyNode = node.append_child("Property");
      propertyNode.append_attribute("name").set_value("ArcTickMatchesRadialAxes");
      propertyNode.append_attribute("id").set_value((id + ".ArcTickMatchesRadialAxes").c_str());
      propertyNode.append_attribute("number_of_elements").set_value(1);

      auto elementNode = propertyNode.append_child("Element");
      elementNode.append_attribute("index").set_value(0);
      elementNode.append_attribute("value").set_value(false);

      auto domainNode = propertyNode.append_child("Domain");
      domainNode.append_attribute("name").set_value("bool");
      domainNode.append_attribute("id").set_value((id + ".ArcTickMatchesRadialAxes.bool").c_str());

      // add EnableOverallColor property
      propertyNode = node.append_child("Property");
      propertyNode.append_attribute("name").set_value("EnableOverallColor");
      propertyNode.append_attribute("id").set_value((id + ".EnableOverallColor").c_str());
      propertyNode.append_attribute("number_of_elements").set_value(1);

      elementNode = propertyNode.append_child("Element");
      elementNode.append_attribute("index").set_value(0);
      elementNode.append_attribute("value").set_value(false);

      domainNode = propertyNode.append_child("Domain");
      domainNode.append_attribute("name").set_value("bool");
      domainNode.append_attribute("id").set_value((id + ".EnableOverallColor.bool").c_str());
    }

    return true;
  }
};

} // end of namespace

vtkStandardNewMacro(vtkSMStateVersionController);
//----------------------------------------------------------------------------
vtkSMStateVersionController::vtkSMStateVersionController() = default;

//----------------------------------------------------------------------------
vtkSMStateVersionController::~vtkSMStateVersionController() = default;

//----------------------------------------------------------------------------
bool vtkSMStateVersionController::Process(vtkPVXMLElement* parent, vtkSMSession* session)
{
  vtkPVXMLElement* root = parent;
  if (parent && strcmp(parent->GetName(), "ServerManagerState") != 0)
  {
    root = root->FindNestedElementByName("ServerManagerState");
  }

  if (!root || strcmp(root->GetName(), "ServerManagerState") != 0)
  {
    vtkErrorMacro("Invalid root element. Expected \"ServerManagerState\"");
    return false;
  }

  vtkSMVersion version(0, 0, 0);
  if (const char* str_version = root->GetAttribute("version"))
  {
    int v[3];
    sscanf(str_version, "%d.%d.%d", &v[0], &v[1], &v[2]);
    version = vtkSMVersion(v[0], v[1], v[2]);
  }

  bool status = true;
  if (version < vtkSMVersion(4, 2, 0))
  {
    vtkWarningMacro(
      "State file version is less than 4.2.0. "
      "We will try to load the state file. It's recommended, however, "
      "that you load the state in ParaView 4.2.0 (up to 5.5.2) and save a newer version "
      "so that it can be loaded more faithfully. "
      "Loading state files generated from ParaView versions older than 4.2.0 "
      "is no longer supported.");

    version = vtkSMVersion(4, 2, 0);
  }

  // A little hackish for now, convert vtkPVXMLElement to string.
  std::ostringstream stream;
  root->PrintXML(stream, vtkIndent());

  // parse using pugi.
  pugi::xml_document document;

  if (!document.load_string(stream.str().c_str()))
  {
    vtkErrorMacro("Failed to convert from vtkPVXMLElement to pugi::xml_document");
    return false;
  }

  if (status && (version < vtkSMVersion(5, 1, 0)))
  {
    status = Process_4_2_to_5_1()(document);
    version = vtkSMVersion(5, 1, 0);
  }

  if (status && (version < vtkSMVersion(5, 4, 0)))
  {
    status = Process_5_1_to_5_4()(document);
    version = vtkSMVersion(5, 4, 0);
  }

  if (status && (version < vtkSMVersion(5, 5, 0)))
  {
    Process_5_4_to_5_5 converter;
    converter.Session = session;
    status = converter(document);
    version = vtkSMVersion(5, 5, 0);
  }

  if (status && (version < vtkSMVersion(5, 7, 0)))
  {
    Process_5_6_to_5_7 converter;
    status = converter(document);
    version = vtkSMVersion(5, 7, 0);
  }

  if (status && (version < vtkSMVersion(5, 8, 0)))
  {
    Process_5_7_to_5_8 converter;
    status = converter(document);
    version = vtkSMVersion(5, 8, 0);
  }

  if (status && (version < vtkSMVersion(5, 9, 0)))
  {
    Process_5_8_to_5_9 converter;
    status = converter(document);
    version = vtkSMVersion(5, 9, 0);
  }

  if (status && (version < vtkSMVersion(5, 10, 0)))
  {
    Process_5_9_to_5_10 converter;
    status = converter(document);
    version = vtkSMVersion(5, 10, 0);
  }

  if (status && (version < vtkSMVersion(5, 11, 0)))
  {
    Process_5_10_to_5_11 converter;
    status = converter(document);
    version = vtkSMVersion(5, 11, 0);
  }

  if (status && (version < vtkSMVersion(5, 12, 0)))
  {
    Process_5_11_to_5_12 converter;
    status = converter(document);
    version = vtkSMVersion(5, 12, 0);
  }

  if (status)
  {
    std::ostringstream stream2;
    document.save(stream2, "  ");

    vtkNew<vtkPVXMLParser> parser;
    if (parser->Parse(stream2.str().c_str()))
    {
      root->RemoveAllNestedElements();
      vtkPVXMLElement* newRoot = parser->GetRootElement();

      newRoot->CopyAttributesTo(root);
      for (unsigned int cc = 0, max = newRoot->GetNumberOfNestedElements(); cc < max; cc++)
      {
        root->AddNestedElement(newRoot->GetNestedElement(cc));
      }
    }
    else
    {
      vtkErrorMacro("Internal error: Error parsing converted XML state file.");
    }
  }
  return status;
}

//----------------------------------------------------------------------------
void vtkSMStateVersionController::PrintSelf(ostream& os, vtkIndent indent)
{
  this->Superclass::PrintSelf(os, indent);
}
