XMLObject.cpp

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#include "XMLObject.h"
#include <xercesc/parsers/XercesDOMParser.hpp>
#include <xercesc/util/BinInputStream.hpp>
#include <xercesc/sax/InputSource.hpp>
#include <iostream>
#include <algorithm>
#include <filesystem>
 
namespace XML {
 
// Utility class for parsing directly from an std::istream.
class IStreamInputSource : public xercesc::InputSource {
protected:
  std::istream &is;
  xercesc::BinInputStream* makeStream() const {
    return new IStreamBinInputStream(is);
  }
 
  class IStreamBinInputStream : public xercesc::BinInputStream {
    std::istream &is;
  public:
    IStreamBinInputStream(std::istream &is) : xercesc::BinInputStream(), is(is) {};
    XMLFilePos curPos(void) const { return (XMLFilePos)is.tellg(); };
    XMLSize_t readBytes(XMLByte* const buf, const XMLSize_t max) {
      is.read((char*)buf, (std::streamsize)max);
      return (XMLSize_t)is.gcount();
    };
    const XMLCh* getContentType() const {
      //TODO: return application/xml
      return NULL;
    };
  };
public:
  IStreamInputSource(std::istream &is) : InputSource(), is(is) {};
};
 
std::string transcode(const XMLCh* xmlChStr) {
  char* cStr = xercesc::XMLString::transcode(xmlChStr);
  if (!cStr) {
    throw std::runtime_error("Failed to transcode XML string");
  }
  std::string result(cStr);
  xercesc::XMLString::release(&cStr);
  return result;
}
 
XMLObject* XMLObject::createFromStream(std::istream& xmlStream) {
  // std::cout << "Create XML object from input stream" << std::endl;
  xercesc::XMLPlatformUtils::Initialize();
  std::unique_ptr<xercesc::XercesDOMParser> parser = std::make_unique<xercesc::XercesDOMParser>();
  parser->setDoNamespaces(true);
  parser->parse(IStreamInputSource(xmlStream));
 
  xercesc::DOMDocument* document = parser->getDocument();
  if (!document) {
    parser.reset(); // delete unique_ptr to parser before calling Terminate
    xercesc::XMLPlatformUtils::Terminate();
    throw std::runtime_error("Failed to parse XML stream");
  }
 
  xercesc::DOMElement* rootElement = document->getDocumentElement();
  if (!rootElement) {
    parser.reset(); // delete unique_ptr to parser before calling Terminate
    xercesc::XMLPlatformUtils::Terminate();
    throw std::runtime_error("Failed to get root element of XML stream");
  }
 
  std::string rootName = transcode(rootElement->getLocalName());
  XMLObject* object = createObject(rootElement);
  parser.reset(); // delete unique_ptr to parser before calling Terminate
  xercesc::XMLPlatformUtils::Terminate();
  return object;
}
 
XMLObject* XMLObject::createFromString(const std::string& xmlString) {
  // std::cout << "Create XML object from string" << std::endl;
  std::istringstream iss(xmlString);
  return createFromStream(iss);
}
 
XMLObject* XMLObject::createFromFile(const std::string& filename) {
  // std::cout << "Create XML object from file" << std::endl;
  const std::filesystem::path filePath(filename);
  if (!std::filesystem::exists(filePath)) {
    throw std::runtime_error("XML file '" + std::filesystem::absolute(filePath).string() + "' not found");
  }
 
  xercesc::XMLPlatformUtils::Initialize();
  std::unique_ptr<xercesc::XercesDOMParser> parser = std::make_unique<xercesc::XercesDOMParser>();
  parser->setDoNamespaces(true);
  XMLCh* xmlFilename = xercesc::XMLString::transcode(filename.c_str());
  parser->parse(xmlFilename);
  xercesc::XMLString::release(&xmlFilename);  // Release memory after usage
 
 
  xercesc::DOMDocument* document = parser->getDocument();
  if (!document) {
    parser.reset(); // delete unique_ptr to parser before calling Terminate
    xercesc::XMLPlatformUtils::Terminate();
    throw std::runtime_error("Failed to load and parse XML file: " + filename);
  }
 
  xercesc::DOMElement* rootElement = document->getDocumentElement();
  if (!rootElement) {
    parser.reset(); // delete unique_ptr to parser before calling Terminate
    xercesc::XMLPlatformUtils::Terminate();
    throw std::runtime_error("Failed to get root element of XML file: " + filename);
  }
 
  std::string rootName = transcode(rootElement->getLocalName());
  
  XMLObject* object = createObject(rootElement);
  parser.reset(); // delete unique_ptr to parser before calling Terminate
  xercesc::XMLPlatformUtils::Terminate();
  return object;
}
 
 
XMLObject* XMLObject::createObject(const xercesc::DOMElement* element) {
  Namespace xmlns = transcode(element->getNamespaceURI());
  ElementName elementName = transcode(element->getLocalName());
  if ( auto it = factory.find(xmlns + ":" + elementName); it != factory.end() ) { 
    return it->second(xmlns, elementName, element); 
  }
  // std::cout << "Unknown element '" << elementName << "' using 'XMLObject' instead" << std::endl;
  return createInstance<XMLObject>(xmlns, "XMLObject", element);
}
 
XMLObject::XMLObject(const Namespace& xmlns, const ClassName& className, const xercesc::DOMElement* element, const Attributes& defaultAttributes) : xmlns(xmlns), className(className) {
 
  prefix = transcode(element->getPrefix());
  elementName = transcode(element->getLocalName());
 
  // set attributes
  xercesc::DOMNamedNodeMap* elementAttributes = element->getAttributes();
  for (XMLSize_t i = 0; i < elementAttributes->getLength(); i++) {
    xercesc::DOMNode* item = elementAttributes->item(i);
    
    AttributeName attributeName = transcode(item->getLocalName());
    // get namespace from atrribute or parent element
    Namespace attributeXmlns = item->getNamespaceURI() ? transcode(item->getNamespaceURI()) : xmlns;
    Namespace attributePrefix = item->getPrefix() ? transcode(item->getPrefix()) : "";
    Value attributeValue(transcode(item->getNodeValue()));
    attributes.push_back( { attributeXmlns, attributePrefix, attributeName, attributeValue } );
  }
 
  // add defaults for missing attributes
  for ( auto& defaultAttribute : defaultAttributes ) {
    if ( !getOptionalAttributeByName(defaultAttribute.name) ) {
      attributes.push_back(defaultAttribute);
    }
  }
 
  // set children
  for (xercesc::DOMElement *childElement = element->getFirstElementChild(); childElement; childElement = childElement->getNextElementSibling()) {
    children.push_back(std::unique_ptr<XMLObject>(createObject(childElement)));
  }
 
  if ( children.empty() ) {
    textContent = transcode(element->getTextContent());
  }
}
 
 
// getRequiredChildByName / getOptionalChildByName / getChildrenByName /
// getRequiredAttributeByName / getOptionalAttributeByName are now defined inline in the
// header as C++23 deducing-this templates so they are const-correct with the receiver.
 
std::string XMLObject::stringify() const {
  std::string xmlString = std::string("<") + (!prefix.empty() ? prefix + ":" : "") + elementName;
  for ( auto& attribute : attributes ) {
    xmlString += std::string(" ") + (!attribute.prefix.empty() ? attribute.prefix + ":" : "") + attribute.name + "=\"" + attribute.value.value +"\"";
  }
  xmlString += ">";
 
  for ( auto& child : children ) {
    xmlString += child->stringify();
  }
  xmlString += textContent;
  xmlString += std::string("</") + (!prefix.empty() ? prefix + ":" : "") + elementName + ">";
  return xmlString;
}
 
std::string XMLObject::format(std::string indentation, unsigned int depth) const {
  // lambda to repeat indentation n times
  auto indent = [&indentation](unsigned int n) -> std::string {
    std::string result;
    for (unsigned int i = 0; i < n; ++i) {
      result += indentation;
    }
    return result;
  };
  
  std::string xmlString = indent(depth) + std::string("<") + (!prefix.empty() ? prefix + ":" : "") + elementName;
  for ( auto& attribute : attributes ) {
    xmlString += std::string(" ") + (!attribute.prefix.empty() ? attribute.prefix + ":" : "") + attribute.name + "=\"" + attribute.value.value +"\"";
  }
  xmlString += ">\n";
 
  for ( auto& child : children ) {
    xmlString += child->format(indentation, depth+1);
  }
  xmlString += textContent;
  if ( !textContent.empty() && !textContent.ends_with("\n") ) {
    xmlString += "\n";
  } 
  xmlString += indent(depth) + std::string("</") + (!prefix.empty() ? prefix + ":" : "") + elementName + ">\n";
  return xmlString;
}
 
std::ostream& operator<< (std::ostream& os, const XMLObject* obj) {
  os << obj->stringify();
  return os;
}
 
std::ostream& operator<< (std::ostream& os, const XMLObject& obj) {
  os << obj.stringify();
  return os;
}
 
} // end namespace XML