draconisplusplus/include/rfl/xml/write.hpp

#ifndef RFL_XML_WRITE_HPP_
#define RFL_XML_WRITE_HPP_

#include <ostream>
#include <pugixml.hpp>
#include <sstream>
#include <string>
#include <type_traits>

#include "../Processors.hpp"
#include "../internal/StringLiteral.hpp"
#include "../internal/get_type_name.hpp"
#include "../internal/remove_namespaces.hpp"
#include "../parsing/Parent.hpp"
#include "Parser.hpp"

namespace rfl {
  namespace xml {

    template <internal::StringLiteral _root, class T>
    consteval auto get_root_name() {
      if constexpr (_root != internal::StringLiteral("")) {
        return _root;
      } else {
        return internal::remove_namespaces<internal::get_type_name<std::remove_cvref_t<T>>()>();
      }
    }

    /// Writes a XML into an ostream.
    template <internal::StringLiteral _root = internal::StringLiteral(""), class... Ps>
    std::ostream&
    write(const auto& _obj, std::ostream& _stream, const std::string& _indent = "    ") {
      using T          = std::remove_cvref_t<decltype(_obj)>;
      using ParentType = parsing::Parent<Writer>;

      constexpr auto root_name = get_root_name<_root, T>();

      static_assert(
        root_name.string_view().find("<") == std::string_view::npos &&
          root_name.string_view().find(">") == std::string_view::npos,
        "The name of an XML root node cannot contain '<' or '>'. "
        "Please assign an "
        "explicit root name to rfl::xml::write(...) like this: "
        "rfl::xml::write<\"root_name\">(...)."
      );

      const auto doc = rfl::Ref<pugi::xml_document>::make();

      auto declaration_node                         = doc->append_child(pugi::node_declaration);
      declaration_node.append_attribute("version")  = "1.0";
      declaration_node.append_attribute("encoding") = "UTF-8";

      auto w = Writer(doc, root_name.str());

      Parser<T, Processors<Ps...>>::write(w, _obj, typename ParentType::Root {});

      doc->save(_stream, _indent.c_str());

      return _stream;
    }

    /// Returns a XML string.
    template <internal::StringLiteral _root = internal::StringLiteral(""), class... Ps>
    std::string write(const auto& _obj, const std::string& _indent = "    ") {
      std::stringstream stream;
      write<_root, Ps...>(_obj, stream);
      return stream.str();
    }

  } // namespace xml
} // namespace rfl

#endif // XML_PARSER_HPP_