89 lines
2.8 KiB
C++
89 lines
2.8 KiB
C++
#ifndef RFL_PARSING_FIELD_VARIANT_PARSER_HPP_
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#define RFL_PARSING_FIELD_VARIANT_PARSER_HPP_
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#include <map>
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#include <stdexcept>
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#include <string>
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#include <type_traits>
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#include <variant>
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#include "../Result.hpp"
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#include "../always_false.hpp"
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#include "FieldVariantReader.hpp"
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#include "Parser_base.hpp"
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#include "schema/Type.hpp"
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namespace rfl {
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namespace parsing {
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/// To be used when all options of the variants are rfl::Field. Essentially,
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/// this is an externally tagged union.
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template <class R, class W, class ProcessorsType, class... FieldTypes>
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requires AreReaderAndWriter<R, W, std::variant<FieldTypes...>>
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struct FieldVariantParser {
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using FieldVariantType = std::variant<FieldTypes...>;
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using ResultType = Result<FieldVariantType>;
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public:
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using InputObjectType = typename R::InputObjectType;
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using InputVarType = typename R::InputVarType;
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using OutputObjectType = typename W::OutputObjectType;
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using OutputVarType = typename W::OutputVarType;
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static ResultType read(const R& _r, const InputVarType& _var) noexcept {
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static_assert(
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internal::no_duplicate_field_names<std::tuple<FieldTypes...>>(),
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"Externally tagged variants cannot have duplicate field "
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"names.");
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const auto to_result = [&](const auto _obj) -> ResultType {
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auto field_variant = std::optional<Result<FieldVariantType>>();
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const auto reader =
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FieldVariantReader<R, W, ProcessorsType, FieldTypes...>(
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&_r, &field_variant);
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auto err = _r.read_object(reader, _obj);
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if (err) {
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return *err;
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}
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if (!field_variant) {
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return Error(
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"Could not parse: Expected the object to have "
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"exactly one field, but found more than one.");
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}
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return std::move(*field_variant);
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};
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return _r.to_object(_var).and_then(to_result);
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}
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template <class P>
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static void write(const W& _w, const std::variant<FieldTypes...>& _v,
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const P& _parent) noexcept {
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static_assert(
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internal::no_duplicate_field_names<std::tuple<FieldTypes...>>(),
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"Externally tagged variants cannot have duplicate field "
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"names.");
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const auto handle = [&](const auto& _field) {
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const auto named_tuple = make_named_tuple(internal::to_ptr_field(_field));
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using NamedTupleType = std::remove_cvref_t<decltype(named_tuple)>;
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Parser<R, W, NamedTupleType, ProcessorsType>::write(_w, named_tuple,
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_parent);
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};
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std::visit(handle, _v);
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}
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static schema::Type to_schema(
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std::map<std::string, schema::Type>* _definitions,
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std::vector<schema::Type> _types = {}) {
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using VariantType = std::variant<NamedTuple<FieldTypes>...>;
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return Parser<R, W, VariantType, ProcessorsType>::to_schema(_definitions);
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}
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};
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} // namespace parsing
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} // namespace rfl
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#endif
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