reflective-rapidjson/generator/jsonserializationcodegenerator.cpp

#include "./jsonserializationcodegenerator.h"

#include "../lib/json/serializable.h"

#include <clang/AST/DeclCXX.h>
#include <clang/AST/DeclTemplate.h>

#include <iostream>

using namespace std;
using namespace ApplicationUtilities;

namespace ReflectiveRapidJSON {

JsonSerializationCodeGenerator::Options::Options()
    : additionalClassesArg("json-classes", '\0', "specifies additional classes to consider for JSON serialization")
{
    additionalClassesArg.setCombinable(true);
    additionalClassesArg.setValueNames({ "class-name" });
    additionalClassesArg.setRequiredValueCount(Argument::varValueCount);
}

/*!
 * \brief Prints an LLVM string reference without instantiating a std::string first.
 */
ostream &operator<<(ostream &os, llvm::StringRef str)
{
    os.write(str.data(), static_cast<streamsize>(str.size()));
    return os;
}

void JsonSerializationCodeGenerator::addDeclaration(clang::Decl *decl)
{
    switch (decl->getKind()) {
    case clang::Decl::Kind::CXXRecord:
    case clang::Decl::Kind::ClassTemplateSpecialization: {
        auto *const record = static_cast<clang::CXXRecordDecl *>(decl);
        // skip forward declarations
        if (!record->hasDefinition()) {
            return;
        }

        // check for template specializations to adapt a 3rd party class/struct
        if (decl->getKind() == clang::Decl::Kind::ClassTemplateSpecialization) {
            auto *const templRecord = static_cast<clang::ClassTemplateSpecializationDecl *>(decl);
            if (templRecord->getQualifiedNameAsString() == JsonReflector::AdaptedJsonSerializable<void>::qualifiedName) {
                const clang::TemplateArgumentList &templateArgs = templRecord->getTemplateArgs();
                if (templateArgs.size() != 1 || templateArgs.get(0).getKind() != clang::TemplateArgument::Type) {
                    return; // FIXME: use Clang diagnostics to print warning
                }
                const clang::CXXRecordDecl *templateRecord = templateArgs.get(0).getAsType()->getAsCXXRecordDecl();
                if (!templateRecord) {
                    return; // FIXME: use Clang diagnostics to print warning
                }
                m_adaptionRecords.emplace_back(templateRecord->getNameAsString());
                return;
            }
        }

        // add any other records
        m_records.emplace_back(record);
    }
    case clang::Decl::Kind::Enum:
        // TODO: add enums
        break;
    default:;
    }
}

void JsonSerializationCodeGenerator::generate(ostream &os) const
{
    // find relevant classes
    std::vector<RelevantClass> relevantClasses;
    for (clang::CXXRecordDecl *record : m_records) {
        string qualifiedName(qualifiedNameIfRelevant(record));
        if (!qualifiedName.empty()) {
            relevantClasses.emplace_back(move(qualifiedName), record);
        }
    }
    if (relevantClasses.empty()) {
        return;
    }

    // put everything into namespace ReflectiveRapidJSON::JsonReflector
    os << "namespace ReflectiveRapidJSON {\n"
          "namespace JsonReflector {\n\n";

    // add push and pull functions for each class, for an example of the resulting
    // output, see ../lib/tests/jsonserializable.cpp (code under comment "pretend serialization code...")
    for (const RelevantClass &relevantClass : relevantClasses) {
        // write comment
        os << "// define code for (de)serializing " << relevantClass.qualifiedName << " objects\n";

        // find relevant base classes
        const vector<const RelevantClass *> relevantBases = findRelevantBaseClasses(relevantClass, relevantClasses);

        // print push method
        os << "template <> inline void push<::" << relevantClass.qualifiedName << ">(const ::" << relevantClass.qualifiedName
           << " &reflectable, ::RAPIDJSON_NAMESPACE::Value::Object &value, ::RAPIDJSON_NAMESPACE::Document::AllocatorType &allocator)\n{\n"
              "    // push base classes\n";
        for (const RelevantClass *baseClass : relevantBases) {
            os << "    push(static_cast<const ::" << baseClass->qualifiedName << " &>(reflectable), value, allocator);\n";
        }
        os << "    // push members\n";
        for (const clang::FieldDecl *field : relevantClass.record->fields()) {
            os << "    push(reflectable." << field->getName() << ", \"" << field->getName() << "\", value, allocator);\n";
        }
        os << "}\n";

        // print pull method
        os << "template <> inline void pull<::" << relevantClass.qualifiedName << ">(::" << relevantClass.qualifiedName
           << " &reflectable, const ::RAPIDJSON_NAMESPACE::GenericValue<::RAPIDJSON_NAMESPACE::UTF8<char>>::ConstObject &value, "
              "JsonDeserializationErrors "
              "*errors)\n{\n"
              "    // pull base classes\n";
        for (const RelevantClass *baseClass : relevantBases) {
            os << "    pull(static_cast<::" << baseClass->qualifiedName << " &>(reflectable), value, errors);\n";
        }
        os << "    // set error context for current record\n"
              "    const char *previousRecord;\n"
              "    if (errors) {\n"
              "        previousRecord = errors->currentRecord;\n"
              "        errors->currentRecord = \""
           << relevantClass.qualifiedName
           << "\";\n"
              "    }\n"
              "    // pull members\n";
        for (const clang::FieldDecl *field : relevantClass.record->fields()) {
            os << "    pull(reflectable." << field->getName() << ", \"" << field->getName() << "\", value, errors);\n";
        }
        os << "    // restore error context for previous record\n"
              "    if (errors) {\n"
              "        errors->currentRecord = previousRecord;\n"
              "    }\n";
        os << "}\n\n";
    }

    // close namespace ReflectiveRapidJSON::JsonReflector
    os << "} // namespace JsonReflector\n"
          "} // namespace ReflectiveRapidJSON\n";
}

/*!
 * \brief Returns the qualified name of the specified \a record if it is considered relevant.
 */
string JsonSerializationCodeGenerator::qualifiedNameIfRelevant(clang::CXXRecordDecl *record) const
{
    // consider all classes inheriting from an instantiation of "JsonSerializable" relevant
    if (inheritsFromInstantiationOf(record, JsonSerializable<void>::qualifiedName)) {
        return record->getQualifiedNameAsString();
    }

    // consider all classes for which a specialization of the "AdaptedJsonSerializable" struct is available
    const string qualifiedName(record->getQualifiedNameAsString());
    for (const string &adaptionRecord : m_adaptionRecords) {
        if (adaptionRecord == qualifiedName) {
            return qualifiedName;
        }
    }

    // consider all classes specified via "--additional-classes" argument relevant
    if (!m_options.additionalClassesArg.isPresent()) {
        return string();
    }

    for (const char *className : m_options.additionalClassesArg.values()) {
        if (className == qualifiedName) {
            return qualifiedName;
        }
    }

    return string();
}

std::vector<const JsonSerializationCodeGenerator::RelevantClass *> JsonSerializationCodeGenerator::findRelevantBaseClasses(
    const RelevantClass &relevantClass, const std::vector<RelevantClass> &relevantBases)
{
    vector<const RelevantClass *> relevantBaseClasses;
    for (const RelevantClass &otherClass : relevantBases) {
        if (relevantClass.record != otherClass.record && relevantClass.record->isDerivedFrom(otherClass.record)) {
            relevantBaseClasses.push_back(&otherClass);
        }
    }
    return relevantBaseClasses;
}

} // namespace ReflectiveRapidJSON