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#include "libexpr/json-to-value.hh"
#include <nlohmann/json.hpp>
#include <variant>
#include <vector>
#include "libexpr/value.hh"
using json = nlohmann::json;
namespace nix {
// for more information, refer to
// https://github.com/nlohmann/json/blob/master/include/nlohmann/detail/input/json_sax.hpp
class JSONSax : nlohmann::json_sax<json> {
class JSONState {
protected:
std::unique_ptr<JSONState> parent;
std::shared_ptr<Value*> v;
public:
virtual std::unique_ptr<JSONState> resolve(EvalState&) {
throw std::logic_error("tried to close toplevel json parser state");
}
explicit JSONState(std::unique_ptr<JSONState>&& p) : parent(std::move(p)) {}
explicit JSONState(Value* v) : v(allocRootValue(v)) {}
JSONState(JSONState& p) = delete;
Value& value(EvalState& state) {
if (!v) v = allocRootValue(state.allocValue());
return **v;
}
virtual ~JSONState() {}
virtual void add() {}
};
class JSONObjectState : public JSONState {
using JSONState::JSONState;
ValueMap attrs = ValueMap();
std::unique_ptr<JSONState> resolve(EvalState& state) override {
Value& v = parent->value(state);
state.mkAttrs(v, attrs.size());
for (auto& i : attrs) v.attrs->push_back(Attr(i.first, i.second));
return std::move(parent);
}
void add() override { v = nullptr; };
public:
void key(string_t& name, EvalState& state) {
attrs[state.symbols.Create(name)] = &value(state);
}
};
class JSONListState : public JSONState {
using JSONState::JSONState;
std::vector<Value*> values;
std::unique_ptr<JSONState> resolve(EvalState& state) override {
Value& v = parent->value(state);
state.mkList(v, values.size());
for (size_t n = 0; n < values.size(); ++n) {
(*v.list)[n] = values[n];
}
return std::move(parent);
}
void add() override {
values.push_back(*v);
v = nullptr;
};
public:
JSONListState(std::unique_ptr<JSONState>&& p, std::size_t reserve)
: JSONState(std::move(p)) {
values.reserve(reserve);
}
};
EvalState& state;
std::unique_ptr<JSONState> rs;
template <typename T, typename... Args>
inline bool handle_value(T f, Args... args) {
f(rs->value(state), args...);
rs->add();
return true;
}
public:
JSONSax(EvalState& state, Value& v) : state(state), rs(new JSONState(&v)){};
bool null() override { return handle_value(mkNull); }
bool boolean(bool val) override { return handle_value(mkBool, val); }
bool number_integer(number_integer_t val) override {
return handle_value(mkInt, val);
}
bool number_unsigned(number_unsigned_t val) override {
return handle_value(mkInt, val);
}
bool number_float(number_float_t val, const string_t&) override {
return handle_value(mkFloat, val);
}
bool string(string_t& val) override {
return handle_value<void(Value&, const char*)>(mkString, val.c_str());
}
#if NLOHMANN_JSON_VERSION_MAJOR >= 3 && NLOHMANN_JSON_VERSION_MINOR >= 8
bool binary(binary_t&) {
// This function ought to be unreachable
assert(false);
return true;
}
#endif
bool start_object(std::size_t) override {
rs = std::make_unique<JSONObjectState>(std::move(rs));
return true;
}
bool key(string_t& name) override {
dynamic_cast<JSONObjectState*>(rs.get())->key(name, state);
return true;
}
bool end_object() override {
rs = rs->resolve(state);
rs->add();
return true;
}
bool end_array() override { return end_object(); }
bool start_array(size_t len) override {
rs = std::make_unique<JSONListState>(
std::move(rs), len != std::numeric_limits<size_t>::max() ? len : 128);
return true;
}
bool parse_error(std::size_t, const std::string&,
const nlohmann::detail::exception& ex) override {
throw JSONParseError(ex.what());
}
};
void parseJSON(EvalState& state, const std::string& s_, Value& v) {
JSONSax parser(state, v);
bool res = json::sax_parse(s_, &parser);
if (!res) throw JSONParseError("Invalid JSON Value");
}
} // namespace nix
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