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#include "json-to-value.hh"
#include <variant>
#include <nlohmann/json.hpp>
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;
RootValue 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;
std::unique_ptr<JSONState> resolve(EvalState & state) override
{
auto attrs2 = state.buildBindings(attrs.size());
for (auto & i : attrs)
attrs2.insert(i.first, i.second);
parent->value(state).mkAttrs(attrs2.alreadySorted());
return std::move(parent);
}
void add() override { v = nullptr; }
public:
void key(string_t & name, EvalState & state)
{
attrs.insert_or_assign(state.symbols.create(name), &value(state));
}
};
class JSONListState : public JSONState {
ValueVector 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.listElems()[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;
public:
JSONSax(EvalState & state, Value & v) : state(state), rs(new JSONState(&v)) {};
bool null()
{
rs->value(state).mkNull();
rs->add();
return true;
}
bool boolean(bool val)
{
rs->value(state).mkBool(val);
rs->add();
return true;
}
bool number_integer(number_integer_t val)
{
rs->value(state).mkInt(val);
rs->add();
return true;
}
bool number_unsigned(number_unsigned_t val)
{
rs->value(state).mkInt(val);
rs->add();
return true;
}
bool number_float(number_float_t val, const string_t & s)
{
rs->value(state).mkFloat(val);
rs->add();
return true;
}
bool string(string_t & val)
{
rs->value(state).mkString(val);
rs->add();
return true;
}
#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 len)
{
rs = std::make_unique<JSONObjectState>(std::move(rs));
return true;
}
bool key(string_t & name)
{
dynamic_cast<JSONObjectState*>(rs.get())->key(name, state);
return true;
}
bool end_object() {
rs = rs->resolve(state);
rs->add();
return true;
}
bool end_array() {
return end_object();
}
bool start_array(size_t len) {
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) {
throw JSONParseError(ex.what());
}
};
void parseJSON(EvalState & state, const string & s_, Value & v)
{
JSONSax parser(state, v);
bool res = json::sax_parse(s_, &parser);
if (!res)
throw JSONParseError("Invalid JSON Value");
}
}
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