jumbf/convert_json.cc

// Copyright 2026 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//    https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//

#include "jumbf/convert_json.h"

#include <cstddef>
#include <cstdint>
#include <memory>
#include <string>
#include <utility>
#include <vector>

#include "absl/log/log.h"
#include "absl/status/status.h"
#include "absl/status/statusor.h"
#include "absl/strings/escaping.h"
#include "absl/strings/str_cat.h"
#include "absl/strings/str_format.h"
#include "absl/strings/string_view.h"
#include "cppbor/cppbor.h"
#include "cppbor/cppbor_parse.h"
#include "jumbf/box.h"
#include "nlohmann/json.hpp"
#include "nlohmann/json_fwd.hpp"

namespace jumbf {
namespace {

using Json = ::nlohmann::json;

std::string EncodePrefixedBase64(absl::string_view raw) {
  return absl::StrCat("b64'", absl::Base64Escape(raw), "'");
}

std::string EncodeCbor(cppbor::Item* item) {
  std::vector<uint8_t> buf;
  buf.resize(item->encodedSize());
  item->encode(buf.data(), buf.data() + buf.size());
  return std::string(reinterpret_cast<const char*>(buf.data()), buf.size());
}

cppbor::Map BstrToB64(cppbor::Map* map);

std::unique_ptr<cppbor::Item> UnwrapTag(std::unique_ptr<cppbor::Item> item) {
  while (item->asSemanticTag() != nullptr) {
    if (auto t = item->asTstr(); t != nullptr) return t->clone();
    if (auto u = item->asUint(); u != nullptr) return u->clone();
    if (auto i = item->asInt(); i != nullptr) return i->clone();
    if (auto b = item->asBool(); b != nullptr) return b->clone();
    if (auto f = item->asFloat(); f != nullptr) return f->clone();
    if (auto d = item->asDouble(); d != nullptr) return d->clone();
    if (auto s = item->asSimple(); s != nullptr) return s->clone();
    break;
  }
  return item;
}

// Recursively replaces all Bstr with base64-encoded Tstr.
cppbor::Array BstrToB64(cppbor::Array* array) {
  cppbor::Array new_array;
  for (auto& item_ref : *array) {
    auto item = UnwrapTag(std::move(item_ref));
    if (auto s = item->asBstr(); s != nullptr) {
      absl::string_view sv(reinterpret_cast<const char*>(s->value().data()),
                           s->value().size());
      new_array.add(cppbor::Tstr(EncodePrefixedBase64(sv)));
    } else if (auto m = item->asMap(); m != nullptr) {
      new_array.add(BstrToB64(m));
    } else if (auto a = item->asArray(); a != nullptr) {
      new_array.add(BstrToB64(a));
    } else {
      new_array.add(std::move(item));
    }
  }
  return new_array;
}

// Recursively replaces all Bstr with base64-encoded Tstr.
cppbor::Map BstrToB64(cppbor::Map* map) {
  cppbor::Map new_map;
  for (auto& [key_ref, value_ref] : *map) {
    auto key = UnwrapTag(std::move(key_ref));
    auto value = UnwrapTag(std::move(value_ref));
    if (auto s = value->asBstr(); s != nullptr) {
      absl::string_view sv(reinterpret_cast<const char*>(s->value().data()),
                           s->value().size());
      new_map.add(std::move(key), cppbor::Tstr(EncodePrefixedBase64(sv)));
    } else if (auto m = value->asMap(); m != nullptr) {
      new_map.add(std::move(key), BstrToB64(m));
    } else if (auto v = value->asArray(); v != nullptr) {
      cppbor::Array new_array = BstrToB64(v);
      new_map.add(std::move(key), std::move(new_array));
    } else {
      new_map.add(std::move(key), std::move(value));
    }
  }
  return new_map;
}

// Recursively replaces all Bstr with base64-encoded Tstr. Supports only arrays
// and maps.
absl::StatusOr<std::string> BstrToB64(absl::string_view raw) {
  auto [item, new_position, error] =
      cppbor::parse(reinterpret_cast<const uint8_t*>(raw.data()), raw.length());
  if (!error.empty()) {
    return absl::InvalidArgumentError(
        absl::StrCat("CBOR parsing failed: ", error));
  }
  if (new_position !=
      reinterpret_cast<const uint8_t*>(raw.data() + raw.length())) {
    return absl::InvalidArgumentError(
        "Trailing bytes after the parsed CBOR item");
  }

  if (auto map = item->asMap(); map != nullptr) {
    auto new_map = BstrToB64(map);
    return EncodeCbor(&new_map);
  } else if (auto array = item->asArray(); array != nullptr) {
    auto new_array = BstrToB64(array);
    return EncodeCbor(&new_array);
  }
  return absl::InvalidArgumentError(
      absl::StrCat("Input CBOR item is ", item->type(),
                   "; expected array (128) or map (160)."));
}

class AllExceptionParser
    : public nlohmann::detail::json_sax_dom_parser<
          Json, nlohmann::detail::iterator_input_adapter<const char*>> {
 public:
  explicit AllExceptionParser(Json& j)
      : nlohmann::detail::json_sax_dom_parser<
            Json, nlohmann::detail::iterator_input_adapter<const char*>>(
            j, false) {}

  bool parse_error(std::size_t position, absl::string_view last_token,
                   const Json::exception& ex) {
    errors_.push_back(absl::StrFormat("%s", ex.what()));
    return false;
  }

  std::vector<std::string> errors() { return errors_; }

 private:
  std::vector<std::string> errors_;
};

}  // namespace

void to_json(Json& j, const DescriptionBox& box) {
  if (box.label.has_value()) {
    j["label"] = box.label.value();
  }
  if (box.id.has_value()) {
    j["id"] = box.id.value();
  }
  if (box.unvalidated_hash.has_value()) {
    j["hash"] = box.unvalidated_hash.value();
  }
  j["uuid"] = box.type_uuid.ToString();
  j["requestable"] = box.requestable;

  for (const auto& box : box.private_content) {
    j["private_content"].push_back(box);
  }

  j["_meta"]["_type"] = "description";
}

void to_json(Json& j, const SuperBox& box) {
  j["description"] = box.description;

  for (const auto& box : box.contents) {
    j["contents"].push_back(box);
  }

  j["_meta"]["_type"] = "super";
}

void to_json(Json& j, const UnknownBox& box) {
  j["type"] = box.type;

  j["_meta"]["_type"] = "unknown";
  j["_meta"]["_payload_size"] = box.payload.size();
}

void to_json(Json& j, const CborBox& box) {
  j["_meta"]["_type"] = "cbor";
  j["_meta"]["_payload_size"] = box.payload.size();

  absl::StatusOr<std::string> encoded = BstrToB64(box.payload);
  if (!encoded.ok()) {
    j["_meta"]["_error"] = encoded.status().ToString();
    return;
  }

  AllExceptionParser parser(j["cbor"]);
  auto ia = nlohmann::detail::input_adapter(*encoded);
  nlohmann::detail::binary_reader<Json, decltype(ia), AllExceptionParser>
      reader(std::move(ia), Json::input_format_t::cbor);
  reader.sax_parse(Json::input_format_t::cbor, &parser, /*strict=*/true,
                   /*tag_handler=*/Json::cbor_tag_handler_t::ignore);
  if (!parser.errors().empty()) {
    j["_meta"]["_error"] = parser.errors();
  }
}

void to_json(Json& j, const SerializedSuperbox& box) {
  j["_meta"]["_type"] = "serialized_superbox";
  j["_meta"]["_serialized_size"] = box.serialized.size();
}

void to_json(Json& j, const EmbeddedFileDescriptionBox& box) {
  j["media_type"] = box.media_type;
  j["external"] = box.external;
  if (box.file_name.has_value()) {
    j["file_name"] = box.file_name.value();
  }

  j["_meta"]["_type"] = "embedded_file_description";
}

void to_json(Json& j, const BinaryDataBox& box) {
  j["_meta"]["_type"] = "binary";
  j["_meta"]["_payload_size"] = box.payload.size();
}

void to_json(Json& j, const C2paSaltBox& box) {
  j["_meta"]["_type"] = "c2pa_salt";
  j["_meta"]["_salt_size"] = box.salt.size();
}

void to_json(Json& j, const JsonBox& box) {
  AllExceptionParser parser(j["json"]);
  Json::sax_parse(box.payload, &parser, Json::input_format_t::json);

  if (!parser.errors().empty()) {
    j["_meta"]["_error"] = parser.errors();
  }
  j["_meta"]["_type"] = "json";
  j["_meta"]["_payload_size"] = box.payload.size();
}

void to_json(Json& j, const ContentBox& box) {
  if (box.Holds<jumbf::SuperBox>()) {
    j = box.Get<jumbf::SuperBox>();
  } else if (box.Holds<jumbf::UnknownBox>()) {
    j = box.Get<jumbf::UnknownBox>();
  } else if (box.Holds<jumbf::CborBox>()) {
    j = box.Get<jumbf::CborBox>();
  } else if (box.Holds<jumbf::SerializedSuperbox>()) {
    j = box.Get<jumbf::SerializedSuperbox>();
  } else if (box.Holds<jumbf::EmbeddedFileDescriptionBox>()) {
    j = box.Get<jumbf::EmbeddedFileDescriptionBox>();
  } else if (box.Holds<jumbf::BinaryDataBox>()) {
    j = box.Get<jumbf::BinaryDataBox>();
  } else if (box.Holds<jumbf::C2paSaltBox>()) {
    j = box.Get<jumbf::C2paSaltBox>();
  } else if (box.Holds<jumbf::JsonBox>()) {
    j = box.Get<jumbf::JsonBox>();
  } else {
    j["_meta"]["_error"] = "Contents Not Accounted For";
  }
}

}  // namespace jumbf