formats/pdf/objects.h

// 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.
//

#ifndef THIRD_PARTY_CREDENTIO_FORMATS_PDF_OBJECTS_H_
#define THIRD_PARTY_CREDENTIO_FORMATS_PDF_OBJECTS_H_

#include <cstdint>
#include <cstdlib>
#include <memory>
#include <optional>
#include <ostream>
#include <sstream>
#include <string>
#include <variant>
#include <vector>

#ifdef __GNUG__
#include <cxxabi.h>  // IWYU pragma: keep
#endif

#include "absl/container/flat_hash_map.h"
#include "absl/status/status.h"
#include "absl/status/statusor.h"
#include "absl/strings/str_cat.h"
#include "absl/strings/string_view.h"
#include "absl/strings/substitute.h"

namespace credentio {

namespace internal {
inline std::string Demangle(const char* mangled) {
#ifdef __GNUG__
  int status = 0;
  std::unique_ptr<char, void (*)(void*)> res{
      abi::__cxa_demangle(mangled, nullptr, nullptr, &status), std::free};
  return (status == 0) ? res.get() : mangled;
#else
  return mangled;
#endif
}

template <typename T>
std::string Stringify(const T& val) {
  std::ostringstream ss;
  ss << val;
  return ss.str();
}
}  // namespace internal

struct Object;

// Represents any PDF object.
// Uses std::variant to hold one of the possible PDF object types.
// See ISO 32000-2 Section 7.3.2 through 7.3.9 for more details.
struct Object {
  // Represents a PDF boolean object.
  struct Boolean {
    bool value;
    friend bool operator==(const Boolean&, const Boolean&) = default;
    friend std::ostream& operator<<(std::ostream& os, const Boolean& b) {
      return os << (b.value ? "true" : "false");
    }
  };

  // Represents a PDF integer object.
  struct Integer {
    int64_t value;
    friend bool operator==(const Integer&, const Integer&) = default;
    friend std::ostream& operator<<(std::ostream& os, const Integer& i) {
      return os << i.value;
    }
  };

  // Represents a PDF real number object.
  struct RealNumber {
    std::string raw_value;
    friend bool operator==(const RealNumber&, const RealNumber&) = default;
    friend std::ostream& operator<<(std::ostream& os, const RealNumber& r) {
      return os << r.raw_value;
    }
  };

  // Represents a PDF literal string object.
  struct LiteralString {
    std::string raw_value;
    friend bool operator==(const LiteralString&,
                           const LiteralString&) = default;
    friend std::ostream& operator<<(std::ostream& os, const LiteralString& s) {
      return os << "(" << s.raw_value << ")";
    }
  };

  // Represents a PDF hexadecimal string object.
  struct HexadecimalString {
    std::string raw_value;
    friend bool operator==(const HexadecimalString&,
                           const HexadecimalString&) = default;
    friend std::ostream& operator<<(std::ostream& os,
                                    const HexadecimalString& s) {
      return os << "<" << s.raw_value << ">";
    }
  };

  // Represents a PDF name object.
  struct Name {
    std::string value;
    friend bool operator==(const Name&, const Name&) = default;
    friend std::ostream& operator<<(std::ostream& os, const Name& n) {
      return os << "/" << n.value;
    }
  };

  // Represents a PDF array object.
  struct Array {
    std::vector<Object> objects;
    friend bool operator==(const Array&, const Array&);
    friend std::ostream& operator<<(std::ostream& os, const Array& a);
  };

  // Represents a PDF dictionary object.
  struct Dictionary {
    absl::flat_hash_map<std::string, Object> entries;
    friend bool operator==(const Dictionary&, const Dictionary&);
    friend std::ostream& operator<<(std::ostream& os, const Dictionary& d);
  };

  // Represents a PDF stream object.
  struct Stream {
    std::string raw_value;
    friend bool operator==(const Stream&, const Stream&) = default;
    friend std::ostream& operator<<(std::ostream& os, const Stream& s) {
      return os << "stream\n" << s.raw_value << "\nendstream";
    }
  };

  // Represents a PDF null object.
  struct Null {
    friend bool operator==(const Null&, const Null&) = default;
    friend std::ostream& operator<<(std::ostream& os, const Null& n) {
      return os << "null";
    }
  };

  // Represents a reference to a PDF indirect object.
  struct IndirectReference {
    uint32_t object_number;
    uint32_t generation_number;
    friend bool operator==(const IndirectReference&,
                           const IndirectReference&) = default;
    friend auto operator<=>(const IndirectReference&,
                            const IndirectReference&) = default;
    friend std::ostream& operator<<(std::ostream& os,
                                    const IndirectReference& r) {
      return os << r.object_number << " " << r.generation_number << " R";
    }
  };

  std::variant<Boolean, Integer, RealNumber, LiteralString, HexadecimalString,
               Name, Array, Dictionary, Stream, Null, IndirectReference>
      value;

  friend bool operator==(const Object& lhs, const Object& rhs) {
    return lhs.value == rhs.value;
  }
  friend std::ostream& operator<<(std::ostream& os, const Object& obj) {
    std::visit([&os](const auto& alternative) { os << alternative; },
               obj.value);
    return os;
  }

  // Returns a copy of the value of type `T` held by `obj.value`. Returns an
  // `InvalidArgumentError` if `obj.value` is not of type `T`.
  template <typename T>
  static absl::StatusOr<T> As(const Object& obj) {
    if (!std::holds_alternative<T>(obj.value)) {
      constexpr size_t kMaxErrorStringLen = 256;
      std::string str = internal::Stringify(obj);
      if (str.size() > kMaxErrorStringLen) {
        str = absl::StrCat(absl::string_view(str).substr(0, kMaxErrorStringLen),
                           "...");
      }
      return absl::InvalidArgumentError(absl::StrCat(
          "Object is not a ", internal::Demangle(typeid(T).name()), ": ", str));
    }
    return std::get<T>(obj.value);
  }
};

// Define these after Object is fully defined because they use Object.
inline bool operator==(const Object::Array& lhs, const Object::Array& rhs) {
  return lhs.objects == rhs.objects;
}

inline bool operator==(const Object::Dictionary& lhs,
                       const Object::Dictionary& rhs) {
  return lhs.entries == rhs.entries;
}

inline std::ostream& operator<<(std::ostream& os, const Object::Array& a) {
  static thread_local int depth = 0;
  if (depth >= 100) {
    return os << "[...]";
  }
  ++depth;
  os << "[";
  for (size_t i = 0; i < a.objects.size(); ++i) {
    if (i > 0) os << " ";
    os << a.objects[i];
  }
  os << "]";
  --depth;
  return os;
}

inline std::ostream& operator<<(std::ostream& os, const Object::Dictionary& d) {
  static thread_local int depth = 0;
  if (depth >= 100) {
    return os << "<<...>>";
  }
  ++depth;
  os << "<<";
  for (const auto& [key, val] : d.entries) {
    os << "/" << key << " " << val;
  }
  os << ">>";
  --depth;
  return os;
}

// Represents a PDF indirect object.
// See ISO 32000-2 Section 7.3.10 for more details.
struct IndirectObject {
  uint32_t object_number;
  uint32_t generation_number;

  // Required if `object` is a stream.
  std::optional<Object::Dictionary> stream_dictionary;

  Object object;

  friend bool operator==(const IndirectObject&,
                         const IndirectObject&) = default;
  friend std::ostream& operator<<(std::ostream& os, const IndirectObject& obj) {
    os << obj.object_number << " " << obj.generation_number << " obj\n";
    if (obj.stream_dictionary.has_value()) {
      os << *obj.stream_dictionary << "\n";
    }
    os << obj.object << "\nendobj";
    return os;
  }
};

template <typename T>
absl::StatusOr<T> FindObjectInDictionary(const Object::Dictionary& dict,
                                         absl::string_view key) {
  const auto it = dict.entries.find(key);
  if (it == dict.entries.end()) {
    return absl::NotFoundError(
        absl::Substitute("Dictionary does not contain a '$0' entry.", key));
  }
  return Object::As<T>(it->second);
}
}  // namespace credentio

#endif  // THIRD_PARTY_CREDENTIO_FORMATS_PDF_OBJECTS_H_