/* Distributed under the OSI-approved BSD 3-Clause License.  See accompanying

   file LICENSE.rst or https://cmake.org/licensing for details.  */

/*

 * Fuzzer for CMake's JSON parsing (via jsoncpp)

 *

 * CMake parses JSON files for CMakePresets.json, compile_commands.json,

 * and various other configuration files. This fuzzer tests the JSON

 * parser for crashes and undefined behavior.

 *

 * Coverage targets:

 * - JSON value parsing (strings, numbers, booleans, null)

 * - Array and object parsing

 * - Nested structures

 * - Unicode handling

 * - Error recovery

 */

#include <cstddef>

#include <cstdint>

#include <sstream>

#include <string>

#include <cm3p/json/reader.h>

#include <cm3p/json/value.h>

// Limit input size

static constexpr size_t kMaxInputSize = 256 * 1024; // 256KB

// Recursive helper to access all values (exercises accessor code)

static void TraverseValue(Json::Value const& value, int depth = 0)

{

  // Prevent stack overflow on deeply nested structures

  if (depth > 100) {

    return;

  }

  switch (value.type()) {

    case Json::nullValue:

      (void)value.isNull();

      break;

    case Json::intValue:

      (void)value.asInt64();

      break;

    case Json::uintValue:

      (void)value.asUInt64();

      break;

    case Json::realValue:

      (void)value.asDouble();

      break;

    case Json::stringValue:

      (void)value.asString();

      break;

    case Json::booleanValue:

      (void)value.asBool();

      break;

    case Json::arrayValue:

      for (Json::ArrayIndex i = 0; i < value.size() && i < 1000; ++i) {

        TraverseValue(value[i], depth + 1);

      }

      break;

    case Json::objectValue:

      for (auto const& name : value.getMemberNames()) {

        (void)name;

        TraverseValue(value[name], depth + 1);

      }

      break;

  }

}

extern "C" int LLVMFuzzerTestOneInput(uint8_t const* data, size_t size)

{

  if (size == 0 || size > kMaxInputSize) {

    return 0;

  }

  std::string input(reinterpret_cast<char const*>(data), size);

  Json::Value root;

  Json::CharReaderBuilder builder;

  std::string errors;

  std::istringstream stream(input);

  // Try parsing with default settings

  bool success = Json::parseFromStream(builder, stream, &root, &errors);

  if (success) {

    // Traverse the parsed structure

    TraverseValue(root);

  }

  // Also try with strict mode

  builder["strictRoot"] = true;

  builder["allowComments"] = false;

  builder["allowTrailingCommas"] = false;

  stream.clear();

  stream.str(input);

  success = Json::parseFromStream(builder, stream, &root, &errors);

  if (success) {

    TraverseValue(root);

  }

  return 0;

}