// libFuzzer harness for the SECS-II decoder.
//
// Feed arbitrary bytes to secs2::decode and assert no crash, no
// UB, no ASan-flagged memory error.  Coverage-guided fuzzing
// explores edges that hand-written tests can't predict.
//
// Build:  cmake -S . -B build-fuzz -G Ninja -DSECSGEM_FUZZ=ON
// Run:    build-fuzz/fuzz_secs2_decode -max_total_time=300 -max_len=65536

#include <cstdint>
#include <cstddef>
#include <vector>

#include "secsgem/secs2/codec.hpp"

extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
  // The decoder is expected to throw secs2::CodecError on malformed
  // input — that's the contract.  Any other exception type, or a
  // segfault / ASan flag, is a bug.
  try {
    std::vector<uint8_t> bytes(data, data + size);
    auto item = secsgem::secs2::decode(bytes);
    (void)item;
  } catch (const secsgem::secs2::CodecError&) {
    // expected: well-defined failure path
  } catch (...) {
    // anything else escaping is a hardening bug — crash so libFuzzer
    // captures the input.
    __builtin_trap();
  }
  return 0;
}