// Copyright 2019 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef UTIL_CRYPTO_OPENSSL_UTIL_H_
#define UTIL_CRYPTO_OPENSSL_UTIL_H_

#include <stddef.h>

#include <cstring>

#include "platform/base/error.h"
#include "platform/base/location.h"

// LOCAL PATCH (breadcast): dropped SSLErrorCodeToError()/GetSSLError(),
// which format an SSL_get_error() result and reference BoringSSL's
// SSL_error_description() (not part of system OpenSSL's public API). Unused
// here -- the TLS CASTV2 control channel is handled by the existing
// rust_cast-based Rust code, not this vendored openscreen subset, which only
// needs the general ERR_*/AES pieces. See vendor/openscreen/PATCHES.md.

namespace openscreen {
// Initialize OpenSSL if it isn't already initialized. This must be called
// before any other OpenSSL functions though it is safe and cheap to call this
// multiple times.
// This function is thread-safe, and OpenSSL will only ever be initialized once.
// OpenSSL will be properly shut down on program exit.
// Multiple sequential calls to EnsureOpenSSLInit or EnsureOpenSSLCleanup are
// ignored by OpenSSL itself.
void EnsureOpenSSLInit();

// Drains the OpenSSL ERR_get_error stack. On a debug build the error codes
// are send to VLOG(1), on a release build they are disregarded. In most
// cases you should pass CURRENT_LOCATION as the `location`.
void ClearOpenSSLERRStack(const Location& location);

// Place an instance of this class on the call stack to automatically clear
// the OpenSSL error stack on function exit.
class OpenSSLErrStackTracer {
 public:
  // Pass CURRENT_LOCATION as `location`, to help track the source of OpenSSL
  // error messages. Note any diagnostic emitted will be tagged with the
  // location of the constructor call as it's not possible to trace a
  // destructor's callsite.
  explicit OpenSSLErrStackTracer(const Location& location)
      : location_(location) {
    EnsureOpenSSLInit();
  }
  OpenSSLErrStackTracer(const OpenSSLErrStackTracer&) = delete;
  OpenSSLErrStackTracer(OpenSSLErrStackTracer&&) noexcept = delete;
  OpenSSLErrStackTracer& operator=(const OpenSSLErrStackTracer&) = delete;
  OpenSSLErrStackTracer& operator=(OpenSSLErrStackTracer&&) = delete;
  ~OpenSSLErrStackTracer() { ClearOpenSSLERRStack(location_); }

 private:
  const Location location_;
};

}  // namespace openscreen

#endif  // UTIL_CRYPTO_OPENSSL_UTIL_H_