// Copyright 2021 The BoringSSL Authors
//
// 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 <openssl/base.h>

#include <functional>
#include <memory>
#include <vector>

#include <openssl/span.h>


namespace bssl {
namespace acvp {

// kMaxArgs is the maximum number of arguments (including the function name)
// that an ACVP request can contain.
constexpr size_t kMaxArgs = 9;
// kMaxNameLength is the maximum length of a function name in an ACVP request.
constexpr size_t kMaxNameLength = 30;

// RequestBuffer holds various buffers needed for parsing an ACVP request. It
// can be reused between requests.
class RequestBuffer {
 public:
  virtual ~RequestBuffer();

  static std::unique_ptr<RequestBuffer> New();
};

// ParseArgsFromFd returns a span of arguments, the first of which is the name
// of the requested function, from |fd|. The return values point into |buffer|
// and so must not be used after |buffer| has been freed or reused for a
// subsequent call. It returns an empty span on error, because std::optional
// is still too new.
Span<const Span<const uint8_t>> ParseArgsFromFd(int fd, RequestBuffer *buffer);

// WriteReplyToFd writes a reply to the given file descriptor.
bool WriteReplyToFd(int fd, const std::vector<Span<const uint8_t>> &spans);

// WriteReplyToBuffer writes a reply to an internal buffer that may be flushed
// with |FlushBuffer|.
bool WriteReplyToBuffer(const std::vector<Span<const uint8_t>> &spans);

// FlushBuffer writes the buffer that |WriteReplyToBuffer| fills, to |fd|.
bool FlushBuffer(int fd);

// ReplyCallback is the type of a callback that writes a reply to an ACVP
// request.
typedef std::function<bool(const std::vector<Span<const uint8_t>> &)>
    ReplyCallback;

// Handler is the type of a function that handles a specific ACVP request. If
// successful it will call |write_reply| with the response arguments and return
// |write_reply|'s return value. Otherwise it will return false. The given args
// must not include the name at the beginning.
typedef bool (*Handler)(const Span<const uint8_t> args[],
                        ReplyCallback write_reply);

// FindHandler returns a |Handler| that can process the given arguments, or logs
// a reason and returns |nullptr| if none is found.
Handler FindHandler(Span<const Span<const uint8_t>> args);

}  // namespace acvp
}  // namespace bssl