/*************************************************************************
 *
 * Copyright 2016 Realm Inc.
 *
 * 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
 *
 * http://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 REALM_UTIL_BASE64_HPP
#define REALM_UTIL_BASE64_HPP

#include <vector>
#include <realm/string_data.hpp>
#include <realm/util/optional.hpp>

namespace realm {
namespace util {


/// base64_encode() encodes the bnary data in \param in_buffer of size \param in_buffer_size .
/// The encoded data is placed in \param out_buffer . The size of \param \out_buffer is passed in
/// \param out_buffer_size . The output buffer out_buffer must be
/// large enough to hold the base64 encoded data. The size can be obtained from the function
/// base64_encoded_size. out_buffer_size is only used to assert that the output buffer is
/// large enough.
size_t base64_encode(const char *in_buffer, size_t in_buffer_size, char* out_buffer, size_t out_buffer_size) noexcept;

/// base64_encoded_size() returns the exact size of the base64 encoded
/// data as a function of the size of the input data.
inline size_t base64_encoded_size(size_t in_buffer_size) noexcept
{
    return 4 * ((in_buffer_size + 2) / 3);
}


/// Decode base64-encoded string in input, and places the result in out_buffer.
/// The length of the out_buffer must be at least 3 * input.size() / 4.
///
/// The input must be padded base64 (i.e. the number of non-whitespace
/// characters in the input must be a multiple of 4). Whitespace (spaces, tabs,
/// newlines) is ignored.
///
/// The algorithm stops when the first character not in the base64 character
/// set is encountered, or when the end of the input is reached.
///
/// \returns the number of successfully decoded bytes written to out_buffer, or
/// none if the whole input was not valid base64.
Optional<size_t> base64_decode(StringData input, char* out_buffer, size_t out_buffer_len) noexcept;

/// Return an upper bound on the decoded size of a Base64-encoded data
/// stream of length \a base64_size. The returned value is suitable for
/// allocation of buffers containing decoded data.
inline size_t base64_decoded_size(size_t base64_size) noexcept
{
    return (base64_size * 3 + 3) / 4;
}



/// base64_decode_to_vector() is a convenience function that decodes \param
/// encoded and returns the result in a std::vector<char> with the correct size.
/// This function returns none if the input is invalid.
Optional<std::vector<char>> base64_decode_to_vector(StringData encoded);

} // namespace util
} // namespace realm

#endif // REALM_UTIL_BASE64_HPP