/*************************************************************************
 *
 * 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 <realm/util/span.hpp>
#include <optional>
#include <vector>

namespace realm::util {

/// `base64_encode()` encodes the binary data in \param in_buffer .
/// The encoded data is placed in \param out_buffer , which must be large
/// enough to hold the base64 encoded data. The size can be obtained from the function
/// `base64_encoded_size()`.
size_t base64_encode(Span<const char> in_buffer, Span<char> out_buffer) 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.
std::optional<size_t> base64_decode(Span<const char> input, Span<char> out_buffer) 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.
std::optional<std::vector<char>> base64_decode_to_vector(Span<const char> encoded);

} // namespace realm::util

#endif // REALM_UTIL_BASE64_HPP