#ifdef __cplusplus
extern "C" {
#endif

#include "bignum.h"

/*!
 * \file
 */

/**
 * \struct
 * \brief The CMixBuffer struct is the temporary storage of messages in each Node.
 * On this buffer, operations like decrypt and permute are performed.
 */
struct CMixBuffer {
	char* buffer; ///< The actual buffer
	unsigned int nr_messages; ///< The number of messages in the buffer
	unsigned int message_length; ///< The length of each message in the buffer
};

/*!
 * \brief The cmix_error enum describes the output state of a each of the cmix functions
 */
enum cmix_error {
	no_error = 0,
	index_out_of_range = 1000,
	cmix_bignum_error = 2000,
};

/*!
 * \brief permutate mixes the messages before sending the messages.
 * \param[in,out] b A buffer of \p nr_messages messages, each message of length *message_len*
 * \return no_error
 */
enum cmix_error permute(struct CMixBuffer b);
 
/*!
 * \brief get_message takes the \p index message of the buffer \p b copies it into \p message 
 * \param[out] message is the output buffer that has to hold at least \p b.message_length bytes.
 * \param[in] b is the buffer from which to copy the message.
 * \param[in] index is the index of the message to copy.
 * \return index_out_of_range if \p index is greater than or equal to \p b.nr_messages , otherwise no_error.
 */
enum cmix_error get_message(char* message, struct CMixBuffer b, unsigned int index);

/*!
 * \brief set_message set the \p index message of the buffer to a copy of \p message.
 * \param[in] message The message to set the part of the buffer to.
 * \param[in,out] b The buffer
 * \param[in] index The index into the buffer
 * \return index_out_of_range if \p index is greater than or equal to \p b.nr_messages , otherwise no_error.
 */
enum cmix_error set_message(char const* message, struct CMixBuffer b, unsigned int index);

/*!
 * \brief calculate_shared_key_part Calculates (partly) the shared key which is needed by all the nodes.
 * \param result Storage for the result
 * \param partial_shared The shared key so far.
 * \param my_share My part to add to the key.
 * \param mod The modulus of the group we are in.
 * \return An error_code.
 */
enum cmix_error calculate_shared_key_part(struct Bignum* result, struct Bignum partial_shared, struct Bignum my_share, struct Bignum mod);

#ifdef __cplusplus
} // extern "C"
#endif