#ifndef XMSS_CORE_H
#define XMSS_CORE_H

#include "params.h"

typedef struct{
    unsigned int h;
    unsigned int next_idx;
    unsigned int stackusage;
    unsigned char completed;
    unsigned char *node;
} treehash_inst;

typedef struct {
    unsigned char *stack;
    unsigned int stackoffset;
    unsigned char *stacklevels;
    unsigned char *auth;
    unsigned char *keep;
    treehash_inst *treehash;
    unsigned char *retain;
    unsigned int next_leaf;
} bds_state;

/**
 * Initialize BDS state struct
 * parameter names are the same as used in the description of the BDS traversal
 */
void xmss_set_bds_state(bds_state *state, unsigned char *stack,
                        int stackoffset, unsigned char *stacklevels,
                        unsigned char *auth, unsigned char *keep,
                        treehash_inst *treehash, unsigned char *retain,
                        int next_leaf);

/**
 * Given a set of parameters, this function returns the size of the secret key.
 * This is implementation specific, as varying choices in tree traversal will
 * result in varying requirements for state storage.
 */
unsigned long long xmss_core_sk_bytes(const xmss_params *params);

/**
 * Generates a XMSS key pair for a given parameter set.
 * Format sk: [(32bit) idx || SK_SEED || SK_PRF || PUB_SEED || root]
 * Format pk: [root || PUB_SEED] omitting algo oid.
 */
int xmss_core_keypair(const xmss_params *params,
                      unsigned char *pk, unsigned char *sk, bds_state *state);
/**
 * Signs a message.
 * Returns
 * 1. an array containing the signature followed by the message AND
 * 2. an updated secret key!
 */
int xmss_core_sign(const xmss_params *params,
                   unsigned char *sk, bds_state *state,
                   unsigned char *sm, unsigned long long *smlen,
                   const unsigned char *m, unsigned long long mlen);
/**
 * Verifies a given message signature pair under a given public key.
 *
 * Note: msg and mlen are pure outputs which carry the message in case verification succeeds. The (input) message is assumed to be within sm which has the form (sig||msg). 
 */
int xmss_core_sign_open(const xmss_params *params,
                        unsigned char *m, unsigned long long *mlen,
                        const unsigned char *sm, unsigned long long smlen,
                        const unsigned char *pk);

/**
 * Given a set of parameters, this function returns the size of the secret key.
 * This is implementation specific, as varying choices in tree traversal will
 * result in varying requirements for state storage.
 */
unsigned long long xmssmt_core_sk_bytes(const xmss_params *params);

/*
 * Generates a XMSSMT key pair for a given parameter set.
 * Format sk: [(ceil(h/8) bit) idx || SK_SEED || SK_PRF || PUB_SEED || root]
 * Format pk: [root || PUB_SEED] omitting algo oid.
 */
int xmssmt_core_keypair(const xmss_params *params,
                        unsigned char *pk, unsigned char *sk,
                        bds_state *states, unsigned char *wots_sigs);

/**
 * Signs a message.
 * Returns
 * 1. an array containing the signature followed by the message AND
 * 2. an updated secret key!
 */
int xmssmt_core_sign(const xmss_params *params,
                     unsigned char *sk,
                     bds_state *states, unsigned char *wots_sigs,
                     unsigned char *sm, unsigned long long *smlen,
                     const unsigned char *m, unsigned long long mlen);

/**
 * Verifies a given message signature pair under a given public key.
 */
int xmssmt_core_sign_open(const xmss_params *params,
                          unsigned char *m, unsigned long long *mlen,
                          const unsigned char *sm, unsigned long long smlen,
                          const unsigned char *pk);
#endif