#include <openssl/evp.h>
#include <openssl/err.h>
#include "log.h"

EVP_MD_CTX * md_ctx = NULL;
EVP_MD * md = NULL;

static int hasher_initialized = 0;

int init_hasher(void){
	if(hasher_initialized){
		printf("hasher already initialized");
		return 1;
	}
	else{
		md = EVP_MD_fetch(NULL, "SHA256", NULL);
		if(md == NULL){
			ERR_print_errors_fp(stderr);
			return 0;
		}
		md_ctx = EVP_MD_CTX_new();
		/*TODO: see whether EVP_MD_CTX_new() ever fails?*/
		if(md_ctx == NULL){
			ERR_print_errors_fp(stderr);
			return 0;
		}
		
	}
	return 1;
}

int deinit_hasher(void){
	if(md != NULL){
		EVP_MD_free(md);
	}
	
	if(md_ctx != NULL){
		EVP_MD_CTX_free(md_ctx);
	}
	return 0;
}

int rounduptoblocksize(int a){
	return a;
}

unsigned char * digest(const unsigned char *in, size_t inlen, unsigned int * outlen){

	if(!EVP_DigestInit_ex(md_ctx, md, NULL)){
		log(LOG_INFO, "Problem encountered while initializing digest");
		ERR_print_errors_fp(stderr);
		return NULL;
	}
	
	if(!EVP_DigestUpdate(md_ctx, in, inlen)){
		log(LOG_INFO, "Problem encountered while adding data to digest");
		ERR_print_errors_fp(stderr);
		return NULL;
	}

	unsigned char *out = OPENSSL_malloc(EVP_MD_get_size(md));
	
	if(!EVP_DigestFinal_ex(md_ctx, out, outlen)){
		log(LOG_INFO, "Problem encountered while retrieving digest");
		ERR_print_errors_fp(stderr);
		return NULL;
	}
	
	return out;
}

int begin_digest(){
	if(!EVP_DigestInit_ex(md_ctx, md, NULL)){
		log(LOG_INFO, "Problem encountered while initializing digest");
		ERR_print_errors_fp(stderr);
		return 0;
	}
	return 1;
}

int digest_part(const unsigned char *in, size_t inlen){
	
	if(!EVP_DigestUpdate(md_ctx, in, inlen)){
		log(LOG_INFO, "Problem encountered while adding data to digest");
		ERR_print_errors_fp(stderr);
		return 0;
	}
	return 1;
}

unsigned char * get_digest(unsigned int * outlen){
	
	unsigned char *out = OPENSSL_malloc(EVP_MD_get_size(md));
	
	if(!EVP_DigestFinal_ex(md_ctx, out, outlen)){
		log(LOG_INFO, "Problem encountered while retrieving digest");
		ERR_print_errors_fp(stderr);
		return NULL;
	}
	
	return out;
}