#include "cmix.h"

#include <string.h>
#include <stdlib.h>

enum cmix_error permutation(struct CMixBuffer b) {
	return no_error;
}

enum cmix_error get_message(char* message, struct CMixBuffer b, unsigned int index)
{
	if(index >= b.message_length) {
		return index_out_of_range;
	}
	
	strncpy(message, b.buffer + index * b.message_length, b.message_length);

	return no_error;
}

enum cmix_error set_message(char const* message, struct CMixBuffer b, unsigned int index)
{
	if(index >= b.message_length) {
		return index_out_of_range;
	}
	
	strncpy(b.buffer + index * b.message_length, message, b.message_length);
	
	return no_error;
}

enum cmix_error calculate_shared_key_part(struct Bignum* result, struct Bignum partial_shared, struct Bignum my_share, struct Bignum mod)
{
	if(multiply_mod(result, partial_shared, my_share, mod) != NoError) {
		return cmix_bignum_error;
	}
	return no_error;
}

struct CMixContext initialize_cmix_context(struct Api api) {
	return (struct CMixContext){
		.api = api,
		.nr_participants = 0,
		.r = NULL,
		.s = NULL,
		.permutation = NULL,
		.pirs = NULL
	};
}

void release_mix(struct CMixContext* ctx) {
	for(size_t i = 0; i < ctx->nr_participants; ++i) {
		ctx->api.free_group_element(ctx->r[i]);
		ctx->api.free_group_element(ctx->s[i]);
		ctx->api.free_group_element(ctx->pirs[i]);
	}
	free(ctx->r);
	free(ctx->s);
	free(ctx->permutation);
	free(ctx->pirs);
}

void deinitialize(struct CMixContext* ctx)
{
	ctx->api.free_keypair(&ctx->keypair);
	release_mix(ctx);
}

void element_to_buffer(struct CMixContext const* ctx, char* out_buffer, GroupElement element) {
	size_t el_size = get_group_element_array_size(ctx);
	
	unsigned char* buffer;
	size_t len;
	
	ctx->api.element_to_array(&buffer, &len, element);
	size_t diff = el_size - len;
	memcpy(out_buffer + diff, buffer, len);
	ctx->api.free_buffer(buffer);
}

enum cmix_error initialize_keypair(struct CMixContext* ctx)
{
	ctx->keypair = ctx->api.create_keypair();
	return no_error;
}

enum cmix_error get_public_key(struct CMixContext const* ctx, char* buffer)
{
	element_to_buffer(ctx, buffer, ctx->keypair.pub);
	return no_error;
}

enum cmix_error add_public_share(struct CMixContext const* ctx, char* buffer, char const* share) {
	size_t len = get_group_element_array_size(ctx);
	
	GroupElement el;
	ctx->api.add_public_share(&el, share, len, ctx->keypair.pub);
	
	element_to_buffer(ctx, buffer, el);
	ctx->api.free_group_element(el);
}

enum cmix_error alloc_mix(struct CMixContext* ctx) {
	ctx->r = (GroupElement*) calloc(ctx->nr_participants, sizeof(GroupElement));
	ctx->s = (GroupElement*) calloc(ctx->nr_participants, sizeof(GroupElement));
	ctx->permutation = (unsigned int*) calloc(ctx->nr_participants, sizeof(unsigned int));
	ctx->pirs = (GroupElement*) calloc(ctx->nr_participants, sizeof(GroupElement));
	if(!ctx->r || !ctx->s || !ctx->permutation || !ctx->pirs) {
		return out_of_memory;
	}
	return no_error;
}

enum cmix_error start_mix(struct CMixContext* ctx, size_t nr_participants) {
	release_mix(ctx);
	ctx->nr_participants = nr_participants;
	return alloc_mix(ctx);
}

enum cmix_error initialize_mix_randomness(struct CMixContext* ctx) {
	for(size_t i = 0; i < ctx->nr_participants; ++i) {
		ctx->r[i] = ctx->api.get_group_element(true);
		ctx->s[i] = ctx->api.get_group_element(true);
		ctx->permutation[i] = i;
	}
	return no_error;
}

size_t get_group_element_array_size(struct CMixContext const* ctx) {
	return ctx->api.get_group_element_array_size();
}

enum cmix_error set_network_key(struct CMixContext* ctx, char const* buffer, size_t len) {
	ctx->network_key = ctx->api.array_to_element(buffer, len, true);
	return no_error;
}

enum cmix_error encrypt_r(struct CMixContext const* ctx, char* random_buffer, char* message_buffer, size_t index) {
	GroupElement random_element;
	GroupElement message_element;
	
	ctx->api.encrypt(&random_element, &message_element, ctx->r[index], ctx->network_key);
	
	element_to_buffer(ctx, random_buffer, random_element);
	element_to_buffer(ctx, message_buffer, message_element);
	
	return no_error;
}

enum cmix_error encrypt_r_and_multiply(struct CMixContext const* ctx, char* random_buffer, char* message_buffer, const char* random_element, const char* message_element, size_t index) {
	GroupElement enc_random_element;
	GroupElement enc_message_element;
	
	ctx->api.encrypt(&enc_random_element, &enc_message_element, ctx->r[index], ctx->network_key);
	
	size_t el_size = get_group_element_array_size(ctx);
	
	GroupElement other_random_element = ctx->api.array_to_element(random_element, el_size, true);
	GroupElement other_message_element = ctx->api.array_to_element(message_element, el_size, true);
	
	GroupElement new_random_element = ctx->api.multiply(enc_random_element, other_random_element, true);
	GroupElement new_message_element = ctx->api.multiply(enc_message_element, other_message_element, true);
	
	element_to_buffer(ctx, random_buffer, new_random_element);
	element_to_buffer(ctx, message_buffer, new_message_element);
		
	ctx->api.free_group_element(enc_random_element);
	ctx->api.free_group_element(enc_message_element);
	ctx->api.free_group_element(other_random_element);
	ctx->api.free_group_element(other_message_element);
	ctx->api.free_group_element(new_random_element);
	ctx->api.free_group_element(new_message_element);
	
	return no_error;
}

enum cmix_error multiply_s(struct CMixContext const* ctx, char* r_out_buffer, char* m_out_buffer, char const* r_in_buffer, char const* m_in_buffer, size_t index) {
	size_t el_size = get_group_element_array_size(ctx);
	
	GroupElement random_r = ctx->api.array_to_element(r_in_buffer, el_size, true);
	GroupElement message_r = ctx->api.array_to_element(m_in_buffer, el_size, true);
	
	GroupElement random_s;
	GroupElement message_s;
	
	ctx->api.encrypt(&random_s, &message_s, ctx->s[ctx->permutation[index]], ctx->network_key);
	
	GroupElement random_pirs = ctx->api.multiply(random_r, random_s, true);
	GroupElement message_pirs = ctx->api.multiply(message_r, message_s, true);
	
	element_to_buffer(ctx, r_out_buffer, random_pirs);
	element_to_buffer(ctx, m_out_buffer, message_pirs);
	
	ctx->api.free_group_element(random_r);
	ctx->api.free_group_element(message_r);
	ctx->api.free_group_element(random_s);
	ctx->api.free_group_element(message_s);
	
	return no_error;
}

enum cmix_error key_exchange(struct CMixContext const* ctx, GroupElement* shared_key, char* public_key_buffer, char* exchange_value_buffer, char const* pubkey, char const* value) {
	GroupElement priv_el = ctx->api.get_group_element(true);
	GroupElement ex_val = ctx->api.get_key_exchange_value(priv_el);
	
	size_t el_len = get_group_element_array_size(ctx);
	
	*shared_key = ctx->api.derive_shared_key(ctx->keypair, (unsigned char*)pubkey, el_len, (unsigned char*)value, el_len, priv_el, true);
	
	element_to_buffer(ctx, public_key_buffer, ctx->keypair.pub);
	element_to_buffer(ctx, exchange_value_buffer, ex_val);
	
	ctx->api.free_group_element(priv_el);
	ctx->api.free_group_element(ex_val);
	
	return no_error;
}