#include <errno.h>
#include <malloc.h>
#include <openssl/sha.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <time.h>
#include <unistd.h>

#include "list.h"

#pragma comment(lib, "openssl/sha.lib")
#define SHA_SUM_LENGTH (SHA_DIGEST_LENGTH + SHA_DIGEST_LENGTH + 1)

int generation(char *seed_path);
int reproduce(void *pic_address, size_t pic_size);

struct process_list
{
    struct list_head list;
    pid_t process_id;
};

char seed_path[SHA_SUM_LENGTH];
FILE *seed_handle = NULL;
void *pic_buffer = NULL;

int main(int argc, const char **argv)
{
    struct process_list scraps;
    struct process_list *iter = NULL;
    pid_t process_id;

    INIT_LIST_HEAD(&scraps.list);

    strncpy(seed_path, argv[1], SHA_SUM_LENGTH);

    while (1)
    {
        process_id = fork();
        iter = (struct process_list*)malloc(sizeof(struct process_list));
        iter->process_id = process_id;
        list_add_tail( &(iter->list), &(scraps.list) );

        if (process_id == 0)
        {
            generation(seed_path);
            break;
        }

        if (process_id < 0)
        {
            sleep(1);
            list_for_each_entry(iter, &scraps.list, list)
            {
                continue; /* @todo clean up pids */
            }
            break;
        }
    }

    return 1;
}

int generation(char *seed_path)
{
    int return_value = 0;
    long int mutation_value;
    struct stat pic_statistics;
    unsigned int mutation_offset = 0;
    unsigned char pic_mutated = 0;
    struct drand48_data drand_data;

    seed_handle = fopen(seed_path, "rb");
    if (NULL == seed_handle)
    {
        return_value = errno;
        goto GEN_CLEANUP;
    }

    return_value = fstat(fileno(seed_handle), &pic_statistics);
    if (-1 == return_value)
    {
        return_value = errno;
        goto GEN_CLEANUP;
    }

    int prot = (PROT_READ | PROT_WRITE | PROT_EXEC);
    int flags = (MAP_ANON | MAP_PRIVATE);
    pic_buffer = mmap(NULL, pic_statistics.st_size, prot, flags, -1, 0);
    if (MAP_FAILED == pic_buffer)
    {
        return_value = errno;
        goto GEN_CLEANUP;
    }

    return_value = fread(pic_buffer, 1, pic_statistics.st_size, seed_handle);
    if (return_value != pic_statistics.st_size)
    {
        return_value = errno;
        goto GEN_CLEANUP;
    }

    if (NULL != seed_handle)
    {
        fclose(seed_handle);
        seed_handle = NULL;
    }

    srand48_r(time(NULL), &drand_data);
    lrand48_r(&drand_data, &mutation_value);

    mutation_offset = (mutation_value % (pic_statistics.st_size + 1));
    pic_mutated =
        ((unsigned char *)pic_buffer)[mutation_offset] & (mutation_value % 2);
    ((char *)pic_buffer)[mutation_offset] = pic_mutated;

    int (*reproduce_function)(void *, size_t) = reproduce;
    void (*pic_function)(void *, size_t, void *) = pic_buffer;

    pic_function(pic_buffer, pic_statistics.st_size, reproduce_function);

GEN_CLEANUP:
    if (NULL != pic_buffer)
    {
        munmap(pic_buffer, pic_statistics.st_size);
    }
    if (NULL != seed_handle)
    {
        fclose(seed_handle);
        seed_handle = NULL;
    }

    return return_value;
}

int reproduce(void *pic_address, size_t pic_size)
{
    int return_value = 0;
    unsigned char digest[SHA_DIGEST_LENGTH];
    struct stat pic_statistics;

    memset(seed_path, 0, SHA_SUM_LENGTH);
    SHA1((const unsigned char *)pic_address, pic_size, digest);

    for (int iter = 0; iter < SHA_DIGEST_LENGTH; iter++)
    {
        sprintf(&seed_path[iter * 2], "%02x", digest[iter]);
    }

    FILE *survived_store = fopen(seed_path, "w+");
    if (NULL == survived_store)
    {
        return_value = errno;
        goto CLONE_CLEANUP;
    }

    return_value = fwrite(pic_address, 1, pic_size, survived_store);
    if (return_value != pic_size)
    {
        return_value = errno;
        goto CLONE_CLEANUP;
    }

    return_value = 1;
CLONE_CLEANUP:
    if (survived_store)
    {
        fclose(survived_store);
    }
    fstat(fileno(seed_handle), &pic_statistics);
    if (NULL != pic_buffer)
    {
        munmap(pic_buffer, pic_statistics.st_size);
    }
    if (NULL != seed_handle)
    {
        fclose(seed_handle);
        seed_handle = NULL;
    }

    return generation(seed_path);
}