#include "shm.h"
#include <sys/mman.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>

struct crt_shm {
    int fd;
    void* ptr;
    size_t size;
    char name[256];
};

crt_shm_t* crt_shm_create(const char* name, size_t size) {
    crt_shm_t* shm = calloc(1, sizeof(crt_shm_t));
    if (!shm) return NULL;

    strncpy(shm->name, name, sizeof(shm->name) - 1);
    shm->size = size;

    shm->fd = shm_open(name, O_CREAT | O_RDWR, 0666);
    if (shm->fd < 0) {
        free(shm);
        return NULL;
    }

    if (ftruncate(shm->fd, size) < 0) {
        close(shm->fd);
        shm_unlink(name);
        free(shm);
        return NULL;
    }

    shm->ptr = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, shm->fd, 0);
    if (shm->ptr == MAP_FAILED) {
        close(shm->fd);
        shm_unlink(name);
        free(shm);
        return NULL;
    }

    memset(shm->ptr, 0, size);
    return shm;
}

crt_shm_t* crt_shm_open(const char* name) {
    crt_shm_t* shm = calloc(1, sizeof(crt_shm_t));
    if (!shm) return NULL;

    strncpy(shm->name, name, sizeof(shm->name) - 1);

    shm->fd = shm_open(name, O_RDWR, 0666);
    if (shm->fd < 0) {
        free(shm);
        return NULL;
    }

    struct stat st;
    if (fstat(shm->fd, &st) < 0) {
        close(shm->fd);
        free(shm);
        return NULL;
    }
    shm->size = st.st_size;

    shm->ptr = mmap(NULL, shm->size, PROT_READ | PROT_WRITE, MAP_SHARED, shm->fd, 0);
    if (shm->ptr == MAP_FAILED) {
        close(shm->fd);
        free(shm);
        return NULL;
    }

    return shm;
}

void crt_shm_close(crt_shm_t* shm) {
    if (!shm) return;
    if (shm->ptr && shm->ptr != MAP_FAILED) {
        munmap(shm->ptr, shm->size);
    }
    if (shm->fd >= 0) {
        close(shm->fd);
    }
    free(shm);
}

void* crt_shm_ptr(crt_shm_t* shm) {
    return shm ? shm->ptr : NULL;
}

size_t crt_shm_size(crt_shm_t* shm) {
    return shm ? shm->size : 0;
}

int crt_shm_resize(crt_shm_t* shm, size_t new_size) {
    if (!shm || !shm->ptr) return -1;

    if (munmap(shm->ptr, shm->size) < 0) return -1;
    if (ftruncate(shm->fd, new_size) < 0) return -1;

    shm->ptr = mmap(NULL, new_size, PROT_READ | PROT_WRITE, MAP_SHARED, shm->fd, 0);
    if (shm->ptr == MAP_FAILED) return -1;

    shm->size = new_size;
    return 0;
}