// gcc -O2 -Wall -Wextra -o main main.c

#define _GNU_SOURCE
#include <sys/fanotify.h>      // <-- прототипы fanotify_*
#include <sys/epoll.h>
#include <sys/uio.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <limits.h>            // PATH_MAX

#ifndef AT_FDCWD
#  include <fcntl.h>
#endif

/* Настройки из твоего D-кода */
#define INIT_FLAGS  (FAN_CLASS_PRE_CONTENT | FAN_CLOEXEC | FAN_NONBLOCK)
#define EVENT_FLAGS (O_RDONLY | O_LARGEFILE | O_CLOEXEC)
#define BASE_FLAGS  (FAN_MARK_ADD)
#define PERM_MASK   (FAN_OPEN_PERM | FAN_ACCESS_PERM | FAN_OPEN_EXEC_PERM | FAN_OPEN | FAN_CLOSE_WRITE)
#define BUF_SZ      (64 * 1024)

/* Простой лог */
static void log_line(const char *s) {
    struct iovec v[2];
    static const char nl = '\n';
    v[0].iov_base = (void*)s; v[0].iov_len = strlen(s);
    v[1].iov_base = (void*)&nl; v[1].iov_len = 1;
    writev(STDERR_FILENO, v, 2);
}

static ssize_t fd_path(int fd, char *buf, size_t cap) {
    char linkpath[64];
    int m = snprintf(linkpath, sizeof(linkpath), "/proc/self/fd/%d", fd);
    if (m <= 0 || (size_t)m >= sizeof(linkpath)) return -1;
    ssize_t r = readlink(linkpath, buf, cap - 1);
    if (r >= 0) buf[r] = '\0';
    return r;
}

int main(void) {
    int fan = fanotify_init(INIT_FLAGS, EVENT_FLAGS);
    if (fan == -1) { perror("fanotify_init"); return 1; }

    /* метим /tmp и /home как файловые системы */
    if (fanotify_mark(fan, BASE_FLAGS | FAN_MARK_FILESYSTEM, PERM_MASK, AT_FDCWD, "/tmp") == -1) {
        perror("fanotify_mark(/tmp)"); return 1;
    }
    if (fanotify_mark(fan, BASE_FLAGS | FAN_MARK_FILESYSTEM, PERM_MASK, AT_FDCWD, "/home") == -1) {
        perror("fanotify_mark(/home)"); return 1;
    }

    int ep = epoll_create1(EPOLL_CLOEXEC);
    if (ep == -1) { perror("epoll_create1"); return 1; }

    struct epoll_event ev = { .events = EPOLLIN | EPOLLONESHOT };
    ev.data.u64 = 1; /* тег */
    if (epoll_ctl(ep, EPOLL_CTL_ADD, fan, &ev) == -1) { perror("epoll_ctl ADD"); return 1; }

    char *buf = malloc(BUF_SZ);
    if (!buf) { perror("malloc"); return 1; }

    log_line("fanomon: started (watching /tmp and /home)");

    for (;;) {
        struct epoll_event out;
        int n = epoll_wait(ep, &out, 1, -1);
        if (n == -1) { if (errno == EINTR) continue; perror("epoll_wait"); break; }

        if ((out.events & EPOLLIN) && out.data.u64 == 1) {
            for (;;) {
                ssize_t len = read(fan, buf, BUF_SZ);
                if (len == -1 && (errno == EAGAIN || errno == EWOULDBLOCK)) break;
                if (len <= 0) break;

                struct fanotify_event_metadata *meta;
                for (meta = (struct fanotify_event_metadata*)buf;
                     FAN_EVENT_OK(meta, len);
                     meta = FAN_EVENT_NEXT(meta, len)) {

                    if (meta->vers != FANOTIFY_METADATA_VERSION) { log_line("metadata version mismatch"); continue; }
                    if (meta->mask & FAN_Q_OVERFLOW)             { log_line("queue overflow"); continue; }

                    /* Быстро отвечаем на PERM-события */
                    if (meta->mask & (FAN_OPEN_PERM | FAN_ACCESS_PERM | FAN_OPEN_EXEC_PERM)) {
                        struct fanotify_response resp = { .fd = meta->fd, .response = FAN_ALLOW };
                        if (write(fan, &resp, sizeof(resp)) == -1) perror("fanotify_response");
                    }

                    /* Лёгкий лог пути (после ответа) */
                    if (meta->fd >= 0) {
                        char path[PATH_MAX];
                        if (fd_path(meta->fd, path, sizeof(path)) >= 0) {
                            char line[PATH_MAX + 16];
                            const char *tag =
                                (meta->mask & FAN_OPEN)             ? "OPEN  " :
                                (meta->mask & FAN_CLOSE_WRITE)      ? "CLOSEW" :
                                (meta->mask & FAN_ACCESS_PERM)      ? "APERM " :
                                (meta->mask & FAN_OPEN_PERM)        ? "OPERM " :
                                (meta->mask & FAN_OPEN_EXEC_PERM)   ? "XPERM " : "EVENT ";
                            snprintf(line, sizeof(line), "%s %s", tag, path);
                            log_line(line);
                        }
                        close(meta->fd);
                    }
                }
            }

            /* Реарм ONE_SHOT */
            ev.events = EPOLLIN | EPOLLONESHOT;
            ev.data.u64 = 1;
            if (epoll_ctl(ep, EPOLL_CTL_MOD, fan, &ev) == -1) { perror("epoll_ctl MOD"); break; }
        }
    }

    free(buf);
    close(ep);
    close(fan);
    return 0;
}