#ifndef _GNU_SOURCE
# define _GNU_SOURCE
#endif

#include <sys/types.h>
#include <stdio.h>
#include <unistd.h>
#include <dirent.h>
#include <dlfcn.h>

static const char* color_ok_programs[] = {
    "/usr/bin/lv",
    "/usr/local/stow/w3m/bin/w3m",
};

static int (*libc_isatty)(int fd) = NULL;

__attribute__((constructor)) static void init() {
    libc_isatty = (int (*)(int))dlsym(RTLD_NEXT, "isatty");
}

int isatty(int fd) {
    usleep(1);

    if (!libc_isatty) return 0;
    if (libc_isatty(fd)) return 1;

    char buf[256];
    sprintf(buf, "/proc/self/fd/%d", fd);
    char fdp[256];
    int sz = readlink(buf, fdp, 255);
    if (sz <= 0 || sz == 255) return 0;
    fdp[sz] = '\0';
    if (strncmp(fdp, "pipe:", 5)) return 0;

    pid_t mypid = getpid();
    pid_t mygrp = getpgrp();
    DIR* dir = opendir("/proc");
    struct dirent* ent;
    while ((ent = readdir(dir)) != NULL) {
        int pid = atoi(ent->d_name);
        if (!pid || pid == mypid) continue;
        pid_t grp = getpgid(pid);
        if (grp == mygrp) {
            char exe[256];
            sprintf(buf, "/proc/%d/exe", pid);
            int sz2 = readlink(buf, exe, 255);
            if (sz2 <= 0 || sz2 == 255) continue;
            exe[sz2] = '\0';
            //printf("EXE %s=>%s\n", buf, exe);
            int i;
            for (i = 0;
                 i < sizeof(color_ok_programs) / sizeof(color_ok_programs[0]);
                 i++) {
                if (!strcmp(exe, color_ok_programs[i])) {
                    closedir(dir);
                    return 1;
                }
            }
        }
    }
    closedir(dir);
    return 0;
}