#include <curses.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <sys/select.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>

static struct menuitem {
  char *cmd;
//char *desc;
} *menu = NULL;

static int entries = 0;
static int selection = 0;
void bye(void) { if (!isendwin()) endwin(); }
void init_menu(void)
{
  initscr(); cbreak(); noecho(); keypad(stdscr, 1); box(stdscr, 0, 0);
  atexit(bye);
}
void menu_add(char *line)
{
  size_t n = strlen(line); // sigh
  if (line[n-1] == '\n')
    line[--n] = '\0';

  char *cmd = strchr(line, '\t');
  if (cmd)
    *cmd++ = '\0';
  else
    cmd = line;

  menu = realloc(menu, sizeof(*menu) * (entries + 1));
  menu[entries].cmd  = strdup(cmd);
//menu[entries].desc = strdup(line);
  mvaddstr(++entries, 7, line);
}
void menu_up(void)
{
  if (selection <= 0)
    return;
  int i;
  for (i = selection - 1; i >= 0; --i)
    if (strlen(menu[i].cmd)) {
      mvaddstr(selection + 1, 3, "   ");
      selection = i;
      mvaddstr(selection + 1, 3, "-->");
      move(selection + 1, 1);
      refresh();
      return;
    }
}
void menu_down(void)
{
  if (selection >= entries - 1)
    return;
  int i;
  for (i = selection + 1; i < entries; ++i)
    if (strlen(menu[i].cmd)) {
      mvaddstr(selection + 1, 3, "   ");
      selection = i;
      mvaddstr(selection + 1, 3, "-->");
      move(selection + 1, 1);
      refresh();
      return;
    }
}
void menu_select(void)
{
  bye();
  execl("/bin/sh", "/bin/sh", "-c", menu[selection].cmd, (char *) NULL);
  perror("exec failed");
  exit(1);
}
void menu_update(void)
{
  if (!selection)
    menu_down(); // TODO: something else
  else
    refresh();
}

int main(int argc, char *argv[])
{
  if (argc != 2) {
    fputs("usage: dynmenu socket-file\n", stderr);
    return 1;
  }
  int fd;
  // O_RDWR on FIFO; see url:
  // http://fixunix.com/unix/350803-use-select-fifo-after-has-closed.html
  if ((fd = open((const char *) argv[1], O_RDWR|O_NONBLOCK)) < 0) {
    perror("error opening socket-file");
    return 1;
  }
  FILE *fifo;
  if ((fifo = fdopen(fd, "r")) == NULL) {
    perror("error opening socket-file: fdopen");
    return 1;
  }

  init_menu();

  fd_set fds;
  int res;
  FD_ZERO(&fds); FD_SET(fd, &fds); FD_SET(0, &fds);
  while ((res = select(fd+1, &fds, NULL, NULL, NULL)) >= 0)
  {
    if (FD_ISSET(0, &fds)) {
      int c = getch();
      if (c == ERR) {
	perror("error reading stdin");
	return 1;
      }
      switch (c) {
	case KEY_UP:   case 'k': menu_up();   break;
	case KEY_DOWN: case 'j': menu_down(); break;
	case KEY_RIGHT:
	case KEY_ENTER: menu_select(); break;
      }
    }
    if (FD_ISSET(fd, &fds)) {
      char line[1024];
      while (fgets(line, sizeof(line), fifo) != NULL)
	menu_add(line); // doesn't redraw right away
      if (ferror(fifo) && errno != EAGAIN) {
	perror("error reading fifo");
	return 1;
      }
      menu_update(); // ok, no more lines; now redraw
    }
    FD_ZERO(&fds); 
    if (!feof(fifo)) // will never eof if it is a fifo
      FD_SET(fd, &fds); // could use inotify here...
    FD_SET(0, &fds);
  }
  fputs("unpossible!", stderr);
  exit(1);
}