// ----------------------------------------------------------------------------
// https://dataswamp.org/~incal/peval/peval.c
// -----------------------------------------------------------------------------

#include "peval.h"
#include <emacs-module.h>

// -----------------------------------------------------------------------------

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>

// -----------------------------------------------------------------------------

int plugin_is_GPL_compatible;

// -----------------------------------------------------------------------------

const int PIPES_R = 0;
const int PIPES_W = 1;
const int MAX_LEN = 256;

// -----------------------------------------------------------------------------
int emacs_module_init (struct emacs_runtime* rnt) {
  /* check for incompatible Emacs binary */
  if (rnt->size < (long int)sizeof(*rnt)) { return 1; }

  /* check for incompatible module API */
  emacs_env* env = rnt->get_environment(rnt);
  if (env->size < (long int)sizeof(*env)) { return 2; }

  /* check for too old Emacs */
  int __attribute__((unused)) emacs_ver;
  if      ((long int)sizeof(struct emacs_env_31) <= env->size) { emacs_ver = 31; }
  else if ((long int)sizeof(struct emacs_env_30) <= env->size) { emacs_ver = 30; }
  else if ((long int)sizeof(struct emacs_env_29) <= env->size) { emacs_ver = 29; }
  else { return 3; }

  /* init module */
  emacs_value peval_func   = env->make_function(env, 0, 8, peval, "`eval' in parallel.", NULL);
  emacs_value peval_symb   = env->intern(env, "peval");
  emacs_value peval_args[] = {peval_symb, peval_func};
  env->funcall(env, env->intern(env, "defalias"), 2, peval_args);

  /* done */
  return 0;
}

// -----------------------------------------------------------------------------

emacs_value peval (emacs_env*   env,
                   ptrdiff_t    nargs,
                   emacs_value* args,
                   void*        data __attribute__((unused))) {
  pid_t wpid;
  pid_t p;
  int status = 0;

  int (*pipes)[2] = malloc(nargs * sizeof(int[2]));
  if (!pipes) { perror("[malloc] error\n"); exit(1); }

  for (int i = 0; i < nargs; i++) {
    if (pipe(pipes[i]) == -1) { perror("[pipe] error\n"); exit(1); }
  }

  for (ptrdiff_t i = 0; i < nargs; i++) {
    p = fork();
    if (p == -1) { perror("[fork] error\n"); exit(1); }
    else if (p == 0) {
      close(pipes[i][PIPES_R]);
      emacs_value es = env->funcall(env, env->intern(env, "peval--eform"),  1, &(args[i]));
      char str[MAX_LEN];
      ptrdiff_t l = 0;
      env->copy_string_contents(env, es, NULL, &l);
      env->copy_string_contents(env, es, str,  &l);
      write(pipes[i][PIPES_W], str, strlen(str));
      close(pipes[i][PIPES_W]);
      exit(0);
    }
  }
  for (int i = 0; i < nargs; i++) {
    close(pipes[i][PIPES_W]);
  }
  while ((wpid = wait(&status)) > 0);
  emacs_value evals[nargs];
  char str[nargs][MAX_LEN];
  for (int i = 0; i < nargs; i++) {
    read(pipes[i][PIPES_R], str[i], MAX_LEN);
    close(pipes[i][PIPES_R]);
    evals[i] = env->make_unibyte_string(env, str[i], strlen(str[i]));
  }
  free(pipes);
  emacs_value lst = env->funcall(env, env->intern(env, "list"), nargs, evals);
  return lst;
}

// -----------------------------------------------------------------------------