/* -*-comment-start: "//";comment-end:""-*-
 * GNU Mes --- Maxwell Equations of Software
 * Copyright © 2016,2017,2018,2019 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
 * Copyright © 2019 Jeremiah Orians <jeremiah@pdp10.guru>
 *
 * This file is part of GNU Mes.
 *
 * GNU Mes is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or (at
 * your option) any later version.
 *
 * GNU Mes is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with GNU Mes.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "mes/lib.h"
#include "mes/mes.h"

#include <fcntl.h>
#include <limits.h>
#include <stdarg.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/wait.h>
#include <time.h>
#include <unistd.h>

int
get_env_value (char *c, int alt)
{
  char *s = getenv (c);
  if (NULL == s)
    return alt;
  return numerate_string (s);
}

int
peekchar ()
{
  if (__stdin >= 0)
    {
      int c = readchar ();
      unreadchar (c);
      return c;
    }

  struct scm *port = current_input_port ();
  struct scm *string = port->cdr;
  size_t length = string->length;

  if (!length)
    {
      return -1;
    }

  char *p = string->cdr->string;
  return p[0];
}

int
readchar ()
{
  if (__stdin >= 0)
    {
      return fdgetc (__stdin);
    }

  struct scm *port = current_input_port ();
  struct scm *string = port->cdr;
  size_t length = string->length;

  if (!length)
    {
      return -1;
    }

  char *p = string->cdr->string;
  int c = p[0];
  p = p + 1;
  port->cdr = make_string (p, length - 1);
  return c;
}

int
unreadchar (int c)
{
  if (__stdin >= 0)
    {
      return fdungetc (c, __stdin);
    }

  struct scm *port = current_input_port ();
  struct scm *string = port->cdr;
  size_t length = string->length;
  char *p = string->cdr->string;
  p = p - 1;
  string = make_string (p, length + 1);
  p = string->cdr->string;
  p[0] = c;
  port->cdr = string;
  return c;
}

struct scm *
peek_byte ()
{
  return make_number (peekchar ());
}

struct scm *
read_byte ()
{
  return make_number (readchar ());
}

struct scm *
unread_byte (struct scm *i)
{
  struct scm *x = i;
  unreadchar (x->value);
  return x;
}

struct scm *
peek_char ()
{
  return make_char (peekchar ());
}

struct scm *
read_char (struct scm *port)    ///((arity . n))
{
  int fd = __stdin;
  struct scm *p = port;

  if (p->type == TPAIR && p->car->type == TNUMBER)
    {
      __stdin = p->car->value;
    }

  struct scm *c = make_char (readchar ());
  __stdin = fd;
  return c;
}

struct scm *
unread_char (struct scm *i)
{
  struct scm *x = i;
  unreadchar (x->value);
  return x;
}

char *
env_lookup (char *token, char **envp)
{
  if (NULL == envp)
    return NULL;
  int i = 0;
  char *ret = NULL;
  do
    {
      if (!strcmp (token, envp[i]))
        ret = envp[i];
      if (NULL != ret)
        return ret;
      i = i + 1;
    }
  while (NULL != envp[i]);
  return NULL;
}

struct scm *
getenv_ (struct scm *s)         ///((name . "getenv"))
{
  struct scm *x = s;
  char *p = x->cdr->string;
  char *pass = env_lookup (p, global_envp);
  if (NULL == pass)
    return cell_f;
  return make_string_ (pass);
}

struct scm *
setenv_ (struct scm *s, struct scm *v)  ///((name . "setenv"))
{
  struct scm *a = s;
  struct scm *b = v;
  char *p1 = a->cdr->string;
  char *p2 = b->cdr->string;
  setenv (p1, p2, 1);
  return cell_unspecified;
}

struct scm *
access_p (struct scm *file_name, struct scm *mode)
{
  struct scm *f = file_name;
  struct scm *m = mode;
  char *p = f->cdr->string;
  return access (p, m->value) == 0 ? cell_t : cell_f;
}

struct scm *
current_input_port ()
{
  if (__stdin >= 0)
    {
      return make_number (__stdin);
    }

  struct scm *x = g_ports;

  while (x->car->port != __stdin)
    {
      x = x->cdr;
    }

  return x->car;
}

struct scm *
open_input_file (struct scm *file_name)
{
  struct scm *f = file_name;
  char *p = f->cdr->string;
  return make_number (mes_open (p, O_RDONLY, 0));
}

struct scm *
open_input_string (struct scm *string)
{
  struct scm *port = make_port (-length__ (g_ports) - 2, string);
  g_ports = cons (port, g_ports);
  return port;
}

struct scm *
set_current_input_port (struct scm *port)
{
  struct scm *prev = current_input_port ();
  struct scm *x = port;

  if (x->type == TNUMBER)
    {
      __stdin = x->value ? x->value : STDIN;
    }
  else if (x->type == TPORT)
    {
      __stdin = x->rac;
    }

  return prev;
}

struct scm *
current_output_port ()
{
  return make_number (__stdout);
}

struct scm *
current_error_port ()
{
  return make_number (__stderr);
}

struct scm *
open_output_file (struct scm *x)        ///((arity . n))
{
  struct scm *y = x;
  struct scm *f = y->car;
  y = y->cdr;
  int mode = S_IRUSR | S_IWUSR;

  if (y->type == TPAIR && f->type == TNUMBER)
    {
      mode = f->value;
    }

  char *p = f->cdr->string;
  SCM fl = mes_open (p, O_WRONLY | O_CREAT | O_TRUNC, mode);
  struct scm *handle = make_number (fl);
  return handle;
}

struct scm *
set_current_output_port (struct scm *port)
{
  struct scm *p = port;
  __stdout = p->value ? p->value : STDOUT;
  return current_output_port ();
}

struct scm *
set_current_error_port (struct scm *port)
{
  struct scm *p = port;
  __stderr = p->value ? p->value : STDERR;
  return current_error_port ();
}

struct scm *
chmod_ (struct scm *file_name, struct scm *mode)        ///((name . "chmod"))
{
  struct scm *f = file_name;
  struct scm *m = mode;
  char *p = f->cdr->string;
  chmod (p, m->value);
  return cell_unspecified;
}

struct scm *
isatty_p (struct scm *port)
{
  struct scm *p = port;
  return isatty (p->value) ? cell_t : cell_f;
}

struct scm *
primitive_fork ()
{
  return make_number (fork ());
}

void
require (int bool, char *error)
{
  if (!bool)
    {
      eputs (error);
      exit (EXIT_FAILURE);
    }
}

struct scm *
execl_ (struct scm *file_name, struct scm *args)        ///((name . "execl"))
{
  struct scm *f = file_name;
  struct scm *a = args;
  char *c_argv[1000];           // POSIX minimum 4096
  int i = 0;

  if (length__ (args) > 1000)
    {
      error (cell_symbol_system_error,
             cons (file_name, cons (make_string_ ("too many arguments"), cons (file_name, args))));
    }

  char *p = f->cdr->string;
  c_argv[i] = p;
  i = i + 1;

  while (a != cell_nil)
    {
      struct scm *aa = a->car;
      assert (aa->type == TSTRING);
      p = aa->cdr->string;
      c_argv[i] = p;
      i = i + 1;
      a = a->cdr;

      if (g_debug > 2)
        {
          eputs ("arg[");
          eputs (itoa (i));
          eputs ("]: ");
          eputs (c_argv[i - 1]);
          eputs ("\n");
        }
    }

  c_argv[i] = 0;
  return make_number (execv (c_argv[0], c_argv));
}

struct scm *
waitpid_ (struct scm *pid, struct scm *options)
{
  struct scm *p = pid;
  struct scm *o = options;
  int status;
  int child = waitpid (p->value, &status, o->value);
  return cons (make_number (child), make_number (status));
}

#if __x86_64__
/* Nanoseconds on 64-bit systems with POSIX timers.  */
#define TIME_UNITS_PER_SECOND 1000000000
#else
/* Milliseconds for everyone else.  */
#define TIME_UNITS_PER_SECOND 1000
#endif

struct timespec g_start_time;
struct scm *
init_time (struct scm *a)       ///((internal))
{
  clock_gettime (CLOCK_PROCESS_CPUTIME_ID, &g_start_time);
  return acons (cell_symbol_internal_time_units_per_second, make_number (TIME_UNITS_PER_SECOND), a);
}

struct scm *
current_time ()
{
  return make_number (time (0));
}

struct scm *
gettimeofday_ ()                ///((name . "gettimeofday"))
{
  struct timeval time;
  gettimeofday (&time, 0);
  return cons (make_number (time.tv_sec), make_number (time.tv_usec));
}

SCM
seconds_and_nanoseconds_to_long (SCM s, SCM ns)
{
  return s * TIME_UNITS_PER_SECOND + ns / (1000000000 / TIME_UNITS_PER_SECOND);
}

struct scm *
get_internal_run_time ()
{
  struct timespec ts;
  clock_gettime (CLOCK_PROCESS_CPUTIME_ID, &ts);
  SCM time =
    seconds_and_nanoseconds_to_long (ts.tv_sec - g_start_time.tv_sec, ts.tv_nsec - g_start_time.tv_nsec);
  return make_number (time);
}

struct scm *
getcwd_ ()                      ///((name . "getcwd"))
{
  char buf[PATH_MAX];
  return make_string_ (getcwd (buf, PATH_MAX));
}

struct scm *
dup_ (struct scm *port)         ///((name . "dup"))
{
  struct scm *p = port;
  return make_number (dup (p->value));
}

struct scm *
dup2_ (struct scm *old, struct scm *new)        ///((name . "dup2"))
{
  struct scm *o = old;
  struct scm *n = new;
  dup2 (o->value, n->value);
  return cell_unspecified;
}

struct scm *
delete_file (struct scm *file_name)
{
  struct scm *f = file_name;
  char *p = f->cdr->string;
  unlink (p);
  return cell_unspecified;
}