/* Interface to Perl from OCaml.
 * Copyright (C) 2003 Merjis Ltd.
 * $Id: perl_c.c,v 1.1 2003-10-11 18:25:52 rich Exp $
 */

#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <unistd.h>
#include <alloca.h>

#include <caml/alloc.h>
#include <caml/callback.h>
#include <caml/fail.h>
#include <caml/memory.h>
#include <caml/mlvalues.h>

/* XXX This was required to avoid an error on my machine when loading the Perl
 * headers. Not clear why this is missing.
 */
#define off64_t __off64_t

#include <EXTERN.h>
#include <perl.h>

/* Perl requires the interpreter to be called literally 'my_perl'! */
static PerlInterpreter *my_perl;

/* Wrap up an arbitrary void pointer in an opaque OCaml object. */
static value Val_voidptr (void *ptr);

/* Unwrap an arbitrary void pointer from an opaque OCaml object. */
#define Voidptr_val(type,rv) ((type *) Field ((rv), 0))

/* Hide Perl types in opaque OCaml objects. */
#define Val_perl(pl) (Val_voidptr ((pl)))
#define Perl_val(plv) (Voidptr_val (PerlInterpreter, (plv)))
#define Val_sv(sv) (Val_voidptr ((sv)))
#define Sv_val(svv) (Voidptr_val (SV, (svv)))

CAMLprim value
perl4caml_init (value unit)
{
  PERL_SYS_INIT3 (NULL, NULL, NULL);
  return Val_unit;
}

CAMLprim value
perl4caml_create (value optargs, value unit)
{
  CAMLparam2 (optargs, unit);
  CAMLlocal1 (args);
  int argc, i;
  char **argv;
  static char *no_args[] = { "", "-e", "0" };

  /* Arguments given? */
  if (optargs == Val_int (0))	/* "None" */
    {
      argc = 3;
      argv = no_args;
    }
  else				/* "Some args" where args is a string array. */
    {
      args = Field (optargs, 0);
      argc = Wosize_val (args);
      argv = alloca (argc * sizeof (char *));
      for (i = 0; i < argc; ++i) argv[i] = String_val (Field (args, i));
    }

  my_perl = perl_alloc ();
  perl_construct (my_perl);
  PL_exit_flags |= PERL_EXIT_DESTRUCT_END;
  perl_parse (my_perl, NULL, argc, argv, NULL);
  perl_run (my_perl);

  CAMLreturn (Val_perl (my_perl));
}

CAMLprim value
perl4caml_destroy (value plv)
{
  CAMLparam1 (plv);
  PerlInterpreter *pl = Perl_val (plv);

  perl_destruct (pl);
  perl_free (pl);

  CAMLreturn (Val_unit);
}

CAMLprim value
perl4caml_set_context (value plv)
{
  CAMLparam1 (plv);
  PerlInterpreter *pl = Perl_val (plv);

  PERL_SET_CONTEXT (pl);
  my_perl = pl;

  CAMLreturn (Val_unit);
}

CAMLprim value
perl4caml_int_of_sv (value svv)
{
  CAMLparam1 (svv);
  SV *sv = Sv_val (svv);
  CAMLreturn (Val_int (SvIV (sv)));
}

CAMLprim value
perl4caml_sv_of_int (value iv)
{
  CAMLparam1 (iv);
  CAMLreturn (Val_sv (newSViv (Int_val (iv))));
}

CAMLprim value
perl4caml_float_of_sv (value svv)
{
  CAMLparam1 (svv);
  SV *sv = Sv_val (svv);
  CAMLlocal1 (f);
  f = copy_double (SvNV (sv));
  CAMLreturn (f);
}

CAMLprim value
perl4caml_sv_of_float (value fv)
{
  CAMLparam1 (fv);
  CAMLreturn (Val_sv (newSViv (Double_val (fv))));
}

CAMLprim value
perl4caml_string_of_sv (value svv)
{
  CAMLparam1 (svv);
  SV *sv = Sv_val (svv);
  char *str;
  STRLEN len;
  CAMLlocal1 (strv);
  str = SvPV (sv, len);
  /* XXX This won't work if the string contains NUL. */
  strv = copy_string (str);
  CAMLreturn (strv);
}

CAMLprim value
perl4caml_sv_of_string (value strv)
{
  CAMLparam1 (strv);
  CAMLreturn (Val_sv (newSVpv (String_val (strv), string_length (strv))));
}

CAMLprim value
perl4caml_call_scalar (value fnname, value arglist)
{
  CAMLparam2 (fnname, arglist);
  dSP;
  int count;
  SV *sv;
  CAMLlocal2 (errv, svv);

  ENTER;
  SAVETMPS;

  /* Push the parameter list. */
  PUSHMARK (SP);
  /* XXX NOT IMPLEMENTED YET. */
  PUTBACK;

  count = call_pv (String_val (fnname), G_EVAL|G_SCALAR);

  SPAGAIN;

  assert (count == 1); /* Pretty sure it should never be anything else. */

  /* Pop return value off the stack and restore Perl stack. Note that the
   * return value on the stack is mortal, so we need to take a copy.
   */
  sv = newSVsv (POPs);
  PUTBACK;
  FREETMPS;
  LEAVE;

  /* Died with an error? */
  if (SvTRUE (ERRSV))
    {
      STRLEN n_a;
      const char *err = SvPV (ERRSV, n_a); /* Equivalent of $@ in Perl. */

      errv = copy_string (err);

      raise_with_arg (*caml_named_value ("perl4caml_perl_failure"), errv);
    }
  else
    {
      svv = Val_sv (sv);
      CAMLreturn (svv);
    }
}

value
Val_voidptr (void *ptr)
{
  value rv = alloc (1, Abstract_tag); /* XXX Is this correct? */
  Field(rv, 0) = (value) ptr;
  return rv;
}