#include "EXTERN.h"
#include "perl.h"
#include "XSUB.h"

// C99 required

#define ASN_BOOLEAN         0x01
#define ASN_INTEGER         0x02
#define ASN_BIT_STR         0x03
#define ASN_OCTET_STR       0x04
#define ASN_NULL            0x05
#define ASN_OBJECT_ID       0x06
#define ASN_SEQUENCE        0x10
#define ASN_SET             0x11

#define ASN_UNIVERSAL       0x00
#define ASN_APPLICATION     0x40
#define ASN_CONTEXT         0x80
#define ASN_PRIVATE         0xc0

#define ASN_PRIMITIVE       0x00
#define ASN_CONSTRUCTOR     0x20

#define ASN_LONG_LEN        0x80
#define ASN_EXTENSION_ID    0x1f
#define ASN_BIT8            0x80

#define BENCHMARK

static SV *msg;
static int errflag;
static U8 *buf, *cur;
static STRLEN len, rem;

static SV *
x_get_cv (SV *cb_sv)
{
  HV *st;
  GV *gvp;
  CV *cv = sv_2cv (cb_sv, &st, &gvp, 0);

  if (!cv)
    croak ("CODE reference expected");

  return (SV *)cv;
}

static void
error (const char *msg)
{
  errflag = 1;

  printf ("<<<%s>>>\n", msg);//D
}

static int
need (int count)
{
  if (count < 0 || (int)rem < count)
    {
      error ("Unexpected end of message buffer");
      return 0;
    }

  return 1;
}

static U8 *
getn (int count, const U8 *errres)
{
  if (!need (count))
    return (U8 *)errres;

  U8 *res = cur;

  cur += count;
  rem -= count;

  return res;
}

static U8
get8 (void)
{
  if (rem <= 0)
    {
      error ("Unexpected end of message buffer");
      return 0;
    }

  rem--;
  return *cur++;
}

static U32
getb (void)
{
  U32 res = 0;

  for (;;)
    {
      U8 c = get8 ();
      res = (res << 7) | (c & 0x7f);

      if (!(c & 0x80))
        return res;
    }
}

#ifdef BENCHMARK
static double t1;

static double
tstamp (void)
{
  struct timeval tv;
  gettimeofday (&tv, 0);
  return tv.tv_sec + tv.tv_usec * 0.000001;
}
#endif

static U32
process_length (void)
{
  U32 res = get8 ();

  if (res & 0x80)
    {
      int cnt = res & 0x7f;
      res = 0;

      switch (cnt)
        {
          case 0:
            error ("Indefinite ASN.1 lengths not supported");
            return 0;

          default:
            error ("ASN.1 length too long");
            return 0;

          case 4: res = (res << 8) | get8 ();
          case 3: res = (res << 8) | get8 ();
          case 2: res = (res << 8) | get8 ();
          case 1: res = (res << 8) | get8 ();
        }
    }

  return res;
}

static AV *av_type;

MODULE = Net::SNMP::XS		PACKAGE = Net::SNMP::XS

PROTOTYPES: ENABLE

BOOT:
	av_type = newAV ();

void
set_type (int type, SV *cv)
	CODE:
        av_store (av_type, type, SvREFCNT_inc (x_get_cv (cv)));

void
set_msg (SV *msg_, SV *buf_)
	CODE:
        errflag = 0;
        msg     = SvREFCNT_inc (msg_);
        buf     = SvPVbyte (buf_, len);
        cur     = buf;
        rem     = len;
#ifdef BENCHMARK
        t1      = tstamp ();
#endif

void
clr_msg ()
	CODE:
        SvREFCNT_dec (msg);
        buf = cur = "";
        len = rem = 0;
#ifdef BENCHMARK
        printf ("%f\n", tstamp () - t1);//D
#endif

MODULE = Net::SNMP::XS		PACKAGE = Net::SNMP::Message

void
_buffer_get (SV *self, int count = -1)
	PPCODE:
{
	// grrr.
	if (count < 0)
          {
            hv_delete ((HV *)SvRV (self), "_index" , 6, G_DISCARD);
            hv_delete ((HV *)SvRV (self), "_length", 7, G_DISCARD);
            SV **svp = hv_fetch ((HV *)SvRV (self), "_buffer", 7, 1);
            XPUSHs (sv_2mortal (newSVsv (*svp)));
            sv_setpvn (*svp, "", 0);
            XSRETURN (1);
          }

        char *data = getn (count, 0);

        if (data)
          XPUSHs (sv_2mortal (newSVpvn (data, count)));
}

U32
index (SV *self, int ndx = -1)
	CODE:
{
        if (ndx >= 0 && ndx < len)
          {
            cur = buf + ndx;
            rem = len - ndx;
          }

        RETVAL = cur - buf;
}
	OUTPUT:
        RETVAL

U32
_process_length (SV *self, ...)
	ALIAS:
        _process_sequence = 0
	CODE:
        RETVAL = process_length ();
	OUTPUT:
        RETVAL

I32
_process_integer32 (SV *self, ...)
	ALIAS:
        _process_counter = 0
        _process_gauge   = 0
	CODE:
{
  	U32 length = process_length ();

        if (length <= 0)
          {
            error ("INTEGER32 length equal to zero");
            XSRETURN_UNDEF;
          }

        U8 *data = getn (length, 0);

        if (!data)
          XSRETURN_UNDEF;

        if (length > 5 || (length > 4 && data [0]))
          {
            error ("INTEGER32 length too long");
            XSRETURN_UNDEF;
          }

        U32 res = data [0] & 0x80 ? 0xffffffff : 0;

        while (length--)
          res = (res << 8) | *data++;

        RETVAL = res;
}
	OUTPUT:
        RETVAL

SV *
_process_object_identifier (SV *self, ...)
	CODE:
{
  	U32 length = process_length ();

        if (length <= 0)
          {
            error ("OBJECT IDENTIFIER length equal to zero");
            XSRETURN_UNDEF;
          }

        U8 *end = cur + length;
        U32 w = getb ();
        
        //TODO: leading_dots

        RETVAL = newSVpvf (".%d.%d", (int)w / 40, (int)w % 40);

        while (cur < end)
          {
            w = getb ();
            sv_catpvf (RETVAL, ".%u", (unsigned int)w);
          }
}
	OUTPUT:
        RETVAL

SV *
_process_octet_string (SV *self, ...)
	ALIAS:
        _process_opaque = 0
	CODE:
{
  	U32 length = process_length ();

        U8 *data = getn (length, 0);
        if (!data)
          {
            error ("OCTET STRING too long");
            XSRETURN_UNDEF;
          }

        RETVAL = newSVpvn (data, length);
}
	OUTPUT:
        RETVAL

SV *
_process_ipaddress (SV *self, ...)
	CODE:
{
  	U32 length = process_length ();
        if (length != 4)
          {
            error ("IP ADDRESS length not four");
            XSRETURN_UNDEF;
          }

        U8 *data = getn (4, "\x00\x00\x00\x00");
        RETVAL = newSVpvf ("%d.%d.%d.%d", data [0], data [1], data [2], data [3]);
}
	OUTPUT:
        RETVAL

SV *
process (SV *self, SV *expected = 0, SV *found = 0)
	PPCODE:
{
	U8 type = get8 ();

        if (expected && SvOK (expected) && type != SvIV (expected))
          {
            error ("Expected a different type than found");
            XSRETURN_UNDEF;
          }

        if (type > AvFILLp (av_type) || !SvTYPE (AvARRAY (av_type)[type]) == SVt_PVCV)
          {
            sv_dump (AvARRAY (av_type)[type]);//D
            error ("Unknown ASN.1 type");
            XSRETURN_UNDEF;
          }

        if (found)
          sv_setiv (found, type);

        SV *res;

        {
          dSP;
          PUSHMARK (SP);
          EXTEND (SP, 2);
          PUSHs (self);
          PUSHs (expected);
          PUTBACK;
          int count = call_sv (AvARRAY (av_type)[type], G_SCALAR);
          SPAGAIN;
          res = count ? TOPs : &PL_sv_undef;
        }

	XPUSHs (res);
}