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

// C99 required

enum {
  // ASN_TAG
  ASN_BOOLEAN           = 0x01,
  ASN_INTEGER32         = 0x02,
  ASN_BIT_STRING        = 0x03,
  ASN_OCTET_STRING      = 0x04,
  ASN_NULL              = 0x05,
  ASN_OBJECT_IDENTIFIER = 0x06,
  ASN_SEQUENCE          = 0x10,

  ASN_TAG_BER           = 0x1f,
  ASN_TAG_MASK          = 0x1f,

  // primitive/constructed
  ASN_CONSTRUCTED       = 0x20,

  // ASN_CLASS
  ASN_UNIVERSAL         = 0x00,
  ASN_APPLICATION       = 0x40,
  ASN_CONTEXT           = 0x80,
  ASN_PRIVATE           = 0xc0,

  ASN_CLASS_MASK        = 0xc0,
  ASN_CLASS_SHIFT       = 6,

  // ASN_APPLICATION
  ASN_IPADDRESS         = 0x00,
  ASN_COUNTER32         = 0x01,
  ASN_UNSIGNED32        = 0x02,
  ASN_TIMETICKS         = 0x03,
  ASN_OPAQUE            = 0x04,
  ASN_COUNTER64         = 0x06,
};

enum {
  BER_CLASS       = 0,
  BER_TAG         = 1,
  BER_CONSTRUCTED = 2,
  BER_DATA        = 3,
  BER_ARRAYSIZE
};

#define MAX_OID_STRLEN 4096

static U8 *buf, *cur;
static STRLEN len, rem;

// for "small" integers, return a readonly sv, otherwise create a new one
static SV *newSVcacheint (int val)
{
  static SV *cache[32];

  if (val < 0 || val >= sizeof (cache))
    return newSViv (val);

  if (!cache [val])
    {
      cache [val] = newSVuv (val);
      SvREADONLY_on (cache [val]);
    }

  return SvREFCNT_inc_NN (cache [val]);
}

/////////////////////////////////////////////////////////////////////////////

static void
error (const char *errmsg)
{
  croak ("%s at offset 0x%04x", errmsg, cur - buf);
}

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;
    }
}

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 U32
process_integer32 (void)
{
  U32 length = process_length ();

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

  U8 *data = getn (length, 0);

  if (!data)
    return 0;

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

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

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

  return res;
}

static SV *
process_integer32_sv (void)
{
  return newSViv ((I32)process_integer32 ());
}

static SV *
process_unsigned32_sv (void)
{
  return newSVuv ((U32)process_integer32 ());
}

#if IVSIZE >= 8

static U64TYPE
process_integer64 (void)
{
  U32 length = process_length ();

  if (length <= 0)
    {
      error ("INTEGER64 length equal to zero");
      return 0;
    }

  U8 *data = getn (length, 0);

  if (!data)
    return 0;

  if (length > 9 || (length > 8 && data [0]))
    {
      error ("INTEGER64 length too long");
      return 0;
    }

  U64TYPE res = data [0] & 0x80 ? 0xffffffffffffffff : 0;

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

  return res;
}

static SV *
process_integer64_sv (void)
{
  return newSViv ((I64TYPE)process_integer64 ());
}

static SV *
process_unsigned64_sv (void)
{
  return newSVuv ((U64TYPE)process_integer64 ());
}

#endif

static SV *
process_octet_string_sv (void)
{
  U32 length = process_length ();

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

  return newSVpvn (data, length);
}

static char *
write_uv (char *buf, U32 u)
{
  // the one-digit case is absolutely predominant, so this pays off (hopefully)
  if (u < 10)
    *buf++ = u + '0';
  else
    {
      char *beg = buf;

      do
        {
          *buf++ = u % 10 + '0';
          u /= 10;
        }
      while (u);

      // reverse digits
      for (char *ptr = buf; --ptr != beg; ++beg)
        {
          char c = *ptr;
          *ptr = *beg;
          *beg = c;
        }
    }

  return buf;
}

static SV *
process_object_identifier_sv (void)
{
  U32 length = process_length ();

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

  U8 *end = cur + length;
  U32 w = getb ();

  static char oid[MAX_OID_STRLEN]; // must be static
  char *app = oid;

  app = write_uv (app, (U8)w / 40);
  *app++ = '.';
  app = write_uv (app, (U8)w % 40);

  // we assume an oid component is never > 64 bytes
  while (cur < end && oid + sizeof (oid) - app > 64)
    {
      w = getb ();
      *app++ = '.';
      app = write_uv (app, w);
    }

  return newSVpvn (oid, app - oid);
}

static SV *
ber_decode ()
{
  int identifier = get8 ();

  SV *res;

  int constructed = identifier & ASN_CONSTRUCTED;
  int klass       = identifier & ASN_CLASS_MASK;
  int tag         = identifier & ASN_TAG_MASK;

  if (tag == ASN_TAG_BER)
    tag = getb ();

  if (tag == ASN_TAG_BER)
    tag = getb ();

  if (constructed)
    {
      U32 len = process_length ();
      U32 seqend = (cur - buf) + len;
      AV *av = (AV *)sv_2mortal ((SV *)newAV ());

      while (cur < buf + seqend)
        av_push (av, ber_decode ());

      if (cur > buf + seqend)
        croak ("constructed type %02x overflow (%x %x)\n", identifier, cur - buf, seqend);

      res = newRV_inc ((SV *)av);
    }
  else
    switch (identifier)
      {
        case ASN_NULL:
          res = &PL_sv_undef;
          break;

        case ASN_OBJECT_IDENTIFIER:
          res = process_object_identifier_sv ();
          break;

        case ASN_INTEGER32:
          res = process_integer32_sv ();
          break;

        case ASN_APPLICATION | ASN_UNSIGNED32:
        case ASN_APPLICATION | ASN_COUNTER32:
        case ASN_APPLICATION | ASN_TIMETICKS:
          res = process_unsigned32_sv ();
          break;

#if 0 // handled by default case
        case ASN_OCTET_STRING:
        case ASN_APPLICATION | ASN_IPADDRESS:
        case ASN_APPLICATION | ASN_OPAQUE:
          res = process_octet_string_sv ();
          break;
#endif

        case ASN_APPLICATION | ASN_COUNTER64:
          res = process_integer64_sv ();
          break;

        default:
          res = process_octet_string_sv ();
          break;
      }

  AV *av = newAV ();
  av_fill (av, BER_ARRAYSIZE - 1);
  AvARRAY (av)[BER_CLASS      ] = newSVcacheint (klass >> ASN_CLASS_SHIFT);
  AvARRAY (av)[BER_TAG        ] = newSVcacheint (tag);
  AvARRAY (av)[BER_CONSTRUCTED] = newSVcacheint (constructed ? 1 : 0);
  AvARRAY (av)[BER_DATA       ] = res;

  return newRV_noinc ((SV *)av);
}

MODULE = Convert::BER::XS		PACKAGE = Convert::BER::XS

PROTOTYPES: ENABLE

BOOT:
{
  HV *stash = gv_stashpv ("Convert::BER::XS", 1);

  static const struct {
    const char *name;
    IV iv;
  } *civ, const_iv[] = {
    { "ASN_BOOLEAN",           ASN_BOOLEAN           },
    { "ASN_INTEGER32",         ASN_INTEGER32         },
    { "ASN_BIT_STRING",        ASN_BIT_STRING        },
    { "ASN_OCTET_STRING",      ASN_OCTET_STRING      },
    { "ASN_NULL",              ASN_NULL              },
    { "ASN_OBJECT_IDENTIFIER", ASN_OBJECT_IDENTIFIER },
    { "ASN_TAG_BER",           ASN_TAG_BER           },
    { "ASN_TAG_MASK",          ASN_TAG_MASK          },
    { "ASN_CONSTRUCTED",       ASN_CONSTRUCTED       },
    { "ASN_UNIVERSAL",         ASN_UNIVERSAL   >> ASN_CLASS_SHIFT },
    { "ASN_APPLICATION",       ASN_APPLICATION >> ASN_CLASS_SHIFT },
    { "ASN_CONTEXT",           ASN_CONTEXT     >> ASN_CLASS_SHIFT },
    { "ASN_PRIVATE",           ASN_PRIVATE     >> ASN_CLASS_SHIFT },
    { "ASN_CLASS_MASK",        ASN_CLASS_MASK        },
    { "ASN_CLASS_SHIFT",       ASN_CLASS_SHIFT       },
    { "ASN_SEQUENCE",          ASN_SEQUENCE          },
    { "ASN_IPADDRESS",         ASN_IPADDRESS         },
    { "ASN_COUNTER32",         ASN_COUNTER32         },
    { "ASN_UNSIGNED32",        ASN_UNSIGNED32        },
    { "ASN_TIMETICKS",         ASN_TIMETICKS         },
    { "ASN_OPAQUE",            ASN_OPAQUE            },
    { "ASN_COUNTER64",         ASN_COUNTER64         },

    { "BER_CLASS"      , BER_CLASS       },
    { "BER_TAG"        , BER_TAG         },
    { "BER_CONSTRUCTED", BER_CONSTRUCTED },
    { "BER_DATA"       , BER_DATA        },
  };

  for (civ = const_iv + sizeof (const_iv) / sizeof (const_iv [0]); civ > const_iv; civ--)
    newCONSTSUB (stash, (char *)civ[-1].name, newSViv (civ[-1].iv));
}

SV *
ber_decode (SV *ber)
	CODE:
{
        buf = SvPVbyte (ber, len);
        cur = buf;
        rem = len;

        RETVAL = ber_decode ();
}
        OUTPUT: RETVAL

void
ber_is (SV *tuple, SV *klass = &PL_sv_undef, SV *tag = &PL_sv_undef, SV *constructed = &PL_sv_undef, SV *data = &PL_sv_undef)
        PROTOTYPE: $;$$$
	PPCODE:
{
	if (!SvOK (tuple))
          XSRETURN_NO;

        if (!SvROK (tuple) || SvTYPE (SvRV (tuple)) != SVt_PVAV)
          croak ("ber_seq: tuple must be ber tuple (array-ref)");

        AV *av = (AV *)SvRV (tuple);

        XPUSHs (
             (!SvOK (klass)       || SvIV  (AvARRAY (av)[BER_CLASS      ]) == SvIV (klass))
          && (!SvOK (tag)         || SvIV  (AvARRAY (av)[BER_TAG        ]) == SvIV (tag))
          && (!SvOK (constructed) || !SvIV (AvARRAY (av)[BER_CONSTRUCTED]) == !SvIV (constructed))
          && (!SvOK (data)        || sv_eq (AvARRAY (av)[BER_DATA       ], data))
          ? &PL_sv_yes : &PL_sv_no);
}

void
ber_is_seq (SV *tuple)
        PROTOTYPE: $
	PPCODE:
{
	if (!SvOK (tuple))
          XSRETURN_UNDEF;

        if (!SvROK (tuple) || SvTYPE (SvRV (tuple)) != SVt_PVAV)
          croak ("ber_seq: tuple must be ber tuple (array-ref)");

        AV *av = (AV *)SvRV (tuple);

        XPUSHs (
             SvIV (AvARRAY (av)[BER_CLASS      ]) == ASN_UNIVERSAL
          && SvIV (AvARRAY (av)[BER_TAG        ]) == ASN_SEQUENCE
          && SvIV (AvARRAY (av)[BER_CONSTRUCTED])
          ? AvARRAY (av)[BER_DATA] : &PL_sv_undef);
}

void
ber_is_i32 (SV *tuple, IV value)
        PROTOTYPE: $$
	PPCODE:
{
	if (!SvOK (tuple))
          XSRETURN_NO;

        if (!SvROK (tuple) || SvTYPE (SvRV (tuple)) != SVt_PVAV)
          croak ("ber_seq: tuple must be ber tuple (array-ref)");

        AV *av = (AV *)SvRV (tuple);

        XPUSHs (
              SvIV (AvARRAY (av)[BER_CLASS      ]) == ASN_UNIVERSAL
          &&  SvIV (AvARRAY (av)[BER_TAG        ]) == ASN_INTEGER32
          && !SvIV (AvARRAY (av)[BER_CONSTRUCTED])
          &&  SvIV (AvARRAY (av)[BER_DATA       ]) == value
          ? &PL_sv_yes : &PL_sv_no);
}

void
ber_is_oid (SV *tuple, SV *oid)
        PROTOTYPE: $$
	PPCODE:
{
	if (!SvOK (tuple))
          XSRETURN_NO;

        if (!SvROK (tuple) || SvTYPE (SvRV (tuple)) != SVt_PVAV)
          croak ("ber_seq: tuple must be ber tuple (array-ref)");

        AV *av = (AV *)SvRV (tuple);

        XPUSHs (
              SvIV (AvARRAY (av)[BER_CLASS      ]) == ASN_UNIVERSAL
          &&  SvIV (AvARRAY (av)[BER_TAG        ]) == ASN_OBJECT_IDENTIFIER
          && !SvIV (AvARRAY (av)[BER_CONSTRUCTED])
          &&  sv_eq (AvARRAY (av)[BER_DATA], oid)
          ? &PL_sv_yes : &PL_sv_no);
}