#include <stdarg.h>
#include <string.h>
#include "asn1.h"

size_t fmt_asn1generic(char* dest,const char* fmt,...) {
  size_t containerstack[100];
  size_t curinstack=0;
  va_list args;
  unsigned long* application=0;
  struct string* s;
  struct oid* o;
  struct string S;
  size_t curlen=0;
  size_t cursor=0;
  size_t seqlen;
  unsigned long desttag=0;
  unsigned long appstore;
  int stringtype;
  va_start(args,fmt);
  while (*fmt) {
    char* realdest=dest?dest+cursor:NULL;
    switch (*fmt) {
    case '*':	// make next tag use APPLICATION with this tag
      appstore=va_arg(args,unsigned long);
      application=&appstore;
      break;
    case '0':	// UNIVERSAL PRIMITIVE NULL length 0
      if (application)
	curlen=fmt_asn1tag(realdest,APPLICATION,PRIMITIVE,_NULL);
      else
	curlen=fmt_asn1tag(realdest,UNIVERSAL,PRIMITIVE,_NULL);
      application=NULL;
      curlen+=fmt_asn1length(realdest?realdest+curlen:NULL,0);
      break;
    case 'B':	// send boolean
      {
	int i=va_arg(args,int);
	if (i!=0 && i!=1) {
	  va_end(args);
	  return 0;
	}
	if (application)
	  curlen=fmt_asn1int(realdest,APPLICATION,PRIMITIVE,*application,i);
	else
	  curlen=fmt_asn1int(realdest,UNIVERSAL,PRIMITIVE,BOOLEAN,i);
	application=NULL;
	break;
      }
    case 'i':	// send integer
      {
	unsigned long i=va_arg(args,unsigned long);
	if (application)
	  curlen=fmt_asn1int(realdest,APPLICATION,PRIMITIVE,*application,i);
	else
	  curlen=fmt_asn1int(realdest,UNIVERSAL,PRIMITIVE,INTEGER,i);
	application=NULL;
	break;
      }
    case 'b':	// send BIT_STRING, using struct string* as arg (expect l to be in bits, not bytes)
      s=va_arg(args,struct string*);
      if (application)
	curlen=fmt_asn1bitstring(realdest,APPLICATION,PRIMITIVE,*application,s->s,s->l);
      else
	curlen=fmt_asn1bitstring(realdest,UNIVERSAL,PRIMITIVE,BIT_STRING,s->s,s->l);
      application=NULL;
      break;
    case 'I':
      stringtype=BIT_STRING;
      goto stringcopy;
    case 'A':
      stringtype=IA5String;
      goto stringcopy;
    case 'P':
      stringtype=PrintableString;
      goto stringcopy;
    case 'S':	// send OCTET_STRING, using struct string* as arg
      stringtype=OCTET_STRING;
stringcopy:
      s=va_arg(args,struct string*);
copystring:
      if (application)
	curlen=fmt_asn1string(realdest,APPLICATION,PRIMITIVE,*application,s->s,s->l);
      else
	curlen=fmt_asn1string(realdest,UNIVERSAL,PRIMITIVE,stringtype,s->s,s->l);
      application=NULL;
      break;
    case 't':
      stringtype=UTCTIME;
      goto stringcopy_alt;
    case 'a':
      stringtype=IA5String;
      goto stringcopy_alt;
    case 'p':
      stringtype=PrintableString;
      goto stringcopy_alt;
    case 's':	// send OCTET_STRING, using const char* with strlen() as arg
      stringtype=OCTET_STRING;
stringcopy_alt:
      S.s=va_arg(args,const char*);
      S.l=strlen(S.s);
      s=&S;
      goto copystring;
    case 'o':	// send OBJECT_IDENTIFIER, using struct oid* as arg
      o=va_arg(args,struct oid*);
      if (application)
	curlen=fmt_asn1OID(realdest,APPLICATION,PRIMITIVE,*application,o->a,o->l);
      else
	curlen=fmt_asn1OID(realdest,UNIVERSAL,PRIMITIVE,OBJECT_IDENTIFIER,o->a,o->l);
      application=NULL;
      break;

    case 'C':	// copy raw ASN.1 DER data, take struct string*
      s=va_arg(args,struct string*);
      if (realdest) memcpy(realdest,s->s,s->l);
      curlen=s->l;
      break;

    case 'c':	// start context specific section
      desttag=va_arg(args,unsigned long);
      // fall through
    case '[':	// start SET
    case '{':	// start SEQUENCE
      if (application)
	curlen=fmt_asn1tag(realdest,APPLICATION,CONSTRUCTED,*application);
      else if (*fmt=='c')
	curlen=fmt_asn1tag(realdest,CONTEXT_SPECIFIC,CONSTRUCTED,desttag);
      else
	curlen=fmt_asn1tag(realdest,UNIVERSAL,CONSTRUCTED,*fmt=='{'?SEQUENCE_OF:SET_OF);
      containerstack[curinstack++]=cursor+curlen;
      application=NULL;
      break;
    case ']':	// end of SET
    case '}':	// end of SEQUENCE
      /* we just wrote the tag and the sequence.  Now that we wrote the
       * sequence, we know the length it took, and we need to move the
       * sequence data backwards to make room to write the ASN.1 length */
      {
	char* anfang;
	if (!curinstack) {
	  va_end(args);
	  return 0;
	}
	anfang=dest+containerstack[--curinstack];
	seqlen=dest+cursor-anfang;
	curlen=fmt_asn1length(NULL,seqlen);
	if (!dest) break;
	memmove(anfang+curlen,anfang,seqlen);
	fmt_asn1length(anfang,seqlen);
	break;
      }
    }
    cursor+=curlen;
    ++fmt;
  }
  va_end(args);
  return cursor;
}