#include <stdio.h>
#include <stdlib.h>

#include "stdio-util.h"

typedef struct indent_priv INDENT_PRIV;

struct indent_priv {
  FILE *inner;
  int atnl;
  const char *(*pfx)(void *);
  void *pfxarg;
  } ;

static int indent_w(void *pv, const char *data, int len)
{
 INDENT_PRIV *p;
 int x0;
 int x;

 p = pv;
 x0 = -1;
 for (x=0;x<len;x++)
  { if (data[x] == '\n')
     { if (x0 >= 0)
	{ if (p->atnl) fputs((*p->pfx)(p->pfxarg),p->inner);
	  fwrite(data+x0,1,x-x0,p->inner);
	  x0 = -1;
	}
       putc('\n',p->inner);
       p->atnl = 1;
     }
    else
     { if (x0 < 0) x0 = x;
     }
  }
 if (x0 >= 0)
  { if (p->atnl) fputs((*p->pfx)(p->pfxarg),p->inner);
    fwrite(data+x0,1,x-x0,p->inner);
    p->atnl = 0;
  }
 return(len);
}

static int indent_c(void *pv)
{
 INDENT_PRIV *p;

 p = pv;
 if (! p->atnl) putc('\n',p->inner);
 free(p);
 return(0);
}

FILE *indent_wrap(FILE *inner, const char *(*pfx)(void *), void *pfxarg)
{
 INDENT_PRIV *p;
 FILE *f;

 p = malloc(sizeof(INDENT_PRIV));
 if (! p) return(0);
 f = funopen(p,0,&indent_w,0,&indent_c);
 if (! f)
  { free(p);
    return(0);
  }
 p->inner = inner;
 p->atnl = 1;
 p->pfx = pfx;
 p->pfxarg = pfxarg;
 return(f);
}