/*
         Copyright (c) 2003, WebThing Ltd
         Author: Nick Kew <nick@webthing.com>

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

*/


/* Namespace Handler for XHTML	(http://www.w3.org/1999/xhtml)

   This will process XHTML markup to Appendix-C compatible XHTML that
   can be sent to current and older web browsers as text/html

   * All HTML is written in the default namespace
   * Empty elements end with " />"
   * Substitutes any META element that sets content-type

PURPOSE:
   * Distributed with mod_xmlns as a sample namespace processor
   * May be useful operationally to post-process XHTML that is not
     Appendix-C compliant.

BUGS:
   * If there is a default namespace defined for something other
     than XHTML, it'll get confused.
   * Doesn't reliably support charset declaration in a META element

COMPILING: minimal example with GCC, in the same directory as mod_xmlns.h
   $ gcc -Wall -O2 -fPIC -shared -I/usr/local/apache/include -o /usr/local/apache/modules/xhtml10.so xhtml10.c

BASIC USAGE with mod_xmlns (or mod_publisher_xml):

   # Load the module
   LoadModule xmlns_module /usr/local/apache/modules/mod_xmlns.so
   # Activate it on selected MIME types
   AddOutputFilterByType xmlns	text/xml application/xml [...]
   # Load support for the XHTML namespace
   LoadNamespace xmlns_xhtml10 /usr/local/apache/modules/xhtml10.so

See the website for details: http://apache.webthing.com/mod_xmlns/

*/
#include "mod_xmlns.h"
#include <util_filter.h>
#include <apr_hash.h>

static int is_empty(const parsedname* name) {
  const char** p ;
  static const char* empty_elts[] = {
    "br" ,
    "link" ,
    "img" ,
    "hr" ,
    "input" ,
    "meta" ,
    "base" ,
    "area" ,
    "param" ,
    "col" ,
    "frame" ,
    "isindex" ,
    "basefont" ,
    NULL
  } ;
  for ( p = empty_elts ; *p ; ++p )
    if ( ( name->eltlen == strlen(*p) )
	&& !strncmp( *p, name->elt, name->eltlen) )
      return 1 ;
  return 0 ;
}
static int hstart(saxctxt* ctx, const parsedname* name3, const XML_Char** atts) {
  int have_default_ns = 0 ;
  apr_hash_index_t* index ;

  if ( ! strncmp(name3->elt, "meta", 4) ) {
    const XML_Char** a ;
    for ( a = atts ; *a ; a += 2 )
      if ( !strcasecmp(a[0], "http-equiv")
	&& a[1]
	&& !strcasecmp(a[1], "content-type")
      ) {
	ap_fputs(F, BB, "<meta http-equiv=\"Content-Type\" content=\"text/html; charset=utf-8\" />") ;
	return 1 ;
      }
  }
  ap_fputc(F, BB, '<') ;
  ap_fwrite(F, BB, name3->elt, name3->eltlen) ;

  if ( atts ) {
    const XML_Char** a ;
    for ( a = atts ; *a ; a += 2 ) {
     ap_fputstrs(F, BB, " ", a[0], "=\"", a[1], "\"", NULL) ;
    }
  }

  for ( index = apr_hash_first(CTX->f->r->pool, CTX->activens) ;
        index ; index = apr_hash_next(index) ) {
    const void* prefix ;
    void* rec ;
    apr_ssize_t len ;
    apr_hash_this(index, &prefix, &len, &rec) ;

    if ( ! ((xmlns_active*)rec)->printed ) {
      if ( prefix && strlen((const char*)prefix) )
        if ( ((xmlns_active*)rec)->ns )
          ap_fputstrs(F, BB, " xmlns:", (const char*)prefix , "=\"",
                ((xmlns_active*)rec)->ns->xmlns, "\"", NULL) ;
        else {
          ap_fputstrs(F, BB, " xmlns:", (const char*)prefix , "=\"", NULL) ;
          ap_fwrite(F, BB, name3->ns, name3->nslen) ;
          ap_fputc(F, BB, '"') ;
        }
      else {
        if ( ((xmlns_active*)rec)->ns )
          ap_fputstrs(F, BB, " xmlns=\"", ((xmlns_active*)rec)->ns->xmlns, "\"", NULL) ;
        else {
          ap_fputs(F, BB, " xmlns=\"") ;
          ap_fwrite(F, BB, name3->ns, name3->nslen) ;
          ap_fputc(F, BB, '"') ;
        }
	have_default_ns = 1 ;
      }
      ((xmlns_active*)rec)->printed = 1 ;
    }
  }

  if ( ! have_default_ns && !strncmp( "html", name3->elt, 4) )
    ap_fputs(F, BB, " xmlns=\"http://www.w3.org/1999/xhtml\">") ;
  else if ( is_empty(name3) )
    ap_fputs(F, BB, " />") ;
  else
    ap_fputc(F, BB, '>') ;
  return 1 ;	/* nonzero return to suppress default */
}
static int hend(saxctxt* ctx, const parsedname* name) {
  if ( ! is_empty(name) ) {
    ap_fputs(F, BB, "</") ;
    ap_fwrite(F, BB, name->elt, name->eltlen) ;
    ap_fputc(F, BB, '>') ;
  }
  return 1 ;	/* nonzero return to suppress default */
}

xmlns xmlns_xhtml10 = {
  "http://www.w3.org/1999/xhtml" ,	/* URI	*/
  hstart ,				/* StartElement	*/
  hend ,				/* EndElement	*/
  NULL ,				/* StartNSDecl	*/
  NULL ,				/* EndNSDecl	*/
  NULL					/* private */
} ;