1/*  Part of SWI-Prolog
    2
    3    Author:        Jan Wielemaker
    4    E-mail:        J.Wielemaker@vu.nl
    5    WWW:           http://www.swi-prolog.org
    6    Copyright (c)  2013-2015, VU University Amsterdam
    7    All rights reserved.
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    9    Redistribution and use in source and binary forms, with or without
   10    modification, are permitted provided that the following conditions
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   13    1. Redistributions of source code must retain the above copyright
   14       notice, this list of conditions and the following disclaimer.
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   16    2. Redistributions in binary form must reproduce the above copyright
   17       notice, this list of conditions and the following disclaimer in
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   21    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   22    "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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   24    FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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   33*/
   34
   35:- module(html_quasi_quotations, [ html/4 ]).   36:- use_module(library(sgml)).   37:- use_module(library(apply)).   38:- use_module(library(error)).   39:- use_module(library(lists)).   40:- use_module(library(quasi_quotations)).

 html(+Content, +Vars, +VarDict, -DOM) is det

The predicate html/4 implements HTML quasi quotations. These quotations produce a DOM term that is suitable for html//1 and other predicates that are declared to consume this format. The quasi quoter only accepts valid, but possibly partial HTML documents. The document must begin with a tag. The quoter replaces attributes or content whose value is a Prolog variable that appears in the argument list of the html indicator. If the variable defines content, it must be the only content. Here is an example, replacing both a content element and an attribute. Note that the document is valid HTML.

  html({|html(Name, URL)||
         <p>Dear <span class="name">Name</span>,

         <p>You can <a href="URL">download</a> the requested
         article now.
         |}

   76:- quasi_quotation_syntax(html).   77
   78html(Content, Vars, Dict, DOM) :-
   79    must_be(list, Dict),
   80    include(qq_var(Vars), Dict, QQDict),
   81    with_quasi_quotation_input(
   82        Content, In,
   83        load_html(In, DOM0,
   84                  [ max_errors(0),
   85                    syntax_errors(print),
   86                    case_preserving_attributes(true)
   87                  ])),
   88    xml_content(QQDict, DOM0, DOM).
   89
   90qq_var(Vars, _=Var) :- member(V, Vars), V == Var, !.
   91
   92xml_content(Dict, [Name], [Var]) :-
   93    atom(Name),
   94    memberchk(Name=Var, Dict),
   95    !.
   96xml_content(Dict, Content0, Content) :-
   97    maplist(xml_content_element(Dict), Content0, Content).
   98
   99xml_content_element(Dict,
  100                    element(Tag, Attrs0, Content0),
  101                    element(Tag, Attrs, Content)) :-
  102    !,
  103    maplist(xml_attribute(Dict), Attrs0, Attrs),
  104    xml_content(Dict, Content0, Content).
  105xml_content_element(_, Element, Element).
  106
  107xml_attribute(Dict, Attr=Name, Attr=Var) :-
  108    memberchk(Name=Var, Dict),
  109    !.
  110xml_attribute(_, Attr, Attr)