/* Part of SWI-Prolog
Author: Jan Wielemaker
E-mail: J.Wielemaker@uva.nl
WWW: http://www.swi-prolog.org
Copyright (C): 2009, University of Amsterdam
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 library; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
As a special exception, if you link this library with other files,
compiled with a Free Software compiler, to produce an executable, this
library does not by itself cause the resulting executable to be covered
by the GNU General Public License. This exception does not however
invalidate any other reasons why the executable file might be covered by
the GNU General Public License.
*/
:- module(html_head,
[ html_resource/2, % +Resource, +Attributes
html_requires//1 % +Resource
]).
:- use_module(library(http/html_write)).
:- use_module(library(http/mimetype)).
:- use_module(library(http/http_path)).
:- use_module(library(error)).
:- use_module(library(settings)).
:- use_module(library(lists)).
:- use_module(library(occurs)).
:- use_module(library(option)).
:- use_module(library(ordsets)).
:- use_module(library(assoc)).
:- use_module(library(ugraphs)).
:- use_module(library(broadcast)).
:- use_module(library(apply)).
:- use_module(library(debug)).
/** <module> Automatic inclusion of CSS and scripts links
This library allows for abstract declaration of available CSS and
Javascript resources and their dependencies using html_resource/2. Based
on these declarations, html generating code can declare that it depends
on specific CSS or Javascript functionality, after which this library
ensures that the proper links appear in the HTML head. The
implementation is based on mail system implemented by html_post/2 of
library html_write.pl.
Declarations come in two forms. First of all http locations are declared
using the http_path.pl library. Second, html_resource/2 specifies HTML
resources to be used in the =head= and their dependencies. Resources are
currently limited to Javascript files (.js) and style sheets (.css). It
is trivial to add support for other material in the head. See
html_include//1.
For usage in HTML generation, there is the DCG rule html_requires//1
that demands named resources in the HTML head.
---++ About resource ordering
All calls to html_requires//1 for the page are collected and duplicates
are removed. Next, the following steps are taken:
1. Add all dependencies to the set
2. Replace multiple members by `aggregate' scripts or css files.
see use_agregates/4.
3. Order all resources by demanding that their dependencies
preceede the resource itself. Note that the ordering of
resources in the dependency list is *ignored*. This implies
that if the order matters the dependency list must be split
and only the primary dependency must be added.
---++ Debugging dependencies
Use ?- debug(html(script)). to see the requested and final set of
resources. All declared resources are in html_resource/3. The edit/1
command recognises the names of HTML resources.
@tbd Possibly we should add img//2 to include images from symbolic
path notation.
@tbd It would be nice if the HTTP file server could use our location
declarations.
*/
:- dynamic
html_resource/3. % Resource, Source, Properties
%% html_resource(+About, +Properties) is det.
%
% Register an HTML head resource. About is either an atom that
% specifies an HTTP location or a term Alias(Sub). This works
% similar to absolute_file_name/2. See http:location_path/2 for
% details. Recognised properties are:
%
% * requires(+Requirements)
% Other required script and css files. If this is a plain
% file name, it is interpreted relative to the declared
% resource. Requirements can be a list, which is equivalent
% to multiple requires properties.
%
% * virtual(+Bool)
% If =true= (default =false=), do not include About itself,
% but only its dependencies. This allows for defining an
% alias for one or more resources.
%
% * aggregate(+List)
% States that About is an aggregate of the resources in
% List.
html_resource(About, Properties) :-
source_location(File, Line), !,
retractall(html_resource(About, File:Line, _)),
assert_resource(About, File:Line, Properties).
html_resource(About, Properties) :-
assert_resource(About, -, Properties).
assert_resource(About, Location, Properties) :-
assert(html_resource(About, Location, Properties)),
clean_same_about_cache,
( memberchk(aggregate(_), Properties)
-> clean_aggregate_cache
; true
).
%% html_requires(+ResourceOrList)// is det.
%
% Include ResourceOrList and all dependencies derived from it and
% add them to the HTML =head= using html_post/2. The actual
% dependencies are computed during the HTML output phase by
% html_insert_resource//1.
html_requires(Required) -->
html_post(head, 'html required'(Required)).
:- multifile
html_write:html_head_expansion/2.
html_write:html_head_expansion(In, Out) :-
require_commands(In, Required, Rest),
Required \== [], !,
flatten(Required, Plain),
Out = [ html_head:(\html_insert_resource(Plain))
| Rest
].
require_commands([], [], []).
require_commands([_:('html required'(Required))|T0], [Required|TR], R) :- !,
require_commands(T0, TR, R).
require_commands([R|T0], TR, [R|T]) :- !,
require_commands(T0, TR, T).
%% html_insert_resource(+ResourceOrList)// is det.
%
% Actually include HTML head resources. Called through
% html_post//2 from html_requires//1 after rewrite by
% html_head_expansion/2. We are guaranteed we will only get one
% call that is passed a flat list of requested requirements. We
% have three jobs:
%
% 1. Figure out all indirect requirements
% 2. See whether we can use any `aggregate' resources
% 3. Put required resources before their requiree.
html_insert_resource(Required) -->
{ requirements(Required, Paths),
debug(html(script), 'Requirements: ~q~nFinal: ~q', [Required, Paths])
},
html_include(Paths).
requirements(Required, Paths) :-
phrase(requires(Required), List),
sort(List, Paths0), % remove duplicates
use_agregates(Paths0, Paths1, AggregatedBy),
order_html_resources(Paths1, AggregatedBy, Paths).
%% use_agregates(+Paths, -Aggregated, -AggregatedBy) is det.
%
% Try to replace sets of resources by an `aggregate', a large
% javascript or css file that combines the content of multiple
% small ones to reduce the number of files that must be
% transferred to the server. The current rule says that aggregates
% are used if at least half of the members are used.
use_agregates(Paths, Aggregated, AggregatedBy) :-
empty_assoc(AggregatedBy0),
use_agregates(Paths, Aggregated, AggregatedBy0, AggregatedBy).
use_agregates(Paths, Aggregated, AggregatedBy0, AggregatedBy) :-
current_aggregate(Aggregate, Parts, Size),
ord_subtract(Paths, Parts, NotCovered),
length(Paths, Len0),
length(NotCovered, Len1),
Covered is Len0-Len1,
Covered >= Size/2, !,
ord_add_element(NotCovered, Aggregate, NewPaths),
add_aggregated_by(Parts, AggregatedBy0, Aggregate, AggregatedBy1),
use_agregates(NewPaths, Aggregated, AggregatedBy1, AggregatedBy).
use_agregates(Paths, Paths, AggregatedBy, AggregatedBy).
add_aggregated_by([], Assoc, _, Assoc).
add_aggregated_by([H|T], Assoc0, V, Assoc) :-
put_assoc(H, Assoc0, V, Assoc1),
add_aggregated_by(T, Assoc1, V, Assoc).
:- dynamic
aggregate_cache_filled/0,
aggregate_cache/3.
:- volatile
aggregate_cache_filled/0,
aggregate_cache/3.
clean_aggregate_cache :-
retractall(aggregate_cache_filled).
%% current_aggregate(-Aggregate, -Parts, -Size) is nondet.
%
% True if Aggregate is a defined aggregate with Size Parts. All
% parts are canonical absolute HTTP locations and Parts is sorted
% to allow for processing using ordered set predicates.
current_aggregate(Path, Parts, Size) :-
aggregate_cache_filled, !,
aggregate_cache(Path, Parts, Size).
current_aggregate(Path, Parts, Size) :-
retractall(aggregate_cache(_,_, _)),
forall(uncached_aggregate(Path, Parts, Size),
assert(aggregate_cache(Path, Parts, Size))),
assert(aggregate_cache_filled),
aggregate_cache(Path, Parts, Size).
uncached_aggregate(Path, APartsS, Size) :-
html_resource(Aggregate, _, Properties),
memberchk(aggregate(Parts), Properties),
http_absolute_location(Aggregate, Path, []),
absolute_paths(Parts, Path, AParts),
sort(AParts, APartsS),
length(APartsS, Size).
absolute_paths([], _, []).
absolute_paths([H0|T0], Base, [H|T]) :-
http_absolute_location(H0, H, [relative_to(Base)]),
absolute_paths(T0, Base, T).
%% requires(+Spec)// is det.
%% requires(+Spec, +Base)// is det.
%
% True if Files is the set of files that need to be loaded for
% Spec. Note that Spec normally appears in Files, but this is not
% necessary (i.e. virtual resources or the usage of aggregate
% resources).
requires(Spec) -->
requires(Spec, /).
requires([], _) --> !,
[].
requires([H|T], Base) --> !,
requires(H, Base),
requires(T, Base).
requires(Spec, Base) -->
requires(Spec, Base, true).
requires(Spec, Base, Virtual) -->
{ res_properties(Spec, Properties),
http_absolute_location(Spec, File, [relative_to(Base)])
},
( { option(virtual(true), Properties)
; Virtual == false
}
-> []
; [File]
),
requires_from_properties(Properties, File).
requires_from_properties([], _) -->
[].
requires_from_properties([H|T], Base) -->
requires_from_property(H, Base),
requires_from_properties(T, Base).
requires_from_property(requires(What), Base) --> !,
requires(What, Base).
requires_from_property(_, _) -->
[].
%% order_html_resources(+Requirements, +AggregatedBy, -Ordered) is det.
%
% Establish a proper order for the collected (sorted and unique)
% list of Requirements.
order_html_resources(Requirements, AggregatedBy, Ordered) :-
requirements_graph(Requirements, AggregatedBy, Graph),
( top_sort(Graph, Ordered)
-> true
; connect_graph(Graph, Start, Connected),
top_sort(Connected, Ordered0),
Ordered0 = [Start|Ordered]
).
%% requirements_graph(+Requirements, +AggregatedBy, -Graph) is det.
%
% Produce an S-graph (see library(ugraphs)) that represents the
% dependencies in the list of Requirements. Edges run from
% required to requirer.
requirements_graph(Requirements, AggregatedBy, Graph) :-
phrase(prerequisites(Requirements, AggregatedBy, Vertices, []), Edges),
vertices_edges_to_ugraph(Vertices, Edges, Graph).
prerequisites([], _, Vs, Vs) -->
[].
prerequisites([R|T], AggregatedBy, Vs, Vt) -->
prerequisites_for(R, AggregatedBy, Vs, Vt0),
prerequisites(T, AggregatedBy, Vt0, Vt).
prerequisites_for(R, AggregatedBy, Vs, Vt) -->
{ phrase(requires(R, /, false), Req) },
( {Req == []}
-> {Vs = [R|Vt]}
; req_edges(Req, AggregatedBy, R),
{Vs = Vt}
).
req_edges([], _, _) -->
[].
req_edges([H|T], AggregatedBy, R) -->
( { get_assoc(H, AggregatedBy, Aggregate) }
-> [Aggregate-R]
; [H-R]
),
req_edges(T, AggregatedBy, R).
%% connect_graph(+Graph, -Start, -Connected) is det.
%
% Turn Graph into a connected graph by putting a shared starting
% point before all vertices.
connect_graph([], 0, []) :- !.
connect_graph(Graph, Start, [Start-Vertices|Graph]) :-
vertices(Graph, Vertices),
Vertices = [First|_],
before(First, Start).
%% before(+Term, -Before) is det.
%
% Unify Before to a term that comes before Term in the standard
% order of terms.
%
% @error instantiation_error if Term is unbound.
before(X, _) :-
var(X), !,
instantiation_error(X).
before(Number, Start) :-
number(Number), !,
Start is Number - 1.
before(_, 0).
%% res_properties(+Spec, -Properties) is det.
%
% True if Properties is the set of defined properties on Spec.
res_properties(Spec, Properties) :-
findall(P, res_property(Spec, P), Properties0),
list_to_set(Properties0, Properties).
res_property(Spec, Property) :-
same_about(Spec, About),
html_resource(About, _, Properties),
member(Property, Properties).
:- dynamic
same_about_cache/2.
:- volatile
same_about_cache/2.
clean_same_about_cache :-
retractall(same_about_cache(_,_)).
same_about(Spec, About) :-
same_about_cache(Spec, Same), !,
member(About, Same).
same_about(Spec, About) :-
findall(A, uncached_same_about(Spec, A), List),
assert(same_about_cache(Spec, List)),
member(About, List).
uncached_same_about(Spec, About) :-
html_resource(About, _, _),
same_resource(Spec, About).
%% same_resource(+R1, +R2) is semidet.
%
% True if R1 an R2 represent the same resource. R1 and R2 are
% resource specifications are defined by http_absolute_location/3.
same_resource(R, R) :- !.
same_resource(R1, R2) :-
resource_base_name(R1, B),
resource_base_name(R2, B),
http_absolute_location(R1, Path, []),
http_absolute_location(R2, Path, []).
:- dynamic
base_cache/2.
:- volatile
base_cache/2.
resource_base_name(Spec, Base) :-
( base_cache(Spec, Base0)
-> Base = Base0
; uncached_resource_base_name(Spec, Base0),
assert(base_cache(Spec, Base0)),
Base = Base0
).
uncached_resource_base_name(Atom, Base) :-
atomic(Atom), !,
file_base_name(Atom, Base).
uncached_resource_base_name(Compound, Base) :-
arg(1, Compound, Base0),
file_base_name(Base0, Base).
%% html_include(+PathOrList)// is det.
%
% Include to HTML resources that must be in the HTML <head>
% element. Currently onlu supports =|.js|= and =|.css|= files.
% Extend this to support more header material. Do not use this
% predicate directly. html_requires//1 is the public interface to
% include HTML resources.
%
% @param HTTP location or list of these.
html_include([]) --> !.
html_include([H|T]) --> !,
html_include(H),
html_include(T).
html_include(Path) -->
{ file_mime_type(Path, Mime) }, !,
html_include(Mime, Path).
html_include(text/css, Path) --> !,
html(link([ rel(stylesheet),
type('text/css'),
href(Path)
], [])).
html_include(text/javascript, Path) --> !,
html(script([ type('text/javascript'),
src(Path)
], [])).
html_include(Mime, Path) -->
{ print_message(warning, html_include(dont_know, Mime, Path))
}.
/*******************************
* CACHE CLEANUP *
*******************************/
:- multifile
user:message_hook/3.
:- dynamic
user:message_hook/3.
user:message_hook(make(done(Reload)), _Level, _Lines) :-
Reload \== [],
clean_same_about_cache,
clean_aggregate_cache,
fail.
/*******************************
* EDIT *
*******************************/
% Allow edit(Location) to edit the :- html_resource declaration.
:- multifile
prolog_edit:locate/3.
prolog_edit:locate(Path, html_resource(Spec), [file(File), line(Line)]) :-
atom(Path),
html_resource(Spec, File:Line, _Properties),
sub_term(Path, Spec).