xmerl_xpath_pred.erl

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%%% The contents of this file are subject to the Erlang Public License,
%%% Version 1.0, (the "License"); you may not use this file except in
%%% compliance with the License. You may obtain a copy of the License at
%%% http://www.erlang.org/license/EPL1_0.txt
%%%
%%% Software distributed under the License is distributed on an "AS IS"
%%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
%%% the License for the specific language governing rights and limitations
%%% under the License.
%%%
%%% The Original Code is xmerl-0.6
%%%
%%% The Initial Developer of the Original Code is Ericsson Telecom
%%% AB. Portions created by Ericsson are Copyright (C), 1998, Ericsson
%%% Telecom AB. All Rights Reserved.
%%%
%%% Contributor(s): ______________________________________.
%%%
%%%----------------------------------------------------------------------
%%% #0.    BASIC INFORMATION
%%%----------------------------------------------------------------------
%%% @private
%%% File:       xmerl_xpath_pred.erl
%%% Author       : Ulf Wiger <[e-mail]>
%%% Description  : Helper module to xmerl_xpath: XPATH predicates.
%%% 
%%% Modules used : lists, string, xmerl_scan, xmerl_xpath
%%% 
%%%----------------------------------------------------------------------

-module(xmerl_xpath_pred).
-vsn('0.6').
-date('00-09-22').
-author('[e-mail]').

%% API
-export([eval/2]).


%% internal functions (called via apply/3)
-export([boolean/1, boolean/2,
	 ceiling/2,
	 concat/2,
	 contains/2,
	 count/2,
	 floor/2,
	 fn_false/2,
	 fn_not/2,
	 fn_true/2,
	 id/2,
	 lang/2,
	 last/2,
	 'local-name'/2,
	 'namespace-uri'/2,
	 nodeset/1,
	 'normalize-space'/2,
	 number/1, number/2,
	 position/2,
	 round/2,
	 'starts-with'/2,
	 string/1,
	 'string-length'/2,
	 substring/2,
	 'substring-after'/2,
	 'substring-before'/2,
	 sum/2,
	 translate/2]).
	 

-include("xmerl.hrl").
-include("xmerl_xpath.hrl").

%% -record(obj, {type,
%% 	      value}).


-define(string(X), #xmlObj{type = string,
			   value = X}).
-define(nodeset(X), #xmlObj{type = nodeset,
			    value = X}).
-define(number(X), #xmlObj{type = number,
			   value = X}).
-define(boolean(X), #xmlObj{type = boolean,
			    value = X}).




eval(Expr, C = #xmlContext{context_node = #xmlNode{pos = Pos}}) ->
    Obj = expr(Expr, C),
    Res = case Obj#xmlObj.type of
	      number when Obj#xmlObj.value == Pos ->
		  true;
	      number ->
		  false;
	      boolean ->
		  Obj#xmlObj.value;
	      _ ->
		  mk_boolean(C, Obj)
	  end,
%    io:format("eval(~p, ~p) -> ~p~n", [Expr, Pos, Res]),
    Res.


string(X) ->
    ?string(X).

nodeset(X) -> 
    ?nodeset(X).

number(X) ->
    ?number(X).

boolean(X) ->
    ?boolean(X).


expr({arith, Op, E1, E2}, C) ->
    arith_expr(Op, E1, E2, C);
expr({comp, Op, E1, E2}, C) ->
    comp_expr(Op, E1, E2, C);
expr({bool, Op, E1, E2}, C) ->
    bool_expr(Op, E1, E2, C);
expr({'negative', E}, C) ->
    N = mk_number(C, E),
    - N;
expr({number, N}, _C) ->
    ?number(N);
expr({literal, S}, _C) ->
    ?string(S);
expr({function_call, F, Args}, C) ->
    case core_function(F) of
	{true, F1} ->
	    ?MODULE:F1(C, Args);
	true ->
	    ?MODULE:F(C, Args);
	false ->
	    %% here, we should look up the function in the context provided 
	    %% by the caller, but we haven't figured this out yet.
	    exit({not_a_core_function, F})
    end;
expr({path, Type, PathExpr}, C) ->
    #state{context=#xmlContext{nodeset = NS}} =
	xmerl_xpath:eval_path(Type, PathExpr, C),
    ?nodeset(NS);
expr(Expr, _C) ->
    exit({unknown_expr, Expr}).


arith_expr('+', E1, E2, C) ->
    ?number(mk_number(C, E1) + mk_number(C, E2));
arith_expr('-', E1, E2, C) ->
    ?number(mk_number(C, E1) - mk_number(C, E2));
arith_expr('*', E1, E2, C) ->
    ?number(mk_number(C, E1) * mk_number(C, E2));
arith_expr('div', E1, E2, C) ->
    ?number(mk_number(C, E1) / mk_number(C, E2));
arith_expr('mod', E1, E2, C) ->
    ?number(mk_number(C, E1) rem mk_number(C, E2)).

comp_expr('>', E1, E2, C) ->
    N1 = expr(E1,C),
    N2 = expr(E2,C),
    ?boolean(compare_ineq_format(N1,N2,C) > compare_ineq_format(N2,N1,C));
comp_expr('<', E1, E2, C) ->
    N1 = expr(E1,C),
    N2 = expr(E2,C),
    ?boolean(compare_ineq_format(N1,N2,C) > compare_ineq_format(N2,N1,C));
comp_expr('>=', E1, E2, C) ->
    N1 = expr(E1,C),
    N2 = expr(E2,C),
    ?boolean(compare_ineq_format(N1,N2,C) > compare_ineq_format(N2,N1,C));
comp_expr('<=', E1, E2, C) ->
    N1 = expr(E1,C),
    N2 = expr(E2,C),
    ?boolean(compare_ineq_format(N1,N2,C) > compare_ineq_format(N2,N1,C));
comp_expr('=', E1, E2, C) ->
    N1 = expr(E1,C),
    N2 = expr(E2,C),
    ?boolean(compare_eq_format(N1,N2,C) == compare_eq_format(N2,N1,C));
comp_expr('!=', E1, E2, C) ->
    N1 = expr(E1,C),
    N2 = expr(E2,C),
    ?boolean(compare_eq_format(N1,N2,C) == compare_eq_format(N2,N1,C)).

bool_expr('or', E1, E2, C) ->
    ?boolean(mk_boolean(C, E1) or mk_boolean(C, E2));
bool_expr('and', E1, E2, C) ->
    ?boolean(mk_boolean(C, E1) and mk_boolean(C, E2)).

%% According to chapter 3.4 in XML Path Language ver 1.0 the format of
%% the compared objects are depending on the type of the other
%% object. 
%% 1. Comparisons involving node-sets is treated equally despite
%% of which comparancy operand is used. In this case:
%% - node-set comp node-set: string values are used
%% - node-set comp number : ((node-set string value) -> number) 
%% - node-set comp boolean : (node-set string value) -> boolean
%% 2. Comparisons when neither object is a node-set and the operand
%% is = or != the following transformation is done before comparison:
%% - if one object is a boolean the other is converted to a boolean.
%% - if one object is a number the other is converted to a number.
%% - otherwise convert both to the string value.
%% 3. Comparisons when neither object is a node-set and the operand is
%% <=, <, >= or > both objects are converted to a number.
compare_eq_format(N1=#xmlObj{type=T1},N2=#xmlObj{type=T2},C) when T1==nodeset;
							      T2==nodeset ->
    compare_nseq_format(N1,N2,C);
compare_eq_format(N1=#xmlObj{type=T1},#xmlObj{type=T2},C) when T1==boolean;
							      T2==boolean ->
    mk_boolean(C,N1);
compare_eq_format(N1=#xmlObj{type=T1},#xmlObj{type=T2},C) when T1==number;
							      T2==number ->
    mk_number(C,N1);
compare_eq_format(N1,_,C) ->
    mk_string(C,string_value(N1)).

compare_ineq_format(N1=#xmlObj{type=T1},
		    N2=#xmlObj{type=T2},C) when T1==nodeset;
						T2==nodeset ->
    compare_nseq_format(N1,N2,C);
compare_ineq_format(N1,_N2,C) ->
    mk_number(C,N1).

compare_nseq_format(N1=#xmlObj{type = number},_N2,C) ->
    mk_number(C,N1);
compare_nseq_format(N1=#xmlObj{type = boolean},_N2,C) ->
    mk_boolean(C,N1);
compare_nseq_format(N1=#xmlObj{type = string},_N2,C) ->
    mk_string(C,N1);
compare_nseq_format(N1=#xmlObj{type = nodeset},_N2=#xmlObj{type=number},C) ->
    %% transform nodeset value to its string-value
    mk_number(C,string_value(N1));
compare_nseq_format(N1=#xmlObj{type = nodeset},_N2=#xmlObj{type=boolean},C) ->
    mk_boolean(C,N1);
compare_nseq_format(N1=#xmlObj{type = nodeset},_N2,C) ->
    mk_string(C,string_value(N1)).


core_function('last') ->		true;
core_function('position') ->		true;
core_function('count') ->		true;
core_function('id') ->			true;
core_function('local-name') ->		true;
core_function('namespace-uri') ->	true;
core_function('name') ->		true;
core_function('string') ->		true;
core_function('concat') ->		true;
core_function('starts-with') ->		true;
core_function('contains') ->		true;
core_function('substring-before') ->	true;
core_function('substring-after') ->	true;
core_function('string-length') ->	true;
core_function('normalize-space') ->	true;
core_function('translate') ->		true;
core_function('boolean') ->		true;
core_function('not') ->			{true, fn_not};
core_function('true') ->		{true, fn_true};
core_function('false') ->		{true, fn_false};
core_function('lang') ->		true;
core_function('number') ->		true;
core_function('sum') ->			true;
core_function('floor') ->		true;
core_function('ceiling') ->		true;
core_function('round') ->		true;
core_function(_) ->
    false.


%%%  node set functions

%% number: last()
last(#xmlContext{nodeset = Set}, []) ->
    ?number(length(Set)).

%% number: position()
position(#xmlContext{context_node = #xmlNode{pos = Pos}}, []) ->
    ?number(Pos).

%% number: count(node-set)
count(C, [Arg]) ->
    ?number(length(mk_nodeset(C, Arg))).

%% node-set: id(object)
id(C, [Arg]) ->
    NS0 = [C#xmlContext.whole_document],
    case Arg#xmlObj.type of
	nodeset ->
	    NodeSet = Arg#xmlObj.value,
	    IdTokens = 
		lists:foldl(
		  fun(N, AccX) ->
			  StrVal = string_value(N),
			  TokensX = id_tokens(StrVal),
			  TokensX ++ AccX
		  end, [], NodeSet),
	    NewNodeSet = 
		xmerl_xpath:axis(descendant_or_self, 
				 fun(Node) ->
					 attribute_test(Node, id, IdTokens)
				 end, C#xmlContext{nodeset = NS0}),
	    ?nodeset(NewNodeSet);
	_ ->
	    StrVal = string_value(Arg#xmlObj.value),
	    IdTokens = id_tokens(StrVal),
	    lists:foldl(
	      fun(Tok, AccX) ->
		      select_on_attribute(NS0, id, Tok, AccX)
	      end, [], IdTokens)
    end.

id_tokens(Str) ->
    string:tokens(Str, " \t\n\r").
			  

attribute_test(#xmlNode{node = #xmlElement{attributes = Attrs}}, 
	       Key, Vals) ->
    case lists:keysearch(Key, #xmlAttribute.name, Attrs) of
	{value, #xmlAttribute{value = V}} ->
	    lists:member(V, Vals);
	_ ->
	    false
    end;
attribute_test(_Node, _Key, _Vals) ->
    false.

%%% CONTINUE HERE!!!!

%% string: local-name(node-set?)
'local-name'(C, []) ->
    local_name1(default_nodeset(C));

'local-name'(C, [Arg]) ->
    local_name1(mk_nodeset(C, Arg)).

local_name1([]) ->
    ?string([]);
local_name1([#xmlElement{name = Name, nsinfo = NSI}|_]) ->
    case NSI of
	{_Prefix, Local} ->
	    ?string(Local);
	[] ->
	    ?string(Name)
    end.

%% string: namespace-uri(node-set?)
'namespace-uri'(C, []) ->
    ns_uri(default_nodeset(C));

'namespace-uri'(C, [Arg]) ->
    ns_uri(mk_nodeset(C, Arg)).


ns_uri([]) ->
    ?string([]);
ns_uri([#xmlElement{nsinfo = NSI, namespace = NS}|_]) ->
    case NSI of
	{Prefix, _} ->
	    case lists:keysearch(Prefix, 1, NS#xmlNamespace.nodes) of
		false ->
		    ?string([]);
		{value, {_K, V}} ->
		    ?string(V)
	    end;
	[] ->
	    []
    end.



%%% String functions

%% string: string(object?)
string(C, []) ->
    ns_string(default_nodeset(C));
string(C, [Arg]) ->
    string_value(mk_object(C, Arg)).

ns_string([Obj|_]) ->