% Register RDF namespaces, for use in the convenience methods at the end
:- rdf_db:rdf_register_ns(nmr, 'http://www.nmrshiftdb.org/onto#').
:- rdf_db:rdf_register_ns(xsd, 'http://www.w3.org/2001/XMLSchema#').

findMolWithPeakValsNear( SearchShiftVals, Mols ) :- 

% Pick the Moleculess in 'Mol', that match the pattern: 
%% listPeakShiftsOfMol( Mol, MolShiftVals ),     
%% containsListElemsNear( SearchShiftVals, MolShiftVals ) 
% and collect them in 'Mols'. 
%
% A Mol(ecule)'s shift values are collected and compared against the given 
% SearchShiftVals. Then, in 'Mols', all 'Mol's, for which their shift values 
% match the SearchShiftVals, are collected.
setof( Mol, 
       (   listPeakShiftsOfMol( Mol, MolShiftVals ), 
           containsListElemsNear( SearchShiftVals, MolShiftVals )), 
       [Mols|MolTail] ). 

% Given a 'Mol', give it's shiftvalues in list form, in 'ListOfPeaks' 
listPeakShiftsOfMol( Mol, ListOfPeaks ) :- 
  hasSpectrum( Mol, Spectrum ), 
  findall( ShiftVal,  
           ( hasPeak( Spectrum, Peak ), 
             hasShiftVal( Peak, ShiftVal ) ),  
             ListOfPeaks ). 
 
% Compare two lists to see if list2 has near-matches for each value in list1 
containsListElemsNear( [ElemHead|ElemTail], List ) :- 
  memberCloseTo( ElemHead, List ), 
  ( containsListElemsNear( ElemTail, List ); 
    ElemTail == [] ).   
 
%%%%%%%%%%%%%%%%%%%%%%%% 
% Recursive construct: % 
%%%%%%%%%%%%%%%%%%%%%%%% 

% Test first the end criterion: 
memberCloseTo( X, [ Y | Tail ] ) :- 
  closeTo( X, Y ). 
% but if the above doesn't validate, do recursively continue with the tail of List2: 
memberCloseTo( X, [ Y | Tail ] ) :- 
  memberCloseTo( X, Tail ). 
                                                                                                 
% Numerical near-match 
closeTo( Val1, Val2 ) :- 
  abs(Val1 - Val2) =< 0.3. 

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
% Convenience accessory methods % 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 

hasShiftVal( Peak, ShiftVal ) :- 
  rdf_db:rdf( Peak, nmr:hasShift, literal(type(xsd:decimal, ShiftValLiteral))), 
  atom_number_create( ShiftValLiteral, ShiftVal ).                          
hasSpectrum( Subject, Predicate ) :-                                                
  rdf_db:rdf( Subject, nmr:hasSpectrum, Predicate).  
hasPeak( Subject, Predicate ) :- 
  rdf_db:rdf( Subject, nmr:hasPeak, Predicate). 

% Wrapper method for the atom_number/2 method which converts atoms (string 
% constants) to number. The wrapper methods avoids exceptions on empty atoms, 
% instead converting into a zero. 
atom_number_create( Atom, Number ) :- 
  % IF atom is not empty                         
  atom_length( Atom, AtomLength ), AtomLength > 0 -> 
  % THEN Convert the atom to a numerical value  
  atom_number( Atom, Number );                       
  % ELSE Convert to a zero
  atom_number( '0', Number ).