% Dispatch Work Station Logical Specification
% move is the responsibility; find_transport, ... are obligations

move(Material) :- 		                     % Response+
	find_transport(Material,Transport),
	find_operator(Transport,Operator),
	make_assignment(Operator,Transport,Material),!.
move(Material) :- 		                     % Response-
    decline_request(Material).

find_transport(Material,Transport) :-		     % Response+
	move_by(Material,Transport),
	equipment(Transport,available).
find_operator(Transport,Operator) :-		     % Response+
	operator(Operator,available),
	operator_skills(Operator,Skills),
	have_skill(Transport,Skills).
make_assignment(Operator,Transport,Material) :-	     % Response+
	assign_operator(Operator),
	assign_transport(Transport),
	issue_work_order(Operator,Transport,Material).
decline_request(Material) :-
	print('resources are not available to move ',Material).

assign_operator(Operator) :-
	retract(operator(Operator,available)),
	assert(operator(Operator,busy)).
assign_transport(Transport) :-
	retract(equipment(Transport,available)),
	assert(equipment(Transport,busy)).
issue_work_order(Operator,Transport,Material) :-
	assert(assignment(Operator,Transport,Material)),
   	print(Operator,' has been assigned to move ',Material).

move_completed(Operator) :-
	assignment(Operator,Transport,_),
	release_transport(Transport),
	release_operator(Operator),
	assignment_completed(Operator),!.
release_operator(Operator) :-
	retract(operator(Operator,busy)),
	assert(operator(Operator,available)).
release_transport(Transport) :-
	retract(equipment(Transport,busy)),
	assert(equipment(Transport,available)).
assignment_completed(Operator) :-
	retract(assignment(Operator,_,_)),
	print(Operator,' has completed move assignment').

% Sample Dispatch Work Station knowledge base facts

% transportation needs (capabilities)
move_by(tank,crane).
move_by(casting,truck).
move_by(parts,cart).

% operator availability status
operator(carl,available).
operator(jill,available).
operator(tom,available).

% operator skills (capabilities)
operator_skills(carl,[truck,cart]).
operator_skills(jill,[crane,cart]).
operator_skills(tom,[truck,cart]).

%equipment availability status
equipment(crane,available). 
equipment(truck,available). 
equipment(cart,available).

%auxiliary logic (used to find if an operator has the needed skill)
have_skill(X, [X|_]).
have_skill(X, [_|Y]) :- have_skill(X,Y).

% a sample behaviour test

test:-
	move(tank),
	move(parts),
	move(casting),
	move_completed(jill),
	move(parts).
test?