(******************************************************************************)
(*  SXSI : XPath evaluator                                                    *)
(*  Kim Nguyen (Kim.Nguyen@nicta.com.au)                                      *)
(*  Copyright NICTA 2008                                                      *)
(*  Distributed under the terms of the LGPL (see LICENCE)                     *)
(******************************************************************************)
INCLUDE "utils.ml"

exception InfiniteSet
module type S =
sig
  type elt
  type t
  type set
  val empty : t
  val any : t
  val is_empty : t -> bool
  val is_any : t -> bool
  val is_finite : t -> bool
  val kind : t -> [ `Finite | `Cofinite ]
  val singleton : elt -> t
  val mem : elt -> t -> bool
  val add : elt -> t -> t
  val remove : elt -> t -> t
  val cup : t -> t -> t
  val cap : t -> t -> t
  val diff : t -> t -> t
  val neg : t -> t
  val compare : t -> t -> int
  val subset : t -> t -> bool
  val kind_split : t list -> t * t
  val fold : (elt -> 'a -> 'a) -> t -> 'a -> 'a
  val for_all : (elt -> bool) -> t -> bool
  val exists : (elt -> bool) -> t -> bool
  val filter : (elt -> bool) -> t -> t
  val partition : (elt -> bool) -> t -> t * t
  val cardinal : t -> int
  val elements : t -> elt list
  val from_list : elt list -> t
  val choose : t -> elt
  val hash : t -> int
  val equal : t -> t -> bool
  val uid : t -> Uid.t
  val positive : t -> set
  val negative : t -> set
  val inj_positive : set -> t
  val inj_negative : set -> t
end

module Make (E : Ptset.S) : S with type elt = E.elt and type set = E.t =
struct

  type elt = E.elt
  type node = Finite of E.t | CoFinite of E.t
  type set = E.t
  module Node = Hcons.Make(struct
			     type t = node
			     let equal a b =
			       match a,b with
				  (Finite(s1),Finite(s2))
				 | (CoFinite(s1),CoFinite(s2)) -> E.equal s1 s2
				 | _ -> false
			     let hash = function
			       Finite (s) -> (E.hash s) lsl 1
			     | CoFinite(s) -> ((E.hash s) lsl 1 ) + 1
			   end)
  type t = Node.t
  let empty = Node.make (Finite E.empty)
  let any = Node.make (CoFinite E.empty)
  let finite x = Node.make (Finite x)
  let cofinite x = Node.make (CoFinite x)

  let is_empty =  function
      { Node.node = Finite s } when E.is_empty s -> true
    | _ -> false

  let is_any = function
      { Node.node = CoFinite s } when E.is_empty s -> true
    | _ -> false

  let is_finite t = match t.Node.node with
    | Finite _ -> true | _ -> false

  let kind t = match t.Node.node with
      Finite _ -> `Finite
    | _ -> `Cofinite

  let mem x t = match t.Node.node with
    | Finite s -> E.mem x s
    | CoFinite s -> not (E.mem x s)

  let singleton x = finite (E.singleton x)

  let add e t = match t.Node.node with
    | Finite s -> finite (E.add e s)
    | CoFinite s -> cofinite (E.remove e s)

  let remove e t = match t.Node.node with
    | Finite s -> finite (E.remove e s)
    | CoFinite s -> cofinite (E.add e s)

  let cup s t = match (s.Node.node,t.Node.node) with
    | Finite s, Finite t -> finite (E.union s t)
    | CoFinite s, CoFinite t -> cofinite ( E.inter s t)
    | Finite s, CoFinite t -> cofinite (E.diff t s)
    | CoFinite s, Finite t-> cofinite (E.diff s t)

  let cap s t = match (s.Node.node,t.Node.node) with
    | Finite s, Finite t -> finite (E.inter s t)
    | CoFinite s, CoFinite t -> cofinite (E.union s t)
    | Finite s, CoFinite t -> finite (E.diff s t)
    | CoFinite s, Finite t-> finite (E.diff t s)

  let diff s t = match (s.Node.node,t.Node.node) with
    | Finite s, Finite t -> finite (E.diff s t)
    | Finite s, CoFinite t -> finite(E.inter s t)
    | CoFinite s, Finite t -> cofinite(E.union t s)
    | CoFinite s, CoFinite t -> finite (E.diff t s)

  let neg t = match t.Node.node with
    | Finite s -> cofinite s
    | CoFinite s -> finite s

  let compare s t = match (s.Node.node,t.Node.node) with
    | Finite s , Finite t -> E.compare s t
    | CoFinite s , CoFinite t -> E.compare t s
    | Finite _, CoFinite _ -> -1
    | CoFinite _, Finite _ -> 1

  let subset s t = match (s.Node.node,t.Node.node) with
    | Finite s , Finite t -> E.subset s t
    | CoFinite s , CoFinite t -> E.subset t s
    | Finite s, CoFinite t -> E.is_empty (E.inter s t)
    | CoFinite _, Finite _ -> false

	(* given a  list l of type t list,
	   returns two sets (f,c) where :
	   - f is the union of all the finite sets of l
	   - c is the union of all the cofinite sets of l
	   - f and c are disjoint
	   Invariant : cup f c = List.fold_left cup empty l

	   We treat the CoFinite part explicitely :
	*)

  let kind_split l =

    let rec next_finite_cofinite facc cacc = function
      | [] -> finite facc, cofinite (E.diff cacc facc)
      | { Node.node = Finite s } ::r -> next_finite_cofinite (E.union s facc) cacc r
      | { Node.node = CoFinite _ } ::r when E.is_empty cacc -> next_finite_cofinite facc cacc r
      | { Node.node = CoFinite s } ::r -> next_finite_cofinite facc (E.inter cacc s) r
    in
    let rec first_cofinite facc = function
      | [] -> empty,empty
      | { Node.node = Finite s } :: r-> first_cofinite (E.union s facc) r
      | { Node.node = CoFinite s } :: r -> next_finite_cofinite facc s r
    in
      first_cofinite E.empty l

  let fold f t a = match t.Node.node with
    | Finite s -> E.fold f s a
    | CoFinite _ -> raise InfiniteSet

  let for_all f t = match t.Node.node with
    | Finite s -> E.for_all f s
    | CoFinite _ -> raise InfiniteSet

  let exists f t = match t.Node.node with
    | Finite s -> E.exists f s
    | CoFinite _ -> raise InfiniteSet

  let filter f t = match t.Node.node with
    | Finite s -> finite (E.filter f s)
    | CoFinite _ -> raise InfiniteSet

  let partition f t = match t.Node.node with
    | Finite s -> let a,b = E.partition f s in finite a,finite b
    | CoFinite _ -> raise InfiniteSet

  let cardinal t = match t.Node.node with
    | Finite s -> E.cardinal s
    | CoFinite _ -> raise InfiniteSet

  let elements t = match t.Node.node with
    | Finite s -> E.elements s
    | CoFinite _ -> raise InfiniteSet

  let from_list l =
    finite (List.fold_left (fun x a -> E.add a x ) E.empty l)

  let choose t = match t.Node.node with
      Finite s -> E.choose s
    | _ -> raise InfiniteSet

  let equal = (==)

  let hash t = t.Node.key

  let uid t = t.Node.id


  let positive t =
    match t.Node.node with
      | Finite x -> x
      | _ -> E.empty

  let negative t =
    match t.Node.node with
      | CoFinite x -> x
      | _ -> E.empty

  let inj_positive t = finite t
  let inj_negative t = cofinite t
end