(***********************************************************************)
(*                                                                     *)
(*                               TAToo                                 *)
(*                                                                     *)
(*                     Kim Nguyen, LRI UMR8623                         *)
(*                   Université Paris-Sud & CNRS                       *)
(*                                                                     *)
(*  Copyright 2010-2013 Université Paris-Sud and Centre National de la *)
(*  Recherche Scientifique. All rights reserved.  This file is         *)
(*  distributed under the terms of the GNU Lesser General Public       *)
(*  License, with the special exception on linking described in file   *)
(*  ../LICENSE.                                                        *)
(*                                                                     *)
(***********************************************************************)

INCLUDE "utils.ml"

open Format

(*

(** Implementation of hashconsed Boolean formulae *)

*)
module type ATOM =
sig
  type t
  val neg : t -> t
  include Hcons.Abstract with type t := t
  include Common_sig.Printable with type t := t
end

type ('formula,'atom) expr =
  | False
  | True
  | Or of 'formula * 'formula
  | And of 'formula * 'formula
  | Atom of 'atom

module Make (P: ATOM) =
struct


  type 'hcons node = {
    pos : ('hcons,P.t) expr;
    mutable neg : 'hcons;
  }

  external hash_const_variant : [> ] -> int = "%identity"
  external vb : bool -> int = "%identity"

  module rec Node : Hcons.S
    with type data = Data.t = Hcons.Make (Data)
    and Data : Common_sig.HashedType  with type t = Node.t node =
  struct
    type t =  Node.t node
    let equal x y =
      match x.pos, y.pos with
      | a,b when a == b -> true
      | Or(xf1, xf2), Or(yf1, yf2)
      | And(xf1, xf2), And(yf1,yf2)  -> xf1 == yf1 && xf2 == yf2
      | Atom(p1), Atom(p2) -> p1 == p2
      | _ -> false

    let hash f =
      match f.pos with
      | False -> 0
      | True -> 1
      | Or (f1, f2) ->
          HASHINT3 (PRIME1, Uid.to_int f1.Node.id, Uid.to_int f2.Node.id)
      | And (f1, f2) ->
          HASHINT3(PRIME3, Uid.to_int f1.Node.id, Uid.to_int f2.Node.id)
      | Atom(p) -> HASHINT2(PRIME5, Uid.to_int (P.uid p))
  end

    type t = Node.t
    let hash x = x.Node.hash
    let uid x = x.Node.id
    let equal = Node.equal
    let expr f = f.Node.node.pos

    let compare f1 f2 = compare f1.Node.id  f2.Node.id
    let prio f =
      match expr f with
      | True | False -> 10
      | Atom _ -> 8
      | And _ -> 6
      | Or _ -> 1

    let rec print ?(parent=false) ppf f =
      if parent then fprintf ppf "(";
      let _ = match expr f with
      | True -> fprintf ppf "%s" Pretty.top
      | False -> fprintf ppf "%s" Pretty.bottom
      | And(f1,f2) ->
          print ~parent:(prio f > prio f1) ppf f1;
          fprintf ppf " %s "  Pretty.wedge;
          print ~parent:(prio f > prio f2) ppf f2;
      | Or(f1,f2) ->
          (print ppf f1);
          fprintf ppf " %s " Pretty.vee;
          (print ppf f2);
      | Atom(p) -> fprintf ppf "%a" P.print p
(*          let _ = flush_str_formatter() in
          let fmt = str_formatter in
          let a_str, d_str =
          match  dir with
          | `Left ->  Pretty.down_arrow, Pretty.subscript 1
          | `Right -> Pretty.down_arrow, Pretty.subscript 2
          | `Epsilon -> Pretty.epsilon, ""
          | `Up1 -> Pretty.up_arrow, Pretty.subscript 1
          | `Up2 -> Pretty.up_arrow, Pretty.subscript 2
        in
        fprintf fmt "%s%s" a_str d_str;
        State.print fmt s;
        let str = flush_str_formatter() in
        if b then fprintf ppf "%s" str
        else Pretty.pp_overline ppf str *)
  in
    if parent then fprintf ppf ")"

let print ppf f =  print ~parent:false ppf f

let is_true f = (expr f) == True
let is_false f = (expr f) == False


let cons pos neg =
  let nnode = Node.make { pos = neg; neg = Obj.magic 0 } in
  let pnode = Node.make { pos = pos; neg = nnode } in
    (Node.node nnode).neg <- pnode; (* works because the neg field isn't taken into
                                       account for hashing ! *)
    pnode,nnode


let true_,false_ = cons True False

let atom_ p = fst (cons (Atom(p)) (Atom(P.neg p)))

let not_ f = f.Node.node.neg

let order f1 f2 = if uid f1 < uid f2 then f2,f1 else f1,f2

let or_ f1 f2 =
  (* Tautologies: x|x, x|not(x) *)

  if equal f1 f2 then f1
  else if equal f1 (not_ f2) then true_

  (* simplification *)
  else if is_true f1 || is_true f2 then true_
  else if is_false f1 && is_false f2 then false_
  else if is_false f1 then f2
  else if is_false f2 then f1

  (* commutativity of | *)
  else
    let f1, f2 = order f1 f2 in
      fst (cons (Or(f1,f2)) (And(not_ f1, not_ f2)))


let and_ f1 f2 =
  not_ (or_ (not_ f1) (not_ f2))


let of_bool = function true -> true_ | false -> false_

let fold f phi acc =
  let rec loop phi acc =
    match expr phi with
    | And (phi1, phi2) | Or(phi1, phi2)  ->
        loop phi2 (loop phi1 (f phi acc))
    | _ -> f phi acc
  in
  loop phi acc

end