(* $Id: clkexprtrans.sml 19 2007-11-27 00:20:37Z tbourke $ *)

(* TODO:

 *   - rename `paritition' to `constraint'

 *     more generally it is used to constrain the applicability of

 *     a set of transitions and is not affected by negation.

 *)

structure ClkExprTrans :> CLK_EXPR_TRANS = let

  structure E    = Expression

        and ClkE = ClockExpression

        and AT   = ActionTrans

        and Env  = Environment

        and ECVT = ExpressionCvt

in struct

  type expr      = Expression.expr

   and ty        = Expression.ty

   and symbol    = Atom.atom

   and symbolset = AtomSet.set

  exception SelectIdConflictsWithForAll of symbol list * symbol list

  infix <+ <- ++ <\ \ =:= ; open Symbol

  (* Invariants:

       - names contains all free names and those bound by select and forall

       - the sets of names of the select and forall lists are disjoint

   *)

  datatype t = CETrans of {actselect: (symbol * E.ty) list,(* SelectSub ids *)

                           gselect:   (symbol * E.ty) list,(* Guard selects *)

                           forall:    (symbol * E.ty) list,(* in prenex form *)

                           partition: Expression.expr,

                           guard:     ClkE.t,

                           action:    ActionTrans.actionsub list,

                           names:     symbolset}

  fun addNameTypes xs = let

      fun add ((n, _), s) = s <+ n

    in foldl add emptyset xs end

  local (*{{{1*)

    fun showCheckedActions []      = ""

      | showCheckedActions (AT.SelectSub s::es)   = "[#" ^ Atom.toString s ^ "#]" ^

                                                 showCheckedActions es

      | showCheckedActions (AT.FreeExprSub e::es) = "[" ^ ECVT.Expr.toString e ^ "]" ^

                                                 showCheckedActions es

    fun symtyToStr (s, ty) = Atom.toString s ^ " : " ^ ECVT.Ty.toString ty

    val symtyList = (ListFormat.fmt {init="(", sep=", ",

                                     final=")", fmt=symtyToStr})

  in (*}}}1*)

  fun toString (CETrans {actselect, gselect, forall,

                         partition, guard, action, names}) = let

    in

      "{actselect: " ^ symtyList actselect          ^ "\n" ^

      " gselect: "   ^ symtyList gselect            ^ "\n" ^

      " forall: "    ^ symtyList forall             ^ "\n" ^

      " partition: " ^ ECVT.Expr.toString partition ^ "\n" ^

      " guard: "     ^ ClkE.toString guard          ^ "\n" ^

      " action: "    ^ showCheckedActions action    ^ "\n" ^

      " names: "     ^ AtomSet.foldl

                       (fn (s, str)=> str ^ " " ^ Atom.toString s) "" names ^

      " }\n"

    end

  end (* local *)

(*

(*TODO: DEBUG ONLY! *)

fun showPartitions showitem partitions = let

    fun showClass c = let in

        TextIO.print "    class[\n";

        map showitem c;

        TextIO.print "    class]\n"

      end

    fun showPart p = let in

        TextIO.print "partition[\n";

        map showClass p;

        TextIO.print "partition]\n"

      end

  in app showPart partitions end

*)

  fun unionNames cetrans = let

      fun f (CETrans {names, ...}, m) = m ++ names

    in foldl f emptyset cetrans end

  fun addDisjointForalls newforall

      (CETrans {actselect, gselect, forall, partition, guard, action, names}) =

    let

      fun addAndCheck ((n, _), s) = if n <- s

                                    then raise Fail "addDisjointForalls"

                                    else s <+ n

    in

      CETrans {actselect=actselect,

               gselect=gselect,

               forall=newforall@forall,

               partition=partition,

               guard=guard,

               action=action,

               names=foldl addAndCheck names newforall}

    end

  fun fromATrans preenv (AT.ActTrans {selectids=sellist,

                                      actionsubs, guard, names}) =

    let

      val senv = List.foldl (Env.addId Env.SelectScope) preenv sellist

      val (guard, forall, used) = ClkE.fromExpr (names, senv, guard)

        (* Note: ClkE.fromExpr ensures:

         *         intersection(selectids, forall) = emptyset

         *       as names includes selectids.

         *)

      val actionNames = AT.addSelectSubNames actionsubs

      fun categorize ([], acts, gs) = (acts, gs)

        | categorize ((s as (n, _))::ss, acts, gs) =

            if n <- actionNames then categorize (ss, s::acts, gs)

                                else categorize (ss, acts, s::gs)

      val (actsels, gsels) = categorize (sellist, [], [])

    in

       CETrans {actselect=actsels,

                gselect=gsels,

                forall=forall,

                partition=E.trueExpr,

                guard=guard,

                action=actionsubs,

                names=used}

    end

  local (**)

    fun toBoundId (s, ty) = E.BoundId (s, ty, E.nopos)

  in (**)

  fun toTrans (CETrans {actselect, gselect, forall,

                        partition, guard, action, ...}) = let

      val preguard = ClkE.toExpr (guard, forall)

      val guard = if E.equal (partition, E.trueExpr) then preguard

                  else E.BinBoolExpr {left=partition, bop=E.AndOp,

                                      right=preguard, pos=E.nopos}

    in

      {selectids=map toBoundId (actselect @ gselect),

       actionsubs=map AT.actionsubToExpr action,

       guard=guard}

    end

  end (* local *)

  fun rename (CETrans {actselect, gselect, forall, partition,

                       guard, action, names}, r as {old, new}) =

    let

      val _ = if new <- names

              then raise Fail "rename: new name is already bound"

              else ()

      fun rsel (sv, sty) = if sv =:= old then (new, sty) else (sv, sty)

      fun renameAction (a as AT.SelectSub n) = if n =:= old

                                               then AT.SelectSub new else a

        | renameAction (AT.FreeExprSub e) = AT.FreeExprSub (E.renameVar (r, e))

    in

      CETrans {actselect=map rsel actselect,

               gselect=map rsel gselect,

               forall=map rsel forall,

               partition=E.renameVar (r, partition),

               guard=ClkE.rename (r, guard),

               action=map renameAction action,

               names=(names <\ old) <+ new}

    end

  local (*{{{1*)

    fun pairwiseIntersect ([], i)    = i

      | pairwiseIntersect (x::ys, i) = let

            fun withEach (y,i) = AtomSet.union (AtomSet.intersection(x,y), i)

          in pairwiseIntersect (ys, foldl withEach i ys) end

    fun makeTrans (actselects, potselects, potforalls, part, act) andx = let

        fun combineAnd (t, e) = ClkE.And (e, ClkE.Term t)

        fun makeAnd []      = ClkE.Term (ClkE.NonClock (E.falseExpr))

          | makeAnd (x::xs) = List.foldl combineAnd (ClkE.Term x) xs

        val e=makeAnd andx

        val exprNames=ClkE.getFree e

        val names=exprNames ++ AT.addActionNames act

        val forAlls=List.filter (fn (nm, _)=> nm<-exprNames) potforalls

      in (CETrans {actselect=actselects,

                   gselect=List.filter (fn (nm,_)=> nm<-names) potselects,

                   forall=forAlls,

                   partition=part,

                   guard=e,

                   action=act,

                   names=names}, addNameTypes forAlls)

      end

  in (*}}}1*)

  fun negate invariant (CETrans {actselect, gselect, forall,

                                 guard, partition, action, names}) =

       let

         val g' = ClkE.negate guard

         val e  = case invariant of

                    ClkE.Term (ClkE.NonClock (E.BoolCExpr true)) => g'

                  | _ => ClkE.And (invariant, g')

         val dnf = ClkE.toDNF e

       in

         if ClkE.conflictExists (addNameTypes gselect, addNameTypes forall, dnf)

         then raise SelectIdConflictsWithForAll (#1 (ListPair.unzip gselect),

                                                 #1 (ListPair.unzip forall))

         else let

           val (trans, fall)=ListPair.unzip (map

                (makeTrans (actselect, forall, gselect, partition, action)) dnf)

                (* NB: forall and gselect are switched! (after having ensured

                 *     names are disjoint, and `non-conflicting') *)

           val splitFAlls=pairwiseIntersect (fall, emptyset)

         in

            if AtomSet.isEmpty splitFAlls then trans

            else (Util.warn ["forall bindings ",

                             ListFormat.fmt {init="(", sep=", ", final=")",

                                             fmt=Atom.toString}

                               (AtomSet.listItems splitFAlls),

                         " are shared across disjuncts: likely split zones"];

                  [CETrans {actselect=actselect,

                            gselect=forall,

                            forall=gselect,

                            partition=partition,

                            guard=e,

                            action=action,

                            names=names}])

            (* An improvement would be to split where possible,

               i.e. partition on shared foralls, transitive on overlap. *)

         end

       end

  end (* local *)

  local (*{{{1*)

    fun equateActions ([], [], e) = e

      | equateActions (AT.FreeExprSub e1::ss1, AT.FreeExprSub e2::ss2, e) =

          if E.equal (e1, e2)

          then equateActions (ss1, ss2, e)

          else let

                 val eq = E.RelExpr {left=e1, rel=E.EqOp, right=e2,

                                     pos=E.nopos}

                 val e' = if E.equal (e, E.trueExpr) then eq

                          else E.BinBoolExpr {left=e, bop=E.AndOp, right=eq,

                                              pos=E.nopos}

               in equateActions (ss1, ss2, e') end

      | equateActions ((AT.SelectSub _)::ss1, (AT.SelectSub _)::ss2, e) =

                equateActions (ss1, ss2, e)

      | equateActions _ = raise Fail "equateActions: assumptions not met"

    fun distinguishActions (ss1, ss2, e) = let

        val ne = E.negate (equateActions (ss1, ss2, E.trueExpr))

      in

        if E.equal (e, E.trueExpr) then ne

        else E.BinBoolExpr {left=e, bop=E.AndOp, right=ne, pos=E.nopos}

      end

    fun equateClass (x::xs, e) = let

        fun equate (x', e) = equateActions (x, x', e)

      in foldl equate e xs end

    (* Form an expression that equates all members of the same class.

       e.g. given: [ [ [e1, e2], [f1, f2], [g1, g2] ],

                     [ [h1, h2], [i1, i2] ] ]

            returns:    (e1 == f1) && (e2 == f2)

                     && (e1 == g1) && (e2 == g2)

                     && (h1 == i1) && (h2 == i2)                    *)

    val equateClasses = foldl equateClass E.trueExpr

    (* Form an expression that distinguish classes across a partition,

       e.g. given: [ [ [e1, e2], [f1, f2], [g1, g2] ],

                     [ [h1, h2], [i1, i2] ]

                     [ [j1, j2], [k1, k2] ] ]

            returns: e && !((e1 == h1) && (e2 == h2))

                       && !((e1 == j1) && (e2 == j2))

                       && !((h1 == j1) && (h2 == j2))               *)

    fun distinguishClasses ([c], e) = e

      | distinguishClasses ((cRep::_)::cs, e) = let

            fun distinguish (oRep::_, e) = distinguishActions (cRep, oRep, e)

          in

            distinguishClasses (cs, foldl distinguish e cs)

          end

    (* Given a partition of action subscripts, form an expression that

       distinguishes the partition from others. *)

    fun formPartitionExpr part = distinguishClasses (part, equateClasses part)

    fun projActions partition = let

        fun projAction (CETrans {action, ...}) = action

      in map (fn class=> map projAction class) partition end

    fun markPartition (CETrans {actselect, gselect, forall, partition,

                                guard, action, names}, partexpr) =

        CETrans {actselect=actselect, gselect=gselect, forall=forall,

               partition=partexpr, guard=guard, action=action, names=names}

  fun renameConflicts ren args = let

  (* args: names_to_check * [] * expr_to_rename_in * conflict_set * usednames *)

    fun doit ([], done, g, conflicts, used) = (rev done, g, used)

      | doit ((s as (n, ty))::ss, done, g, conflicts, used) =

      if n <- conflicts

        then let val n' = getNewName (n, used)

                 val g' = ren ({old=n, new=n'}, g)

             in

               doit (ss, (n', ty)::done, g', conflicts, used <+ n')

             end

        else doit (ss, s::done, g, conflicts, used)

    in doit args end

    fun mergeTrans partexpr

        (CETrans {actselect=asel1, gselect=gsel1, forall=fa1,

                  partition=p1, guard=g1, action=act1, names=n1},

         CETrans {actselect=asel2, gselect=gsel2, forall=fa2,

                  partition=p2, guard=g2, action=act2, names=n2}) =

      let

        val asel1names = addNameTypes asel1

        val clash = asel1names ++ addNameTypes gsel1 ++ addNameTypes fa1

        val (gsel2', g2', names') = renameConflicts ClkE.rename

                                      (gsel2, [], g2, clash, n1++n2)

        val (fa2',   g2', names') = renameConflicts ClkE.rename

                                      (fa2, [], g2', clash, names')

      in

        CETrans {actselect=asel1

                     @ List.filter (fn (n,_)=> not (n<- asel1names)) asel2,

                     (* probably unnecessary after ATrans.ensureConsistency *)

                 gselect=gsel1 @ gsel2',

                 forall=fa1 @ fa2',

                 partition=partexpr,

                 guard=ClkE.Or (g1, g2'),

                 action=act1,

                 names=names'}

      end

  in (*}}}1*)

  (* Map each class in a partition to a single transition.

     All transitions are stamped with the same partition expression *)

  fun formPartitionReps [[]] = []

    | formPartitionReps trpart = let

          val partexpr = formPartitionExpr (projActions trpart)

          val mergeT = mergeTrans partexpr

          fun mergeClass (c::cs) = foldl mergeT (markPartition (c, partexpr)) cs

        in map mergeClass trpart end

  end (* local *)

end

end