(* Copyright (c) 2008, Adam Chlipala
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * - Redistributions of source code must retain the above copyright notice,
 *   this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright notice,
 *   this list of conditions and the following disclaimer in the documentation
 *   and/or other materials provided with the distribution.
 * - The names of contributors may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *)

(* Simplify a Core program algebraically *)

structure Specialize :> SPECIALIZE = struct

open Core

structure E = CoreEnv
structure U = CoreUtil

val liftConInCon = E.liftConInCon
val subConInCon = E.subConInCon

structure CK = struct
type ord_key = con list
val compare = Order.joinL U.Con.compare
end

structure CM = BinaryMapFn(CK)
structure IM = IntBinaryMap

type datatyp' = {
     name : int,
     constructors : int IM.map
}

type datatyp = {
     name : string,
     params : int,
     constructors : (string * int * con option) list,
     specializations : datatyp' CM.map
}

type state = {
     count : int,
     datatypes : datatyp IM.map,
     constructors : int IM.map,
     decls : decl list
}

fun kind (k, st) = (k, st)

val isOpen = U.Con.exists {kind = fn _ => false,
                           con = fn c =>
                                    case c of
                                        CRel _ => true
                                      | _ => false}

fun considerSpecialization (st : state, n, args, dt : datatyp) =
    case CM.find (#specializations dt, args) of
        SOME dt' => (#name dt', #constructors dt', st)
      | NONE =>
        let
            (*val () = Print.prefaces "Args" [("args", Print.p_list (CorePrint.p_con CoreEnv.empty) args)]*)

            val n' = #count st

            val nxs = length args - 1
            fun sub t = ListUtil.foldli (fn (i, arg, t) =>
                                            subConInCon (nxs - i, arg) t) t args

            val (cons, (count, cmap)) =
                ListUtil.foldlMap (fn ((x, n, to), (count, cmap)) =>
                                      let
                                          val to = Option.map sub to
                                      in
                                          ((x, count, to),
                                           (count + 1,
                                            IM.insert (cmap, n, count)))
                                      end) (n' + 1, IM.empty) (#constructors dt)

            val st = {count = count,
                      datatypes = IM.insert (#datatypes st, n,
                                             {name = #name dt,
                                              params = #params dt,
                                              constructors = #constructors dt,
                                              specializations = CM.insert (#specializations dt,
                                                                           args,
                                                                           {name = n',
                                                                            constructors = cmap})}),
                      constructors = #constructors st,
                      decls = #decls st}

            val (cons, st) = ListUtil.foldlMap (fn ((x, n, NONE), st) => ((x, n, NONE), st)
                                                 | ((x, n, SOME t), st) =>
                                                   let
                                                       val (t, st) = specCon st t
                                                   in
                                                       ((x, n, SOME t), st)
                                                   end) st cons

            val d = (DDatatype (#name dt ^ "_s",
                                n',
                                [],
                                cons), #2 (List.hd args))
        in
            (n', cmap, {count = #count st,
                        datatypes = #datatypes st,
                        constructors = #constructors st,
                        decls = d :: #decls st})
        end

and con (c, st : state) =
    let
        fun findApp (c, args) =
            case c of
                CApp ((c', _), arg) => findApp (c', arg :: args)
              | CNamed n => SOME (n, args)
              | _ => NONE
    in
        case findApp (c, []) of
            SOME (n, args as (_ :: _)) =>
            if List.exists isOpen args then
                (c, st)
            else
                (case IM.find (#datatypes st, n) of
                     NONE => (c, st)
                   | SOME dt =>
                     if length args <> #params dt then
                         (c, st)
                     else
                         let
                             val (n, _, st) = considerSpecialization (st, n, args, dt)
                         in
                             (CNamed n, st)
                         end)
          | _ => (c, st)
    end

and specCon st = U.Con.foldMap {kind = kind, con = con} st

fun pat (p, st) =
    case #1 p of
        PWild => (p, st)
      | PVar _ => (p, st)
      | PPrim _ => (p, st)
      | PCon (dk, PConVar pn, args as (_ :: _), po) =>
        let
            val (po, st) =
                case po of
                    NONE => (NONE, st)
                  | SOME p =>
                    let
                        val (p, st) = pat (p, st)
                    in
                        (SOME p, st)
                    end
            val p = (PCon (dk, PConVar pn, args, po), #2 p)
        in
            if List.exists isOpen args then
                (p, st)
            else
                case IM.find (#constructors st, pn) of
                    NONE => (p, st)
                  | SOME n =>
                    case IM.find (#datatypes st, n) of
                        NONE => (p, st)
                      | SOME dt =>
                        let
                            val (n, cmap, st) = considerSpecialization (st, n, args, dt)
                        in
                            case IM.find (cmap, pn) of
                                NONE => raise Fail "Specialize: Missing datatype constructor (pat)"
                              | SOME pn' => ((PCon (dk, PConVar pn', [], po), #2 p), st)
                        end
        end
      | PCon _ => (p, st)
      | PRecord xps =>
        let
            val (xps, st) = ListUtil.foldlMap (fn ((x, p, t), st) =>
                                                  let
                                                      val (p, st) = pat (p, st)
                                                  in
                                                      ((x, p, t), st)
                                                  end)
                            st xps
        in
            ((PRecord xps, #2 p), st)
        end

fun exp (e, st) =
    case e of
        ECon (dk, PConVar pn, args as (_ :: _), eo) =>
        if List.exists isOpen args then
            (e, st)
        else
            (case IM.find (#constructors st, pn) of
                 NONE => (e, st)
               | SOME n =>
                 case IM.find (#datatypes st, n) of
                     NONE => (e, st)
                   | SOME dt =>
                     let
                         val (n, cmap, st) = considerSpecialization (st, n, args, dt)
                     in
                         case IM.find (cmap, pn) of
                             NONE => raise Fail "Specialize: Missing datatype constructor"
                           | SOME pn' => (ECon (dk, PConVar pn', [], eo), st)
                     end)
      | ECase (e, pes, r) =>
        let
            val (pes, st) = ListUtil.foldlMap (fn ((p, e), st) =>
                                                  let
                                                      val (p, st) = pat (p, st)
                                                  in
                                                      ((p, e), st)
                                                  end) st pes
        in
            (ECase (e, pes, r), st)
        end
      | _ => (e, st)

fun decl (d, st) = (d, st)

val specDecl = U.Decl.foldMap {kind = kind, con = con, exp = exp, decl = decl}

fun specialize file =
    let
        fun doDecl (all as (d, _), st : state) =
            let
                (*val () = Print.preface ("decl:", CorePrint.p_decl CoreEnv.empty all)*)
            in
                case d of
                    DDatatype (x, n, xs, xnts) =>
                    ([all], {count = #count st,
                             datatypes = IM.insert (#datatypes st, n,
                                                    {name = x,
                                                     params = length xs,
                                                     constructors = xnts,
                                                     specializations = CM.empty}),
                             constructors = foldl (fn ((_, n', _), constructors) =>
                                                      IM.insert (constructors, n', n))
                                                  (#constructors st) xnts,
                             decls = []})
                  | _ =>
                    let
                        val (d, st) = specDecl st all
                    in
                        (rev (d :: #decls st),
                         {count = #count st,
                          datatypes = #datatypes st,
                          constructors = #constructors st,
                          decls = []})
                    end
            end

        val (ds, _) = ListUtil.foldlMapConcat doDecl
                      {count = U.File.maxName file + 1,
                       datatypes = IM.empty,
                       constructors = IM.empty,
                       decls = []} file
    in
        ds
    end


end