(* 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.
 *)

structure ESpecialize :> ESPECIALIZE = struct

open Core

structure E = CoreEnv
structure U = CoreUtil

type skey = exp

structure K = struct
type ord_key = exp list
val compare = Order.joinL U.Exp.compare
end

structure KM = BinaryMapFn(K)
structure IM = IntBinaryMap
structure IS = IntBinarySet

val sizeOf = U.Exp.fold {kind = fn (_, n) => n,
                         con = fn (_, n) => n,
                         exp = fn (_, n) => n + 1}
                        0

val isOpen = U.Exp.existsB {kind = fn _ => false,
                            con = fn ((nc, _), c) =>
                                    case c of
                                        CRel n => n >= nc
                                      | _ => false,
                            exp = fn ((_, ne), e) =>
                                     case e of
                                         ERel n => n >= ne
                                       | _ => false,
                            bind = fn ((nc, ne), b) =>
                                      case b of
                                          U.Exp.RelC _ => (nc + 1, ne)
                                        | U.Exp.RelE _ => (nc, ne + 1)
                                        | _ => (nc, ne)}
             (0, 0)

fun baseBad (e, _) =
    case e of
        EAbs (_, _, _, e) => sizeOf e > 20
      | ENamed _ => false
      | _ => true

fun isBad e =
    case e of
        (ERecord xes, _) =>
        length xes > 10
        orelse List.exists (fn (_, e, _) => baseBad e) xes
      | _ => baseBad e

fun skeyIn e =
    if isBad e orelse isOpen e then
        NONE
    else
        SOME e

fun skeyOut e = e

type func = {
     name : string,
     args : int KM.map,
     body : exp,
     typ : con,
     tag : string
}

type state = {
     maxName : int,
     funcs : func IM.map,
     decls : (string * int * con * exp * string) list
}

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

fun specialize' file =
    let
        fun default (_, fs) = fs

        fun actionableExp (e, fs) =
            case e of
                ERecord xes =>
                foldl (fn (((CName s, _), e, _), fs) =>
                          if s = "Action" orelse s = "Link" then
                              let
                                  fun findHead (e, _) =
                                      case e of
                                          ENamed n => IS.add (fs, n)
                                        | EApp (e, _) => findHead e
                                        | _ => fs
                              in
                                  findHead e
                              end
                          else
                              fs
                        | (_, fs) => fs)
                fs xes
              | _ => fs

        val actionable =
            U.File.fold {kind = default,
                         con = default,
                         exp = actionableExp,
                         decl = default}
            IS.empty file

        fun exp (e, st : state) =
            let
                fun getApp e =
                    case e of
                        ENamed f => SOME (f, [], [])
                      | EApp (e1, e2) =>
                        (case getApp (#1 e1) of
                             NONE => NONE
                           | SOME (f, xs, xs') =>
                             let
                                 val k =
                                     if List.null xs' then
                                         skeyIn e2
                                     else
                                         NONE
                             in
                                 case k of
                                     NONE => SOME (f, xs, xs' @ [e2])
                                   | SOME k => SOME (f, xs @ [k], xs')
                             end)
                      | _ => NONE
            in
                case getApp e of
                    NONE => (e, st)
                  | SOME (f, [], []) => (e, st)
                  | SOME (f, [], xs') =>
                    (case IM.find (#funcs st, f) of
                         NONE => (e, st)
                       | SOME {typ, body, ...} =>
                         let
                             val functionInside = U.Con.exists {kind = fn _ => false,
                                                                con = fn TFun _ => true
                                                                       | CFfi ("Basis", "transaction") => true
                                                                       | _ => false}

                             fun hasFunarg (t, xs) =
                                 case (t, xs) of
                                     ((TFun (dom, ran), _), _ :: xs) =>
                                     functionInside dom
                                     orelse hasFunarg (ran, xs)
                                   | _ => false
                         in
                             if List.all (fn (ERel _, _) => false | _ => true) xs'
                                andalso not (IS.member (actionable, f))
                                andalso hasFunarg (typ, xs') then
                                 (#1 (foldl (fn (arg, e) => (EApp (e, arg), ErrorMsg.dummySpan))
                                            body xs'),
                                  st)
                             else
                                 (e, st)
                         end)
                                   | SOME (f, xs, xs') =>
                                     case IM.find (#funcs st, f) of
                                         NONE => (e, st)
                                       | SOME {name, args, body, typ, tag} =>
                                         case KM.find (args, xs) of
                                             SOME f' => (#1 (foldl (fn (arg, e) => (EApp (e, arg), ErrorMsg.dummySpan))
                                                                   (ENamed f', ErrorMsg.dummySpan) xs'),
                                                         st)
                                           | NONE =>
                                             let
                                                 fun subBody (body, typ, xs) =
                                                     case (#1 body, #1 typ, xs) of
                                                         (_, _, []) => SOME (body, typ)
                                                       | (EAbs (_, _, _, body'), TFun (_, typ'), x :: xs) =>
                                                         let
                                                             val body'' = E.subExpInExp (0, skeyOut x) body'
                                                         in
                                                             subBody (body'',
                                                                      typ',
                                                                      xs)
                                                         end
                                                       | _ => NONE
                                             in
                                                 case subBody (body, typ, xs) of
                                                     NONE => (e, st)
                                                   | SOME (body', typ') =>
                                                     let
                                                         val f' = #maxName st
                                                         val funcs = IM.insert (#funcs st, f, {name = name,
                                                                                               args = KM.insert (args,
                                                                                                                 xs, f'),
                                                                                               body = body,
                                                                                               typ = typ,
                                                                                               tag = tag})
                                                         val st = {
                                                             maxName = f' + 1,
                                                             funcs = funcs,
                                                             decls = #decls st
                                                         }

                                                         val (body', st) = specExp st body'
                                                         val e' = foldl (fn (arg, e) => (EApp (e, arg), ErrorMsg.dummySpan))
                                                                        (ENamed f', ErrorMsg.dummySpan) xs'
                                                     in
                                                         (#1 e',
                                                          {maxName = #maxName st,
                                                           funcs = #funcs st,
                                                           decls = (name, f', typ', body', tag) :: #decls st})
                                                     end
                                             end
                         end

        and specExp st = U.Exp.foldMap {kind = kind, con = con, exp = exp} st

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

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



        fun doDecl (d, (st : state, changed)) =
            let
                val funcs = #funcs st
                val funcs = 
                    case #1 d of
                        DValRec vis =>
                        foldl (fn ((x, n, c, e, tag), funcs) =>
                                  IM.insert (funcs, n, {name = x,
                                                        args = KM.empty,
                                                        body = e,
                                                        typ = c,
                                                        tag = tag}))
                              funcs vis
                      | _ => funcs

                val st = {maxName = #maxName st,
                          funcs = funcs,
                          decls = []}

                (*val () = Print.prefaces "decl" [("d", CorePrint.p_decl CoreEnv.empty d)]*)
                val (d', st) = specDecl st d
                (*val () = print "/decl\n"*)

                val funcs = #funcs st
                val funcs =
                    case #1 d of
                        DVal (x, n, c, e as (EAbs _, _), tag) =>
                        IM.insert (funcs, n, {name = x,
                                              args = KM.empty,
                                              body = e,
                                              typ = c,
                                              tag = tag})
                      | DVal (_, n, _, (ENamed n', _), _) =>
                        (case IM.find (funcs, n') of
                             NONE => funcs
                           | SOME v => IM.insert (funcs, n, v))
                      | _ => funcs

                val (changed, ds) =
                    case #decls st of
                        [] => (changed, [d'])
                      | vis =>
                        (true, case d' of
                                   (DValRec vis', _) => [(DValRec (vis @ vis'), ErrorMsg.dummySpan)]
                                 | _ => [(DValRec vis, ErrorMsg.dummySpan), d'])
            in
                (ds, ({maxName = #maxName st,
                       funcs = funcs,
                       decls = []}, changed))
            end

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

fun specialize file =
    let
        val (changed, file) = specialize' file
    in
        if changed then
            specialize (ReduceLocal.reduce file)
        else
            file
    end

end