(* 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 ElabUtil :> ELAB_UTIL = struct

open Elab

structure S = Search

structure Kind = struct

fun mapfold f =
    let
        fun mfk k acc =
            S.bindP (mfk' k acc, f)

        and mfk' (kAll as (k, loc)) =
            case k of
                KType => S.return2 kAll

              | KArrow (k1, k2) =>
                S.bind2 (mfk k1,
                      fn k1' =>
                         S.map2 (mfk k2,
                              fn k2' =>
                                 (KArrow (k1', k2'), loc)))

              | KName => S.return2 kAll

              | KRecord k =>
                S.map2 (mfk k,
                        fn k' =>
                           (KRecord k', loc))

              | KError => S.return2 kAll

              | KUnif (_, ref (SOME k)) => mfk' k
              | KUnif _ => S.return2 kAll
    in
        mfk
    end

fun exists f k =
    case mapfold (fn k => fn () =>
                             if f k then
                                 S.Return ()
                             else
                                 S.Continue (k, ())) k () of
        S.Return _ => true
      | S.Continue _ => false

end

structure Con = struct

datatype binder =
         Rel of string * Elab.kind
       | Named of string * Elab.kind

fun mapfoldB {kind = fk, con = fc, bind} =
    let
        val mfk = Kind.mapfold fk

        fun mfc ctx c acc =
            S.bindP (mfc' ctx c acc, fc ctx)

        and mfc' ctx (cAll as (c, loc)) =
            case c of
                TFun (c1, c2) =>
                S.bind2 (mfc ctx c1,
                      fn c1' =>
                         S.map2 (mfc ctx c2,
                              fn c2' =>
                                 (TFun (c1', c2'), loc)))
              | TCFun (e, x, k, c) =>
                S.bind2 (mfk k,
                      fn k' =>
                         S.map2 (mfc (bind (ctx, Rel (x, k))) c,
                              fn c' =>
                                 (TCFun (e, x, k', c'), loc)))
              | TRecord c =>
                S.map2 (mfc ctx c,
                        fn c' =>
                           (TRecord c', loc))

              | CRel _ => S.return2 cAll
              | CNamed _ => S.return2 cAll
              | CApp (c1, c2) =>
                S.bind2 (mfc ctx c1,
                      fn c1' =>
                         S.map2 (mfc ctx c2,
                              fn c2' =>
                                 (CApp (c1', c2'), loc)))
              | CAbs (x, k, c) =>
                S.bind2 (mfk k,
                      fn k' =>
                         S.map2 (mfc (bind (ctx, Rel (x, k))) c,
                              fn c' =>
                                 (CAbs (x, k', c'), loc)))

              | CName _ => S.return2 cAll

              | CRecord (k, xcs) =>
                S.bind2 (mfk k,
                      fn k' =>
                         S.map2 (ListUtil.mapfold (fn (x, c) =>
                                                      S.bind2 (mfc ctx x,
                                                            fn x' =>
                                                               S.map2 (mfc ctx c,
                                                                    fn c' =>
                                                                       (x', c'))))
                                 xcs,
                              fn xcs' =>
                                 (CRecord (k', xcs'), loc)))
              | CConcat (c1, c2) =>
                S.bind2 (mfc ctx c1,
                      fn c1' =>
                         S.map2 (mfc ctx c2,
                              fn c2' =>
                                 (CConcat (c1', c2'), loc)))

              | CError => S.return2 cAll
              | CUnif (_, _, ref (SOME c)) => mfc' ctx c
              | CUnif _ => S.return2 cAll
    in
        mfc
    end

fun mapfold {kind = fk, con = fc} =
    mapfoldB {kind = fk,
              con = fn () => fc,
              bind = fn ((), _) => ()} ()

fun mapB {kind, con, bind} ctx c =
    case mapfoldB {kind = fn k => fn () => S.Continue (kind k, ()),
                   con = fn ctx => fn c => fn () => S.Continue (con ctx c, ()),
                   bind = bind} ctx c () of
        S.Continue (c, ()) => c
      | S.Return _ => raise Fail "Con.mapB: Impossible"

fun exists {kind, con} k =
    case mapfold {kind = fn k => fn () =>
                                    if kind k then
                                        S.Return ()
                                    else
                                        S.Continue (k, ()),
                  con = fn c => fn () =>
                                    if con c then
                                        S.Return ()
                                    else
                                        S.Continue (c, ())} k () of
        S.Return _ => true
      | S.Continue _ => false

end

structure Exp = struct

datatype binder =
         RelC of string * Elab.kind
       | NamedC of string * Elab.kind
       | RelE of string * Elab.con
       | NamedE of string * Elab.con

fun mapfoldB {kind = fk, con = fc, exp = fe, bind} =
    let
        val mfk = Kind.mapfold fk

        fun bind' (ctx, b) =
            let
                val b' = case b of
                             Con.Rel x => RelC x
                           | Con.Named x => NamedC x
            in
                bind (ctx, b')
            end
        val mfc = Con.mapfoldB {kind = fk, con = fc, bind = bind'}

        fun mfe ctx e acc =
            S.bindP (mfe' ctx e acc, fe ctx)

        and mfe' ctx (eAll as (e, loc)) =
            case e of
                ERel _ => S.return2 eAll
              | ENamed _ => S.return2 eAll
              | EApp (e1, e2) =>
                S.bind2 (mfe ctx e1,
                      fn e1' =>
                         S.map2 (mfe ctx e2,
                              fn e2' =>
                                 (EApp (e1', e2'), loc)))
              | EAbs (x, t, e) =>
                S.bind2 (mfc ctx t,
                      fn t' =>
                         S.map2 (mfe (bind (ctx, RelE (x, t))) e,
                              fn e' =>
                                 (EAbs (x, t', e'), loc)))

              | ECApp (e, c) =>
                S.bind2 (mfe ctx e,
                      fn e' =>
                         S.map2 (mfc ctx c,
                              fn c' =>
                                 (ECApp (e', c'), loc)))
              | ECAbs (expl, x, k, e) =>
                S.bind2 (mfk k,
                      fn k' =>
                         S.map2 (mfe (bind (ctx, RelC (x, k))) e,
                              fn e' =>
                                 (ECAbs (expl, x, k', e'), loc)))

              | ERecord xes =>
                S.map2 (ListUtil.mapfold (fn (x, e) =>
                                             S.bind2 (mfc ctx x,
                                                   fn x' =>
                                                      S.map2 (mfe ctx e,
                                                           fn e' =>
                                                              (x', e'))))
                                         xes,
                     fn xes' =>
                        (ERecord xes', loc))
              | EField (e, c, {field, rest}) =>
                S.bind2 (mfe ctx e,
                      fn e' =>
                         S.bind2 (mfc ctx c,
                              fn c' =>
                                 S.bind2 (mfc ctx field,
                                          fn field' =>
                                             S.map2 (mfc ctx rest,
                                                  fn rest' =>
                                                     (EField (e', c', {field = field', rest = rest'}), loc)))))

              | EError => S.return2 eAll
    in
        mfe
    end

fun mapfold {kind = fk, con = fc, exp = fe} =
    mapfoldB {kind = fk,
              con = fn () => fc,
              exp = fn () => fe,
              bind = fn ((), _) => ()} ()

fun exists {kind, con, exp} k =
    case mapfold {kind = fn k => fn () =>
                                    if kind k then
                                        S.Return ()
                                    else
                                        S.Continue (k, ()),
                  con = fn c => fn () =>
                                    if con c then
                                        S.Return ()
                                    else
                                        S.Continue (c, ()),
                  exp = fn e => fn () =>
                                    if exp e then
                                        S.Return ()
                                    else
                                        S.Continue (e, ())} k () of
        S.Return _ => true
      | S.Continue _ => false

end

end