(* 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 ElabOps :> ELAB_OPS = struct

open Elab

structure E = ElabEnv
structure U = ElabUtil

val liftConInCon = E.liftConInCon

val subConInCon =
    U.Con.mapB {kind = fn k => k,
                con = fn (xn, rep) => fn c =>
                                  case c of
                                      CRel xn' =>
                                      (case Int.compare (xn', xn) of
                                           EQUAL => #1 rep
                                         | GREATER => CRel (xn' - 1)
                                         | LESS => c)
                                    (*| CUnif _ => raise SynUnif*)
                                    | _ => c,
                bind = fn ((xn, rep), U.Con.Rel _) => (xn+1, liftConInCon 0 rep)
                        | (ctx, _) => ctx}

fun subStrInSgn (m1, m2) =
    U.Sgn.map {kind = fn k => k,
               con = fn c as CModProj (m1', ms, x) =>
                        if m1 = m1' then
                            CModProj (m2, ms, x)
                        else
                            c
                      | c => c,
               sgn_item = fn sgi => sgi,
               sgn = fn sgn => sgn}


fun hnormCon env (cAll as (c, loc)) =
    case c of
        CUnif (_, _, _, ref (SOME c)) => hnormCon env c

      | CNamed xn =>
        (case E.lookupCNamed env xn of
             (_, _, SOME c') => hnormCon env c'
           | _ => cAll)

      | CModProj (n, ms, x) =>
        let
            val (_, sgn) = E.lookupStrNamed env n
            val (str, sgn) = foldl (fn (m, (str, sgn)) =>
                                       case E.projectStr env {sgn = sgn, str = str, field = m} of
                                           NONE => raise Fail "hnormCon: Unknown substructure"
                                         | SOME sgn => ((StrProj (str, m), loc), sgn))
                             ((StrVar n, loc), sgn) ms
        in
            case E.projectCon env {sgn = sgn, str = str, field = x} of
                NONE => raise Fail "kindof: Unknown con in structure"
              | SOME (_, NONE) => cAll
              | SOME (_, SOME c) => hnormCon env c
        end

      | CApp (c1, c2) =>
        (case #1 (hnormCon env c1) of
             CAbs (x, k, cb) =>
             let
                 val sc = (hnormCon env (subConInCon (0, c2) cb))
                     handle SynUnif => cAll
                 (*val env' = E.pushCRel env x k*)
             in
                 (*eprefaces "Subst" [("x", Print.PD.string x),
                                    ("cb", p_con env' cb),
                                    ("c2", p_con env c2),
                                    ("sc", p_con env sc)];*)
                 sc
             end
           | CApp (c', i) =>
             (case #1 (hnormCon env c') of
                  CApp (c', f) =>
                  (case #1 (hnormCon env c') of
                       CFold ks =>
                       (case #1 (hnormCon env c2) of
                            CRecord (_, []) => hnormCon env i
                          | CRecord (k, (x, c) :: rest) =>
                            hnormCon env
                                     (CApp ((CApp ((CApp (f, x), loc), c), loc),
                                               (CApp ((CApp ((CApp ((CFold ks, loc), f), loc), i), loc),
                                                         (CRecord (k, rest), loc)), loc)), loc)
                          | CConcat ((CRecord (k, (x, c) :: rest), _), rest') =>
                            let
                                val rest'' = (CConcat ((CRecord (k, rest), loc), rest'), loc)

                                (*val ccc = (CApp ((CApp ((CApp (f, x), loc), c), loc),
                                                   (CApp ((CApp ((CApp ((CFold ks, loc), f), loc), i), loc),
                                                             rest''), loc)), loc)*)
                            in
                                (*eprefaces "Red to" [("ccc", p_con env ccc), ("ccc'", p_con env (hnormCon env ccc))];*)
                                hnormCon env
                                         (CApp ((CApp ((CApp (f, x), loc), c), loc),
                                                   (CApp ((CApp ((CApp ((CFold ks, loc), f), loc), i), loc),
                                                             rest''), loc)), loc)
                            end
                          | _ => cAll)
                     | _ => cAll)
                | _ => cAll)
           | _ => cAll)

      | CConcat (c1, c2) =>
        (case (hnormCon env c1, hnormCon env c2) of
             ((CRecord (k, xcs1), loc), (CRecord (_, xcs2), _)) =>
             (CRecord (k, xcs1 @ xcs2), loc)
           | ((CRecord (_, []), _), c2') => c2'
           | ((CConcat (c11, c12), loc), c2') =>
             hnormCon env (CConcat (c11, (CConcat (c12, c2'), loc)), loc)
           | (c1', (CRecord (_, []), _)) => c1'
           | _ => cAll)

      | CProj (c, n) =>
        (case hnormCon env c of
             (CTuple cs, _) => hnormCon env (List.nth (cs, n - 1))
           | _ => cAll)

      | _ => cAll

end