(* 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 ElabEnv :> ELAB_ENV = struct

open Elab

structure IM = IntBinaryMap
structure SM = BinaryMapFn(struct
                           type ord_key = string
                           val compare = String.compare
                           end)

exception UnboundRel of int
exception UnboundNamed of int

datatype var' =
         CRel' of int * kind
       | CNamed' of int * kind

datatype var =
         CNotBound
       | CRel of int * kind
       | CNamed of int * kind

type env = {
     renameC : var' SM.map,
     relC : (string * kind) list,
     namedC : (string * kind) IM.map
}

val namedCounter = ref 0

val empty = {
    renameC = SM.empty,
    relC = [],
    namedC = IM.empty
}

fun pushCRel (env : env) x k =
    let
        val renameC = SM.map (fn CRel' (n, k) => CRel' (n+1, k)
                               | x => x) (#renameC env)
    in
        {renameC = SM.insert (renameC, x, CRel' (0, k)),
         relC = (x, k) :: #relC env,
         namedC = #namedC env}
    end

fun lookupCRel (env : env) n =
    (List.nth (#relC env, n))
    handle Subscript => raise UnboundRel n

fun pushCNamed (env : env) x k =
    let
        val n = !namedCounter
    in
        namedCounter := n + 1;
        ({renameC = SM.insert (#renameC env, x, CNamed' (n, k)),
          relC = #relC env,
          namedC = IM.insert (#namedC env, n, (x, k))},
         n)
    end

fun lookupCNamed (env : env) n =
    case IM.find (#namedC env, n) of
        NONE => raise UnboundNamed n
      | SOME x => x

fun lookupC (env : env) x =
    case SM.find (#renameC env, x) of
        NONE => CNotBound
      | SOME (CRel' x) => CRel x
      | SOME (CNamed' x) => CNamed x

end