(* 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 'a var' =
         Rel' of int * 'a
       | Named' of int * 'a

datatype 'a var =
         NotBound
       | Rel of int * 'a
       | Named of int * 'a

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

     renameE : con var' SM.map,
     relE : (string * con) list,
     namedE : (string * con) IM.map
}

val namedCounter = ref 0

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

    renameE = SM.empty,
    relE = [],
    namedE = IM.empty
}

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

         renameE = #renameE env,
         relE = #relE env,
         namedE = #namedE env}
    end

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

fun pushCNamedAs (env : env) x n k co =
    {renameC = SM.insert (#renameC env, x, Named' (n, k)),
     relC = #relC env,
     namedC = IM.insert (#namedC env, n, (x, k, co)),

     renameE = #renameE env,
     relE = #relE env,
     namedE = #namedE env}

fun pushCNamed env x k co =
    let
        val n = !namedCounter
    in
        namedCounter := n + 1;
        (pushCNamedAs env x n k co, 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 => NotBound
      | SOME (Rel' x) => Rel x
      | SOME (Named' x) => Named x

fun pushERel (env : env) x t =
    let
        val renameE = SM.map (fn Rel' (n, t) => Rel' (n+1, t)
                               | x => x) (#renameE env)
    in
        {renameC = #renameC env,
         relC = #relC env,
         namedC = #namedC env,

         renameE = SM.insert (renameE, x, Rel' (0, t)),
         relE = (x, t) :: #relE env,
         namedE = #namedE env}
    end

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

fun pushENamedAs (env : env) x n t =
    {renameC = #renameC env,
     relC = #relC env,
     namedC = #namedC env,

     renameE = SM.insert (#renameE env, x, Named' (n, t)),
     relE = #relE env,
     namedE = IM.insert (#namedE env, n, (x, t))}

fun pushENamed env x t =
    let
        val n = !namedCounter
    in
        namedCounter := n + 1;
        (pushENamedAs env x n t, n)
    end

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

fun lookupE (env : env) x =
    case SM.find (#renameE env, x) of
        NONE => NotBound
      | SOME (Rel' x) => Rel x
      | SOME (Named' x) => Named x

end