(* 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 Tag :> TAG = struct

open Core

structure U = CoreUtil
structure E = CoreEnv

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

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

fun both (loc, f) = (ErrorMsg.errorAt loc ("Function " ^ f ^ " needed for both a link and a form");
                     TextIO.output (TextIO.stdErr,
                                    "Make sure that the signature of the containing module hides any form handlers.\n"))

fun exp env (e, s) =
    let
        fun tagIt (e, ek : export_kind, newAttr, (count, tags, byTag, newTags)) =
            let
                val loc = #2 e

                val eOrig = e

                fun unravel (e, _) =
                    case e of
                        ENamed n => (n, [])
                      | EApp (e1, e2) =>
                        let
                            val (n, es) = unravel e1
                        in
                            (n, es @ [e2])
                        end
                      | _ => (ErrorMsg.errorAt loc ("Invalid " ^ newAttr
                                                    ^ " expression");
                              Print.epreface ("Expression",
                                              CorePrint.p_exp CoreEnv.empty eOrig);
                              (0, []))

                val (f, args) = unravel e

                val (cn, count, tags, newTags) =
                    case IM.find (tags, f) of
                        NONE =>
                        (count, count + 1, IM.insert (tags, f, count),
                         (ek, f, count) :: newTags)
                      | SOME cn => (cn, count, tags, newTags)
                                   
                val (_, _, _, s) = E.lookupENamed env f

                val byTag = case SM.find (byTag, s) of
                                NONE => SM.insert (byTag, s, (ek, f))
                              | SOME (ek', f') =>
                                (if f = f' then
                                     ()
                                 else
                                     ErrorMsg.errorAt loc 
                                                      ("Duplicate HTTP tag "
                                                       ^ s);
                                 if ek = ek' then
                                     ()
                                 else
                                     both (loc, s);
                                 byTag)

                val e = (EClosure (cn, args), loc)
            in
                (e, (count, tags, byTag, newTags))
            end
    in
        case e of
            EApp (
            (EApp (
             (EApp (
              (EApp (
               (ECApp (
                (ECApp (
                 (ECApp (
                  (ECApp (
                   (ECApp (
                    (ECApp (
                     (ECApp (
                      (ECApp (
                       (EFfi ("Basis", "tag"),
                        loc), given), _), absent), _), outer), _), inner), _),
                   useOuter), _), useInner), _), bindOuter), _), bindInner), _),
               class), _),
              attrs), _),
             tag), _),
            xml) =>
            (case attrs of
                 (ERecord xets, _) =>
                 let
                     val (xets, s) =
                         ListUtil.foldlMap (fn ((x, e, t), s) =>
                                               let
                                                   fun tagIt' (ek, newAttr) =
                                                       let
                                                           val (e', s) = tagIt (e, ek, newAttr, s)
                                                           val t = (CFfi ("Basis", "string"), loc)
                                                       in
                                                           (((CName newAttr, loc), e', t), s)
                                                       end
                                               in
                                                   case x of
                                                       (CName "Link", _) => tagIt' (Link, "Link")
                                                     | (CName "Action", _) => tagIt' (Action ReadWrite, "Action")
                                                     | _ => ((x, e, t), s)
                                               end)
                                           s xets
                 in
                     (EApp (
                      (EApp (
                       (EApp (
                        (EApp (
                         (ECApp (
                          (ECApp (
                           (ECApp (
                            (ECApp (
                             (ECApp (
                              (ECApp (
                               (ECApp (
                                (ECApp (
                                 (EFfi ("Basis", "tag"),
                                  loc), given), loc), absent), loc), outer), loc), inner), loc),
                             useOuter), loc), useInner), loc), bindOuter), loc), bindInner), loc),
                         class), loc),
                        (ERecord xets, loc)), loc),
                       tag), loc),
                      xml), s)
                 end
               | _ => (ErrorMsg.errorAt loc "Attribute record is too complex";
                       (e, s)))

          | EFfiApp ("Basis", "url", [(ERel 0, _)]) => (e, s)

          | EFfiApp ("Basis", "url", [e]) =>
            let
                val (e, s) = tagIt (e, Link, "Url", s)
            in
                (EFfiApp ("Basis", "url", [e]), s)
            end

          | EApp ((ENamed n, _), e') =>
            let
                val (_, _, eo, _) = E.lookupENamed env n
            in
                case eo of
                    SOME (EAbs (_, _, _, (EFfiApp ("Basis", "url", [(ERel 0, _)]), _)), _) =>
                    let
                        val (e, s) = tagIt (e', Link, "Url", s)
                    in
                        (EFfiApp ("Basis", "url", [e]), s)
                    end
                  | _ => (e, s)
            end

          | _ => (e, s)
    end

fun decl (d, s) = (d, s)

fun tag file =
    let
        val count = U.File.maxName file

        fun doDecl (d as (d', loc), (env, count, tags, byTag)) =
            case d' of
                DExport (ek, n, _) =>
                let
                    val (_, _, _, s) = E.lookupENamed env n
                in
                    case SM.find (byTag, s) of
                        NONE => ([d], (env, count, tags, byTag))
                      | SOME (ek', n') =>
                        (if ek = ek' then
                             ()
                         else
                             both (loc, s);
                         ([], (env, count, tags, byTag)))
                end
              | _ =>
                let
                    val env' = E.declBinds env d
                    val env'' = case d' of
                                    DValRec _ => env'
                                  | _ => env

                    val (d, (count, tags, byTag, newTags)) =
                        U.Decl.foldMap {kind = kind,
                                        con = con,
                                        exp = exp env'',
                                        decl = decl}
                                       (count, tags, byTag, []) d

                    val env = env'

                    val newDs = map
                                    (fn (ek, f, cn) =>
                                        let
                                            val unit = (TRecord (CRecord ((KType, loc), []), loc), loc)

                                            fun unravel (all as (t, _)) =
                                                case t of
                                                    TFun (dom, ran) =>
                                                    let
                                                        val (args, result) = unravel ran
                                                    in
                                                        (dom :: args, result)
                                                    end
                                                  | _ => ([], all)

                                            val (fnam, t, _, tag) = E.lookupENamed env f
                                            val (args, result) = unravel t

                                            val (abs, t) =
                                                case args of
                                                    [] =>
                                                    let
                                                        val app = (EApp ((ENamed f, loc), (ERecord [], loc)), loc)
                                                        val body = (EWrite app, loc)
                                                    in
                                                        (body,
                                                         (TFun (unit, unit), loc))
                                                    end
                                                  | _ =>
                                                    let
                                                        val (app, _) = foldl (fn (t, (app, n)) =>
                                                                                 ((EApp (app, (ERel n, loc)), loc),
                                                                                  n - 1))
                                                                             ((ENamed f, loc), length args - 1) args
                                                        val app = (EApp (app, (ERecord [], loc)), loc)
                                                        val body = (EWrite app, loc)
                                                        val t = (TFun (unit, unit), loc)
                                                        val (abs, _, t) = foldr (fn (t, (abs, n, rest)) =>
                                                                                    ((EAbs ("x" ^ Int.toString n,
                                                                                            t,
                                                                                            rest,
                                                                                            abs), loc),
                                                                                     n + 1,
                                                                                     (TFun (t, rest), loc)))
                                                                                (body, 0, t) args
                                                    in
                                                        (abs, t)
                                                    end
                                        in
                                            (("wrap_" ^ fnam, cn, t, abs, tag),
                                             (DExport (ek, cn, false), loc))
                                        end) newTags

                    val (newVals, newExports) = ListPair.unzip newDs

                    val ds = case d of
                                 (DValRec vis, _) => [(DValRec (vis @ newVals), loc)]
                               | _ => map (fn vi => (DVal vi, loc)) newVals @ [d]
                in
                    (ds @ newExports, (env, count, tags, byTag))
                end

        val (file, _) = ListUtil.foldlMapConcat doDecl (CoreEnv.empty, count+1, IM.empty, SM.empty) file
    in
        file
    end

end