(**************************************************************************)
(*  -*- tuareg -*-                                                        *)
(*                                                                        *)
(*  Copyright (C) 2017,2018 Yann Régis-Gianas, Nicolas Jeannerod,         *)
(*  Ralf Treinen.                                                         *)
(*                                                                        *)
(*  This is free software: you can redistribute it and/or modify it       *)
(*  under the terms of the GNU General Public License, version 3.         *)
(*                                                                        *)
(*  Additional terms apply, due to the reproduction of portions of        *)
(*  the POSIX standard. Please refer to the file COPYING for details.     *)
(**************************************************************************)

open ExtPervasives
open ExtMenhirLib
open Parser
open Parser.Incremental
open Parser.MenhirInterpreter
open MenhirLib.General
open CST
open Name
open Keyword

(**specification

   [Assignment preceding command name]

   [When the first word]

   If the TOKEN does not contain the character '=', rule 1 is
   applied. Otherwise, 7b shall be applied.

   [Not the first word]

   If the TOKEN contains the <equals-sign> character:

   If it begins with '=', the token WORD shall be returned.

   If all the characters preceding '=' form a valid name (see XBD
   Name), the token ASSIGNMENT_WORD shall be returned. (Quoted
   characters cannot participate in forming a valid name.)

   Otherwise, it is unspecified whether it is ASSIGNMENT_WORD or WORD
   that is returned.

   Assignment to the NAME shall occur as specified in Simple Commands.

*)

let recognize_assignment checkpoint pretoken word_cst = FirstSuccessMonad.(
    match word_cst with
    | [WordAssignmentWord ((Name n) as name, w)] ->
       if is_name n then
         let (_, pstart, pstop) = pretoken in
         let token = ASSIGNMENT_WORD (name, w) in
         if accepted_token checkpoint (token, pstart, pstop) <> Wrong then
           return token
         else
           fail
       else
         fail
    | _ ->
       fail
)