(* getopt.sml
 *
 * COPYRIGHT (c) 1998 Bell Labs, Lucent Technologies.
 * 
 * See comments in getopt-sig.sml
 * 
 *)


structure GetOpt :> GET_OPT = 
  struct

    datatype 'a arg_order
      = RequireOrder		
      | Permute
      | ReturnInOrder of string -> 'a

    datatype 'a arg_descr
      = NoArg of unit -> 'a
      | ReqArg of (string -> 'a) * string
      | OptArg of (string option -> 'a) * string

    type 'a opt_descr = {
        short : string,		
        long : string list,	
        desc : 'a arg_descr,	
        help : string		
      }

    datatype 'a opt_kind 
      = Opt of 'a
      | NonOpt

    structure SS = Substring
    structure S = String


    (* helper functions *)
    fun sepBy (sep, []) = ""
      | sepBy (sep, x::xs) =
	  concat (x::foldr (fn (elem,l) => sep::elem::l) [] xs)

    val breakeq = SS.splitl (fn #"=" => false | _ => true)


    (* formatting of options *)

    fun fmtShort (NoArg _) so = concat ["-", str so]
      | fmtShort (ReqArg (_,ad)) so = concat ["-", str so," ",ad]
      | fmtShort (OptArg (_,ad)) so = concat ["-", str so,"[",ad,"]"]

    fun fmtLong (NoArg _) lo = concat ["--",lo]
      | fmtLong (ReqArg (_,ad)) lo = concat ["--",lo,"=",ad]
      | fmtLong (OptArg (_,ad)) lo = concat ["--",lo,"[=",ad,"]"]

    fun fmtOpt {short=sos, long=los, desc=ad, help=descr} = (
          String.concatWith ", " (map (fmtShort ad) (S.explode sos)),
          String.concatWith ", " (map (fmtLong ad) los),
          descr)

  (* Usage information *)
    fun usageInfo {header, options} = let
          fun unlines l = sepBy ("\n", l)
          val fmtOptions = List.map fmtOpt options
          val (ms1, ms2) = foldl
		(fn ((e1,e2,_), (m1,m2)) => (
		    Int.max (size e1, m1), 
                    Int.max (size e2, m2)
		  )) (0,0) fmtOptions
	  val indent = StringCvt.padLeft #" " (ms1 + ms2 + 6)
	  val pad = StringCvt.padRight #" "
	  fun doEntry ((e1, e2, e3), l) = (
		case String.fields (fn #"\n" => true | _ => false) e3
		 of [] => concat["  ", pad ms1 e1, "  ", pad ms2 e2] :: l
		  | [e3] => concat["  ", pad ms1 e1, "  ", pad ms2 e2, "  ", e3] :: l
		  | fst::rest =>
		      concat["  ", pad ms1 e1, "  ", pad ms2 e2, "  ", fst]
		        :: List.foldr (fn (s, l) => (indent "" ^ s) :: l) l rest
		(* end case *))
          val table = List.foldr doEntry [""] fmtOptions
          in
            String.concatWith "\n" (header::table)
          end

    (* entry point of the library
     *)
 
    fun getOpt {argOrder, options : 'a opt_descr list, errFn} = let
       (* Some error handling functions *)
	  fun errAmbig optStr = errFn(usageInfo{
		  header = concat[
		      "option `", optStr, "' is ambiguous; could be one of:"
		    ],
		  options = options
		})
	  fun errReq (d, optStr) = errFn(concat[
		  "option `", optStr, "' requires an argument ", d
		])
	  fun errUnrec optStr = errFn(concat[
		  "unrecognized option `", optStr, "'"
		])
	  fun errNoArg optStr = errFn(concat[
		  "option `", optStr, "' does not allow an argument"
		])
	(* handle long option
	 * this is messy because you cannot pattern-match on substrings
	 *)
	  fun longOpt (subs, rest) = let
		val (opt, arg) = breakeq subs
        	val opt' = SS.string opt
        	val options = List.filter
		      (fn {long,...} => List.exists (S.isPrefix opt') long)
			options
        	val optStr = "--"^opt'
        	fun long (_::(_::_), _, rest') = (
		      errAmbig optStr; (NonOpt, rest'))
        	  | long ([NoArg a], x, rest') = 
                      if (SS.isEmpty x)
                	then (Opt(a()),rest')
                      else if (SS.isPrefix "=" x) 
                	then (errNoArg optStr; (NonOpt, rest'))
                	else raise Fail "long: impossible"
        	  | long ([ReqArg(f,d)], x, []) = 
                      if (SS.isEmpty x)
                	then (errReq(d, optStr); (NonOpt, []))
                      else if (SS.isPrefix "=" x)
                	then (Opt(f (SS.string (SS.triml 1 x))), [])
                	else raise Fail "long: impossible"
        	  | long ([ReqArg(f,d)], x, rest' as (r::rs)) = 
                      if (SS.isEmpty x)
                	then (Opt(f r), rs)
                      else if (SS.isPrefix "=" x)
                	then (Opt(f (SS.string (SS.triml 1 x))), rest')
                	else raise Fail "long: impossible"
        	  | long ([OptArg(f,_)], x, rest') = 
                      if (SS.isEmpty x)
                	then (Opt(f NONE), rest')
                      else if (SS.isPrefix "=" x)
                	then (Opt(f (SOME (SS.string (SS.triml 1 x)))), rest')
                	else raise Fail "long: impossible"
        	  | long ([], _, rest') = (
		      errUnrec optStr; (NonOpt, rest'))
        	in
                  long (map #desc options, arg, rest)
        	end
	(* handle short option.  x is the option character, subs is the
	 * rest of the option string, rest is the rest of the command-line
	 * options.
	 *)
	  fun shortOpt (x, subs, rest) = let 
        	val options =
		      List.filter (fn {short,...} => Char.contains short x) options
        	val ads = map #desc options
        	val optStr = "-"^(str x)
        	in
		  case (ads, rest)
		   of (_::_::_, rest1) => (errAmbig optStr; (NonOpt, rest1))
		    | ((NoArg a)::_, rest') =>
                	if (SS.isEmpty subs)
                	  then (Opt(a()), rest')
                	  else (Opt(a()), ("-"^(SS.string subs))::rest')
        	    | ((ReqArg(f,d))::_, []) => 
                	if (SS.isEmpty subs) 
                	  then (errReq(d, optStr); (NonOpt, []))
                	  else (Opt(f (SS.string subs)), [])
        	    | ((ReqArg(f,_))::_, rest' as (r::rs)) => 
                	if (SS.isEmpty subs)
                	  then (Opt(f r), rs)
                	  else (Opt(f (SS.string subs)), rest')
        	    | ((OptArg(f,_))::_, rest') => 
                	if (SS.isEmpty subs)
                	  then (Opt(f NONE), rest')
                	  else (Opt(f (SOME(SS.string subs))), rest')
        	    | ([], rest') => (errUnrec optStr; (NonOpt, rest'))
		  (* end case *)
        	end
	  fun get ([], opts, nonOpts) = (List.rev opts, List.rev nonOpts)
	    | get ("--"::rest, opts, nonOpts) = let
		val nonOpts = List.revAppend(nonOpts, rest)
		in
		  case argOrder
		   of ReturnInOrder f => (List.revAppend(opts, List.map f nonOpts), [])
		    | _ => (List.rev opts, nonOpts)
		  (* end case *)
		end
	    | get (arg::rest, opts, nonOpts) = let
		val arg' = SS.full arg
		fun addOpt (Opt opt, rest) = get(rest, opt::opts, nonOpts)
		  | addOpt (NonOpt, rest) = get(rest, opts, arg::nonOpts)
		in
		  if (SS.isPrefix "--" arg')
		    then addOpt(longOpt (SS.triml 2 arg', rest))
        	  else if (SS.isPrefix "-" arg')
		    then addOpt(shortOpt (SS.sub(arg', 1), SS.triml 2 arg', rest))
        	  else (case argOrder
		     of RequireOrder => (List.rev opts, List.revAppend(nonOpts, arg::rest))
		      | Permute => get(rest, opts, arg::nonOpts)
		      | ReturnInOrder f => get(rest, f arg :: opts, nonOpts)
		    (* end case *))
		end
	  in
	    fn args => get(args, [], [])
	  end (* getOpt *)

  end

