(*  Title:      mime_types.ML

     Author:     Timothy Bourke, NICTA

 Rudimentary support for mime_types.

 *)

 signature MIME =

 sig

   datatype t = Type of {

       main : string,

       sub : string, 

       params : (string * string) list

     }

   val plain : t

   val html : t

   val parse_type : string -> t option

   val show_type : t -> string

 end;

 structure Mime: MIME =

 struct

 datatype t = Type of {

     main : string,

     sub : string, 

     params : (string * string) list

   };

 val strip =

   Substring.dropl Char.isSpace

   #> Substring.dropr Char.isSpace;

 val split_fields =

   Substring.splitl (fn c => c <> #"=")

   #> apsnd (Substring.triml 1)

   #> pairself (Substring.string o strip);

 fun show_param (n, v) = concat ["; ", n, "=", v];

 fun show_type (Type {main, sub, params}) =

       concat ([main, "/", sub] @ map show_param params);

 fun parse_type s =

   (case Substring.fields (Char.contains "/;") (Substring.full s) of

      t::s::ps => SOME (Type { main = (Substring.string o strip) t,

                               sub = (Substring.string o strip) s,

                               params = map split_fields ps })

    | _ => NONE);

 val plain = the (parse_type "text/plain; charset=utf-8");

 val html = the (parse_type "text/html; charset=utf-8");

 end;