%{

exception Error of string

let first (pair:'a*'a):'a =
        match pair with
        |(x,_) -> x

let second (pair:'a*'a):'a =
        match pair with
        |(_,y) -> y

let attr_list_of_string (s:string):(string*string) list=
        match s with
        |""->[]
        |_->
                let str_list:string list=String.split_on_char '\"' s in
                let trimmed_str_list:string list=List.map String.trim str_list in
                let rec pair (x:string list):(string*string) list = (
                        match x with
                        |[] | [""] -> []
                        |a::(b::tl) -> ((String.concat "" (String.split_on_char '=' a),b)::(pair tl))
                        |_ -> raise (Error (String.concat "%" trimmed_str_list))
                )
                in pair trimmed_str_list

%}

%token                          EOF
%token <string>                 PCDATA
%token <string*string>          TAG_OPEN
%token <string*string>          TAG_OPEN_CLOSE
%token <string>                 TAG_CLOSE

%start main
%type <Xml.xml> main

%%
main:
        |TAG_OPEN xml_list TAG_CLOSE EOF        { Xml.Element (first $1, attr_list_of_string (second $1), $2) }
        |TAG_OPEN_CLOSE EOF                     { Xml.Element (first $1, attr_list_of_string (second $1),[]) }
        |TAG_OPEN TAG_CLOSE EOF                 { Xml.Element (first $1, attr_list_of_string (second $1),[]) }
;

xml_list:
        |xml                                    { $1::[] }
        |xml xml_list                           { $1::$2 }
;

xml:
        |PCDATA                                 { Xml.PCData $1 }
        |TAG_OPEN xml_list TAG_CLOSE            { Xml.Element (first $1, attr_list_of_string (second $1), $2) }
        |TAG_OPEN_CLOSE                         { Xml.Element (first $1, attr_list_of_string (second $1),[]) }
        |TAG_OPEN TAG_CLOSE                     { Xml.Element (first $1, attr_list_of_string (second $1),[]) }
;