(*  Title:      HOL/SPARK/Tools/fdl_lexer.ML

     Author:     Stefan Berghofer

     Copyright:  secunet Security Networks AG

 Lexical analyzer for fdl files.

 *)

 signature FDL_LEXER =

 sig

   type T

   type chars

   type banner

   type date

   type time

   datatype kind = Keyword | Ident | Long_Ident | Traceability | Number | Comment | EOF

   val tokenize: (chars -> 'a * chars) -> (chars -> T * chars) ->

     Position.T -> string -> 'a * T list

   val position_of: T -> Position.T

   val pos_of: T -> string

   val is_eof: T -> bool

   val stopper: T Scan.stopper

   val kind_of: T -> kind

   val content_of: T -> string

   val unparse: T -> string

   val is_proper: T -> bool

   val is_digit: string -> bool

   val c_comment: chars -> T * chars

   val curly_comment: chars -> T * chars

   val percent_comment: chars -> T * chars

   val vcg_header: chars -> (banner * (date * time) option) * chars

   val siv_header: chars ->

     (banner * (date * time) * (date * time) * (string * string)) * chars

 end;

 structure Fdl_Lexer: FDL_LEXER =

 struct

 (** tokens **)

 datatype kind = Keyword | Ident | Long_Ident | Traceability | Number | Comment | EOF;

 datatype T = Token of kind * string * Position.T;

 fun make_token k xs = Token (k, implode (map fst xs),

   case xs of [] => Position.none | (_, p) :: _ => p);

 fun kind_of (Token (k, _, _)) = k;

 fun is_proper (Token (Comment, _, _)) = false

   | is_proper _ = true;

 fun content_of (Token (_, s, _)) = s;

 fun unparse (Token (Traceability, s, _)) = "For " ^ s ^ ":"

   | unparse (Token (_, s, _)) = s;

 fun position_of (Token (_, _, pos)) = pos;

 val pos_of = Position.str_of o position_of;

 fun is_eof (Token (EOF, _, _)) = true

   | is_eof _ = false;

 fun mk_eof pos = Token (EOF, "", pos);

 val eof = mk_eof Position.none;

 val stopper =

   Scan.stopper (fn [] => eof | toks => mk_eof (position_of (List.last toks))) is_eof;

 fun leq_token (Token (_, s, _), Token (_, s', _)) = size s <= size s';

 (** split up a string into a list of characters (with positions) **)

 type chars = (string * Position.T) list;

 fun is_char_eof ("", _) = true

   | is_char_eof _ = false;

 val char_stopper = Scan.stopper (K ("", Position.none)) is_char_eof;

 fun symbol (x : string, _ : Position.T) = x;

 fun explode_pos s pos = fst (fold_map (fn x => fn pos =>

   ((x, pos), Position.advance x pos)) (raw_explode s) pos);

 (** scanners **)

 val any = Scan.one (not o Scan.is_stopper char_stopper);

 fun prfx [] = Scan.succeed []

   | prfx (x :: xs) = Scan.one (equal x o symbol) ::: prfx xs;

 val $$$ = prfx o raw_explode;

 val lexicon = Scan.make_lexicon (map raw_explode

   ["rule_family",

    "title",

    "For",

    ":",

    "[",

    "]",

    "(",

    ")",

    ",",

    "&",

    ";",

    "=",

    ".",

    "..",

    "requires",

    "may_be_replaced_by",

    "may_be_deduced",

    "may_be_deduced_from",

    "are_interchangeable",

    "if",

    "end",

    "function",

    "procedure",

    "type",

    "var",

    "const",

    "array",

    "record",

    ":=",

    "of",

    "**",

    "*",

    "/",

    "div",

    "mod",

    "+",

    "-",

    "<>",

    "<",

    ">",

    "<=",

    ">=",

    "<->",

    "->",

    "not",

    "and",

    "or",

    "for_some",

    "for_all",

    "***",

    "!!!",

    "element",

    "update",

    "pending"]);

 fun keyword s = Scan.literal lexicon :|--

   (fn xs => if map symbol xs = raw_explode s then Scan.succeed xs else Scan.fail);

 fun is_digit x = "0" <= x andalso x <= "9";

 fun is_alpha x = "a" <= x andalso x <= "z" orelse "A" <= x andalso x <= "Z";

 val is_underscore = equal "_";

 val is_tilde = equal "~";

 val is_newline = equal "\n";

 val is_tab = equal "\t";

 val is_space = equal " ";

 val is_whitespace = is_space orf is_tab orf is_newline;

 val is_whitespace' = is_space orf is_tab;

 val number = Scan.many1 (is_digit o symbol);

 val identifier =

   Scan.one (is_alpha o symbol) :::

   Scan.many

     ((is_alpha orf is_digit orf is_underscore) o symbol) @@@

    Scan.optional (Scan.one (is_tilde o symbol) >> single) [];

 val long_identifier =

   identifier @@@ (Scan.repeat1 ($$$ "." @@@ identifier) >> flat);

 val whitespace = Scan.many (is_whitespace o symbol);

 val whitespace' = Scan.many (is_whitespace' o symbol);

 val newline = Scan.one (is_newline o symbol);

 fun beginning n cs =

   let

     val drop_blanks = #1 o take_suffix is_whitespace;

     val all_cs = drop_blanks cs;

     val dots = if length all_cs > n then " ..." else "";

   in

     (drop_blanks (take n all_cs)

       |> map (fn c => if is_whitespace c then " " else c)

       |> implode) ^ dots

   end;

 fun !!! text scan =

   let

     fun get_pos [] = " (past end-of-text!)"

       | get_pos ((_, pos) :: _) = Position.str_of pos;

     fun err (syms, msg) = fn () =>

       text ^ get_pos syms ^ " at " ^ beginning 10 (map symbol syms) ^

         (case msg of NONE => "" | SOME m => "\n" ^ m ());

   in Scan.!! err scan end;

 val any_line' =

   Scan.many (not o (Scan.is_stopper char_stopper orf (is_newline o symbol)));

 val any_line = whitespace' |-- any_line' --|

   newline >> (implode o map symbol);

 fun gen_comment a b = $$$ a |-- !!! "missing end of comment"

   (Scan.repeat (Scan.unless ($$$ b) any) --| $$$ b) >> make_token Comment;

 val c_comment = gen_comment "/*" "*/";

 val curly_comment = gen_comment "{" "}";

 val percent_comment = $$$ "%" |-- any_line' >> make_token Comment;

 fun repeatn 0 _ = Scan.succeed []

   | repeatn n p = Scan.one p ::: repeatn (n-1) p;

 (** header of *.vcg and *.siv files (see simplifier/load_provenance.pro) **)

 type banner = string * string * string;

 type date = string * string * string;

 type time = string * string * string * string option;

 val asterisks = Scan.repeat1 (Scan.one (equal "*" o symbol));

 fun alphan n = repeatn n (is_alpha o symbol) >> (implode o map symbol);

 fun digitn n = repeatn n (is_digit o symbol) >> (implode o map symbol);

 val time =

   digitn 2 --| $$$ ":" -- digitn 2 --| $$$ ":" -- digitn 2 --

   Scan.option ($$$ "." |-- digitn 2) >>

     (fn (((hr, mi), s), ms) => (hr, mi, s, ms));

 val date =

   digitn 2 --| $$$ "-" -- alphan 3 --| $$$ "-" -- digitn 4 >>

     (fn ((d, m), y) => (d, m, y));

 val banner = 

   whitespace' |-- asterisks --| whitespace' --| newline :|-- (fn xs =>

     (any_line -- any_line -- any_line >>

        (fn ((l1, l2), l3) => (l1, l2, l3))) --|

     whitespace' --| prfx (map symbol xs) --| whitespace' --| newline);

 val vcg_header = banner -- Scan.option (whitespace |--

   $$$ "DATE :" |-- whitespace |-- date --| whitespace --|

   Scan.option ($$$ "TIME :" -- whitespace) -- time);

 val siv_header = banner --| whitespace --

   ($$$ "CREATED" |-- whitespace |-- (date --| $$$ "," --| whitespace -- time)) --|

   whitespace --

   ($$$ "SIMPLIFIED" |-- whitespace |-- (date --| $$$ "," --| whitespace -- time)) --|

   newline --| newline -- (any_line -- any_line) >>

     (fn (((b, c), s), ls) => (b, c, s, ls));

 (** the main tokenizer **)

 fun scan header comment =

   !!! "bad header" header --| whitespace --

   Scan.repeat (Scan.unless (Scan.one is_char_eof)

     (!!! "bad input"

        (   comment

         || (keyword "For" -- whitespace) |--

               Scan.repeat1 (Scan.unless (keyword ":") any) --|

               keyword ":" >> make_token Traceability

         || Scan.max leq_token

              (Scan.literal lexicon >> make_token Keyword)

              (   long_identifier >> make_token Long_Ident

               || identifier >> make_token Ident)

         || number >> make_token Number) --|

      whitespace));

 fun tokenize header comment pos s =

   fst (Scan.finite char_stopper

     (Scan.error (scan header comment)) (explode_pos s pos));

 end;