(*  Title:      Pure/General/symbol_pos.ML

     Author:     Makarius

 Symbols with explicit position information.

 *)

 signature SYMBOL_POS =

 sig

   type T = Symbol.symbol * Position.T

   val symbol: T -> Symbol.symbol

   val $$$ : Symbol.symbol -> T list -> T list * T list

   val ~$$$ : Symbol.symbol -> T list -> T list * T list

   val content: T list -> string

   val untabify_content: T list -> string

   val is_eof: T -> bool

   val stopper: T Scan.stopper

   val !!! : string -> (T list -> 'a) -> T list -> 'a

   val change_prompt: ('a -> 'b) -> 'a -> 'b

   val scan_pos: T list -> Position.T * T list

   val scan_string: T list -> (Position.T * (T list * Position.T)) * T list

   val scan_alt_string: T list -> (Position.T * (T list * Position.T)) * T list

   val scan_quoted: T list -> T list * T list

   val scan_comment: (string -> (T list -> T list * T list) -> T list -> T list * T list) ->

     T list -> T list * T list

   val scan_comment_body: (string -> (T list -> T list * T list) -> T list -> T list * T list) ->

     T list -> T list * T list

   val source: Position.T -> (Symbol.symbol, 'a) Source.source ->

     (T, Position.T * (Symbol.symbol, 'a) Source.source) Source.source

   type text = string

   val implode: T list -> text

   val range: T list -> Position.range

   val implode_range: Position.T -> Position.T -> T list -> text * Position.range

   val explode: text * Position.T -> T list

 end;

 structure Symbol_Pos: SYMBOL_POS =

 struct

 (* type T *)

 type T = Symbol.symbol * Position.T;

 fun symbol ((s, _): T) = s;

 (* content *)

 val content = implode o map symbol;

 val tab_width = (8: int);

 fun untabify ("\t", pos) =

       (case Position.column_of pos of

         SOME n => Symbol.spaces (tab_width - ((n - 1) mod tab_width))

       | NONE => Symbol.space)

   | untabify (s, _) = s;

 val untabify_content = implode o map untabify;

 (* stopper *)

 fun mk_eof pos = (Symbol.eof, pos);

 val eof = mk_eof Position.none;

 val is_eof = Symbol.is_eof o symbol;

 val stopper =

   Scan.stopper (fn [] => eof | inp => mk_eof (List.last inp |-> Position.advance)) is_eof;

 (* basic scanners *)

 fun !!! text scan =

   let

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

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

     fun err (syms, msg) =

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

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

   in Scan.!! err scan end;

 fun change_prompt scan = Scan.prompt "# " scan;

 fun $$$ s = Scan.one (fn x => symbol x = s) >> single;

 fun ~$$$ s = Scan.one (fn x => symbol x <> s) >> single;

 val scan_pos = Scan.ahead (Scan.one (K true)) >> (fn (_, pos): T => pos);

 (* Isabelle strings *)

 local

 val char_code =

   Scan.one (Symbol.is_ascii_digit o symbol) --

   Scan.one (Symbol.is_ascii_digit o symbol) --

   Scan.one (Symbol.is_ascii_digit o symbol) :|--

   (fn (((a, pos), (b, _)), (c, _)) =>

     let val (n, _) = Library.read_int [a, b, c]

     in if n <= 255 then Scan.succeed [(chr n, pos)] else Scan.fail end);

 fun scan_str q =

   $$$ "\\" |-- !!! "bad escape character in string" ($$$ q || $$$ "\\" || char_code) ||

   Scan.one (fn (s, _) => s <> q andalso s <> "\\" andalso Symbol.is_regular s) >> single;

 fun scan_strs q =

   (scan_pos --| $$$ q) -- !!! "missing quote at end of string"

     (change_prompt ((Scan.repeat (scan_str q) >> flat) -- ($$$ q |-- scan_pos)));

 in

 val scan_string = scan_strs "\"";

 val scan_alt_string = scan_strs "`";

 val scan_quoted = Scan.trace (scan_string || scan_alt_string) >> #2;

 end;

 (* ML-style comments *)

 local

 val scan_cmt =

   Scan.depend (fn (d: int) => $$$ "(" @@@ $$$ "*" >> pair (d + 1)) ||

   Scan.depend (fn 0 => Scan.fail | d => $$$ "*" @@@ $$$ ")" >> pair (d - 1)) ||

   Scan.lift ($$$ "*" --| Scan.ahead (~$$$ ")")) ||

   Scan.lift (Scan.one (fn (s, _) => s <> "*" andalso Symbol.is_regular s)) >> single;

 val scan_body = change_prompt (Scan.pass 0 (Scan.repeat scan_cmt >> flat));

 in

 fun scan_comment cut =

   $$$ "(" @@@ $$$ "*" @@@ cut "missing end of comment" (scan_body @@@ $$$ "*" @@@ $$$ ")");

 fun scan_comment_body cut =

   $$$ "(" |-- $$$ "*" |-- cut "missing end of comment" (scan_body --| $$$ "*" --| $$$ ")");

 end;

 (* source *)

 fun source pos =

   Source.source' pos Symbol.stopper (Scan.bulk (Scan.depend (fn pos =>

     Scan.one Symbol.not_eof >> (fn s => (Position.advance s pos, (s, pos)))))) NONE;

 (* compact representation -- with Symbol.DEL padding *)

 type text = string;

 fun pad [] = []

   | pad [(s, _)] = [s]

   | pad ((s1, pos1) :: (rest as (_, pos2) :: _)) =

       let

         val end_pos1 = Position.advance s1 pos1;

         val d = Int.max (0, Position.distance_of end_pos1 pos2);

       in s1 :: replicate d Symbol.DEL @ pad rest end;

 val implode = implode o pad;

 fun range (syms as (_, pos) :: _) =

       let val pos' = List.last syms |-> Position.advance

       in Position.range pos pos' end

   | range [] = Position.no_range;

 fun implode_range pos1 pos2 syms =

   let val syms' = (("", pos1) :: syms @ [("", pos2)])

   in (implode syms', range syms') end;

 fun explode (str, pos) =

   let

     val (res, _) =

       fold (fn s => fn (res, p) => ((s, p) :: res, Position.advance s p))

         (Symbol.explode str) ([], Position.reset_range pos);

   in fold (fn (s, p) => if s = Symbol.DEL then I else cons (s, p)) res [] end;

 end;

 structure Basic_Symbol_Pos =   (*not open by default*)

 struct

   val $$$ = Symbol_Pos.$$$;

   val ~$$$ = Symbol_Pos.~$$$;

 end;