(*  Title:      HOL/Tools/Sledgehammer/sledgehammer_util.ML

    Author:     Jasmin Blanchette, TU Muenchen

General-purpose functions used by the Sledgehammer modules.

*)

signature SLEDGEHAMMER_UTIL =

sig

  val plural_s : int -> string

  val serial_commas : string -> string list -> string list

  val timestamp : unit -> string

  val strip_spaces : string -> string

  val parse_bool_option : bool -> string -> string -> bool option

  val parse_time_option : string -> string -> Time.time option

  val scan_integer : string list -> int * string list

  val nat_subscript : int -> string

  val unyxml : string -> string

  val maybe_quote : string -> string

  val monomorphic_term : Type.tyenv -> term -> term

  val specialize_type : theory -> (string * typ) -> term -> term

end;

structure Sledgehammer_Util : SLEDGEHAMMER_UTIL =

struct

fun plural_s n = if n = 1 then "" else "s"

fun serial_commas _ [] = ["??"]

  | serial_commas _ [s] = [s]

  | serial_commas conj [s1, s2] = [s1, conj, s2]

  | serial_commas conj [s1, s2, s3] = [s1 ^ ",", s2 ^ ",", conj, s3]

  | serial_commas conj (s :: ss) = s ^ "," :: serial_commas conj ss

val timestamp = Date.fmt "%Y-%m-%d %H:%M:%S" o Date.fromTimeLocal o Time.now

fun is_ident_char c = Char.isAlphaNum c orelse c = #"_"

fun strip_spaces_in_list [] = ""

  | strip_spaces_in_list [c1] = if Char.isSpace c1 then "" else str c1

  | strip_spaces_in_list [c1, c2] =

    strip_spaces_in_list [c1] ^ strip_spaces_in_list [c2]

  | strip_spaces_in_list (c1 :: c2 :: c3 :: cs) =

    if Char.isSpace c1 then

      strip_spaces_in_list (c2 :: c3 :: cs)

    else if Char.isSpace c2 then

      if Char.isSpace c3 then

        strip_spaces_in_list (c1 :: c3 :: cs)

      else

        str c1 ^ (if forall is_ident_char [c1, c3] then " " else "") ^

        strip_spaces_in_list (c3 :: cs)

    else

      str c1 ^ strip_spaces_in_list (c2 :: c3 :: cs)

val strip_spaces = strip_spaces_in_list o String.explode

fun parse_bool_option option name s =

  (case s of

     "smart" => if option then NONE else raise Option

   | "false" => SOME false

   | "true" => SOME true

   | "" => SOME true

   | _ => raise Option)

  handle Option.Option =>

         let val ss = map quote ((option ? cons "smart") ["true", "false"]) in

           error ("Parameter " ^ quote name ^ " must be assigned " ^

                  space_implode " " (serial_commas "or" ss) ^ ".")

         end

fun parse_time_option _ "none" = NONE

  | parse_time_option name s =

    let

      val msecs =

        case space_explode " " s of

          [s1, "min"] => 60000 * the (Int.fromString s1)

        | [s1, "s"] => 1000 * the (Int.fromString s1)

        | [s1, "ms"] => the (Int.fromString s1)

        | _ => 0

    in

      if msecs <= 0 then

        error ("Parameter " ^ quote name ^ " must be assigned a positive time \

               \value (e.g., \"60 s\", \"200 ms\") or \"none\".")

      else

        SOME (Time.fromMilliseconds msecs)

    end

fun is_head_digit s = Char.isDigit (String.sub (s, 0))

val scan_integer = Scan.many1 is_head_digit >> (the o Int.fromString o implode)

val subscript = implode o map (prefix "\<^isub>") o explode

fun nat_subscript n =

  n |> string_of_int |> print_mode_active Symbol.xsymbolsN ? subscript

fun plain_string_from_xml_tree t =

  Buffer.empty |> XML.add_content t |> Buffer.content

val unyxml = plain_string_from_xml_tree o YXML.parse

val is_long_identifier = forall Syntax.is_identifier o space_explode "."

fun maybe_quote y =

  let val s = unyxml y in

    y |> ((not (is_long_identifier (perhaps (try (unprefix "'")) s)) andalso

           not (is_long_identifier (perhaps (try (unprefix "?")) s))) orelse

           Keyword.is_keyword s) ? quote

  end

fun monomorphic_term subst t =

  map_types (map_type_tvar (fn v =>

      case Type.lookup subst v of

        SOME typ => typ

      | NONE => raise TERM ("monomorphic_term: uninstanitated schematic type \

                            \variable", [t]))) t

fun specialize_type thy (s, T) t =

  let

    fun subst_for (Const (s', T')) =

      if s = s' then

        SOME (Sign.typ_match thy (T', T) Vartab.empty)

        handle Type.TYPE_MATCH => NONE

      else

        NONE

    | subst_for (t1 $ t2) =

      (case subst_for t1 of SOME x => SOME x | NONE => subst_for t2)

    | subst_for (Abs (_, _, t')) = subst_for t'

    | subst_for _ = NONE

  in

    case subst_for t of

      SOME subst => monomorphic_term subst t

    | NONE => raise Type.TYPE_MATCH

  end

end;