/*  Title:      Pure/General/symbol.scala

    Author:     Makarius

Detecting and recoding Isabelle symbols.

*/

package isabelle

import scala.io.Source

import scala.collection.mutable

import scala.util.matching.Regex

object Symbol

{

  /* spaces */

  val spc = ' '

  val space = " "

  private val static_spaces = space * 4000

  def spaces(k: Int): String =

  {

    require(k >= 0)

    if (k < static_spaces.length) static_spaces.substring(0, k)

    else space * k

  }

  /* Symbol regexps */

  private val plain = new Regex("""(?xs)

    [^\\ \ud800-\udfff] | [\ud800-\udbff][\udc00-\udfff] """)

  private val symbol = new Regex("""(?xs)

      \\ < (?:

      \^? [A-Za-z][A-Za-z0-9_']* |

      \^raw: [\x20-\x7e\u0100-\uffff && [^.>]]* ) >""")

  // FIXME cover bad surrogates!?

  // FIXME check wrt. ML version

  private val bad_symbol = new Regex("(?xs) (?!" + symbol + ")" +

    """ \\ < (?: (?! \s | [\"`\\] | \(\* | \*\) | \{\* | \*\} ) . )*""")

  // total pattern

  val regex = new Regex(plain + "|" + symbol + "|" + bad_symbol + "| .")

  /* basic matching */

  def is_plain(c: Char): Boolean = !(c == '\\' || '\ud800' <= c && c <= '\udfff')

  def is_wellformed(s: CharSequence): Boolean =

    s.length == 1 && is_plain(s.charAt(0)) || !bad_symbol.pattern.matcher(s).matches

  class Matcher(text: CharSequence)

  {

    private val matcher = regex.pattern.matcher(text)

    def apply(start: Int, end: Int): Int =

    {

      require(0 <= start && start < end && end <= text.length)

      if (is_plain(text.charAt(start))) 1

      else {

        matcher.region(start, end).lookingAt

        matcher.group.length

      }

    }

  }

  /* iterator */

  def iterator(text: CharSequence) = new Iterator[CharSequence]

  {

    private val matcher = new Matcher(text)

    private var i = 0

    def hasNext = i < text.length

    def next = {

      val n = matcher(i, text.length)

      val s = text.subSequence(i, i + n)

      i += n

      s

    }

  }

  /* decoding offsets */

  class Index(text: CharSequence)

  {

    case class Entry(chr: Int, sym: Int)

    val index: Array[Entry] =

    {

      val matcher = new Matcher(text)

      val buf = new mutable.ArrayBuffer[Entry]

      var chr = 0

      var sym = 0

      while (chr < text.length) {

        val n = matcher(chr, text.length)

        chr += n

        sym += 1

        if (n > 1) buf += Entry(chr, sym)

      }

      buf.toArray

    }

    def decode(sym: Int): Int =

    {

      val end = index.length

      def bisect(a: Int, b: Int): Int =

      {

        if (a < b) {

          val c = (a + b) / 2

          if (sym < index(c).sym) bisect(a, c)

          else if (c + 1 == end || sym < index(c + 1).sym) c

          else bisect(c + 1, b)

        }

        else -1

      }

      val i = bisect(0, end)

      if (i < 0) sym

      else index(i).chr + sym - index(i).sym

    }

  }

  /* recoding text */

  private class Recoder(list: List[(String, String)])

  {

    private val (min, max) =

    {

      var min = '\uffff'

      var max = '\u0000'

      for ((x, _) <- list) {

        val c = x(0)

        if (c < min) min = c

        if (c > max) max = c

      }

      (min, max)

    }

    private val table = Map[String, String]() ++ list

    def recode(text: String): String =

    {

      val len = text.length

      val matcher = regex.pattern.matcher(text)

      val result = new StringBuilder(len)

      var i = 0

      while (i < len) {

        val c = text(i)

        if (min <= c && c <= max) {

          matcher.region(i, len).lookingAt

          val x = matcher.group

          result.append(table.get(x) getOrElse x)

          i = matcher.end

        }

        else { result.append(c); i += 1 }

      }

      result.toString

    }

  }

  /** Symbol interpretation **/

  class Interpretation(symbol_decls: List[String])

  {

    /* read symbols */

    private val empty = new Regex("""(?xs) ^\s* (?: \#.* )? $ """)

    private val key = new Regex("""(?xs) (.+): """)

    private def read_decl(decl: String): (String, Map[String, String]) =

    {

      def err() = error("Bad symbol declaration: " + decl)

      def read_props(props: List[String]): Map[String, String] =

      {

        props match {

          case Nil => Map()

          case _ :: Nil => err()

          case key(x) :: y :: rest => read_props(rest) + (x -> y)

          case _ => err()

        }

      }

      decl.split("\\s+").toList match {

        case sym :: props if sym.length > 1 && is_wellformed(sym) => (sym, read_props(props))

        case _ => err()

      }

    }

    private val symbols: List[(String, Map[String, String])] =

      for (decl <- symbol_decls if !empty.pattern.matcher(decl).matches)

        yield read_decl(decl)

    /* misc properties */

    val names: Map[String, String] =

    {

      val name = new Regex("""\\<([A-Za-z][A-Za-z0-9_']*)>""")

      Map((for ((sym @ name(a), _) <- symbols) yield (sym -> a)): _*)

    }

    val abbrevs: Map[String, String] = Map((

      for ((sym, props) <- symbols if props.isDefinedAt("abbrev"))

        yield (sym -> props("abbrev"))): _*)

    /* main recoder methods */

    private val (decoder, encoder) =

    {

      val mapping =

        for {

          (sym, props) <- symbols

          val code =

            try { Integer.decode(props("code")).intValue }

            catch {

              case _: NoSuchElementException => error("Missing code for symbol " + sym)

              case _: NumberFormatException => error("Bad code for symbol " + sym)

            }

          val ch = new String(Character.toChars(code))

        } yield {

          if (code < 128) error("Illegal ASCII code for symbol " + sym)

          else (sym, ch)

        }

      (new Recoder(mapping),

       new Recoder(mapping map { case (x, y) => (y, x) }))

    }

    def decode(text: String): String = decoder.recode(text)

    def encode(text: String): String = encoder.recode(text)

    /* classification */

    private object Decode_Set

    {

      def apply(elems: String*): Set[String] =

      {

        val content = elems.toList

        Set((content ::: content.map(decode)): _*)

      }

    }

    private val letters = Decode_Set(

      "A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M",

      "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z",

      "a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m",

      "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z",

      "\\<A>", "\\<B>", "\\<C>", "\\<D>", "\\<E>", "\\<F>", "\\<G>",

      "\\<H>", "\\<I>", "\\<J>", "\\<K>", "\\<L>", "\\<M>", "\\<N>",

      "\\<O>", "\\<P>", "\\<Q>", "\\<R>", "\\<S>", "\\<T>", "\\<U>",

      "\\<V>", "\\<W>", "\\<X>", "\\<Y>", "\\<Z>", "\\<a>", "\\<b>",

      "\\<c>", "\\<d>", "\\<e>", "\\<f>", "\\<g>", "\\<h>", "\\<i>",

      "\\<j>", "\\<k>", "\\<l>", "\\<m>", "\\<n>", "\\<o>", "\\<p>",

      "\\<q>", "\\<r>", "\\<s>", "\\<t>", "\\<u>", "\\<v>", "\\<w>",

      "\\<x>", "\\<y>", "\\<z>",

      "\\<AA>", "\\<BB>", "\\<CC>", "\\<DD>", "\\<EE>", "\\<FF>",

      "\\<GG>", "\\<HH>", "\\<II>", "\\<JJ>", "\\<KK>", "\\<LL>",

      "\\<MM>", "\\<NN>", "\\<OO>", "\\<PP>", "\\<QQ>", "\\<RR>",

      "\\<SS>", "\\<TT>", "\\<UU>", "\\<VV>", "\\<WW>", "\\<XX>",

      "\\<YY>", "\\<ZZ>", "\\<aa>", "\\<bb>", "\\<cc>", "\\<dd>",

      "\\<ee>", "\\<ff>", "\\<gg>", "\\<hh>", "\\<ii>", "\\<jj>",

      "\\<kk>", "\\<ll>", "\\<mm>", "\\<nn>", "\\<oo>", "\\<pp>",

      "\\<qq>", "\\<rr>", "\\<ss>", "\\<tt>", "\\<uu>", "\\<vv>",

      "\\<ww>", "\\<xx>", "\\<yy>", "\\<zz>",

      "\\<alpha>", "\\<beta>", "\\<gamma>", "\\<delta>", "\\<epsilon>",

      "\\<zeta>", "\\<eta>", "\\<theta>", "\\<iota>", "\\<kappa>",

      "\\<mu>", "\\<nu>", "\\<xi>", "\\<pi>", "\\<rho>", "\\<sigma>",

      "\\<tau>", "\\<upsilon>", "\\<phi>", "\\<chi>", "\\<psi>",

      "\\<omega>", "\\<Gamma>", "\\<Delta>", "\\<Theta>", "\\<Lambda>",

      "\\<Xi>", "\\<Pi>", "\\<Sigma>", "\\<Upsilon>", "\\<Phi>",

      "\\<Psi>", "\\<Omega>",

      "\\<^isub>", "\\<^isup>")

    private val blanks =

      Decode_Set(space, "\t", "\n", "\u000B", "\f", "\r", "\\<spacespace>", "\\<^newline>")

    private val sym_chars =

      Set("!", "#", "$", "%", "&", "*", "+", "-", "/", "<", "=", ">", "?", "@", "^", "_", "|", "~")

    def is_letter(sym: String): Boolean = letters.contains(sym)

    def is_digit(sym: String): Boolean = sym.length == 1 && '0' <= sym(0) && sym(0) <= '9'

    def is_quasi(sym: String): Boolean = sym == "_" || sym == "'"

    def is_letdig(sym: String): Boolean = is_letter(sym) || is_digit(sym) || is_quasi(sym)

    def is_blank(sym: String): Boolean = blanks.contains(sym)

    def is_symbolic_char(sym: String): Boolean = sym_chars.contains(sym)

    def is_symbolic(sym: String): Boolean = sym.startsWith("\\<") && !sym.startsWith("\\<^")

  }

}