src/Pure/General/symbol.scala

added elements: Interator;
first isHighSurrogate, not isLowSurrogate;
misc tuning and generalization;

/*  Title:      Pure/General/symbol.scala
    Author:     Makarius

Detecting and recoding Isabelle symbols.
*/

package isabelle

import scala.io.Source
import scala.collection.{jcl, mutable}
import scala.util.matching.Regex


object Symbol
{
  /* 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 && [^.>]]* ) >""")

  private val bad_symbol = new Regex("(?xs) (?!" + symbol + ")" +
    """ \\ < (?: (?! \s | [\"`\\] | \(\* | \*\) | \{\* | \*\} ) . )*""")

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

  // prefix of another symbol
  def is_open(s: CharSequence): Boolean =
  {
    val len = s.length
    len == 1 && Character.isHighSurrogate(s.charAt(0)) ||
    s == "\\" ||
    s == "\\<" ||
    len > 2 && s.charAt(len - 1) != '>'
  }


  /* elements */

  private def could_open(c: Char): Boolean =
    c == '\\' || Character.isHighSurrogate(c)

  def elements(text: CharSequence) = new Iterator[CharSequence] {
    private val matcher = regex.pattern.matcher(text)
    private var i = 0
    def hasNext = i < text.length
    def next = {
      val len =
        if (could_open(text.charAt(i))) {
          matcher.region(i, text.length).lookingAt
          matcher.group.length
        }
        else 1
      val s = text.subSequence(i, i + len)
      i += len
      s
    }
  }


  /* decoding offsets */

  class Index(text: CharSequence)
  {
    case class Entry(chr: Int, sym: Int)
    val index: Array[Entry] =
    {
      val matcher = regex.pattern.matcher(text)
      val buf = new mutable.ArrayBuffer[Entry]
      var chr = 0
      var sym = 0
      while (chr < text.length) {
        val len =
          if (could_open(text.charAt(chr))) {
            matcher.region(chr, text.length).lookingAt
            matcher.group.length
          }
          else 1
        chr += len
        sym += 1
        if (len > 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 =
    {
      val table = new jcl.HashMap[String, String]   // reasonably efficient?
      for ((x, y) <- list) table + (x -> y)
      table
    }
    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: Iterator[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 Nil => err()
        case sym :: props => (sym, read_props(props))
      }
    }

    private val symbols: List[(String, Map[String, String])] =
      for (decl <- symbol_decls.toList 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 (sym, ch)
      (new Recoder(mapping),
       new Recoder(mapping map { case (x, y) => (y, x) }))
    }

    def decode(text: String) = decoder.recode(text)
    def encode(text: String) = encoder.recode(text)
  }
}