/*  Title:      Pure/General/symbol.scala

    ID:         $Id$

    Author:     Makarius

Detecting and recoding Isabelle symbols.

*/

package isabelle

import java.util.regex.{Pattern, Matcher}

import java.io.File

import scala.io.Source

import scala.collection.jcl.HashMap

object Symbol {

  /** Symbol regexps **/

  private def compile(s: String) =

    Pattern.compile(s, Pattern.COMMENTS | Pattern.DOTALL)

  val char_pattern = compile(""" [^\ud800-\udfff] | [\ud800-\udbff][\udc00-\udfff] """)

  val symbol_pattern = compile(""" \\ \\? < (?:

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

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

  val bad_symbol_pattern = compile("(?!" + symbol_pattern + ")" +

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

  val pattern = compile(char_pattern + "|" + symbol_pattern + "|" + bad_symbol_pattern)

  /** Symbol interpretation **/

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

    private val pattern = compile((for ((x, _) <- list) yield Pattern.quote(x)).mkString("|"))

    private val table = {

      val table = new HashMap[String, String]

      for ((x, y) <- list) table + (x -> Matcher.quoteReplacement(y))

      table

    }

    def recode(text: String) = {

      val output = new StringBuffer(text.length)

      val matcher = pattern.matcher(text)

      while(matcher.find) matcher.appendReplacement(output, table(matcher.group))

      matcher.appendTail(output)

      output.toString

    }

  }

  class Interpretation {

    class BadSymbol(val msg: String) extends Exception

    private var symbols = new HashMap[String, HashMap[String, String]]

    private var decoder: Recoder = null

    private var encoder: Recoder = null

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

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

    /* read symbols */

    private val empty_pattern = compile(""" ^\s* (?: \#.* )? $ """)

    private val blank_pattern = compile(""" \s+ """)

    private val key_pattern = compile(""" (.+): """)

    private def read_line(line: String) = {

      def err() = throw new BadSymbol(line)

      def read_props(props: List[String], tab: HashMap[String, String]): Unit = {

        props match {

          case Nil => ()

          case _ :: Nil => err()

          case key :: value :: rest => {

            val key_matcher = key_pattern.matcher(key)

            if (key_matcher.matches) {

              tab + (key_matcher.group(1) -> value)

              read_props(rest, tab)

            }

            else err ()

          }

        }

      }

      if (!empty_pattern.matcher(line).matches) {

        blank_pattern.split(line).toList match {

          case Nil => err()

          case symbol :: props => {

            val tab = new HashMap[String, String]

            read_props(props, tab)

            symbols + (symbol -> tab)

          }

        }

      }

    }

    private def read_symbols(base: String) = {

      val file = new File(base + File.separator + "etc" + File.separator + "symbols")

      if (file.canRead) {

        for (line <- Source.fromFile(file).getLines) read_line(line)

      }

    }

    /* init tables */

    private def get_code(entry: (String, HashMap[String, String])) = {

      val (symbol, props) = entry

      val code =

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

        catch {

          case e: NoSuchElementException => throw new BadSymbol(symbol)

          case e: NumberFormatException => throw new BadSymbol(symbol)

        }

      (symbol, new String(Character.toChars(code)))

    }

    private def init_recoders() = {

      val list = symbols.elements.toList.map(get_code)

      decoder = new Recoder(list)

      encoder = new Recoder(list.map((p: (String, String)) => (p._2, p._1)))

    }

    /* constructor */

    read_symbols(IsabelleSystem.ISABELLE_HOME)

    read_symbols(IsabelleSystem.ISABELLE_HOME_USER)

    init_recoders()

  }

}