/*  Title:      Pure/General/symbol.scala

    ID:         $Id$

    Author:     Makarius

Detecting and recoding Isabelle symbols.

*/

package isabelle

import java.util.regex.Pattern

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)

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

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

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

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

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

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

  // total pattern

  val pattern = compile(plain_pattern + "|" + symbol_pattern + "|" + bad_symbol_pattern + "| .")

  /** Recoding **/

  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 HashMap[String, String]

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

      table

    }

    def recode(text: String) = {

      val len = text.length

      val matcher = 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)

          matcher.lookingAt

          val x = matcher.group

          table.get(x) match {

            case Some(y) => result.append(y)

            case None => result.append(x)

          }

          i = matcher.end

        }

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

      }

      result.toString

    }

  }

  /** Symbol interpretation **/

  class Interpretation {

    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() = error("Bad symbol specification (line " + 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(path: String) = {

      val file = new File(IsabelleSystem.platform_path(path))

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

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

        }

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

    }

    private def init_recoders() = {

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

      decoder = new Recoder(list ::: (for ((x, y) <- list) yield ("\\" + x, y)))

      encoder = new Recoder(for ((x, y) <- list) yield (y, x))

    }

    /* constructor */

    read_symbols("$ISABELLE_HOME/etc/symbols")

    read_symbols("$ISABELLE_HOME_USER/etc/symbols")

    init_recoders()

  }

}