/*  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[String] {

     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.toString

     }

   }

   /* 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)

   }

 }