/*  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)

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

   private val physical_newline = new Regex("""(?xs) \n | \r\n | \r """)

   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. Isabelle/ML version

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

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

   // total pattern

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

   /* basic matching */

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

   def is_physical_newline(s: CharSequence): Boolean =

     "\n".contentEquals(s) || "\r".contentEquals(s) || "\r\n".contentEquals(s)

   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(sym1: Int): Int =

     {

       val sym = sym1 - 1

       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

     }

     def decode(range: Text.Range): Text.Range = range.map(decode(_))

   }

   /* 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 =

     {

       var tab = Map[String, String]()

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

         tab.get(x) match {

           case None => tab += (x -> y)

           case Some(z) =>

             error("Duplicate mapping of \"" + x + "\" to \"" + y + "\" vs. \"" + z + "\"")

         }

       }

       tab

     }

     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])] =

       Map((

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

           yield read_decl(decl)): _*) toList

     /* 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("\\<^")

   }

 }