//
// Sreader.java : S 式の Reader クラス定義
//
//              This is a part of miolisp sourcefile
//              Copyright (C) 1998  Nishiyama, Naoki / Mio software lab. 
//
//  This program is free software; you can redistribute it and/or modify
//  it under the terms of the GNU General Public License as published by
//  the Free Software Foundation; either version 2 of the License, or
//  (at your option) any later version.
//
//  This program is distributed in the hope that it will be useful,
//  but WITHOUT ANY WARRANTY; without even the implied warranty of
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//  GNU General Public License for more details.
//
//  You should have received a copy of the GNU General Public License
//  along with this program; if not, write to the Free Software
//  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
//

import java.io.* ;

// S 式のリーダ
class Sreader {
  static final int COMMENTCHAR = ';',DOTCHAR = '.', QUOTECHAR = '\'',
                   ESCAPECHAR  = '\\',STRTERMCHAR = '\"' , COMMACHAR = ',',
                   ATCHAR = '@' , BQCHAR = '`' ;

  Reader r ;
  StreamTokenizer st ;

  Sreader(InputStream i) {
    this(new InputStreamReader(i)) ;
  }

  Sreader(Reader re) {
    r = re ; 
    st = new StreamTokenizer(r) ;
    streset() ;
  }

  boolean ready() throws IOException {
    return r.ready() ;
  }

  void streset() {
    st.commentChar(COMMENTCHAR) ;     // コメントはセミコロン
    st.eolIsSignificant(false) ;      // 行の終りは単なる空白
    st.slashStarComments(false) ;
    st.slashSlashComments(false) ;
    st.lowerCaseMode(false) ;
    st.quoteChar(STRTERMCHAR) ;
    st.ordinaryChar(QUOTECHAR) ;
    st.ordinaryChar(DOTCHAR) ;        // '.' が 0.0 になるのを防ぐ
    st.wordChars(DOTCHAR,DOTCHAR) ;   // '.' が 0.0 になるのを防ぐ
    st.wordChars('+','+') ;
    st.wordChars('*','*') ;
    st.wordChars('/','/') ;
    st.wordChars('=','=') ;
    st.wordChars(':',':') ;
    st.wordChars('&','&') ;           // for &aux &rest
    st.wordChars('$','$') ;           // 
    st.wordChars(128,255) ;           // 
  }

  // 指定の入力から S 式を 1 つ読み込む
  Object read() throws IOException,SreaderException {
    Object res ;
    int ttype ;
    ttype = st.nextToken() ;

    switch(ttype) {
    case StreamTokenizer.TT_WORD:
      if (st.sval.charAt(0) == DOTCHAR) {
        throw new SreaderException("Badly placed dot.") ;
      }
      res = SAtom.getSAtom(st.sval) ;
      break ;
    case StreamTokenizer.TT_NUMBER:
      res = new Double(st.nval) ;
      break ;
    case '(':
      Object a,d ;
      try {
        a = read() ;
      } catch(SreaderException e) {
        // () の処理
        if (!e.getMessage().equals(")")) throw e ;
        res = SAtom.nil ;
        break ;
      }
      d = readcdr() ;
      res = new Cons(a,d) ;
      break ;
    case ')':
      throw new SreaderException(")") ;
    case QUOTECHAR :
      res = new Cons(SAtom.quote,new Cons(read(),SAtom.nil)) ;
      break ;
    case STRTERMCHAR :
      res = st.sval ;
      break ;
    case COMMACHAR :
      if (st.nextToken() == ATCHAR) { // ,@ ?
        res = new Cons(SAtom.commaat,new Cons(read(),SAtom.nil)) ;
      } else {
        st.pushBack() ;
        res = new Cons(SAtom.comma,new Cons(read(),SAtom.nil)) ;
      }
      break ;
    case BQCHAR :
      res = new Cons(SAtom.bquote,new Cons(read(),SAtom.nil)) ;
      break ;
    case StreamTokenizer.TT_EOF:
      throw new SreaderException("Sexpr not ended at EOF") ;
    default :
      throw new SreaderException("Unknown char : "+ttype) ;
    }
    return res ;
  }

  // in から S 式を 1 つ読み込む
  Object readcdr() throws IOException,SreaderException {
    Object res ;
    int ttype ;
    ttype = st.nextToken() ;

    switch(ttype) {
    case StreamTokenizer.TT_WORD:
      if (st.sval.charAt(0) == DOTCHAR) {
        try {
           res = read() ;
        } catch(SreaderException e) {
          // () の処理
          if (!e.getMessage().equals(")")) throw e ; 
          res = SAtom.nil ;
          break ;
        }
        ttype = st.nextToken() ; // ')' の空読み
        if (ttype == ')') break ;
        throw new SreaderException(") expected after dot pair.") ;
      } else {
        res = new Cons(SAtom.getSAtom(st.sval),readcdr()) ;
      }
      break ;
    case StreamTokenizer.TT_NUMBER:
      res = new Cons(new Double(st.nval),readcdr()) ; 
      break ;
    case '(':
      Object a,d ;
      try {
        a = read() ;
      } catch(SreaderException e) {
        // () の処理
        if (!e.getMessage().equals(")")) throw e ;
        res = new Cons(SAtom.nil,readcdr()) ;
        break ;
      }
      d = readcdr() ;
      Cons c = new Cons(a,d) ;
      res = new Cons(c,readcdr()) ;
      break ;
    case ')':
      res = SAtom.nil ;
      break ;
    case QUOTECHAR :
      c = new Cons(SAtom.quote,new Cons(read(),SAtom.nil)) ;
      res = new Cons(c,readcdr()) ;
      break ;
    case STRTERMCHAR :
      res = new Cons(st.sval,readcdr()) ;
      break ;
    case COMMACHAR :
      if (st.nextToken() == ATCHAR) { // ,@ ?
        c = new Cons(SAtom.commaat,new Cons(read(),SAtom.nil)) ;
      } else {
        st.pushBack() ;
        c = new Cons(SAtom.comma,new Cons(read(),SAtom.nil)) ;
      }
      res = new Cons(c,readcdr()) ;
      break ;
    case BQCHAR :
      c = new Cons(SAtom.bquote,new Cons(read(),SAtom.nil)) ;
      res = new Cons(c,readcdr()) ;
      break ;
    case StreamTokenizer.TT_EOF:
      throw new SreaderException("Sexpr not ended at EOF") ;
    default :
      throw new SreaderException("Unknown char : "+ttype) ;
    }
    return res ;
  }
}