//
// Evalutil.java : S 式評価ルーチン作成補助 クラス
//
//              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.* ;
import java.util.* ;
import java.lang.reflect.* ;

public class Evalutil {
  // (native ...) メソッド検索のため、クラス名を Object[] に展開
  // (native ...) メソッドを呼び出すために引数を Object[] に展開 するのに使用
  public static Vector listtovector(Object o) throws EvalException {
    Vector v = new Vector() ;
    Object mark = o ;

    while (o != SAtom.nil){
      if (o instanceof Cons) {
        Cons c = (Cons)o ;
        v.addElement(c.car) ;
        o = c.cdr ;
        if (mark == o) break ; // 循環リスト？
      } else {
        throw new EvalException("Arg is not a valid list") ;
      }
    }
    return v ;
  }

  public static Object[] listtoarg(Object o) throws EvalException {
    Vector v = listtovector(o) ;
    Object[] res = new Object[v.size()] ;
    v.copyInto(res) ;
    return res ;
  }

  // 引数が 1 つの場合のチェックと引数の切り出し
  public static Object getarg1(String msg,Object o) throws EvalException{
    if (!(o instanceof Cons)) {
      throw new EvalException(msg+" Argument must be supplied") ;
    }
    if (((Cons)o).cdr != SAtom.nil) {
      throw new EvalException(msg+" needs just one argument ") ;
    }
    return ((Cons)o).car ;
  }

  // Cons かどうかのチェックとキャスト
  public static Cons mustbecons(String msg,Object o) throws EvalException{
    if (!(o instanceof Cons)) {
      throw new EvalException(msg+" Argument must be Cons") ;
    }
    return (Cons)o ;
  }

  // SAtom かどうかのチェックとキャスト
  public static SAtom mustbesatom(String msg,Object o) throws EvalException{
    if (!(o instanceof SAtom)) {
      throw new EvalException(msg+" Argument must be SymbolAtom") ;
    }
    return (SAtom)o ;
  }

  // リストに現れる要素を順に評価したリストを作成して返す
  public static Object evalall(int minargs,int maxargs,Object a,Environment e) throws Exception {
    int argcount = 0 ;
    Object result = SAtom.nil ;
    Vector v = new Vector() ; 

    // 引数を数えつつ、一旦ベクタにコピー
    while(a != SAtom.nil) {
      Cons c = mustbecons("evalall :",a) ;
      ++argcount ;
      if ((maxargs != -1) && (argcount > maxargs)) {
        throw new EvalException("evalall : Too much argument (At most "+maxargs+")") ;
      }
      v.addElement(c.car) ;
      a = c.cdr ;
    }

    if ((minargs != -1) && (argcount < minargs)) {
      throw new EvalException("evalall : Too few argument (At least "+minargs+" needs)") ;
    }

    // 評価を行いつつ、戻り値になるリストを接続する
    if (argcount > 0) {
      Enumeration en = v.elements() ;
      Cons last,next ;
      last = new Cons(Eval.eval(en.nextElement(),e),SAtom.nil) ;
      result = last ;

      while(en.hasMoreElements()) {
        next = new Cons(Eval.eval(en.nextElement(),e),SAtom.nil) ;
        last.cdr = next ;
        last = next ;
      }
    } else {
      result = SAtom.nil ; // とりあえずごまかし^^;
    }

    return result ;
  }

  // リストに現れる要素を順に評価し、最後の評価値を返す
  public static Object evprogn(Object ol,Environment env) throws Exception {
    Object res = SAtom.nil ,mark = ol ;

    while (ol != SAtom.nil){
      if (ol instanceof Cons) {
        Cons c = (Cons)ol ;
        res = Eval.eval(c.car,env) ; // 評価
        ol = c.cdr ;
        if (mark == ol) break ; // 循環リスト？
      } else {
        throw new EvalException("Eval : Arg is not a valid list") ;
      }
    }
    return res ;
  }


  // リストの引数が minargs 以上、maxargs 以下であるかどうかチェックする。
  public static void argchk(int minargs,int maxargs,Object a) throws Exception {
    int argcount = 0 ;

    // 引数をカウントするのみ
    while(a != SAtom.nil) {
      Cons c = mustbecons("argchk :",a) ;
      ++argcount ;
      if ((maxargs != -1) && (argcount > maxargs)) {
        throw new EvalException("evalall : Too much argument (At most "+maxargs+")") ;
      }
      a = c.cdr ;
    }

    if ((minargs != -1) && (argcount < minargs)) {
      throw new EvalException("argchk : Too few argument (At least "+minargs+" needs)") ;
    }
  }

  // 文字列を S 式として読み込み、評価する
  public static Object Evalstring(String s,Environment e) throws Exception {
    Sreader sr = new Sreader(new StringReader(s)) ;
    return Eval.eval(sr.read(),e) ;
  }
}