/*
 *
 * Copyright (C) 1997, 1998 Yuuji ICHISUGI
 *
 * Permission to use, copy, modify and redistribution this software in
 * whole and in part, for evaluation or research purposes and without fee
 * is hereby granted provided this copyright notice.
 * See CopyrightAndLicensing.txt for licensing condition.
 */

#epp "Symbol"
#epp "SystemMixin"
#epp "AutoSplitFiles"
#epp "BackQuote"


package PComp;
import epp.*;
import java.util.Vector;


public class PlugIn extends SystemMixinLoader {

  // NOTE: This method will be invoked when #epp "PComp" is specified.
  public void load(){
    
    // Remove system mixins which define original comparison grammars.
    SystemMixin[] oldSetupList = new SystemMixin[SystemMixin.setupList.size()];
    SystemMixin.setupList.copyInto(oldSetupList);
    Vector newSetupList = new Vector();
    for (int i = 0; i < oldSetupList.length; i++){
      Symbol name = (Symbol)oldSetupList[i].name;
      if (name != :LT && name != :GT && name != :LE && name != :GE &&
	  name != :EQ && name != :NE){
	newSetupList.addElement(oldSetupList[i]);
      }
    }
    SystemMixin.setupList = newSetupList;


    // NOTE: The class PComp will be automatically
    // generated by SystemMixin plug-in.
    new PComp().load();
  }
  
}


SystemMixin PComp {
  class Epp {
    
    extend Tree equalityExpressionLeft(Tree tree) {
      Token token = lookahead();
      if (token == :"<" || token == :">" || token == :"<=" || token == :">=" ||
	  token == :"==" || token == :"!=") {
	return `(PComp
		 ,(new Identifier((Symbol)matchAny()))
		 ,tree
		 ,(equalityExpression1()));
      } else {
	return original(tree);
      }
    }

    extend void initMacroTable() {
      original();
      defineMacro(:PComp, new PCompMacro());
    }

    extend void initEmitterTable() {
      original();
      defineEmitter(:"<", new SimpleEmitter("(%) < (%)"));
      defineEmitter(:">", new SimpleEmitter("(%) > (%)"));
      defineEmitter(:"<=", new SimpleEmitter("(%) <= (%)"));
      defineEmitter(:">=", new SimpleEmitter("(%) >= (%)"));
      defineEmitter(:"==", new SimpleEmitter("(%) == (%)"));
      defineEmitter(:"!=", new SimpleEmitter("(%) != (%)"));
    }
  }
}


class PCompMacro extends Macro {
  public Tree call(Tree tree){
    checkArgsLength(tree, 3);

    Tree[] args = tree.args();
    Tree comp	= args[0];
    Tree exp1	= args[1];
    Tree exp2	= args[2];

    if (exp1.tag() == :PComp){
      // ((a < b) < c) should be expanded into ((a < (tmp = b)) && tmp < c)
      // The method invocation expandNestedPythonStyleComparison("a < b") will
      // return two trees, "a < (tmp = b)" and "tmp" .
      Tree[] trees = expandNestedPythonStyleComparison(exp1);
      Tree newExp1 = trees[0];
      Tree tmp =  trees[1];
      return `(&&
	       ,newExp1
	       ,(new Tree(comp.idName(), tmp, macroExpandTree(exp2))));
    } else {
      // (a < b) is simply translated to (a < b)
      return new Tree(comp.idName(),
		      macroExpandTree(exp1),
		      macroExpandTree(exp2));
    }
  }


  Tree[] expandNestedPythonStyleComparison(Tree tree){
    Tree[] args = tree.args();
    Tree comp	= args[0];
    Tree exp1	= args[1];
    Tree exp2	= args[2];
    Tree tmp	= new Identifier(genTemp("_T"));
    
    // Add a temporary variable declaration.
    ((TreeVec)Dynamic.get(:beforeCurrentBlockStatement))
      .add(`(decl (modifiers)
	     (id int)		// Auguments are assumed to be int !!
	     (vardecls ,tmp)));
    
    if (exp1.tag() == :PComp){
      // "(a < b) < c"
      //	->	"(a < (tmp0 = b)) && (tmp0 < (tmp = c))" and "tmp"
      Tree[] trees = expandNestedPythonStyleComparison(exp1);
      Tree newExp1 = trees[0];
      Tree tmp0 =  trees[1];
      Tree[] ret = {
	`(&&
	  ,newExp1
	  ,(new Tree(comp.idName(),
		     tmp0,
		     `(= ,tmp ,(macroExpandTree(exp2)))))),
	tmp};
      return ret;
    } else {
      // "a < b"	->	"a < (tmp = b)" and "tmp"
      Tree[] ret = {
	new Tree(comp.idName(),
		 macroExpandTree(exp1),
		 `(= ,tmp ,(macroExpandTree(exp2)))),
	tmp};
      return ret;
    }
  }
}