public class QueryPlanVisitor extends SQLASTvisitor {
    private Hashtable tableDictionary;
    private Hashtable col2Table;
    public QueryPlan qPlan;
    private Vector colVec = null;


    public void visit(SelectStatement selectStatement) {
        tableDictionary = new Hashtable();
        selectStatement.tables.accept(this);
        makeCol2Table();
        
        selectStatement.whereexpression.accept(this);

        colVec = new Vector();
        selectStatement.columns.accept(this);
        String[] colNames = (String[]) colVec.toArray(new String[0]);
        qPlan = new Project(colNames, qPlan);
    }


    public void visit(ColumnList columnList) {
        visit(columnList.columnrecur);
        colVec.add(columnList.column.toString());
    }


    public void visit(ColumnRecur columnRecur) {
        if (columnRecur.isNullObject)
            return;
        visit(columnRecur.columnlist);
    }


    public void visit(TableList tableList) {
        visit(tableList.tablerecur);
        String tableName = tableList.table.toString();
        tableDictionary.put(tableName, sql.Table.byName(tableName));
    }


   public void visit(TableRecur tableRecur) {
        if (tableRecur.isNullObject)
            return;
        visit(tableRecur.tablelist);
    }

    private void makeCol2Table() {
        col2Table = new Hashtable();
        Enumeration e = tableDictionary.elements();
        while (e.hasMoreElements()) {
            Table table = (Table) e.nextElement();
            String[] colNames = table.getColumnNames();
            for (int i = 0; i < colNames.length; i++) {
                col2Table.put(colNames[i], table);
            }
        }
    }


   public void visit(ColumnFilterExpression exp) {
        Binop binOp = exp.binop;
        Table table = (Table) col2Table.get(exp.column.toString());
        String colName = exp.column.toString();
        String valAsString = exp.t_int.toString();
        Op op = Op.opFor(binOp.toString());
        int value = Integer.parseInt(valAsString);
        qPlan = new Select(colName, op, value, table);
    }


    public void visit(IntFilterExpression exp) {
        Binop binOp = exp.binop;
        Table table = (Table) col2Table.get(exp.column.toString());
        String colName = exp.column.toString();
        String valAsString = exp.t_int.toString();
        Op op = Op.opFor(binOp.toString());
        int value = Integer.parseInt(valAsString);
        qPlan = new Select(colName, op.invert(), value, table);
    }


    public void visit(JoinExpression joinExpression) {
        String selfColName = joinExpression.column.toString();
        String otherColName = joinExpression.rightcolumn.toString();
        Table otherTable = (Table) col2Table.get(otherColName);
        Table selfTable = (Table) col2Table.get(selfColName);
        qPlan = new Join(selfTable, selfColName, otherTable, otherColName);
    }

}