content: /*
   * Copyright 1999-2017 Alibaba Group Holding Ltd.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package com.alibaba.druid.sql.visitor.functions;
  
  import com.alibaba.druid.sql.ast.SQLExpr;
  import com.alibaba.druid.sql.ast.expr.SQLMethodInvokeExpr;
  import com.alibaba.druid.sql.visitor.SQLEvalVisitor;
  
  import java.util.List;
  
  import static com.alibaba.druid.sql.visitor.SQLEvalVisitor.EVAL_VALUE;
  
  public class Lpad implements Function {
      public static final Lpad instance = new Lpad();
  
      public Object eval(SQLEvalVisitor visitor, SQLMethodInvokeExpr x) {
          List<SQLExpr> params = x.getArguments();
          int paramSize = params.size();
          if (paramSize != 3) {
              return SQLEvalVisitor.EVAL_ERROR;
          }
  
          SQLExpr param0 = params.get(0);
          SQLExpr param1 = params.get(1);
          SQLExpr param2 = params.get(2);
  
          param0.accept(visitor);
          param1.accept(visitor);
          param2.accept(visitor);
  
          Object param0Value = param0.getAttributes().get(EVAL_VALUE);
          Object param1Value = param1.getAttributes().get(EVAL_VALUE);
          Object param2Value = param2.getAttributes().get(EVAL_VALUE);
          if (param0Value == null || param1Value == null || param2Value == null) {
              return SQLEvalVisitor.EVAL_ERROR;
          }
  
          String strValue0 = param0Value.toString();
          int len = ((Number) param1Value).intValue();
          String strValue1 = param2Value.toString();
  
          if (strValue0.length() > len) {
              return strValue0.substring(0, len);
          }
          if (strValue0.length() == len) {
              return strValue0;
          }
          int needLen = len - strValue0.length();
          StringBuilder result = new StringBuilder(len);
          while (result.length() < needLen) {
              result.insert(0, strValue1);
          }
          if (result.length() > needLen) {
              result.delete(needLen, result.length());
          }
          result.append(strValue0);
          return result.toString();
      }
  }
  