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 static com.alibaba.druid.sql.visitor.SQLEvalVisitor.EVAL_VALUE;
  
  public class Insert implements Function {
      public static final Insert instance = new Insert();
  
      public Object eval(SQLEvalVisitor visitor, SQLMethodInvokeExpr x) {
          if (x.getArguments().size() != 4) {
              return SQLEvalVisitor.EVAL_ERROR;
          }
  
          SQLExpr param0 = x.getArguments().get(0);
          SQLExpr param1 = x.getArguments().get(1);
          SQLExpr param2 = x.getArguments().get(2);
          SQLExpr param3 = x.getArguments().get(3);
          param0.accept(visitor);
          param1.accept(visitor);
          param2.accept(visitor);
          param3.accept(visitor);
  
          Object param0Value = param0.getAttributes().get(EVAL_VALUE);
          Object param1Value = param1.getAttributes().get(EVAL_VALUE);
          Object param2Value = param2.getAttributes().get(EVAL_VALUE);
          Object param3Value = param3.getAttributes().get(EVAL_VALUE);
  
          if (!(param0Value instanceof String)) {
              return SQLEvalVisitor.EVAL_ERROR;
          }
          if (!(param1Value instanceof Number)) {
              return SQLEvalVisitor.EVAL_ERROR;
          }
          if (!(param2Value instanceof Number)) {
              return SQLEvalVisitor.EVAL_ERROR;
          }
          if (!(param3Value instanceof String)) {
              return SQLEvalVisitor.EVAL_ERROR;
          }
  
          String str = (String) param0Value;
          int pos = ((Number) param1Value).intValue();
          int len = ((Number) param2Value).intValue();
          String newstr = (String) param3Value;
  
          if (pos <= 0) {
              return str;
          }
  
          if (pos == 1) {
              if (len > str.length()) {
                  return newstr;
              }
              return newstr + str.substring(len);
          }
  
          String first = str.substring(0, pos - 1);
          if (pos + len - 1 > str.length()) {
              return first + newstr;
          }
  
          return first + newstr + str.substring(pos + len - 1);
      }
  }
  