studio.raptor.sqlparser.visitor.functions.Left Maven / Gradle / Ivy

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/*
 * 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 studio.raptor.sqlparser.visitor.functions;

import static studio.raptor.sqlparser.visitor.SQLEvalVisitor.EVAL_VALUE;

import studio.raptor.sqlparser.ast.SQLExpr;
import studio.raptor.sqlparser.ast.expr.SQLMethodInvokeExpr;
import studio.raptor.sqlparser.visitor.SQLEvalVisitor;
import studio.raptor.sqlparser.visitor.SQLEvalVisitorUtils;

public class Left implements Function {

  public final static Left instance = new Left();

  public Object eval(SQLEvalVisitor visitor, SQLMethodInvokeExpr x) {
    if (x.getParameters().size() != 2) {
      return SQLEvalVisitor.EVAL_ERROR;
    }

    SQLExpr param0 = x.getParameters().get(0);
    SQLExpr param1 = x.getParameters().get(1);
    param0.accept(visitor);
    param1.accept(visitor);

    Object param0Value = param0.getAttributes().get(EVAL_VALUE);
    Object param1Value = param1.getAttributes().get(EVAL_VALUE);
    if (param0Value == null || param1Value == null) {
      return SQLEvalVisitor.EVAL_ERROR;
    }

    String strValue = param0Value.toString();
    int intValue = SQLEvalVisitorUtils.castToInteger(param1Value);

    if (intValue > strValue.length()) {
      return SQLEvalVisitor.EVAL_ERROR;
    }

    String result = strValue.substring(0, intValue);

    return result;
  }
}