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    • org.ehrbase.aql.compiler.WhereClauseUtil Maven / Gradle / Ivy

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    /*
 * Copyright (c) 2020 vitasystems GmbH and Hannover Medical School.
 *
 * This file is part of project EHRbase
 *
 * 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
 *
 *     https://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 org.ehrbase.aql.compiler;

import java.util.List;
import java.util.Stack;

/**
 * utility class to check some validity factors of a WHERE expression (f.e. balanced parenthesis)
 */
class WhereClauseUtil {

    private List expression;
    private String unbalanced;

    WhereClauseUtil(List expression) {
        this.expression = expression;
    }

    /**
     * check if an expression block is balanced
     * A block is delimited by '[...]', '{...}' or '(...)'
     * @return true if the block is balanced, false otherwise
     */
    boolean isBalancedBlocks() {

        Stack stack = new Stack<>();

        for (Object item : expression) {
            if (item.toString().length() == 1 && item.toString().matches("\\(|}|\\[")) stack.push(item);
            else if (item.toString().length() == 1 && item.toString().matches("\\)|\\{|\\]")) {
                if (stack.empty()) return false;
                else if (!isBalanced(stack.pop(), item)) return false;
            }
        }

        return stack.empty();
    }

    private boolean isBalanced(Object fromStack, Object actual) {
        boolean result = false;
        if (actual.toString().equals(")")) result = fromStack.toString().equals("(");
        else if (actual.toString().equals("]")) result = fromStack.toString().equals("[");
        if (actual.toString().equals("}")) result = fromStack.toString().equals("{");

        if (!result) unbalanced = actual.toString();

        return result;
    }

    /**
     * return the balanced state of the last check
     * @return boolean
     */
    String getUnbalanced() {
        return unbalanced;
    }
}
    
    
    
    

    




    
    
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