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package yalep.code; |
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import org.antlr.v4.runtime.CharStreams; |
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import org.antlr.v4.runtime.CommonTokenStream; |
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import yalep.antlr.LogicalExpressionErrorListener; |
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import yalep.antlr.generated.LogicalExpressionLexer; |
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import yalep.antlr.generated.LogicalExpressionParser; |
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import yalep.exceptions.WrongExpressionFormatException; |
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import java.util.HashSet; |
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import java.util.Set; |
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public class LogicalExpressionValidityChecker { |
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// on change of grammar should change it too |
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private static final String ALLOWED_TOKENS = "()!&|^ABCDEFGHIJKLMNOPQRSTUVWXYZ"; |
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protected static void expressionIsValid(String rawExpression) throws WrongExpressionFormatException { |
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rawExpression = rawExpression.replaceAll(" ",""); |
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String expression = getLogicalExpressionAndValidateBasics(rawExpression); |
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checkSyntaxErrors(expression); |
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checkInvalidTokens(expression); |
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} |
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private static void checkSyntaxErrors(String expression) throws WrongExpressionFormatException { |
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LogicalExpressionLexer lexer = new LogicalExpressionLexer(CharStreams.fromString(expression)); |
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lexer.removeErrorListeners(); |
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CommonTokenStream tokens = new CommonTokenStream(lexer); |
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LogicalExpressionParser parser = new LogicalExpressionParser(tokens); |
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parser.removeErrorListeners(); |
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parser.addErrorListener(new LogicalExpressionErrorListener()); |
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try { |
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parser.eval(); |
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} catch (RuntimeException e) { |
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throw new WrongExpressionFormatException(e.getMessage()); |
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} |
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if (parser.getNumberOfSyntaxErrors() != 0) { |
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throw new WrongExpressionFormatException("Expression has syntax errors"); |
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} |
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} |
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private static void checkInvalidTokens(String expression) throws WrongExpressionFormatException { |
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Set<Character> tokenSet = new HashSet<>(); |
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for (Character c : ALLOWED_TOKENS.toCharArray()) { |
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tokenSet.add(c); |
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} |
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for (Character c : expression.toCharArray()) { |
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if (!tokenSet.contains(c)) { |
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throw new WrongExpressionFormatException("Expression contains wrong tokens"); |
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} |
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} |
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} |
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private static String getLogicalExpressionAndValidateBasics(String rawExpression) throws WrongExpressionFormatException { |
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int equalSignPos = rawExpression.indexOf("="); |
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if (equalSignPos == -1) { |
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throw new WrongExpressionFormatException("Expression doesn't contain '='"); |
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} |
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String answerString = rawExpression.substring(equalSignPos + 1); |
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if (!(answerString.equals("1") || answerString.equals("0"))) { |
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throw new WrongExpressionFormatException("Wrong answer format"); |
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} |
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return rawExpression.substring(0, equalSignPos); |
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} |
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} |
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Dimakl /
YALEP
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