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PetitParser library

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package org.petitparser.parser.actions;

import org.petitparser.context.Context;
import org.petitparser.context.Result;
import org.petitparser.parser.Parser;
import org.petitparser.parser.combinators.DelegateParser;

import java.util.Objects;
import java.util.function.Function;

/**
 * A parser that performs a transformation with a given function on the successful parse result of
 * the delegate.
 *
 * @param  The type of the function argument.
 * @param  The type of the function result.
 */
public class ActionParser extends DelegateParser {

  protected final Function function;

  public ActionParser(Parser delegate, Function function) {
    super(delegate);
    this.function = Objects.requireNonNull(function, "Undefined function");
  }

  @Override
  public Result parseOn(Context context) {
    Result result = delegate.parseOn(context);
    if (result.isSuccess()) {
      return result.success(function.apply(result.get()));
    } else {
      return result;
    }
  }

  @Override
  protected boolean hasEqualProperties(Parser other) {
    return super.hasEqualProperties(other) &&
        Objects.equals(function, ((ActionParser) other).function);
  }

  @Override
  public ActionParser copy() {
    return new ActionParser<>(delegate, function);
  }
}