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A utility to reduce boilerplate code in Bukkit plugins.
There is a newer version: 5.6.14
/*
 * This file is part of helper, licensed under the MIT License.
 *
 *  Copyright (c) lucko (Luck) 
 *  Copyright (c) contributors
 *
 *  Permission is hereby granted, free of charge, to any person obtaining a copy
 *  of this software and associated documentation files (the "Software"), to deal
 *  in the Software without restriction, including without limitation the rights
 *  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 *  copies of the Software, and to permit persons to whom the Software is
 *  furnished to do so, subject to the following conditions:
 *
 *  The above copyright notice and this permission notice shall be included in all
 *  copies or substantial portions of the Software.
 *
 *  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 *  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 *  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 *  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 *  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 *  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 *  SOFTWARE.
 */

package me.lucko.helper.command.argument;

import me.lucko.helper.command.CommandInterruptException;
import me.lucko.helper.utils.annotation.NonnullByDefault;

import java.util.Optional;

import javax.annotation.Nonnull;

/**
 * Parses an argument from a String
 *
 * @param  the value type
 */
@NonnullByDefault
public interface ArgumentParser {

    /**
     * Parses the value from a string
     *
     * @param s the string
     * @return the value, if parsing was successful
     */
    Optional parse(@Nonnull String s);

    /**
     * Parses the value from a string, throwing an interrupt exception if
     * parsing failed.
     *
     * @param s the string
     * @return the value
     */
    @Nonnull
    default T parseOrFail(@Nonnull String s) throws CommandInterruptException {
        Optional ret = parse(s);
        if (!ret.isPresent()) {
            throw new CommandInterruptException("&cUnable to parse argument: " + s);
        }
        return ret.get();
    }

    /**
     * Tries to parse the value from the argument
     *
     * @param argument the argument
     * @return the value, if parsing was successful
     */
    @Nonnull
    default Optional parse(@Nonnull Argument argument) {
        return argument.value().flatMap(this::parse);
    }

    /**
     * Parses the value from an argument, throwing an interrupt exception if
     * parsing failed.
     *
     * @param argument the argument
     * @return the value
     */
    @Nonnull
    default T parseOrFail(@Nonnull Argument argument) throws CommandInterruptException {
        Optional ret = parse(argument);
        if (!ret.isPresent()) {
            throw new CommandInterruptException("&cUnable to parse argument at index " + argument.index() + ".");
        }
        return ret.get();
    }

    /**
     * Creates a new parser which first tries to obtain a value from
     * this parser, then from another if the former was not successful.
     *
     * @param other the other parser
     * @return the combined parser
     */
    @Nonnull
    default ArgumentParser thenTry(@Nonnull ArgumentParser other) {
        ArgumentParser first = this;
        return t -> {
            Optional ret = first.parse(t);
            return ret.isPresent() ? ret : other.parse(t);
        };
    }
}