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Kiwi is a utility library. We really like Google's Guava, and also use Apache Commons. But if they don't have something we need, and we think it is useful, this is where we put it.

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package org.kiwiproject.net;

import static com.google.common.base.Preconditions.checkState;
import static org.apache.commons.lang3.StringUtils.isBlank;
import static org.kiwiproject.base.KiwiPreconditions.checkArgumentNotBlank;

import lombok.AccessLevel;
import lombok.AllArgsConstructor;
import lombok.EqualsAndHashCode;
import lombok.Getter;

/**
 * Inspired by Guava's {@link com.google.common.net.HostAndPort} but much simpler in implementation.
 * (go look at the code in {@link com.google.common.net.HostAndPort#fromString(String)} if you don't believe me.)
 * Because it is much simpler, it also only handles a very specific host/port format, which is {@code host:port}.
 * 
 * It also does not attempt to validate anything about the host or port, e.g., it will happily accept a negative port
 * value or a one-character long host name.
 */
@EqualsAndHashCode
@AllArgsConstructor(access = AccessLevel.PRIVATE)
public class SimpleHostAndPort {

    @Getter
    private final String host;

    @Getter
    private final int port;

    /**
     * Parse {@code hostPortString} assuming format {@code host:port}; if it is blank, use the specified
     * {@code defaultHost} and {@code defaultPort} values to create a link {@link SimpleHostAndPort}.
     * 
     * No validation is performed on the default values.
     *
     * @param hostPortString a string containing host and port, e.g., acme.com:8001
     * @param defaultHost    a default host if the host/port string is blank
     * @param defaultPort    a default port if the host/port string is blank
     * @return a new SimpleHostAndPort instance
     */
    public static SimpleHostAndPort from(String hostPortString, String defaultHost, int defaultPort) {
        if (isBlank(hostPortString)) {
            return new SimpleHostAndPort(defaultHost, defaultPort);
        }

        return from(hostPortString);
    }

    /**
     * Parse {@code hostPortString} assuming format {@code host:port}
     *
     * @param hostPortString a string containing host and port, e.g., foo.com:9000
     * @return a new SimpleHostAndPort instance
     * @throws IllegalStateException if not in the expected format
     * @throws IllegalArgumentException if hostPortString is blank or port is not a valid number
     * @implNote Does no validation on the host part
     */
    public static SimpleHostAndPort from(String hostPortString) {
        checkArgumentNotBlank(hostPortString, "hostAndPortString must not be blank");

        var split = hostPortString.split(":");
        checkState(split.length == 2, "%s is not in format host:port", hostPortString);

        var port = getPortOrThrow(split);
        return new SimpleHostAndPort(split[0], port);
    }

    private static int getPortOrThrow(String[] split) {
        try {
            return Integer.parseInt(split[1], 10);
        } catch (NumberFormatException e) {
            throw new IllegalArgumentException(e);
        }
    }

    /**
     * Return a string in {@code host:port} format.
     */
    @Override
    public String toString() {
        return host + ":" + port;
    }
}