/*
 * Copyright (C) 2011 The Guava Authors
 *
 * 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
 *
 * http://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 com.google.common.net;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Preconditions.checkState;
import static com.google.common.base.Strings.isNullOrEmpty;

import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;
import com.google.common.annotations.J2ktIncompatible;
import com.google.common.primitives.Ints;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import com.google.errorprone.annotations.Immutable;
import java.io.Serializable;
import java.util.Objects;
import org.jspecify.annotations.Nullable;

/**
 * An immutable representation of a host and port.
 *
 * <p>Example usage:
 *
 * <pre>
 * HostAndPort hp = HostAndPort.fromString("[2001:db8::1]")
 *     .withDefaultPort(80)
 *     .requireBracketsForIPv6();
 * hp.getHost();   // returns "2001:db8::1"
 * hp.getPort();   // returns 80
 * hp.toString();  // returns "[2001:db8::1]:80"
 * </pre>
 *
 * <p>Here are some examples of recognized formats:
 *
 * <ul>
 *   <li>example.com
 *   <li>example.com:80
 *   <li>192.0.2.1
 *   <li>192.0.2.1:80
 *   <li>[2001:db8::1] - {@link #getHost()} omits brackets
 *   <li>[2001:db8::1]:80 - {@link #getHost()} omits brackets
 *   <li>2001:db8::1 - Use {@link #requireBracketsForIPv6()} to prohibit this
 * </ul>
 *
 * <p>Note that this is not an exhaustive list, because these methods are only concerned with
 * brackets, colons, and port numbers. Full validation of the host field (if desired) is the
 * caller's responsibility.
 *
 * @author Paul Marks
 * @since 10.0
 */
@Immutable
@GwtCompatible
public final class HostAndPort implements Serializable {
  /** Magic value indicating the absence of a port number. */
  private static final int NO_PORT = -1;

  /** Hostname, IPv4/IPv6 literal, or unvalidated nonsense. */
  private final String host;

  /** Validated port number in the range [0..65535], or NO_PORT */
  private final int port;

  /** True if the parsed host has colons, but no surrounding brackets. */
  private final boolean hasBracketlessColons;

  private HostAndPort(String host, int port, boolean hasBracketlessColons) {
    this.host = host;
    this.port = port;
    this.hasBracketlessColons = hasBracketlessColons;
  }

  /**
   * Returns the portion of this {@code HostAndPort} instance that should represent the hostname or
   * IPv4/IPv6 literal.
   *
   * <p>A successful parse does not imply any degree of sanity in this field. For additional
   * validation, see the {@link HostSpecifier} class.
   *
   * @since 20.0 (since 10.0 as {@code getHostText})
   */
  public String getHost() {
    return host;
  }

  /** Return true if this instance has a defined port. */
  public boolean hasPort() {
    return port >= 0;
  }

  /**
   * Get the current port number, failing if no port is defined.
   *
   * @return a validated port number, in the range [0..65535]
   * @throws IllegalStateException if no port is defined. You can use {@link #withDefaultPort(int)}
   *     to prevent this from occurring.
   */
  public int getPort() {
    checkState(hasPort());
    return port;
  }

  /** Returns the current port number, with a default if no port is defined. */
  public int getPortOrDefault(int defaultPort) {
    return hasPort() ? port : defaultPort;
  }

  /**
   * Build a HostAndPort instance from separate host and port values.
   *
   * <p>Note: Non-bracketed IPv6 literals are allowed. Use {@link #requireBracketsForIPv6()} to
   * prohibit these.
   *
   * @param host the host string to parse. Must not contain a port number.
   * @param port a port number from [0..65535]
   * @return if parsing was successful, a populated HostAndPort object.
   * @throws IllegalArgumentException if {@code host} contains a port number, or {@code port} is out
   *     of range.
   */
  public static HostAndPort fromParts(String host, int port) {
    checkArgument(isValidPort(port), "Port out of range: %s", port);
    HostAndPort parsedHost = fromString(host);
    checkArgument(!parsedHost.hasPort(), "Host has a port: %s", host);
    return new HostAndPort(parsedHost.host, port, parsedHost.hasBracketlessColons);
  }

  /**
   * Build a HostAndPort instance from a host only.
   *
   * <p>Note: Non-bracketed IPv6 literals are allowed. Use {@link #requireBracketsForIPv6()} to
   * prohibit these.
   *
   * @param host the host-only string to parse. Must not contain a port number.
   * @return if parsing was successful, a populated HostAndPort object.
   * @throws IllegalArgumentException if {@code host} contains a port number.
   * @since 17.0
   */
  public static HostAndPort fromHost(String host) {
    HostAndPort parsedHost = fromString(host);
    checkArgument(!parsedHost.hasPort(), "Host has a port: %s", host);
    return parsedHost;
  }

  /**
   * Split a freeform string into a host and port, without strict validation.
   *
   * <p>Note that the host-only formats will leave the port field undefined. You can use {@link
   * #withDefaultPort(int)} to patch in a default value.
   *
   * @param hostPortString the input string to parse.
   * @return if parsing was successful, a populated HostAndPort object.
   * @throws IllegalArgumentException if nothing meaningful could be parsed.
   */
  @CanIgnoreReturnValue // TODO(b/219820829): consider removing
  public static HostAndPort fromString(String hostPortString) {
    checkNotNull(hostPortString);
    String host;
    String portString = null;
    boolean hasBracketlessColons = false;

    if (hostPortString.startsWith("[")) {
      String[] hostAndPort = getHostAndPortFromBracketedHost(hostPortString);
      host = hostAndPort[0];
      portString = hostAndPort[1];
    } else {
      int colonPos = hostPortString.indexOf(':');
      if (colonPos >= 0 && hostPortString.indexOf(':', colonPos + 1) == -1) {
        // Exactly 1 colon. Split into host:port.
        host = hostPortString.substring(0, colonPos);
        portString = hostPortString.substring(colonPos + 1);
      } else {
        // 0 or 2+ colons. Bare hostname or IPv6 literal.
        host = hostPortString;
        hasBracketlessColons = colonPos >= 0;
      }
    }

    Integer port;
    if (isNullOrEmpty(portString)) {
      port = NO_PORT;
    } else {
      port = Ints.tryParse(portString);
      checkArgument(port != null, "Unparseable port number: %s", hostPortString);
      checkArgument(isValidPort(port), "Port number out of range: %s", hostPortString);
    }

    return new HostAndPort(host, port, hasBracketlessColons);
  }

  /**
   * Parses a bracketed host-port string, throwing IllegalArgumentException if parsing fails.
   *
   * @param hostPortString the full bracketed host-port specification. Port might not be specified.
   * @return an array with 2 strings: host and port, in that order.
   * @throws IllegalArgumentException if parsing the bracketed host-port string fails.
   */
  private static String[] getHostAndPortFromBracketedHost(String hostPortString) {
    checkArgument(
        hostPortString.charAt(0) == '[',
        "Bracketed host-port string must start with a bracket: %s",
        hostPortString);
    int colonIndex = hostPortString.indexOf(':');
    int closeBracketIndex = hostPortString.lastIndexOf(']');
    checkArgument(
        colonIndex > -1 && closeBracketIndex > colonIndex,
        "Invalid bracketed host/port: %s",
        hostPortString);

    String host = hostPortString.substring(1, closeBracketIndex);
    if (closeBracketIndex + 1 == hostPortString.length()) {
      return new String[] {host, ""};
    } else {
      checkArgument(
          hostPortString.charAt(closeBracketIndex + 1) == ':',
          "Only a colon may follow a close bracket: %s",
          hostPortString);
      for (int i = closeBracketIndex + 2; i < hostPortString.length(); ++i) {
        checkArgument(
            Character.isDigit(hostPortString.charAt(i)),
            "Port must be numeric: %s",
            hostPortString);
      }
      return new String[] {host, hostPortString.substring(closeBracketIndex + 2)};
    }
  }

  /**
   * Provide a default port if the parsed string contained only a host.
   *
   * <p>You can chain this after {@link #fromString(String)} to include a port in case the port was
   * omitted from the input string. If a port was already provided, then this method is a no-op.
   *
   * @param defaultPort a port number, from [0..65535]
   * @return a HostAndPort instance, guaranteed to have a defined port.
   */
  public HostAndPort withDefaultPort(int defaultPort) {
    checkArgument(isValidPort(defaultPort));
    if (hasPort()) {
      return this;
    }
    return new HostAndPort(host, defaultPort, hasBracketlessColons);
  }

  /**
   * Generate an error if the host might be a non-bracketed IPv6 literal.
   *
   * <p>URI formatting requires that IPv6 literals be surrounded by brackets, like "[2001:db8::1]".
   * Chain this call after {@link #fromString(String)} to increase the strictness of the parser, and
   * disallow IPv6 literals that don't contain these brackets.
   *
   * <p>Note that this parser identifies IPv6 literals solely based on the presence of a colon. To
   * perform actual validation of IP addresses, see the {@link InetAddresses#forString(String)}
   * method.
   *
   * @return {@code this}, to enable chaining of calls.
   * @throws IllegalArgumentException if bracketless IPv6 is detected.
   */
  @CanIgnoreReturnValue
  public HostAndPort requireBracketsForIPv6() {
    checkArgument(!hasBracketlessColons, "Possible bracketless IPv6 literal: %s", host);
    return this;
  }

  @Override
  public boolean equals(@Nullable Object other) {
    if (this == other) {
      return true;
    }
    if (other instanceof HostAndPort) {
      HostAndPort that = (HostAndPort) other;
      return Objects.equals(this.host, that.host) && this.port == that.port;
    }
    return false;
  }

  @Override
  public int hashCode() {
    return Objects.hash(host, port);
  }

  /** Rebuild the host:port string, including brackets if necessary. */
  @Override
  public String toString() {
    // "[]:12345" requires 8 extra bytes.
    StringBuilder builder = new StringBuilder(host.length() + 8);
    if (host.indexOf(':') >= 0) {
      builder.append('[').append(host).append(']');
    } else {
      builder.append(host);
    }
    if (hasPort()) {
      builder.append(':').append(port);
    }
    return builder.toString();
  }

  /** Return true for valid port numbers. */
  private static boolean isValidPort(int port) {
    return port >= 0 && port <= 65535;
  }

  @GwtIncompatible @J2ktIncompatible private static final long serialVersionUID = 0;
}
