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package sun.net.spi;

import java.net.InetSocketAddress;
import java.net.Proxy;
import java.net.ProxySelector;
import java.net.SocketAddress;
import java.net.URI;
import java.util.Collections;
import java.util.List;
import java.io.IOException;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.Locale;
import java.util.StringJoiner;
import java.util.regex.Pattern;
import java.util.stream.Stream;
import sun.net.NetProperties;
import sun.net.SocksProxy;
import static java.util.regex.Pattern.quote;
import static java.util.stream.Collectors.collectingAndThen;
import static java.util.stream.Collectors.toList;

/**
 * Supports proxy settings using system properties This proxy selector
 * provides backward compatibility with the old http protocol handler
 * as far as how proxy is set
 *
 * Most of the implementation copied from the old http protocol handler
 *
 * Supports http/https/ftp.proxyHost, http/https/ftp.proxyPort,
 * proxyHost, proxyPort, and http/https/ftp.nonProxyHost, and socks.
 */
public class DefaultProxySelector extends ProxySelector {

    /**
     * This is where we define all the valid System Properties we have to
     * support for each given protocol.
     * The format of this 2 dimensional array is :
     * - 1 row per protocol (http, ftp, ...)
     * - 1st element of each row is the protocol name
     * - subsequent elements are prefixes for Host & Port properties
     *   listed in order of priority.
     * Example:
     * {"ftp", "ftp.proxy", "ftpProxy", "proxy", "socksProxy"},
     * means for FTP we try in that order:
     *          + ftp.proxyHost & ftp.proxyPort
     *          + ftpProxyHost & ftpProxyPort
     *          + proxyHost & proxyPort
     *          + socksProxyHost & socksProxyPort
     *
     * Note that the socksProxy should *always* be the last on the list
     */
    static final String[][] props = {
        /*
         * protocol, Property prefix 1, Property prefix 2, ...
         */
        {"http", "http.proxy", "proxy", "socksProxy"},
        {"https", "https.proxy", "proxy", "socksProxy"},
        {"ftp", "ftp.proxy", "ftpProxy", "proxy", "socksProxy"},
        {"socket", "socksProxy"}
    };

    private static final String SOCKS_PROXY_VERSION = "socksProxyVersion";

    private static boolean hasSystemProxies = false;

    private static final List<Proxy> NO_PROXY_LIST = List.of(Proxy.NO_PROXY);

    static {
        final String key = "java.net.useSystemProxies";
        @SuppressWarnings("removal")
        Boolean b = AccessController.doPrivileged(
            new PrivilegedAction<Boolean>() {
                public Boolean run() {
                    return NetProperties.getBoolean(key);
                }});
        if (b != null && b.booleanValue()) {
            jdk.internal.loader.BootLoader.loadLibrary("net");
            hasSystemProxies = init();
        }
    }

    @SuppressWarnings("removal")
    public static int socksProxyVersion() {
        return AccessController.doPrivileged(
                new PrivilegedAction<Integer>() {
                    @Override public Integer run() {
                        return NetProperties.getInteger(SOCKS_PROXY_VERSION, 5);
                    }
                });
    }

    /**
     * How to deal with "non proxy hosts":
     * since we do have to generate a pattern we don't want to do that if
     * it's not necessary. Therefore we do cache the result, on a per-protocol
     * basis, and change it only when the "source", i.e. the system property,
     * did change.
     */

    static class NonProxyInfo {
        // Default value for nonProxyHosts, this provides backward compatibility
        // by excluding localhost and its literal notations.
        static final String defStringVal = "localhost|127.*|[::1]|0.0.0.0|[::0]";

        String hostsSource;
        Pattern pattern;
        final String property;
        final String defaultVal;
        static NonProxyInfo ftpNonProxyInfo = new NonProxyInfo("ftp.nonProxyHosts", null, null, defStringVal);
        static NonProxyInfo httpNonProxyInfo = new NonProxyInfo("http.nonProxyHosts", null, null, defStringVal);
        static NonProxyInfo socksNonProxyInfo = new NonProxyInfo("socksNonProxyHosts", null, null, defStringVal);

        NonProxyInfo(String p, String s, Pattern pattern, String d) {
            property = p;
            hostsSource = s;
            this.pattern = pattern;
            defaultVal = d;
        }
    }


    /**
     * select() method. Where all the hard work is done.
     * Build a list of proxies depending on URI.
     * Since we're only providing compatibility with the system properties
     * from previous releases (see list above), that list will typically
     * contain one single proxy, default being NO_PROXY.
     * If we can get a system proxy it might contain more entries.
     */
    public java.util.List<Proxy> select(URI uri) {
        if (uri == null) {
            throw new IllegalArgumentException("URI can't be null.");
        }
        String protocol = uri.getScheme();
        String host = uri.getHost();

        if (host == null) {
            // This is a hack to ensure backward compatibility in two
            // cases: 1. hostnames contain non-ascii characters,
            // internationalized domain names. in which case, URI will
            // return null, see BugID 4957669; 2. Some hostnames can
            // contain '_' chars even though it's not supposed to be
            // legal, in which case URI will return null for getHost,
            // but not for getAuthority() See BugID 4913253
            String auth = uri.getAuthority();
            if (auth != null) {
                int i;
                i = auth.indexOf('@');
                if (i >= 0) {
                    auth = auth.substring(i+1);
                }
                i = auth.lastIndexOf(':');
                if (i >= 0) {
                    auth = auth.substring(0,i);
                }
                host = auth;
            }
        }

        if (protocol == null || host == null) {
            throw new IllegalArgumentException("protocol = "+protocol+" host = "+host);
        }

        NonProxyInfo pinfo = null;

        if ("http".equalsIgnoreCase(protocol)) {
            pinfo = NonProxyInfo.httpNonProxyInfo;
        } else if ("https".equalsIgnoreCase(protocol)) {
            // HTTPS uses the same property as HTTP, for backward
            // compatibility
            pinfo = NonProxyInfo.httpNonProxyInfo;
        } else if ("ftp".equalsIgnoreCase(protocol)) {
            pinfo = NonProxyInfo.ftpNonProxyInfo;
        } else if ("socket".equalsIgnoreCase(protocol)) {
            pinfo = NonProxyInfo.socksNonProxyInfo;
        }

        /**
         * Let's check the System properties for that protocol
         */
        final String proto = protocol;
        final NonProxyInfo nprop = pinfo;
        final String urlhost = host.toLowerCase(Locale.ROOT);

        /**
         * This is one big doPrivileged call, but we're trying to optimize
         * the code as much as possible. Since we're checking quite a few
         * System properties it does help having only 1 call to doPrivileged.
         * Be mindful what you do in here though!
         */
        @SuppressWarnings("removal")
        Proxy[] proxyArray = AccessController.doPrivileged(
            new PrivilegedAction<Proxy[]>() {
                public Proxy[] run() {
                    int i, j;
                    String phost =  null;
                    int pport = 0;
                    String nphosts =  null;
                    InetSocketAddress saddr = null;

                    // Then let's walk the list of protocols in our array
                    for (i=0; i<props.length; i++) {
                        if (props[i][0].equalsIgnoreCase(proto)) {
                            for (j = 1; j < props[i].length; j++) {
                                /* System.getProp() will give us an empty
                                 * String, "" for a defined but "empty"
                                 * property.
                                 */
                                phost =  NetProperties.get(props[i][j]+"Host");
                                if (phost != null && phost.length() != 0)
                                    break;
                            }
                            if (phost == null || phost.isEmpty()) {
                                /**
                                 * No system property defined for that
                                 * protocol. Let's check System Proxy
                                 * settings (Gnome, MacOsX & Windows) if
                                 * we were instructed to.
                                 */
                                if (hasSystemProxies) {
                                    String sproto;
                                    if (proto.equalsIgnoreCase("socket"))
                                        sproto = "socks";
                                    else
                                        sproto = proto;
                                    return getSystemProxies(sproto, urlhost);
                                }
                                return null;
                            }
                            // If a Proxy Host is defined for that protocol
                            // Let's get the NonProxyHosts property
                            if (nprop != null) {
                                nphosts = NetProperties.get(nprop.property);
                                synchronized (nprop) {
                                    if (nphosts == null) {
                                        if (nprop.defaultVal != null) {
                                            nphosts = nprop.defaultVal;
                                        } else {
                                            nprop.hostsSource = null;
                                            nprop.pattern = null;
                                        }
                                    } else if (!nphosts.isEmpty()) {
                                        // add the required default patterns
                                        // but only if property no set. If it
                                        // is empty, leave empty.
                                        nphosts += "|" + NonProxyInfo
                                                         .defStringVal;
                                    }
                                    if (nphosts != null) {
                                        if (!nphosts.equals(nprop.hostsSource)) {
                                            nprop.pattern = toPattern(nphosts);
                                            nprop.hostsSource = nphosts;
                                        }
                                    }
                                    if (shouldNotUseProxyFor(nprop.pattern, urlhost)) {
                                        return null;
                                    }
                                }
                            }
                            // We got a host, let's check for port

                            pport = NetProperties.getInteger(props[i][j]+"Port", 0).intValue();
                            if (pport == 0 && j < (props[i].length - 1)) {
                                // Can't find a port with same prefix as Host
                                // AND it's not a SOCKS proxy
                                // Let's try the other prefixes for that proto
                                for (int k = 1; k < (props[i].length - 1); k++) {
                                    if ((k != j) && (pport == 0))
                                        pport = NetProperties.getInteger(props[i][k]+"Port", 0).intValue();
                                }
                            }

                            // Still couldn't find a port, let's use default
                            if (pport == 0) {
                                if (j == (props[i].length - 1)) // SOCKS
                                    pport = defaultPort("socket");
                                else
                                    pport = defaultPort(proto);
                            }
                            // We did find a proxy definition.
                            // Let's create the address, but don't resolve it
                            // as this will be done at connection time
                            saddr = InetSocketAddress.createUnresolved(phost, pport);
                            // Socks is *always* the last on the list.
                            if (j == (props[i].length - 1)) {
                                return new Proxy[] {SocksProxy.create(saddr, socksProxyVersion())};
                            }
                            return new Proxy[] {new Proxy(Proxy.Type.HTTP, saddr)};
                        }
                    }
                    return null;
                }});


        if (proxyArray != null) {
            // Remove duplicate entries, while preserving order.
            return Stream.of(proxyArray).distinct().collect(
                    collectingAndThen(toList(), Collections::unmodifiableList));
        }

        // If no specific proxy was found, return a standard list containing
        // only one NO_PROXY entry.
        return NO_PROXY_LIST;
    }

    public void connectFailed(URI uri, SocketAddress sa, IOException ioe) {
        if (uri == null || sa == null || ioe == null) {
            throw new IllegalArgumentException("Arguments can't be null.");
        }
        // ignored
    }


    private int defaultPort(String protocol) {
        if ("http".equalsIgnoreCase(protocol)) {
            return 80;
        } else if ("https".equalsIgnoreCase(protocol)) {
            return 443;
        } else if ("ftp".equalsIgnoreCase(protocol)) {
            return 80;
        } else if ("socket".equalsIgnoreCase(protocol)) {
            return 1080;
        } else {
            return -1;
        }
    }

    private static native boolean init();
    private synchronized native Proxy[] getSystemProxies(String protocol, String host);

    /**
     * @return {@code true} if given this pattern for non-proxy hosts and this
     *         urlhost the proxy should NOT be used to access this urlhost
     */
    static boolean shouldNotUseProxyFor(Pattern pattern, String urlhost) {
        if (pattern == null || urlhost.isEmpty())
            return false;
        boolean matches = pattern.matcher(urlhost).matches();
        return matches;
    }

    /**
     * @param mask non-null mask
     * @return {@link java.util.regex.Pattern} corresponding to this mask
     *         or {@code null} in case mask should not match anything
     */
    static Pattern toPattern(String mask) {
        boolean disjunctionEmpty = true;
        StringJoiner joiner = new StringJoiner("|");
        for (String disjunct : mask.split("\\|")) {
            if (disjunct.isEmpty())
                continue;
            disjunctionEmpty = false;
            String regex = disjunctToRegex(disjunct.toLowerCase());
            joiner.add(regex);
        }
        return disjunctionEmpty ? null : Pattern.compile(joiner.toString());
    }

    /**
     * @param disjunct non-null mask disjunct
     * @return java regex string corresponding to this mask
     */
    static String disjunctToRegex(String disjunct) {
        String regex;
        if (disjunct.equals("*")) {
            regex = ".*";
        } else if (disjunct.startsWith("*") && disjunct.endsWith("*")) {
            regex = ".*" + quote(disjunct.substring(1, disjunct.length() - 1)) + ".*";
        } else if (disjunct.startsWith("*")) {
            regex = ".*" + quote(disjunct.substring(1));
        } else if (disjunct.endsWith("*")) {
            regex = quote(disjunct.substring(0, disjunct.length() - 1)) + ".*";
        } else {
            regex = quote(disjunct);
        }
        return regex;
    }
}
