/*

 * Copyright (c) 2015, 2018, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package jdk.internal.net.http.common;

import java.net.http.HttpHeaders;

import sun.net.NetProperties;

import sun.net.util.IPAddressUtil;

import sun.net.www.HeaderParser;

import java.io.ByteArrayOutputStream;

import java.io.Closeable;

import java.io.IOException;

import java.io.PrintStream;

import java.io.UncheckedIOException;

import java.io.UnsupportedEncodingException;

import java.lang.System.Logger;

import java.lang.System.Logger.Level;

import java.net.InetSocketAddress;

import java.net.URI;

import java.net.URLPermission;

import java.nio.ByteBuffer;

import java.nio.charset.Charset;

import java.nio.charset.StandardCharsets;

import java.security.AccessController;

import java.security.PrivilegedAction;

import java.util.Arrays;

import java.util.Collection;

import java.util.Collections;

import java.util.List;

import java.util.Set;

import java.util.TreeSet;

import java.util.concurrent.CompletionException;

import java.util.concurrent.ExecutionException;

import java.util.function.BiPredicate;

import java.util.function.Predicate;

import java.util.function.Supplier;

import java.util.stream.Collectors;

import java.util.stream.Stream;

import javax.net.ssl.SSLParameters;

import javax.net.ssl.SSLSession;

import javax.net.ssl.ExtendedSSLSession;

import static java.util.stream.Collectors.joining;

/**

 * Miscellaneous utilities

 */

public final class Utils {

    public static final boolean ASSERTIONSENABLED;

    static {

        boolean enabled = false;

        assert enabled = true;

        ASSERTIONSENABLED = enabled;

    }

//    public static final boolean TESTING;

//    static {

//        if (ASSERTIONSENABLED) {

//            PrivilegedAction<String> action = () -> System.getProperty("test.src");

//            TESTING = AccessController.doPrivileged(action) != null;

//        } else TESTING = false;

//    }

    public static final boolean DEBUG = // Revisit: temporary dev flag.

            getBooleanProperty(DebugLogger.HTTP_NAME, false);

    public static final boolean DEBUG_HPACK = // Revisit: temporary dev flag.

            getBooleanProperty(DebugLogger.HPACK_NAME, false);

    public static final boolean TESTING = DEBUG;

    public static final boolean isHostnameVerificationDisabled = // enabled by default

    /**

     * Allocated buffer size. Must never be higher than 16K. But can be lower

     * if smaller allocation units preferred. HTTP/2 mandates that all

     * implementations support frame payloads of at least 16K.

     */

    private static final int DEFAULT_BUFSIZE = 16 * 1024;

    public static final int BUFSIZE = getIntegerNetProperty(

            "jdk.httpclient.bufsize", DEFAULT_BUFSIZE

    );

    private static final Set<String> DISALLOWED_HEADERS_SET;

    static {

        // A case insensitive TreeSet of strings.

        TreeSet<String> treeSet = new TreeSet<>(String.CASE_INSENSITIVE_ORDER);

        treeSet.addAll(Set.of("connection", "content-length",

                "date", "expect", "from", "host", "origin",

                "referer", "upgrade",

                "via", "warning"));

        DISALLOWED_HEADERS_SET = Collections.unmodifiableSet(treeSet);

    }

    public static final Predicate<String>

        ALLOWED_HEADERS = header -> !DISALLOWED_HEADERS_SET.contains(header);

    private static final Predicate<String> IS_PROXY_HEADER = (k) ->

            k != null && k.length() > 6 && "proxy-".equalsIgnoreCase(k.substring(0,6));

    private static final Predicate<String> NO_PROXY_HEADER =

            IS_PROXY_HEADER.negate();

    private static final Predicate<String> ALL_HEADERS = (s) -> true;

    private static final Set<String> PROXY_AUTH_DISABLED_SCHEMES;

    private static final Set<String> PROXY_AUTH_TUNNEL_DISABLED_SCHEMES;

    static {

        String proxyAuthDisabled =

                getNetProperty("jdk.http.auth.proxying.disabledSchemes");

        String proxyAuthTunnelDisabled =

                getNetProperty("jdk.http.auth.tunneling.disabledSchemes");

        PROXY_AUTH_DISABLED_SCHEMES =

                proxyAuthDisabled == null ? Set.of() :

                        Stream.of(proxyAuthDisabled.split(","))

                                .map(String::trim)

                                .filter((s) -> !s.isEmpty())

                                .collect(Collectors.toUnmodifiableSet());

        PROXY_AUTH_TUNNEL_DISABLED_SCHEMES =

                proxyAuthTunnelDisabled == null ? Set.of() :

                        Stream.of(proxyAuthTunnelDisabled.split(","))

                                .map(String::trim)

                                .filter((s) -> !s.isEmpty())

                                .collect(Collectors.toUnmodifiableSet());

    }

    private static final String WSPACES = " \t\r\n";

    private static final boolean isAllowedForProxy(String name,

                                                   List<String> value,

                                                   Set<String> disabledSchemes,

                                                   Predicate<String> allowedKeys) {

        if (!allowedKeys.test(name)) return false;

        if (disabledSchemes.isEmpty()) return true;

        if (name.equalsIgnoreCase("proxy-authorization")) {

            if (value.isEmpty()) return false;

            for (String scheme : disabledSchemes) {

                int slen = scheme.length();

                for (String v : value) {

                    int vlen = v.length();

                    if (vlen == slen) {

                        if (v.equalsIgnoreCase(scheme)) {

                            return false;

                        }

                    } else if (vlen > slen) {

                        if (v.substring(0,slen).equalsIgnoreCase(scheme)) {

                            int c = v.codePointAt(slen);

                            if (WSPACES.indexOf(c) > -1

                                    || Character.isSpaceChar(c)

                                    || Character.isWhitespace(c)) {

                                return false;

                            }

                        }

                    }

                }

            }

        }

        return true;

    }

    public static final BiPredicate<String, List<String>> PROXY_TUNNEL_FILTER =

            (s,v) -> isAllowedForProxy(s, v, PROXY_AUTH_TUNNEL_DISABLED_SCHEMES,

                    IS_PROXY_HEADER);

    public static final BiPredicate<String, List<String>> PROXY_FILTER =

            (s,v) -> isAllowedForProxy(s, v, PROXY_AUTH_DISABLED_SCHEMES,

                    ALL_HEADERS);

    public static final BiPredicate<String, List<String>> NO_PROXY_HEADERS_FILTER =

            (n,v) -> Utils.NO_PROXY_HEADER.test(n);

    public static boolean proxyHasDisabledSchemes(boolean tunnel) {

        return tunnel ? ! PROXY_AUTH_TUNNEL_DISABLED_SCHEMES.isEmpty()

                      : ! PROXY_AUTH_DISABLED_SCHEMES.isEmpty();

    }

    public static ByteBuffer getBuffer() {

        return ByteBuffer.allocate(BUFSIZE);

    }

    public static Throwable getCompletionCause(Throwable x) {

        if (!(x instanceof CompletionException)

                && !(x instanceof ExecutionException)) return x;

        final Throwable cause = x.getCause();

        if (cause == null) {

            throw new InternalError("Unexpected null cause", x);

        }

        return cause;

    }

    public static IOException getIOException(Throwable t) {

        if (t instanceof IOException) {

            return (IOException) t;

        }

        Throwable cause = t.getCause();

        if (cause != null) {

            return getIOException(cause);

        }

        return new IOException(t);

    }

    private Utils() { }

    /**

     * Returns the security permissions required to connect to the proxy, or

     * {@code null} if none is required or applicable.

     */

    public static URLPermission permissionForProxy(InetSocketAddress proxyAddress) {

        if (proxyAddress == null)

            return null;

        StringBuilder sb = new StringBuilder();

        sb.append("socket://")

          .append(proxyAddress.getHostString()).append(":")

          .append(proxyAddress.getPort());

        String urlString = sb.toString();

        return new URLPermission(urlString, "CONNECT");

    }

    /**

     * Returns the security permission required for the given details.

     */

    public static URLPermission permissionForServer(URI uri,

                                                    String method,

                                                    Stream<String> headers) {

        String urlString = new StringBuilder()

                .append(uri.getScheme()).append("://")

                .append(uri.getAuthority())

                .append(uri.getPath()).toString();

        StringBuilder actionStringBuilder = new StringBuilder(method);

        String collected = headers.collect(joining(","));

        if (!collected.isEmpty()) {

            actionStringBuilder.append(":").append(collected);

        }

        return new URLPermission(urlString, actionStringBuilder.toString());

    }

    // ABNF primitives defined in RFC 7230

    private static final boolean[] tchar      = new boolean[256];

    private static final boolean[] fieldvchar = new boolean[256];

    static {

        char[] allowedTokenChars =

                ("!#$%&'*+-.^_`|~0123456789" +

                 "abcdefghijklmnopqrstuvwxyz" +

                 "ABCDEFGHIJKLMNOPQRSTUVWXYZ").toCharArray();

        for (char c : allowedTokenChars) {

            tchar[c] = true;

        }

        for (char c = 0x21; c < 0xFF; c++) {

            fieldvchar[c] = true;

        }

        fieldvchar[0x7F] = false; // a little hole (DEL) in the range

    }

    /*

     * Validates a RFC 7230 field-name.

     */

    public static boolean isValidName(String token) {

        for (int i = 0; i < token.length(); i++) {

            char c = token.charAt(i);

            if (c > 255 || !tchar[c]) {

                return false;

            }

        }

        return !token.isEmpty();

    }

    /**

     * If the address was created with a domain name, then return

     * the domain name string. If created with a literal IP address

     * then return null except if the literal is loopback.

     * We do this to avoid doing a reverse lookup

     * Used to populate the TLS SNI parameter. So, SNI is only set

     * when a domain name was supplied except in case of loopback

     * where we return "localhost".

     */

    public static String getServerName(InetSocketAddress addr) {

        String host = addr.getHostString();

        byte[] literal = IPAddressUtil.textToNumericFormatV4(host);

        if (literal == null) {

            // not IPv4 literal

            literal = IPAddressUtil.textToNumericFormatV6(host);

            if (literal == null) {

                // not IPv6 literal. Must be domain name

                return host;

            } else { // check if loopback

                if (isLoopbackLiteral(literal))

                    return "localhost";

                else

                    return null;

            }

        } else {

            // check if IPv4 loopback

            if (isLoopbackLiteral(literal))

                    return "localhost";

                else

                    return null;

        }

    }

    private static boolean isLoopbackLiteral(byte[] bytes) {

        if (bytes.length == 4) {

            return bytes[0] == 127;

        } else if (bytes.length == 16) {

            for (int i=0; i<14; i++)

                if (bytes[i] != 0)

                    return false;

            if (bytes[15] != 1)

                return false;

            return true;

        } else

            throw new InternalError();

    }

    /*

     * Validates a RFC 7230 field-value.

     *

     * "Obsolete line folding" rule

     *

     *     obs-fold = CRLF 1*( SP / HTAB )

     *

     * is not permitted!

     */

    public static boolean isValidValue(String token) {

        boolean accepted = true;

        for (int i = 0; i < token.length(); i++) {

            char c = token.charAt(i);

            if (c > 255) {

                return false;

            }

            if (accepted) {

                if (c == ' ' || c == '\t') {

                    accepted = false;

                } else if (!fieldvchar[c]) {

                    return false; // forbidden byte

                }

            } else {

                if (c != ' ' && c != '\t') {

                    if (fieldvchar[c]) {

                        accepted = true;

                    } else {

                        return false; // forbidden byte

                    }

                }

            }

        }

        return accepted;

    }

    public static int getIntegerNetProperty(String name, int defaultValue) {

        return AccessController.doPrivileged((PrivilegedAction<Integer>) () ->

                NetProperties.getInteger(name, defaultValue));

    }

    public static String getNetProperty(String name) {

        return AccessController.doPrivileged((PrivilegedAction<String>) () ->

                NetProperties.get(name));

    }

    public static boolean getBooleanProperty(String name, boolean def) {

        return AccessController.doPrivileged((PrivilegedAction<Boolean>) () ->

                Boolean.parseBoolean(System.getProperty(name, String.valueOf(def))));

    }

    public static SSLParameters copySSLParameters(SSLParameters p) {

        SSLParameters p1 = new SSLParameters();

        p1.setAlgorithmConstraints(p.getAlgorithmConstraints());

        p1.setCipherSuites(p.getCipherSuites());

        // JDK 8 EXCL START

        p1.setEnableRetransmissions(p.getEnableRetransmissions());

        p1.setMaximumPacketSize(p.getMaximumPacketSize());

        // JDK 8 EXCL END

        p1.setEndpointIdentificationAlgorithm(p.getEndpointIdentificationAlgorithm());

        p1.setNeedClientAuth(p.getNeedClientAuth());

        String[] protocols = p.getProtocols();

        if (protocols != null) {

            p1.setProtocols(protocols.clone());

        }

        p1.setSNIMatchers(p.getSNIMatchers());

        p1.setServerNames(p.getServerNames());

        p1.setUseCipherSuitesOrder(p.getUseCipherSuitesOrder());

        p1.setWantClientAuth(p.getWantClientAuth());

        return p1;

    }

    /**

     * Set limit to position, and position to mark.

     */

    public static void flipToMark(ByteBuffer buffer, int mark) {

        buffer.limit(buffer.position());

        buffer.position(mark);

    }

    public static String stackTrace(Throwable t) {

        ByteArrayOutputStream bos = new ByteArrayOutputStream();

        String s = null;

        try {

            PrintStream p = new PrintStream(bos, true, "US-ASCII");

            t.printStackTrace(p);

            s = bos.toString("US-ASCII");

        } catch (UnsupportedEncodingException ex) {

            throw new InternalError(ex); // Can't happen

        }

        return s;

    }

    /**

     * Copies as much of src to dst as possible.

     * Return number of bytes copied

     */

    public static int copy(ByteBuffer src, ByteBuffer dst) {

        int srcLen = src.remaining();

        int dstLen = dst.remaining();

        if (srcLen > dstLen) {

            int diff = srcLen - dstLen;

            int limit = src.limit();

            src.limit(limit - diff);

            dst.put(src);

            src.limit(limit);

        } else {

            dst.put(src);

        }

        return srcLen - src.remaining();

    }

    /** Threshold beyond which data is no longer copied into the current

     * buffer, if that buffer has enough unused space. */

    private static final int COPY_THRESHOLD = 8192;

    /**

     * Adds the data from buffersToAdd to currentList. Either 1) appends the

     * data from a particular buffer to the last buffer in the list ( if

     * there is enough unused space ), or 2) adds it to the list.

     *

     * @return the number of bytes added

     */

    public static long accumulateBuffers(List<ByteBuffer> currentList,

                                         List<ByteBuffer> buffersToAdd) {

        long accumulatedBytes = 0;

        for (ByteBuffer bufferToAdd : buffersToAdd) {

            int remaining = bufferToAdd.remaining();

            if (remaining <= 0)

                continue;

            int listSize = currentList.size();

            if (listSize == 0) {

                currentList.add(bufferToAdd);

                accumulatedBytes = remaining;

                continue;

            }

            ByteBuffer lastBuffer = currentList.get(listSize - 1);

            int freeSpace = lastBuffer.capacity() - lastBuffer.limit();

            if (remaining <= COPY_THRESHOLD && freeSpace >= remaining) {

                // append the new data to the unused space in the last buffer

                int position = lastBuffer.position();

                int limit = lastBuffer.limit();

                lastBuffer.position(limit);

                lastBuffer.limit(limit + remaining);

                lastBuffer.put(bufferToAdd);

                lastBuffer.position(position);

            } else {

                currentList.add(bufferToAdd);

            }

            accumulatedBytes += remaining;

        }

        return accumulatedBytes;

    }

    public static ByteBuffer copy(ByteBuffer src) {

        ByteBuffer dst = ByteBuffer.allocate(src.remaining());

        dst.put(src);