/*

 * 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.incubator.http.internal.common;

import jdk.incubator.http.HttpHeaders;

import sun.net.NetProperties;

import sun.net.util.IPAddressUtil;

import sun.net.www.HeaderParser;

import javax.net.ssl.SSLParameters;

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.List;

import java.util.Set;

import java.util.concurrent.CompletionException;

import java.util.concurrent.ExecutionException;

import java.util.function.Predicate;

import java.util.function.Supplier;

import java.util.stream.Stream;

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;

    /**

     * 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

    );

    public static final Predicate<String>

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

    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. 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.

     */

    public static String getServerName(InetSocketAddress addr) {

        String host = addr.getHostString();

        if (IPAddressUtil.textToNumericFormatV4(host) != null)

            return null;

        if (IPAddressUtil.textToNumericFormatV6(host) != null)

            return null;

        return host;

    }

    /*

     * 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));

    }

    static String getNetProperty(String name) {

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

                NetProperties.get(name));

    }

    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);

        dst.flip();

        return dst;

    }

    public static String dump(Object... objects) {

        return Arrays.toString(objects);

    }

    public static String stringOf(Collection<?> source) {

        // We don't know anything about toString implementation of this

        // collection, so let's create an array

        return Arrays.toString(source.toArray());

    }

    public static long remaining(ByteBuffer[] bufs) {

        long remain = 0;

        for (ByteBuffer buf : bufs) {

            remain += buf.remaining();

        }

        return remain;

    }

    public static boolean hasRemaining(List<ByteBuffer> bufs) {

        synchronized (bufs) {

            for (ByteBuffer buf : bufs) {

                if (buf.hasRemaining())

                    return true;

            }

        }

        return false;

    }

    public static long remaining(List<ByteBuffer> bufs) {

        long remain = 0;

        synchronized (bufs) {

            for (ByteBuffer buf : bufs) {

                remain += buf.remaining();

            }

        }

        return remain;

    }

    public static int remaining(List<ByteBuffer> bufs, int max) {

        long remain = 0;

        synchronized (bufs) {

            for (ByteBuffer buf : bufs) {

                remain += buf.remaining();

                if (remain > max) {

                    throw new IllegalArgumentException("too many bytes");

                }

            }

        }

        return (int) remain;

    }

    public static long remaining(ByteBufferReference[] refs) {

        long remain = 0;

        for (ByteBufferReference ref : refs) {

            remain += ref.get().remaining();

        }

        return remain;

    }

    public static int remaining(ByteBufferReference[] refs, int max) {

        long remain = 0;

        for (ByteBufferReference ref : refs) {

            remain += ref.get().remaining();

            if (remain > max) {

                throw new IllegalArgumentException("too many bytes");

            }

        }

        return (int) remain;

    }

    public static int remaining(ByteBuffer[] refs, int max) {

        long remain = 0;

        for (ByteBuffer b : refs) {

            remain += b.remaining();

            if (remain > max) {

                throw new IllegalArgumentException("too many bytes");

            }

        }

        return (int) remain;

    }

    public static void close(Closeable... closeables) {

        for (Closeable c : closeables) {

            try {

                c.close();

            } catch (IOException ignored) { }

        }

    }

    // Put all these static 'empty' singletons here

    public static final ByteBuffer EMPTY_BYTEBUFFER = ByteBuffer.allocate(0);

    public static final ByteBuffer[] EMPTY_BB_ARRAY = new ByteBuffer[0];

    public static final List<ByteBuffer> EMPTY_BB_LIST = List.of();

    public static final ByteBufferReference[] EMPTY_BBR_ARRAY = new ByteBufferReference[0];

    public static ByteBuffer slice(ByteBuffer buffer, int amount) {

        ByteBuffer newb = buffer.slice();

        newb.limit(amount);

        buffer.position(buffer.position() + amount);

        return newb;

    }

    /**

     * Get the Charset from the Content-encoding header. Defaults to

     * UTF_8

     */

    public static Charset charsetFrom(HttpHeaders headers) {

        String type = headers.firstValue("Content-type")

                .orElse("text/html; charset=utf-8");

        int i = type.indexOf(";");

        if (i >= 0) type = type.substring(i+1);

        try {

            HeaderParser parser = new HeaderParser(type);

            String value = parser.findValue("charset");

            if (value == null) return StandardCharsets.UTF_8;

            return Charset.forName(value);

        } catch (Throwable x) {

            Log.logTrace("Can't find charset in \"{0}\" ({1})", type, x);

            return StandardCharsets.UTF_8;

        }

    }

    public static UncheckedIOException unchecked(IOException e) {

        return new UncheckedIOException(e);

    }