/*

 * Copyright (c) 2015, 2016, 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.internal.misc.InnocuousThread;

import sun.net.NetProperties;

import javax.net.ssl.SSLParameters;

import java.io.ByteArrayOutputStream;

import java.io.Closeable;

import java.io.IOException;

import java.io.UncheckedIOException;

import java.io.PrintStream;

import java.io.UnsupportedEncodingException;

import java.net.NetPermission;

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.Map;

import java.util.Optional;

import java.util.Set;

import java.util.concurrent.BlockingQueue;

import java.util.concurrent.CompletableFuture;

import java.util.concurrent.Executor;

import java.util.concurrent.ExecutorService;

import java.util.concurrent.Executors;

import java.util.concurrent.LinkedBlockingQueue;

import java.util.function.Predicate;

import jdk.incubator.http.HttpHeaders;

/**

 * Miscellaneous utilities

 */

public final class Utils {

    /**

     * 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.

     */

    public 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 = Set.of(

            "authorization", "connection", "cookie", "content-length",

            "date", "expect", "from", "host", "origin", "proxy-authorization",

            "referer", "user-agent", "upgrade", "via", "warning");

    public static final Predicate<String>

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

    public static final Predicate<String>

        ALL_HEADERS = header -> true;

    public static ByteBuffer getBuffer() {

        return ByteBuffer.allocate(BUFSIZE);

    }

    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);

    }

    /**

     * We use the same buffer for reading all headers and dummy bodies in an Exchange.

     */

    public static ByteBuffer getExchangeBuffer() {

        ByteBuffer buf = getBuffer();

        // Force a read the first time it is used

        buf.limit(0);

        return buf;

    }

    /**

     * Puts position to limit and limit to capacity so we can resume reading

     * into this buffer, but if required > 0 then limit may be reduced so that

     * no more than required bytes are read next time.

     */

    static void resumeChannelRead(ByteBuffer buf, int required) {

        int limit = buf.limit();

        buf.position(limit);

        int capacity = buf.capacity() - limit;

        if (required > 0 && required < capacity) {

            buf.limit(limit + required);

        } else {

            buf.limit(buf.capacity());

        }

    }

    private Utils() { }

    public static ExecutorService innocuousThreadPool() {

        return Executors.newCachedThreadPool(

                (r) -> InnocuousThread.newThread("DefaultHttpClient", r));

    }

    // 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();

    }

    /*

     * 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;

    }

    /**

     * Returns the security permission required for the given details.

     * If method is CONNECT, then uri must be of form "scheme://host:port"

     */

    public static URLPermission getPermission(URI uri,

                                              String method,

                                              Map<String, List<String>> headers) {

        StringBuilder sb = new StringBuilder();

        String urlstring, actionstring;

        if (method.equals("CONNECT")) {

            urlstring = uri.toString();

            actionstring = "CONNECT";

        } else {

            sb.append(uri.getScheme())

                    .append("://")

                    .append(uri.getAuthority())

                    .append(uri.getPath());

            urlstring = sb.toString();

            sb = new StringBuilder();

            sb.append(method);

            if (headers != null && !headers.isEmpty()) {

                sb.append(':');

                Set<String> keys = headers.keySet();

                boolean first = true;

                for (String key : keys) {

                    if (!first) {

                        sb.append(',');

                    }

                    sb.append(key);

                    first = false;

                }

            }

            actionstring = sb.toString();

        }

        return new URLPermission(urlstring, actionstring);

    }

    public static void checkNetPermission(String target) {

        SecurityManager sm = System.getSecurityManager();

        if (sm == null) {

            return;

        }

        NetPermission np = new NetPermission(target);

        sm.checkPermission(np);

    }

    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));

    }

    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) {

            // 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();

    }

    // copy up to amount from src to dst, but no more

    public static int copyUpTo(ByteBuffer src, ByteBuffer dst, int amount) {

        int toCopy = Math.min(src.remaining(), Math.min(dst.remaining(), amount));

        copy(src, dst, toCopy);

        return toCopy;

    }

    /**

     * Copy amount bytes from src to dst. at least amount must be

     * available in both dst and in src

     */

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

        int excess = src.remaining() - amount;

        assert excess >= 0;

        if (excess > 0) {

            int srclimit = src.limit();

            src.limit(srclimit - excess);

            dst.put(src);

            src.limit(srclimit);

        } else {

            dst.put(src);

        }

    }

    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 int remaining(ByteBuffer[] bufs) {

        int remain = 0;

        for (ByteBuffer buf : bufs) {

            remain += buf.remaining();

        }

        return remain;

    }

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

        int remain = 0;

        for (ByteBuffer buf : bufs) {

            remain += buf.remaining();

        }

        return remain;

    }

    public static int remaining(ByteBufferReference[] refs) {

        int remain = 0;

        for (ByteBufferReference ref : refs) {

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

        }

        return remain;

    }

    // assumes buffer was written into starting at position zero

    static void unflip(ByteBuffer buf) {

        buf.position(buf.limit());

        buf.limit(buf.capacity());

    }

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

        for (Closeable c : closeables) {

            try {

                c.close();

            } catch (IOException ignored) { }

        }

    }

    public static void close(Throwable t, Closeable... closeables) {

        for (Closeable c : closeables) {

            try {

                ExceptionallyCloseable.close(t, c);

            } catch (IOException ignored) { }

        }

    }

    /**

     * Returns an array with the same buffers, but starting at position zero

     * in the array.

     */

    public static ByteBuffer[] reduce(ByteBuffer[] bufs, int start, int number) {

        if (start == 0 && number == bufs.length) {

            return bufs;

        }

        ByteBuffer[] nbufs = new ByteBuffer[number];

        int j = 0;

        for (int i=start; i<start+number; i++) {

            nbufs[j++] = bufs[i];

        }

        return nbufs;

    }

    static String asString(ByteBuffer buf) {

        byte[] b = new byte[buf.remaining()];

        buf.get(b);

        return new String(b, StandardCharsets.US_ASCII);

    }

    /**

     * Returns a single threaded executor which uses one invocation

     * of the parent executor to execute tasks (in sequence).

     *

     * Use a null valued Runnable to terminate.

     */

    // TODO: this is a blocking way of doing this;

    public static Executor singleThreadExecutor(Executor parent) {

        BlockingQueue<Optional<Runnable>> queue = new LinkedBlockingQueue<>();

        parent.execute(() -> {

            while (true) {

                try {

                    Optional<Runnable> o = queue.take();

                    if (!o.isPresent()) {

                        return;

                    }

                    o.get().run();

                } catch (InterruptedException ex) {

                    return;

                }

            }

        });

        return new Executor() {

            @Override

            public void execute(Runnable command) {

                queue.offer(Optional.ofNullable(command));

            }

        };

    }

    private static void executeInline(Runnable r) {

        r.run();

    }

    static Executor callingThreadExecutor() {

        return Utils::executeInline;

    }

    // Put all these static 'empty' singletons here

    @SuppressWarnings("rawtypes")

    public static final CompletableFuture[] EMPTY_CFARRAY = new CompletableFuture[0];

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

    public static final ByteBuffer[] EMPTY_BB_ARRAY = new ByteBuffer[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 encoding = headers.firstValue("Content-encoding")

                .orElse("UTF_8");

        try {

            return Charset.forName(encoding);

        } catch (IllegalArgumentException e) {

            return StandardCharsets.UTF_8;

        }

    }

    public static UncheckedIOException unchecked(IOException e) {

        return new UncheckedIOException(e);

    }

}