/*
 * Copyright 2015 The Netty Project
 *
 * The Netty Project licenses this file to you 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 io.netty.handler.codec.http;

import io.netty.util.AsciiString;
import io.netty.util.CharsetUtil;
import io.netty.util.NetUtil;

import java.net.InetSocketAddress;
import java.net.URI;
import java.util.ArrayList;
import java.nio.charset.Charset;
import java.nio.charset.UnsupportedCharsetException;
import java.util.Iterator;
import java.util.List;

/**
 * Utility methods useful in the HTTP context.
 */
public final class HttpUtil {

    private static final AsciiString CHARSET_EQUALS = AsciiString.of(HttpHeaderValues.CHARSET + "=");
    private static final AsciiString SEMICOLON = AsciiString.cached(";");

    private HttpUtil() { }

    /**
     * Determine if a uri is in origin-form according to
     * <a href="https://tools.ietf.org/html/rfc7230#section-5.3">rfc7230, 5.3</a>.
     */
    public static boolean isOriginForm(URI uri) {
        return uri.getScheme() == null && uri.getSchemeSpecificPart() == null &&
               uri.getHost() == null && uri.getAuthority() == null;
    }

    /**
     * Determine if a uri is in asterisk-form according to
     * <a href="https://tools.ietf.org/html/rfc7230#section-5.3">rfc7230, 5.3</a>.
     */
    public static boolean isAsteriskForm(URI uri) {
        return "*".equals(uri.getPath()) &&
                uri.getScheme() == null && uri.getSchemeSpecificPart() == null &&
                uri.getHost() == null && uri.getAuthority() == null && uri.getQuery() == null &&
                uri.getFragment() == null;
    }

    /**
     * Returns {@code true} if and only if the connection can remain open and
     * thus 'kept alive'.  This methods respects the value of the.
     * {@code "Connection"} header first and then the return value of
     * {@link HttpVersion#isKeepAliveDefault()}.
     */
    public static boolean isKeepAlive(HttpMessage message) {
        CharSequence connection = message.headers().get(HttpHeaderNames.CONNECTION);
        if (connection != null && HttpHeaderValues.CLOSE.contentEqualsIgnoreCase(connection)) {
            return false;
        }

        if (message.protocolVersion().isKeepAliveDefault()) {
            return !HttpHeaderValues.CLOSE.contentEqualsIgnoreCase(connection);
        } else {
            return HttpHeaderValues.KEEP_ALIVE.contentEqualsIgnoreCase(connection);
        }
    }

    /**
     * Sets the value of the {@code "Connection"} header depending on the
     * protocol version of the specified message. This getMethod sets or removes
     * the {@code "Connection"} header depending on what the default keep alive
     * mode of the message's protocol version is, as specified by
     * {@link HttpVersion#isKeepAliveDefault()}.
     * <ul>
     * <li>If the connection is kept alive by default:
     *     <ul>
     *     <li>set to {@code "close"} if {@code keepAlive} is {@code false}.</li>
     *     <li>remove otherwise.</li>
     *     </ul></li>
     * <li>If the connection is closed by default:
     *     <ul>
     *     <li>set to {@code "keep-alive"} if {@code keepAlive} is {@code true}.</li>
     *     <li>remove otherwise.</li>
     *     </ul></li>
     * </ul>
     * @see #setKeepAlive(HttpHeaders, HttpVersion, boolean)
     */
    public static void setKeepAlive(HttpMessage message, boolean keepAlive) {
        setKeepAlive(message.headers(), message.protocolVersion(), keepAlive);
    }

    /**
     * Sets the value of the {@code "Connection"} header depending on the
     * protocol version of the specified message. This getMethod sets or removes
     * the {@code "Connection"} header depending on what the default keep alive
     * mode of the message's protocol version is, as specified by
     * {@link HttpVersion#isKeepAliveDefault()}.
     * <ul>
     * <li>If the connection is kept alive by default:
     *     <ul>
     *     <li>set to {@code "close"} if {@code keepAlive} is {@code false}.</li>
     *     <li>remove otherwise.</li>
     *     </ul></li>
     * <li>If the connection is closed by default:
     *     <ul>
     *     <li>set to {@code "keep-alive"} if {@code keepAlive} is {@code true}.</li>
     *     <li>remove otherwise.</li>
     *     </ul></li>
     * </ul>
     */
    public static void setKeepAlive(HttpHeaders h, HttpVersion httpVersion, boolean keepAlive) {
        if (httpVersion.isKeepAliveDefault()) {
            if (keepAlive) {
                h.remove(HttpHeaderNames.CONNECTION);
            } else {
                h.set(HttpHeaderNames.CONNECTION, HttpHeaderValues.CLOSE);
            }
        } else {
            if (keepAlive) {
                h.set(HttpHeaderNames.CONNECTION, HttpHeaderValues.KEEP_ALIVE);
            } else {
                h.remove(HttpHeaderNames.CONNECTION);
            }
        }
    }

    /**
     * Returns the length of the content. Please note that this value is
     * not retrieved from {@link HttpContent#content()} but from the
     * {@code "Content-Length"} header, and thus they are independent from each
     * other.
     *
     * @return the content length
     *
     * @throws NumberFormatException
     *         if the message does not have the {@code "Content-Length"} header
     *         or its value is not a number
     */
    public static long getContentLength(HttpMessage message) {
        String value = message.headers().get(HttpHeaderNames.CONTENT_LENGTH);
        if (value != null) {
            return Long.parseLong(value);
        }

        // We know the content length if it's a Web Socket message even if
        // Content-Length header is missing.
        long webSocketContentLength = getWebSocketContentLength(message);
        if (webSocketContentLength >= 0) {
            return webSocketContentLength;
        }

        // Otherwise we don't.
        throw new NumberFormatException("header not found: " + HttpHeaderNames.CONTENT_LENGTH);
    }

    /**
     * Returns the length of the content or the specified default value if the message does not have the {@code
     * "Content-Length" header}. Please note that this value is not retrieved from {@link HttpContent#content()} but
     * from the {@code "Content-Length"} header, and thus they are independent from each other.
     *
     * @param message      the message
     * @param defaultValue the default value
     * @return the content length or the specified default value
     * @throws NumberFormatException if the {@code "Content-Length"} header does not parse as a long
     */
    public static long getContentLength(HttpMessage message, long defaultValue) {
        String value = message.headers().get(HttpHeaderNames.CONTENT_LENGTH);
        if (value != null) {
            return Long.parseLong(value);
        }

        // We know the content length if it's a Web Socket message even if
        // Content-Length header is missing.
        long webSocketContentLength = getWebSocketContentLength(message);
        if (webSocketContentLength >= 0) {
            return webSocketContentLength;
        }

        // Otherwise we don't.
        return defaultValue;
    }

    /**
     * Get an {@code int} representation of {@link #getContentLength(HttpMessage, long)}.
     * @return the content length or {@code defaultValue} if this message does
     *         not have the {@code "Content-Length"} header or its value is not
     *         a number. Not to exceed the boundaries of integer.
     */
    public static int getContentLength(HttpMessage message, int defaultValue) {
        return (int) Math.min(Integer.MAX_VALUE, getContentLength(message, (long) defaultValue));
    }

    /**
     * Returns the content length of the specified web socket message. If the
     * specified message is not a web socket message, {@code -1} is returned.
     */
    private static int getWebSocketContentLength(HttpMessage message) {
        // WebSocket messages have constant content-lengths.
        HttpHeaders h = message.headers();
        if (message instanceof HttpRequest) {
            HttpRequest req = (HttpRequest) message;
            if (HttpMethod.GET.equals(req.method()) &&
                    h.contains(HttpHeaderNames.SEC_WEBSOCKET_KEY1) &&
                    h.contains(HttpHeaderNames.SEC_WEBSOCKET_KEY2)) {
                return 8;
            }
        } else if (message instanceof HttpResponse) {
            HttpResponse res = (HttpResponse) message;
            if (res.status().code() == 101 &&
                    h.contains(HttpHeaderNames.SEC_WEBSOCKET_ORIGIN) &&
                    h.contains(HttpHeaderNames.SEC_WEBSOCKET_LOCATION)) {
                return 16;
            }
        }

        // Not a web socket message
        return -1;
    }

    /**
     * Sets the {@code "Content-Length"} header.
     */
    public static void setContentLength(HttpMessage message, long length) {
        message.headers().set(HttpHeaderNames.CONTENT_LENGTH, length);
    }

    public static boolean isContentLengthSet(HttpMessage m) {
        return m.headers().contains(HttpHeaderNames.CONTENT_LENGTH);
    }

    /**
     * Returns {@code true} if and only if the specified message contains an expect header and the only expectation
     * present is the 100-continue expectation. Note that this method returns {@code false} if the expect header is
     * not valid for the message (e.g., the message is a response, or the version on the message is HTTP/1.0).
     *
     * @param message the message
     * @return {@code true} if and only if the expectation 100-continue is present and it is the only expectation
     * present
     */
    public static boolean is100ContinueExpected(HttpMessage message) {
        if (!isExpectHeaderValid(message)) {
            return false;
        }

        final String expectValue = message.headers().get(HttpHeaderNames.EXPECT);
        // unquoted tokens in the expect header are case-insensitive, thus 100-continue is case insensitive
        return HttpHeaderValues.CONTINUE.toString().equalsIgnoreCase(expectValue);
    }

    /**
     * Returns {@code true} if the specified message contains an expect header specifying an expectation that is not
     * supported. Note that this method returns {@code false} if the expect header is not valid for the message
     * (e.g., the message is a response, or the version on the message is HTTP/1.0).
     *
     * @param message the message
     * @return {@code true} if and only if an expectation is present that is not supported
     */
    static boolean isUnsupportedExpectation(HttpMessage message) {
        if (!isExpectHeaderValid(message)) {
            return false;
        }

        final String expectValue = message.headers().get(HttpHeaderNames.EXPECT);
        return expectValue != null && !HttpHeaderValues.CONTINUE.toString().equalsIgnoreCase(expectValue);
    }

    private static boolean isExpectHeaderValid(final HttpMessage message) {
        /*
         * Expect: 100-continue is for requests only and it works only on HTTP/1.1 or later. Note further that RFC 7231
         * section 5.1.1 says "A server that receives a 100-continue expectation in an HTTP/1.0 request MUST ignore
         * that expectation."
         */
        return message instanceof HttpRequest &&
                message.protocolVersion().compareTo(HttpVersion.HTTP_1_1) >= 0;
    }

    /**
     * Sets or removes the {@code "Expect: 100-continue"} header to / from the
     * specified message. If {@code expected} is {@code true},
     * the {@code "Expect: 100-continue"} header is set and all other previous
     * {@code "Expect"} headers are removed.  Otherwise, all {@code "Expect"}
     * headers are removed completely.
     */
    public static void set100ContinueExpected(HttpMessage message, boolean expected) {
        if (expected) {
            message.headers().set(HttpHeaderNames.EXPECT, HttpHeaderValues.CONTINUE);
        } else {
            message.headers().remove(HttpHeaderNames.EXPECT);
        }
    }

    /**
     * Checks to see if the transfer encoding in a specified {@link HttpMessage} is chunked
     *
     * @param message The message to check
     * @return True if transfer encoding is chunked, otherwise false
     */
    public static boolean isTransferEncodingChunked(HttpMessage message) {
        return message.headers().contains(HttpHeaderNames.TRANSFER_ENCODING, HttpHeaderValues.CHUNKED, true);
    }

    /**
     * Set the {@link HttpHeaderNames#TRANSFER_ENCODING} to either include {@link HttpHeaderValues#CHUNKED} if
     * {@code chunked} is {@code true}, or remove {@link HttpHeaderValues#CHUNKED} if {@code chunked} is {@code false}.
     * @param m The message which contains the headers to modify.
     * @param chunked if {@code true} then include {@link HttpHeaderValues#CHUNKED} in the headers. otherwise remove
     * {@link HttpHeaderValues#CHUNKED} from the headers.
     */
    public static void setTransferEncodingChunked(HttpMessage m, boolean chunked) {
        if (chunked) {
            m.headers().set(HttpHeaderNames.TRANSFER_ENCODING, HttpHeaderValues.CHUNKED);
            m.headers().remove(HttpHeaderNames.CONTENT_LENGTH);
        } else {
            List<String> encodings = m.headers().getAll(HttpHeaderNames.TRANSFER_ENCODING);
            if (encodings.isEmpty()) {
                return;
            }
            List<CharSequence> values = new ArrayList<CharSequence>(encodings);
            Iterator<CharSequence> valuesIt = values.iterator();
            while (valuesIt.hasNext()) {
                CharSequence value = valuesIt.next();
                if (HttpHeaderValues.CHUNKED.contentEqualsIgnoreCase(value)) {
                    valuesIt.remove();
                }
            }
            if (values.isEmpty()) {
                m.headers().remove(HttpHeaderNames.TRANSFER_ENCODING);
            } else {
                m.headers().set(HttpHeaderNames.TRANSFER_ENCODING, values);
            }
        }
    }

    /**
     * Fetch charset from message's Content-Type header.
     *
     * @param message entity to fetch Content-Type header from
     * @return the charset from message's Content-Type header or {@link CharsetUtil#ISO_8859_1}
     * if charset is not presented or unparsable
     */
    public static Charset getCharset(HttpMessage message) {
        return getCharset(message, CharsetUtil.ISO_8859_1);
    }

    /**
     * Fetch charset from Content-Type header value.
     *
     * @param contentTypeValue Content-Type header value to parse
     * @return the charset from message's Content-Type header or {@link CharsetUtil#ISO_8859_1}
     * if charset is not presented or unparsable
     */
    public static Charset getCharset(CharSequence contentTypeValue) {
        if (contentTypeValue != null) {
            return getCharset(contentTypeValue, CharsetUtil.ISO_8859_1);
        } else {
            return CharsetUtil.ISO_8859_1;
        }
    }

    /**
     * Fetch charset from message's Content-Type header.
     *
     * @param message entity to fetch Content-Type header from
     * @param defaultCharset result to use in case of empty, incorrect or doesn't contain required part header value
     * @return the charset from message's Content-Type header or {@code defaultCharset}
     * if charset is not presented or unparsable
     */
    public static Charset getCharset(HttpMessage message, Charset defaultCharset) {
        CharSequence contentTypeValue = message.headers().get(HttpHeaderNames.CONTENT_TYPE);
        if (contentTypeValue != null) {
            return getCharset(contentTypeValue, defaultCharset);
        } else {
            return defaultCharset;
        }
    }

    /**
     * Fetch charset from Content-Type header value.
     *
     * @param contentTypeValue Content-Type header value to parse
     * @param defaultCharset result to use in case of empty, incorrect or doesn't contain required part header value
     * @return the charset from message's Content-Type header or {@code defaultCharset}
     * if charset is not presented or unparsable
     */
    public static Charset getCharset(CharSequence contentTypeValue, Charset defaultCharset) {
        if (contentTypeValue != null) {
            CharSequence charsetCharSequence = getCharsetAsSequence(contentTypeValue);
            if (charsetCharSequence != null) {
                try {
                    return Charset.forName(charsetCharSequence.toString());
                } catch (UnsupportedCharsetException ignored) {
                    return defaultCharset;
                }
            } else {
                return defaultCharset;
            }
        } else {
            return defaultCharset;
        }
    }

    /**
     * Fetch charset from message's Content-Type header as a char sequence.
     *
     * A lot of sites/possibly clients have charset="CHARSET", for example charset="utf-8". Or "utf8" instead of "utf-8"
     * This is not according to standard, but this method provide an ability to catch desired mistakes manually in code
     *
     * @param message entity to fetch Content-Type header from
     * @return the {@code CharSequence} with charset from message's Content-Type header
     * or {@code null} if charset is not presented
     * @deprecated use {@link #getCharsetAsSequence(HttpMessage)}
     */
    @Deprecated
    public static CharSequence getCharsetAsString(HttpMessage message) {
        return getCharsetAsSequence(message);
    }

    /**
     * Fetch charset from message's Content-Type header as a char sequence.
     *
     * A lot of sites/possibly clients have charset="CHARSET", for example charset="utf-8". Or "utf8" instead of "utf-8"
     * This is not according to standard, but this method provide an ability to catch desired mistakes manually in code
     *
     * @return the {@code CharSequence} with charset from message's Content-Type header
     * or {@code null} if charset is not presented
     */
    public static CharSequence getCharsetAsSequence(HttpMessage message) {
        CharSequence contentTypeValue = message.headers().get(HttpHeaderNames.CONTENT_TYPE);
        if (contentTypeValue != null) {
            return getCharsetAsSequence(contentTypeValue);
        } else {
            return null;
        }
    }

    /**
     * Fetch charset from Content-Type header value as a char sequence.
     *
     * A lot of sites/possibly clients have charset="CHARSET", for example charset="utf-8". Or "utf8" instead of "utf-8"
     * This is not according to standard, but this method provide an ability to catch desired mistakes manually in code
     *
     * @param contentTypeValue Content-Type header value to parse
     * @return the {@code CharSequence} with charset from message's Content-Type header
     * or {@code null} if charset is not presented
     * @throws NullPointerException in case if {@code contentTypeValue == null}
     */
    public static CharSequence getCharsetAsSequence(CharSequence contentTypeValue) {
        if (contentTypeValue == null) {
            throw new NullPointerException("contentTypeValue");
        }
        int indexOfCharset = AsciiString.indexOfIgnoreCaseAscii(contentTypeValue, CHARSET_EQUALS, 0);
        if (indexOfCharset != AsciiString.INDEX_NOT_FOUND) {
            int indexOfEncoding = indexOfCharset + CHARSET_EQUALS.length();
            if (indexOfEncoding < contentTypeValue.length()) {
                return contentTypeValue.subSequence(indexOfEncoding, contentTypeValue.length());
            }
        }
        return null;
    }

    /**
     * Fetch MIME type part from message's Content-Type header as a char sequence.
     *
     * @param message entity to fetch Content-Type header from
     * @return the MIME type as a {@code CharSequence} from message's Content-Type header
     * or {@code null} if content-type header or MIME type part of this header are not presented
     * <p/>
     * "content-type: text/html; charset=utf-8" - "text/html" will be returned <br/>
     * "content-type: text/html" - "text/html" will be returned <br/>
     * "content-type: " or no header - {@code null} we be returned
     */
    public static CharSequence getMimeType(HttpMessage message) {
        CharSequence contentTypeValue = message.headers().get(HttpHeaderNames.CONTENT_TYPE);
        if (contentTypeValue != null) {
            return getMimeType(contentTypeValue);
        } else {
            return null;
        }
    }

    /**
     * Fetch MIME type part from Content-Type header value as a char sequence.
     *
     * @param contentTypeValue Content-Type header value to parse
     * @return the MIME type as a {@code CharSequence} from message's Content-Type header
     * or {@code null} if content-type header or MIME type part of this header are not presented
     * <p/>
     * "content-type: text/html; charset=utf-8" - "text/html" will be returned <br/>
     * "content-type: text/html" - "text/html" will be returned <br/>
     * "content-type: empty header - {@code null} we be returned
     * @throws NullPointerException in case if {@code contentTypeValue == null}
     */
    public static CharSequence getMimeType(CharSequence contentTypeValue) {
        if (contentTypeValue == null) {
            throw new NullPointerException("contentTypeValue");
        }

        int indexOfSemicolon = AsciiString.indexOfIgnoreCaseAscii(contentTypeValue, SEMICOLON, 0);
        if (indexOfSemicolon != AsciiString.INDEX_NOT_FOUND) {
            return contentTypeValue.subSequence(0, indexOfSemicolon);
        } else {
            return contentTypeValue.length() > 0 ? contentTypeValue : null;
        }
    }

    /**
     * Formats the host string of an address so it can be used for computing an HTTP component
     * such as an URL or a Host header
     * @param addr the address
     * @return the formatted String
     */
    public static String formatHostnameForHttp(InetSocketAddress addr) {
        String hostString = NetUtil.getHostname(addr);
        if (NetUtil.isValidIpV6Address(hostString)) {
            if (!addr.isUnresolved()) {
                hostString = NetUtil.toAddressString(addr.getAddress());
            }
            return "[" + hostString + "]";
        }
        return hostString;
    }
}
