/*
 * Copyright (c) 2010, 2020 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0, which is available at
 * http://www.eclipse.org/legal/epl-2.0.
 *
 * This Source Code may also be made available under the following Secondary
 * Licenses when the conditions for such availability set forth in the
 * Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
 * version 2 with the GNU Classpath Exception, which is available at
 * https://www.gnu.org/software/classpath/license.html.
 *
 * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 */

package org.glassfish.jersey.message.internal;

import java.util.Collections;
import java.util.Comparator;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.logging.Level;
import java.util.logging.Logger;
import java.util.stream.Collectors;

import javax.ws.rs.core.AbstractMultivaluedMap;
import javax.ws.rs.core.Configuration;
import javax.ws.rs.core.MultivaluedMap;
import javax.ws.rs.core.NewCookie;
import javax.ws.rs.ext.RuntimeDelegate;
import javax.ws.rs.ext.RuntimeDelegate.HeaderDelegate;

import org.glassfish.jersey.internal.RuntimeDelegateDecorator;
import org.glassfish.jersey.internal.LocalizationMessages;
import org.glassfish.jersey.internal.util.collection.ImmutableMultivaluedMap;
import org.glassfish.jersey.internal.util.collection.StringKeyIgnoreCaseMultivaluedMap;
import org.glassfish.jersey.internal.util.collection.Views;

Utility class supporting the processing of message headers.
Author:
Marek Potociar, Michal Gajdos, Libor Kramolis/**
 * Utility class supporting the processing of message headers.
 *
 * @author Marek Potociar
 * @author Michal Gajdos
 * @author Libor Kramolis
 */
public final class HeaderUtils {

    private static final Logger LOGGER = Logger.getLogger(HeaderUtils.class.getName());

    
Create an empty inbound message headers container. Created container is mutable.
Returns:
a new empty mutable container for storing inbound message headers./**
     * Create an empty inbound message headers container. Created container is mutable.
     *
     * @return a new empty mutable container for storing inbound message headers.
     */
    public static AbstractMultivaluedMap<String, String> createInbound() {
        return new StringKeyIgnoreCaseMultivaluedMap<String>();
    }

    
Get immutable empty message headers container. The factory method can be
used to for both message header container types  –  inbound
as well as outbound.
Type parameters:
<V> – header value type. Typically Object in case of the outbound headers and String in case of the inbound headers.
Returns:
an immutable empty message headers container./**
     * Get immutable empty message headers container. The factory method can be
     * used to for both message header container types&nbsp;&nbsp;&ndash;&nbsp;&nbsp;inbound
     * as well as outbound.
     *
     * @param <V> header value type. Typically {@link Object} in case of the outbound
     *            headers and {@link String} in case of the inbound headers.
     * @return an immutable empty message headers container.
     */
    public static <V> MultivaluedMap<String, V> empty() {
        return ImmutableMultivaluedMap.empty();
    }

    
Create an empty outbound message headers container. Created container is mutable.
Returns:
a new empty mutable container for storing outbound message headers./**
     * Create an empty outbound message headers container. Created container is mutable.
     *
     * @return a new empty mutable container for storing outbound message headers.
     */
    public static AbstractMultivaluedMap<String, Object> createOutbound() {
        return new StringKeyIgnoreCaseMultivaluedMap<Object>();
    }

    
Convert a message header value, represented as a general object, to it's string representation. If the supplied header value is null, this method returns null. 
 This method defers to RuntimeDelegate.createHeaderDelegate to obtain a HeaderDelegate or HeaderDelegateProvider to convert the value to a String. If neither is found then the toString() method on the header object is utilized. 
Params:
headerValue – the header value represented as an object.
rd –  runtime delegate instance to be used for header delegate retrieval. If null, a default RuntimeDelegate instance will be obtained and used.
Returns:
the string representation of the supplied header value or null if the supplied header value is null./**
     * Convert a message header value, represented as a general object, to it's
     * string representation. If the supplied header value is {@code null},
     * this method returns {@code null}.
     * <p>
     * This method defers to {@link RuntimeDelegate#createHeaderDelegate} to
     * obtain a {@link HeaderDelegate} or {@link org.glassfish.jersey.spi.HeaderDelegateProvider}
     * to convert the value to a {@code String}.
     * If neither is found then the {@code toString()}
     * method on the header object is utilized.
     *
     * @param headerValue the header value represented as an object.
     * @param rd          runtime delegate instance to be used for header delegate
     *                    retrieval. If {@code null}, a default {@code RuntimeDelegate}
     *                    instance will be {@link RuntimeDelegate#getInstance() obtained} and
     *                    used.
     * @return the string representation of the supplied header value or {@code null}
     *         if the supplied header value is {@code null}.
     */
    @SuppressWarnings("unchecked")
    private static String asString(final Object headerValue, RuntimeDelegate rd) {
        if (headerValue == null) {
            return null;
        }
        if (headerValue instanceof String) {
            return (String) headerValue;
        }
        if (rd == null) {
            rd = RuntimeDelegate.getInstance();
        }

        final HeaderDelegate hp = rd.createHeaderDelegate(headerValue.getClass());
        return (hp != null) ? hp.toString(headerValue) : headerValue.toString();
    }

    
Convert a message header value, represented as a general object, to it's string representation. If the supplied header value is null, this method returns null. 
 This method defers to RuntimeDelegate.createHeaderDelegate to obtain a HeaderDelegate or HeaderDelegateProvider to convert the value to a String. If neither is found then the toString() method on the header object is utilized. 
Params:
headerValue –   the header value represented as an object.
configuration – the Configuration that may contain CommonProperties.METAINF_SERVICES_LOOKUP_DISABLE property preventing the HeaderDelegateProvider to be used by the default RuntimeDelegate instance.
Returns:
the string representation of the supplied header value or null if the supplied header value is null./**
     * Convert a message header value, represented as a general object, to it's
     * string representation. If the supplied header value is {@code null},
     * this method returns {@code null}.
     * <p>
     * This method defers to {@link RuntimeDelegate#createHeaderDelegate} to
     * obtain a {@link HeaderDelegate} or {@link org.glassfish.jersey.spi.HeaderDelegateProvider}
     * to convert the value to a {@code String}.
     * If neither is found then the {@code toString()}
     * method on the header object is utilized.
     *
     * @param headerValue   the header value represented as an object.
     * @param configuration the {@link Configuration} that may contain
     *                      {@link org.glassfish.jersey.CommonProperties#METAINF_SERVICES_LOOKUP_DISABLE}
     *                      property preventing the {@link org.glassfish.jersey.spi.HeaderDelegateProvider}
     *                      to be used by the default {@code RuntimeDelegate} {@link RuntimeDelegate#getInstance() instance}.
     * @return the string representation of the supplied header value or {@code null}
     *         if the supplied header value is {@code null}.
     */
    public static String asString(final Object headerValue, Configuration configuration) {
        return asString(headerValue, RuntimeDelegateDecorator.configured(configuration));
    }

    
Returns string view of list of header values. Any modifications to the underlying list are visible to the view,
the view also supports removal of elements. Does not support other modifications.
Params:
headerValues – header values.
rd –  RuntimeDelegate instance or null (in that case RuntimeDelegate.getInstance() will be called for before element conversion.
Returns:
String view of header values./**
     * Returns string view of list of header values. Any modifications to the underlying list are visible to the view,
     * the view also supports removal of elements. Does not support other modifications.
     *
     * @param headerValues header values.
     * @param rd           RuntimeDelegate instance or {@code null} (in that case {@link RuntimeDelegate#getInstance()}
     *                     will be called for before element conversion.
     * @return String view of header values.
     */
    private static List<String> asStringList(final List<Object> headerValues, final RuntimeDelegate rd) {
        if (headerValues == null || headerValues.isEmpty()) {
            return Collections.emptyList();
        }

        return Views.listView(headerValues, input -> (input == null)
                ? "[null]"
                : HeaderUtils.asString(input, rd));
    }

    
Returns string view of list of header values. Any modifications to the underlying list are visible to the view,
the view also supports removal of elements. Does not support other modifications.
Params:
headerValues – header values.
configuration – the Configuration that may contain CommonProperties.METAINF_SERVICES_LOOKUP_DISABLE property preventing the HeaderDelegateProvider to be used by the default RuntimeDelegate instance.
Returns:
String view of header values./**
     * Returns string view of list of header values. Any modifications to the underlying list are visible to the view,
     * the view also supports removal of elements. Does not support other modifications.
     *
     * @param headerValues header values.
     * @param configuration the {@link Configuration} that may contain
     *                      {@link org.glassfish.jersey.CommonProperties#METAINF_SERVICES_LOOKUP_DISABLE}
     *                      property preventing the {@link org.glassfish.jersey.spi.HeaderDelegateProvider}
     *                      to be used by the default {@code RuntimeDelegate} {@link RuntimeDelegate#getInstance() instance}.
     * @return String view of header values.
     */
    public static List<String> asStringList(final List<Object> headerValues, final Configuration configuration) {
        return asStringList(headerValues, RuntimeDelegateDecorator.configured(configuration));
    }

    
Returns string view of passed headers. Any modifications to the headers are visible to the view, the view also
supports removal of elements. Does not support other modifications.
Params:
headers – headers.
configuration – the Configuration that may contain CommonProperties.METAINF_SERVICES_LOOKUP_DISABLE property preventing the HeaderDelegateProvider to be used by the default RuntimeDelegate instance.
Returns:
String view of headers or null if {code headers} input parameter is null./**
     * Returns string view of passed headers. Any modifications to the headers are visible to the view, the view also
     * supports removal of elements. Does not support other modifications.
     *
     * @param headers headers.
     * @param configuration the {@link Configuration} that may contain
     *                      {@link org.glassfish.jersey.CommonProperties#METAINF_SERVICES_LOOKUP_DISABLE}
     *                      property preventing the {@link org.glassfish.jersey.spi.HeaderDelegateProvider}
     *                      to be used by the default {@code RuntimeDelegate} {@link RuntimeDelegate#getInstance() instance}.
     * @return String view of headers or {@code null} if {code headers} input parameter is {@code null}.
     */
    public static MultivaluedMap<String, String> asStringHeaders(
            final MultivaluedMap<String, Object> headers, Configuration configuration) {
        if (headers == null) {
            return null;
        }

        final RuntimeDelegate rd = RuntimeDelegateDecorator.configured(configuration);
        return new AbstractMultivaluedMap<String, String>(
                Views.mapView(headers, input -> HeaderUtils.asStringList(input, rd))
        ) {
        };
    }

    
Transforms multi value map of headers to single String value map. Returned map is immutable. Map values are formatted using method asHeaderString(List<Object>, RuntimeDelegate). 
Params:
headers – headers to be formatted
configuration – the Configuration that may contain CommonProperties.METAINF_SERVICES_LOOKUP_DISABLE property preventing the HeaderDelegateProvider to be used by the default RuntimeDelegate instance.
Returns:
immutable single String value map or null if headers input parameter is null./**
     * Transforms multi value map of headers to single {@code String} value map.
     *
     * Returned map is immutable. Map values are formatted using method {@link #asHeaderString(List, RuntimeDelegate)}.
     *
     * @param headers headers to be formatted
     * @param configuration the {@link Configuration} that may contain
     *                      {@link org.glassfish.jersey.CommonProperties#METAINF_SERVICES_LOOKUP_DISABLE}
     *                      property preventing the {@link org.glassfish.jersey.spi.HeaderDelegateProvider}
     *                      to be used by the default {@code RuntimeDelegate} {@link RuntimeDelegate#getInstance() instance}.
     * @return immutable single {@code String} value map or
     *      {@code null} if {@code headers} input parameter is {@code null}.
     */
    public static Map<String, String> asStringHeadersSingleValue(
            final MultivaluedMap<String, Object> headers, Configuration configuration) {
        if (headers == null) {
            return null;
        }

        final RuntimeDelegate rd = RuntimeDelegateDecorator.configured(configuration);
        return Collections.unmodifiableMap(headers.entrySet().stream()
                                           .collect(Collectors.toMap(
                                                   Map.Entry::getKey,
                                                   entry -> asHeaderString(entry.getValue(), rd))));
    }

    
Converts a list of message header values to a single string value (with individual values separated by ','). Each single header value is converted to String using a HeaderDelegate if one is available via RuntimeDelegate.createHeaderDelegate(Class<Object>) for the header value class or using its toString() method if a header delegate is not available. 
Params:
values – list of individual header values.
rd –  RuntimeDelegate instance or null (in that case RuntimeDelegate.getInstance() will be called for before conversion of elements).
Returns:
single string consisting of all the values passed in as a parameter. If values parameter is null, null is returned. If the list of values is empty, an empty string is returned./**
     * Converts a list of message header values to a single string value (with individual values separated by
     * {@code ','}).
     *
     * Each single header value is converted to String using a
     * {@link javax.ws.rs.ext.RuntimeDelegate.HeaderDelegate} if one is available
     * via {@link javax.ws.rs.ext.RuntimeDelegate#createHeaderDelegate(java.lang.Class)}
     * for the header value class or using its {@code toString()} method if a header
     * delegate is not available.
     *
     * @param values list of individual header values.
     * @param rd     {@link RuntimeDelegate} instance or {@code null} (in that case {@link RuntimeDelegate#getInstance()}
     *               will be called for before conversion of elements).
     * @return single string consisting of all the values passed in as a parameter. If values parameter is {@code null},
     *         {@code null} is returned. If the list of values is empty, an empty string is returned.
     */
    public static String asHeaderString(final List<Object> values, final RuntimeDelegate rd) {
        if (values == null) {
            return null;
        }
        final Iterator<String> stringValues = asStringList(values, rd).iterator();
        if (!stringValues.hasNext()) {
            return "";
        }

        final StringBuilder buffer = new StringBuilder(stringValues.next());
        while (stringValues.hasNext()) {
            buffer.append(',').append(stringValues.next());
        }

        return buffer.toString();
    }

    
Compares two snapshots of headers from jersey ClientRequest and logs WARNING in case of difference. Current container implementations does not support header modification in WriterInterceptor and MessageBodyWriter. The method checks there are some newly added headers (probably by WI or MBW) and logs WARNING message about it. 
Params:
headersSnapshot – first immutable snapshot of headers
currentHeaders –  current instance of headers tobe compared to
connectorName –   name of connector the method is invoked from, used just in logged message
configuration – the Configuration that may contain CommonProperties.METAINF_SERVICES_LOOKUP_DISABLE property preventing the HeaderDelegateProvider to be used by the default RuntimeDelegate instance.
See Also:
JERSEY-2341/**
     * Compares two snapshots of headers from jersey {@code ClientRequest} and logs {@code WARNING} in case of difference.
     *
     * Current container implementations does not support header modification in {@link javax.ws.rs.ext.WriterInterceptor}
     * and {@link javax.ws.rs.ext.MessageBodyWriter}. The method checks there are some newly added headers
     * (probably by WI or MBW) and logs {@code WARNING} message about it.
     *
     * @param headersSnapshot first immutable snapshot of headers
     * @param currentHeaders  current instance of headers tobe compared to
     * @param connectorName   name of connector the method is invoked from, used just in logged message
     * @param configuration the {@link Configuration} that may contain
     *                      {@link org.glassfish.jersey.CommonProperties#METAINF_SERVICES_LOOKUP_DISABLE}
     *                      property preventing the {@link org.glassfish.jersey.spi.HeaderDelegateProvider}
     *                      to be used by the default {@code RuntimeDelegate} {@link RuntimeDelegate#getInstance() instance}.
     * @see <a href="https://java.net/jira/browse/JERSEY-2341">JERSEY-2341</a>
     */
    public static void checkHeaderChanges(final Map<String, String> headersSnapshot,
                                          final MultivaluedMap<String, Object> currentHeaders,
                                          final String connectorName,
                                          final Configuration configuration) {
        if (HeaderUtils.LOGGER.isLoggable(Level.WARNING)) {
            final RuntimeDelegate rd = RuntimeDelegateDecorator.configured(configuration);
            final Set<String> changedHeaderNames = new HashSet<String>();
            for (final Map.Entry<? extends String, ? extends List<Object>> entry : currentHeaders.entrySet()) {
                if (!headersSnapshot.containsKey(entry.getKey())) {
                    changedHeaderNames.add(entry.getKey());
                } else {
                    final String prevValue = headersSnapshot.get(entry.getKey());
                    final String newValue = asHeaderString(currentHeaders.get(entry.getKey()), rd);
                    if (!prevValue.equals(newValue)) {
                        changedHeaderNames.add(entry.getKey());
                    }
                }
            }
            if (!changedHeaderNames.isEmpty()) {
                if (HeaderUtils.LOGGER.isLoggable(Level.WARNING)) {
                    HeaderUtils.LOGGER.warning(LocalizationMessages.SOME_HEADERS_NOT_SENT(connectorName,
                            changedHeaderNames.toString()));
                }
            }
        }
    }

    
Compare two NewCookies having the same name. See documentation RFC.
Params:
first –    NewCookie to be compared.
second – NewCookie to be compared.
Returns:
the preferred NewCookie according to rules :
             - the latest maxAge.
             - if equal, compare the expiry date
             - if equal, compare name length/**
     * Compare two NewCookies having the same name. See documentation RFC.
     *
     * @param first    NewCookie to be compared.
     * @param second NewCookie to be compared.
     * @return the preferred NewCookie according to rules :
     *              - the latest maxAge.
     *              - if equal, compare the expiry date
     *              - if equal, compare name length
     */
    public static NewCookie getPreferredCookie(NewCookie first, NewCookie second) {

        if (first == null) {
            return second;
        } else if (second == null) {
            return first;
        }

        if (first.getMaxAge() != second.getMaxAge()){
            return Comparator.comparing(NewCookie::getMaxAge).compare(first, second) > 0 ? first : second;
        } else if (first.getExpiry() != null && second.getExpiry() != null && !first.getExpiry().equals(second.getExpiry())) {
            return Comparator.comparing(NewCookie::getExpiry).compare(first, second) > 0 ? first : second;
        } else {
            return first.getPath().length() > second.getPath().length() ? first : second;
        }
    }

    
Convert a message header value, represented as a general object, to it's string representation. If the supplied header value is null, this method returns null. 
Params:
headerValue –   the header value represented as an object.
See Also:
asString(Object, Configuration)
Returns:
the string representation of the supplied header value or null if the supplied header value is null./**
     * Convert a message header value, represented as a general object, to it's
     * string representation. If the supplied header value is {@code null},
     * this method returns {@code null}.
     *
     * @param headerValue   the header value represented as an object.
     * @return the string representation of the supplied header value or {@code null}
     *         if the supplied header value is {@code null}.
     * @see #asString(Object, Configuration)
     */
    @Deprecated
    public static String asString(final Object headerValue) {
        return asString(headerValue, (Configuration) null);
    }

    
Returns string view of list of header values. Any modifications to the underlying list are visible to the view,
the view also supports removal of elements. Does not support other modifications.
Params:
headerValues – header values.
See Also:
asStringList(List<Object>, Configuration)
Returns:
String view of header values./**
     * Returns string view of list of header values. Any modifications to the underlying list are visible to the view,
     * the view also supports removal of elements. Does not support other modifications.
     *
     * @param headerValues header values.
     * @return String view of header values.
     * @see #asStringList(List, Configuration)
     */
    @Deprecated
    public static List<String> asStringList(final List<Object> headerValues) {
        return asStringList(headerValues, (Configuration) null);
    }

    
Returns string view of passed headers. Any modifications to the headers are visible to the view, the view also
supports removal of elements. Does not support other modifications.
Params:
headers – headers.
See Also:
asStringHeaders(MultivaluedMap<String,Object>, Configuration)
Returns:
String view of headers or null if {code headers} input parameter is null./**
     * Returns string view of passed headers. Any modifications to the headers are visible to the view, the view also
     * supports removal of elements. Does not support other modifications.
     *
     * @param headers headers.
     * @return String view of headers or {@code null} if {code headers} input parameter is {@code null}.
     * @see #asStringHeaders(MultivaluedMap, Configuration)
     */
    @Deprecated
    public static MultivaluedMap<String, String> asStringHeaders(final MultivaluedMap<String, Object> headers) {
        return asStringHeaders(headers, (Configuration) null);
    }

    
Transforms multi value map of headers to single String value map. Returned map is immutable. Map values are formatted using method asHeaderString(List<Object>, RuntimeDelegate). 
Params:
headers – headers to be formatted
See Also:
asStringHeadersSingleValue(MultivaluedMap<String,Object>, Configuration)
Returns:
immutable single String value map or null if headers input parameter is null./**
     * Transforms multi value map of headers to single {@code String} value map.
     *
     * Returned map is immutable. Map values are formatted using method {@link #asHeaderString(List, RuntimeDelegate)}.
     *
     * @param headers headers to be formatted
     * @return immutable single {@code String} value map or
     *      {@code null} if {@code headers} input parameter is {@code null}.
     * @see #asStringHeadersSingleValue(MultivaluedMap, Configuration)
     */
    @Deprecated
    public static Map<String, String> asStringHeadersSingleValue(final MultivaluedMap<String, Object> headers) {
        return asStringHeadersSingleValue(headers, (Configuration) null);
    }

    
Compares two snapshots of headers from jersey ClientRequest and logs WARNING in case of difference. Current container implementations does not support header modification in WriterInterceptor and MessageBodyWriter. The method checks there are some newly added headers (probably by WI or MBW) and logs WARNING message about it. 
Params:
headersSnapshot – first immutable snapshot of headers
currentHeaders –  current instance of headers tobe compared to
connectorName –   name of connector the method is invoked from, used just in logged message
See Also:
checkHeaderChanges(Map<String,String>, MultivaluedMap<String,Object>, String, Configuration)/**
     * Compares two snapshots of headers from jersey {@code ClientRequest} and logs {@code WARNING} in case of difference.
     *
     * Current container implementations does not support header modification in {@link javax.ws.rs.ext.WriterInterceptor}
     * and {@link javax.ws.rs.ext.MessageBodyWriter}. The method checks there are some newly added headers
     * (probably by WI or MBW) and logs {@code WARNING} message about it.
     *
     * @param headersSnapshot first immutable snapshot of headers
     * @param currentHeaders  current instance of headers tobe compared to
     * @param connectorName   name of connector the method is invoked from, used just in logged message
     * @see #checkHeaderChanges(Map, MultivaluedMap, String, Configuration)
     */
    @Deprecated
    public static void checkHeaderChanges(final Map<String, String> headersSnapshot,
                                          final MultivaluedMap<String, Object> currentHeaders,
                                          final String connectorName) {
        checkHeaderChanges(headersSnapshot, currentHeaders, connectorName, (Configuration) null);
    }

    
Preventing instantiation.
/**
     * Preventing instantiation.
     */
    private HeaderUtils() {
        throw new AssertionError("No instances allowed.");
    }
}