/*
 * Copyright 2002-2019 the original author or authors.
 *
 * Licensed 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
 *
 *      https://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 org.springframework.http.server.reactive;

import java.io.UnsupportedEncodingException;
import java.net.URI;
import java.net.URLDecoder;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import org.apache.commons.logging.Log;

import org.springframework.http.HttpCookie;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpLogging;
import org.springframework.http.server.RequestPath;
import org.springframework.lang.Nullable;
import org.springframework.util.CollectionUtils;
import org.springframework.util.LinkedMultiValueMap;
import org.springframework.util.MultiValueMap;
import org.springframework.util.ObjectUtils;
import org.springframework.util.StringUtils;

/**
 * Common base class for {@link ServerHttpRequest} implementations.
 *
 * @author Rossen Stoyanchev
 * @since 5.0
 */
public abstract class AbstractServerHttpRequest implements ServerHttpRequest {

        private static final Pattern QUERY_PATTERN = Pattern.compile("([^&=]+)(=?)([^&]+)?");


        protected final Log logger = HttpLogging.forLogName(getClass());

        private final URI uri;

        private final RequestPath path;

        private final HttpHeaders headers;

        @Nullable
        private MultiValueMap<String, String> queryParams;

        @Nullable
        private MultiValueMap<String, HttpCookie> cookies;

        @Nullable
        private SslInfo sslInfo;

        @Nullable
        private String id;

        @Nullable
        private String logPrefix;


        /**
         * Constructor with the URI and headers for the request.
         * @param uri the URI for the request
         * @param contextPath the context path for the request
         * @param headers the headers for the request
         */
        public AbstractServerHttpRequest(URI uri, @Nullable String contextPath, HttpHeaders headers) {
                this.uri = uri;
                this.path = RequestPath.parse(uri, contextPath);
                this.headers = HttpHeaders.readOnlyHttpHeaders(headers);
        }


        @Override
        public String getId() {
                if (this.id == null) {
                        this.id = initId();
                        if (this.id == null) {
                                this.id = ObjectUtils.getIdentityHexString(this);
                        }
                }
                return this.id;
        }

        /**
         * Obtain the request id to use, or {@code null} in which case the Object
         * identity of this request instance is used.
         * @since 5.1
         */
        @Nullable
        protected String initId() {
                return null;
        }

        @Override
        public URI getURI() {
                return this.uri;
        }

        @Override
        public RequestPath getPath() {
                return this.path;
        }

        @Override
        public HttpHeaders getHeaders() {
                return this.headers;
        }

        @Override
        public MultiValueMap<String, String> getQueryParams() {
                if (this.queryParams == null) {
                        this.queryParams = CollectionUtils.unmodifiableMultiValueMap(initQueryParams());
                }
                return this.queryParams;
        }

        /**
         * A method for parsing of the query into name-value pairs. The return
         * value is turned into an immutable map and cached.
         * <p>Note that this method is invoked lazily on first access to
         * {@link #getQueryParams()}. The invocation is not synchronized but the
         * parsing is thread-safe nevertheless.
         */
        protected MultiValueMap<String, String> initQueryParams() {
                MultiValueMap<String, String> queryParams = new LinkedMultiValueMap<>();
                String query = getURI().getRawQuery();
                if (query != null) {
                        Matcher matcher = QUERY_PATTERN.matcher(query);
                        while (matcher.find()) {
                                String name = decodeQueryParam(matcher.group(1));
                                String eq = matcher.group(2);
                                String value = matcher.group(3);
                                value = (value != null ? decodeQueryParam(value) : (StringUtils.hasLength(eq) ? "" : null));
                                queryParams.add(name, value);
                        }
                }
                return queryParams;
        }

        @SuppressWarnings("deprecation")
        private String decodeQueryParam(String value) {
                try {
                        return URLDecoder.decode(value, "UTF-8");
                }
                catch (UnsupportedEncodingException ex) {
                        if (logger.isWarnEnabled()) {
                                logger.warn(getLogPrefix() + "Could not decode query value [" + value + "] as 'UTF-8'. " +
                                                "Falling back on default encoding: " + ex.getMessage());
                        }
                        return URLDecoder.decode(value);
                }
        }

        @Override
        public MultiValueMap<String, HttpCookie> getCookies() {
                if (this.cookies == null) {
                        this.cookies = CollectionUtils.unmodifiableMultiValueMap(initCookies());
                }
                return this.cookies;
        }

        /**
         * Obtain the cookies from the underlying "native" request and adapt those to
         * an {@link HttpCookie} map. The return value is turned into an immutable
         * map and cached.
         * <p>Note that this method is invoked lazily on access to
         * {@link #getCookies()}. Sub-classes should synchronize cookie
         * initialization if the underlying "native" request does not provide
         * thread-safe access to cookie data.
         */
        protected abstract MultiValueMap<String, HttpCookie> initCookies();

        @Nullable
        @Override
        public SslInfo getSslInfo() {
                if (this.sslInfo == null) {
                        this.sslInfo = initSslInfo();
                }
                return this.sslInfo;
        }

        /**
         * Obtain SSL session information from the underlying "native" request.
         * @return the session information, or {@code null} if none available
         * @since 5.0.2
         */
        @Nullable
        protected abstract SslInfo initSslInfo();

        /**
         * Return the underlying server response.
         * <p><strong>Note:</strong> This is exposed mainly for internal framework
         * use such as WebSocket upgrades in the spring-webflux module.
         */
        public abstract <T> T getNativeRequest();

        /**
         * For internal use in logging at the HTTP adapter layer.
         * @since 5.1
         */
        String getLogPrefix() {
                if (this.logPrefix == null) {
                        this.logPrefix = "[" + getId() + "] ";
                }
                return this.logPrefix;
        }

}