/*
 * 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.apache.commons.logging.LogFactory;

import org.springframework.http.HttpCookie;
import org.springframework.http.HttpHeaders;
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.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("([^&=]+)(=?)([^&]+)?");


	private static final Log logger = LogFactory.getLog(ServerHttpRequest.class);

	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;


	/**
	 * 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 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("Could not decode query param [" + value + "] as 'UTF-8'. " +
						"Falling back on default encoding; exception message: " + 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();

}
