/*
 * Copyright 2002-2020 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.web.reactive.function.client;

import java.util.Collections;
import java.util.List;
import java.util.Optional;
import java.util.OptionalLong;
import java.util.function.Consumer;

import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;

import org.springframework.core.ParameterizedTypeReference;
import org.springframework.core.io.buffer.DataBuffer;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpRequest;
import org.springframework.http.HttpStatus;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseCookie;
import org.springframework.http.ResponseEntity;
import org.springframework.http.client.reactive.ClientHttpResponse;
import org.springframework.http.codec.HttpMessageReader;
import org.springframework.http.codec.HttpMessageWriter;
import org.springframework.util.MultiValueMap;
import org.springframework.web.reactive.function.BodyExtractor;

/**
 * Represents an HTTP response, as returned by {@link WebClient} and also
 * {@link ExchangeFunction}. Provides access to the response status and
 * headers, and also methods to consume the response body.
 *
 * <p><strong>NOTE:</strong> When using a {@link ClientResponse}
 * through the {@code WebClient}
 * {@link WebClient.RequestHeadersSpec#exchange() exchange()} method,
 * you have to make sure that the body is consumed or released by using
 * one of the following methods:
 * <ul>
 * <li>{@link #body(BodyExtractor)}</li>
 * <li>{@link #bodyToMono(Class)} or
 *     {@link #bodyToMono(ParameterizedTypeReference)}</li>
 * <li>{@link #bodyToFlux(Class)} or
 *     {@link #bodyToFlux(ParameterizedTypeReference)}</li>
 * <li>{@link #toEntity(Class)} or
 *     {@link #toEntity(ParameterizedTypeReference)}</li>
 * <li>{@link #toEntityList(Class)} or
 *     {@link #toEntityList(ParameterizedTypeReference)}</li>
*  <li>{@link #toBodilessEntity()}</li>
 * <li>{@link #releaseBody()}</li>
 * </ul>
 * You can also use {@code bodyToMono(Void.class)} if no response content is
 * expected. However keep in mind the connection will be closed, instead of
 * being placed back in the pool, if any content does arrive. This is in
 * contrast to {@link #releaseBody()} which does consume the full body and
 * releases any content received.
 *
 * @author Brian Clozel
 * @author Arjen Poutsma
 * @since 5.0
 */
public interface ClientResponse {

        /**
         * Return the HTTP status code as an {@link HttpStatus} enum value.
         * @return the HTTP status as an HttpStatus enum value (never {@code null})
         * @throws IllegalArgumentException in case of an unknown HTTP status code
         * @since #getRawStatusCode()
         * @see HttpStatus#valueOf(int)
         */
        HttpStatus statusCode();

        /**
         * Return the (potentially non-standard) status code of this response.
         * @return the HTTP status as an integer value
         * @since 5.1
         * @see #statusCode()
         * @see HttpStatus#resolve(int)
         */
        int rawStatusCode();

        /**
         * Return the headers of this response.
         */
        Headers headers();

        /**
         * Return the cookies of this response.
         */
        MultiValueMap<String, ResponseCookie> cookies();

        /**
         * Return the strategies used to convert the body of this response.
         */
        ExchangeStrategies strategies();

        /**
         * Extract the body with the given {@code BodyExtractor}.
         * @param extractor the {@code BodyExtractor} that reads from the response
         * @param <T> the type of the body returned
         * @return the extracted body
         */
        <T> T body(BodyExtractor<T, ? super ClientHttpResponse> extractor);

        /**
         * Extract the body to a {@code Mono}.
         * @param elementClass the class of element in the {@code Mono}
         * @param <T> the element type
         * @return a mono containing the body of the given type {@code T}
         */
        <T> Mono<T> bodyToMono(Class<? extends T> elementClass);

        /**
         * Extract the body to a {@code Mono}.
         * @param elementTypeRef the type reference of element in the {@code Mono}
         * @param <T> the element type
         * @return a mono containing the body of the given type {@code T}
         */
        <T> Mono<T> bodyToMono(ParameterizedTypeReference<T> elementTypeRef);

        /**
         * Extract the body to a {@code Flux}.
         * @param elementClass the class of elements in the {@code Flux}
         * @param <T> the element type
         * @return a flux containing the body of the given type {@code T}
         */
        <T> Flux<T> bodyToFlux(Class<? extends T> elementClass);

        /**
         * Extract the body to a {@code Flux}.
         * @param elementTypeRef the type reference of elements in the {@code Flux}
         * @param <T> the element type
         * @return a flux containing the body of the given type {@code T}
         */
        <T> Flux<T> bodyToFlux(ParameterizedTypeReference<T> elementTypeRef);

        /**
         * Release the body of this response.
         * @return a completion signal
         * @since 5.2
         * @see org.springframework.core.io.buffer.DataBufferUtils#release(DataBuffer)
         */
        Mono<Void> releaseBody();

        /**
         * Return this response as a delayed {@code ResponseEntity}.
         * @param bodyClass the expected response body type
         * @param <T> response body type
         * @return {@code Mono} with the {@code ResponseEntity}
         */
        <T> Mono<ResponseEntity<T>> toEntity(Class<T> bodyClass);

        /**
         * Return this response as a delayed {@code ResponseEntity}.
         * @param bodyTypeReference a type reference describing the expected response body type
         * @param <T> response body type
         * @return {@code Mono} with the {@code ResponseEntity}
         */
        <T> Mono<ResponseEntity<T>> toEntity(ParameterizedTypeReference<T> bodyTypeReference);

        /**
         * Return this response as a delayed list of {@code ResponseEntity}s.
         * @param elementClass the expected response body list element class
         * @param <T> the type of elements in the list
         * @return {@code Mono} with the list of {@code ResponseEntity}s
         */
        <T> Mono<ResponseEntity<List<T>>> toEntityList(Class<T> elementClass);

        /**
         * Return this response as a delayed list of {@code ResponseEntity}s.
         * @param elementTypeRef the expected response body list element reference type
         * @param <T> the type of elements in the list
         * @return {@code Mono} with the list of {@code ResponseEntity}s
         */
        <T> Mono<ResponseEntity<List<T>>> toEntityList(ParameterizedTypeReference<T> elementTypeRef);

        /**
         * Return this response as a delayed {@code ResponseEntity} containing
         * status and headers, but no body. Calling this method will
         * {@linkplain #releaseBody() release} the body of the response.
         * @return {@code Mono} with the bodiless {@code ResponseEntity}
         * @since 5.2
         */
        Mono<ResponseEntity<Void>> toBodilessEntity();

        /**
         * Create a {@link WebClientResponseException} that contains the response
         * status, headers, body, and the originating request.
         * @return a {@code Mono} with the created exception
         * @since 5.2
         */
        Mono<WebClientResponseException> createException();

        /**
         * Return a log message prefix to use to correlate messages for this exchange.
         * <p>The prefix is based on {@linkplain ClientRequest#logPrefix()}, which
         * itself is based on the value of the {@link ClientRequest#LOG_ID_ATTRIBUTE
         * LOG_ID_ATTRIBUTE} request attribute, further surrounded with "[" and "]".
         * @return the log message prefix or an empty String if the
         * {@link ClientRequest#LOG_ID_ATTRIBUTE LOG_ID_ATTRIBUTE} is not set
         * @since 5.2.3
         */
        String logPrefix();


        // Static builder methods

        /**
         * Create a builder with the status, headers, and cookies of the given response.
         * @param other the response to copy the status, headers, and cookies from
         * @return the created builder
         */
        static Builder from(ClientResponse other) {
                return new DefaultClientResponseBuilder(other);
        }

        /**
         * Create a response builder with the given status code and using default strategies for
         * reading the body.
         * @param statusCode the status code
         * @return the created builder
         */
        static Builder create(HttpStatus statusCode) {
                return create(statusCode, ExchangeStrategies.withDefaults());
        }

        /**
         * Create a response builder with the given status code and strategies for reading the body.
         * @param statusCode the status code
         * @param strategies the strategies
         * @return the created builder
         */
        static Builder create(HttpStatus statusCode, ExchangeStrategies strategies) {
                return new DefaultClientResponseBuilder(strategies).statusCode(statusCode);
        }

        /**
         * Create a response builder with the given raw status code and strategies for reading the body.
         * @param statusCode the status code
         * @param strategies the strategies
         * @return the created builder
         * @since 5.1.9
         */
        static Builder create(int statusCode, ExchangeStrategies strategies) {
                return new DefaultClientResponseBuilder(strategies).rawStatusCode(statusCode);
        }

        /**
         * Create a response builder with the given status code and message body readers.
         * @param statusCode the status code
         * @param messageReaders the message readers
         * @return the created builder
         */
        static Builder create(HttpStatus statusCode, List<HttpMessageReader<?>> messageReaders) {
                return create(statusCode, new ExchangeStrategies() {
                        @Override
                        public List<HttpMessageReader<?>> messageReaders() {
                                return messageReaders;
                        }
                        @Override
                        public List<HttpMessageWriter<?>> messageWriters() {
                                // not used in the response
                                return Collections.emptyList();
                        }
                });
        }


        /**
         * Represents the headers of the HTTP response.
         * @see ClientResponse#headers()
         */
        interface Headers {

                /**
                 * Return the length of the body in bytes, as specified by the
                 * {@code Content-Length} header.
                 */
                OptionalLong contentLength();

                /**
                 * Return the {@linkplain MediaType media type} of the body, as specified
                 * by the {@code Content-Type} header.
                 */
                Optional<MediaType> contentType();

                /**
                 * Return the header value(s), if any, for the header of the given name.
                 * <p>Return an empty list if no header values are found.
                 * @param headerName the header name
                 */
                List<String> header(String headerName);

                /**
                 * Return the headers as an {@link HttpHeaders} instance.
                 */
                HttpHeaders asHttpHeaders();
        }


        /**
         * Defines a builder for a response.
         */
        interface Builder {

                /**
                 * Set the status code of the response.
                 * @param statusCode the new status code
                 * @return this builder
                 */
                Builder statusCode(HttpStatus statusCode);

                /**
                 * Set the raw status code of the response.
                 * @param statusCode the new status code
                 * @return this builder
                 * @since 5.1.9
                 */
                Builder rawStatusCode(int statusCode);

                /**
                 * Add the given header value(s) under the given name.
                 * @param headerName the header name
                 * @param headerValues the header value(s)
                 * @return this builder
                 * @see HttpHeaders#add(String, String)
                 */
                Builder header(String headerName, String... headerValues);

                /**
                 * Manipulate this response's headers with the given consumer.
                 * <p>The headers provided to the consumer are "live", so that the consumer
                 * can be used to {@linkplain HttpHeaders#set(String, String) overwrite}
                 * existing header values, {@linkplain HttpHeaders#remove(Object) remove}
                 * values, or use any of the other {@link HttpHeaders} methods.
                 * @param headersConsumer a function that consumes the {@code HttpHeaders}
                 * @return this builder
                 */
                Builder headers(Consumer<HttpHeaders> headersConsumer);

                /**
                 * Add a cookie with the given name and value(s).
                 * @param name the cookie name
                 * @param values the cookie value(s)
                 * @return this builder
                 */
                Builder cookie(String name, String... values);

                /**
                 * Manipulate this response's cookies with the given consumer.
                 * <p>The map provided to the consumer is "live", so that the consumer can be used to
                 * {@linkplain MultiValueMap#set(Object, Object) overwrite} existing cookie values,
                 * {@linkplain MultiValueMap#remove(Object) remove} values, or use any of the other
                 * {@link MultiValueMap} methods.
                 * @param cookiesConsumer a function that consumes the cookies map
                 * @return this builder
                 */
                Builder cookies(Consumer<MultiValueMap<String, ResponseCookie>> cookiesConsumer);

                /**
                 * Set the body of the response.
                 * <p>Calling this methods will
                 * {@linkplain org.springframework.core.io.buffer.DataBufferUtils#release(DataBuffer) release}
                 * the existing body of the builder.
                 * @param body the new body
                 * @return this builder
                 */
                Builder body(Flux<DataBuffer> body);

                /**
                 * Set the body of the response to the UTF-8 encoded bytes of the given string.
                 * <p>Calling this methods will
                 * {@linkplain org.springframework.core.io.buffer.DataBufferUtils#release(DataBuffer) release}
                 * the existing body of the builder.
                 * @param body the new body
                 * @return this builder
                 */
                Builder body(String body);

                /**
                 * Set the request associated with the response.
                 * @param request the request
                 * @return this builder
                 * @since 5.2
                 */
                Builder request(HttpRequest request);

                /**
                 * Build the response.
                 */
                ClientResponse build();
        }

}