/*
 * 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
 *
 *      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 org.springframework.security.oauth2.client.endpoint;

import org.springframework.core.convert.converter.Converter;
import org.springframework.http.RequestEntity;
import org.springframework.http.ResponseEntity;
import org.springframework.http.converter.FormHttpMessageConverter;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.security.oauth2.client.http.OAuth2ErrorResponseErrorHandler;
import org.springframework.security.oauth2.core.OAuth2AuthorizationException;
import org.springframework.security.oauth2.core.OAuth2Error;
import org.springframework.security.oauth2.core.endpoint.OAuth2AccessTokenResponse;
import org.springframework.security.oauth2.core.http.converter.OAuth2AccessTokenResponseHttpMessageConverter;
import org.springframework.util.Assert;
import org.springframework.util.CollectionUtils;
import org.springframework.web.client.ResponseErrorHandler;
import org.springframework.web.client.RestClientException;
import org.springframework.web.client.RestOperations;
import org.springframework.web.client.RestTemplate;

import java.util.Arrays;

/**
 * The default implementation of an {@link OAuth2AccessTokenResponseClient}
 * for the {@link JwtBearerGrantRequest#JWT_BEARER_GRANT_TYPE jwt-bearer} grant.
 * This implementation uses a {@link RestOperations} when requesting
 * an access token credential at the Authorization Server's Token Endpoint.
 *
 * @author Joe Grandja
 * @since 5.2
 * @see OAuth2AccessTokenResponseClient
 * @see JwtBearerGrantRequest
 * @see OAuth2AccessTokenResponse
 * @see <a target="_blank" href="https://tools.ietf.org/html/rfc7523#section-2.1">Section 2.1 JWTs as Authorization Grants</a>
 */
public final class DefaultJwtBearerTokenResponseClient implements OAuth2AccessTokenResponseClient<JwtBearerGrantRequest> {
	private static final String INVALID_TOKEN_RESPONSE_ERROR_CODE = "invalid_token_response";

	private Converter<JwtBearerGrantRequest, RequestEntity<?>> requestEntityConverter =
			new JwtBearerGrantRequestEntityConverter();

	private RestOperations restOperations;

	public DefaultJwtBearerTokenResponseClient() {
		RestTemplate restTemplate = new RestTemplate(Arrays.asList(
				new FormHttpMessageConverter(), new OAuth2AccessTokenResponseHttpMessageConverter()));
		restTemplate.setErrorHandler(new OAuth2ErrorResponseErrorHandler());
		this.restOperations = restTemplate;
	}

	@Override
	public OAuth2AccessTokenResponse getTokenResponse(JwtBearerGrantRequest jwtBearerGrantRequest) {
		Assert.notNull(jwtBearerGrantRequest, "jwtBearerGrantRequest cannot be null");

		RequestEntity<?> request = this.requestEntityConverter.convert(jwtBearerGrantRequest);

		ResponseEntity<OAuth2AccessTokenResponse> response;
		try {
			response = this.restOperations.exchange(request, OAuth2AccessTokenResponse.class);
		} catch (RestClientException ex) {
			OAuth2Error oauth2Error = new OAuth2Error(INVALID_TOKEN_RESPONSE_ERROR_CODE,
					"An error occurred while attempting to retrieve the OAuth 2.0 Access Token Response: " + ex.getMessage(), null);
			throw new OAuth2AuthorizationException(oauth2Error, ex);
		}

		OAuth2AccessTokenResponse tokenResponse = response.getBody();

		if (CollectionUtils.isEmpty(tokenResponse.getAccessToken().getScopes())) {
			// As per spec, in Section 5.1 Successful Access Token Response
			// https://tools.ietf.org/html/rfc6749#section-5.1
			// If AccessTokenResponse.scope is empty, then default to the scope
			// originally requested by the client in the Token Request
			tokenResponse = OAuth2AccessTokenResponse.withResponse(tokenResponse)
					.scopes(jwtBearerGrantRequest.getClientRegistration().getScopes())
					.build();
		}

		return tokenResponse;
	}

	/**
	 * Sets the {@link Converter} used for converting the {@link JwtBearerGrantRequest}
	 * to a {@link RequestEntity} representation of the OAuth 2.0 Access Token Request.
	 *
	 * @param requestEntityConverter the {@link Converter} used for converting to a {@link RequestEntity} representation of the Access Token Request
	 */
	public void setRequestEntityConverter(Converter<JwtBearerGrantRequest, RequestEntity<?>> requestEntityConverter) {
		Assert.notNull(requestEntityConverter, "requestEntityConverter cannot be null");
		this.requestEntityConverter = requestEntityConverter;
	}

	/**
	 * Sets the {@link RestOperations} used when requesting the OAuth 2.0 Access Token Response.
	 *
	 * <p>
	 * <b>NOTE:</b> At a minimum, the supplied {@code restOperations} must be configured with the following:
	 * <ol>
	 *  <li>{@link HttpMessageConverter}'s - {@link FormHttpMessageConverter} and {@link OAuth2AccessTokenResponseHttpMessageConverter}</li>
	 *  <li>{@link ResponseErrorHandler} - {@link OAuth2ErrorResponseErrorHandler}</li>
	 * </ol>
	 *
	 * @param restOperations the {@link RestOperations} used when requesting the Access Token Response
	 */
	public void setRestOperations(RestOperations restOperations) {
		Assert.notNull(restOperations, "restOperations cannot be null");
		this.restOperations = restOperations;
	}
}