/*
 * 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.security.oauth2.client.authentication;

import java.util.Collection;
import java.util.Map;

import reactor.core.publisher.Mono;

import org.springframework.security.authentication.ReactiveAuthenticationManager;
import org.springframework.security.core.Authentication;
import org.springframework.security.core.GrantedAuthority;
import org.springframework.security.core.authority.mapping.GrantedAuthoritiesMapper;
import org.springframework.security.oauth2.client.endpoint.OAuth2AuthorizationCodeGrantRequest;
import org.springframework.security.oauth2.client.endpoint.ReactiveOAuth2AccessTokenResponseClient;
import org.springframework.security.oauth2.client.userinfo.OAuth2UserRequest;
import org.springframework.security.oauth2.client.userinfo.ReactiveOAuth2UserService;
import org.springframework.security.oauth2.core.OAuth2AccessToken;
import org.springframework.security.oauth2.core.OAuth2AuthenticationException;
import org.springframework.security.oauth2.core.OAuth2AuthorizationException;
import org.springframework.security.oauth2.core.user.OAuth2User;
import org.springframework.util.Assert;

/**
 * An implementation of an
 * {@link org.springframework.security.authentication.AuthenticationProvider} for OAuth
 * 2.0 Login, which leverages the OAuth 2.0 Authorization Code Grant Flow.
 *
 * This {@link org.springframework.security.authentication.AuthenticationProvider} is
 * responsible for authenticating an Authorization Code credential with the Authorization
 * Server's Token Endpoint and if valid, exchanging it for an Access Token credential.
 * <p>
 * It will also obtain the user attributes of the End-User (Resource Owner) from the
 * UserInfo Endpoint using an
 * {@link org.springframework.security.oauth2.client.userinfo.OAuth2UserService}, which
 * will create a {@code Principal} in the form of an {@link OAuth2User}. The
 * {@code OAuth2User} is then associated to the {@link OAuth2LoginAuthenticationToken} to
 * complete the authentication.
 *
 * @author Rob Winch
 * @since 5.1
 * @see OAuth2LoginAuthenticationToken
 * @see org.springframework.security.oauth2.client.endpoint.ReactiveOAuth2AccessTokenResponseClient
 * @see org.springframework.security.oauth2.client.userinfo.ReactiveOAuth2UserService
 * @see OAuth2User
 * @see <a target="_blank" href="https://tools.ietf.org/html/rfc6749#section-4.1">Section
 * 4.1 Authorization Code Grant Flow</a>
 * @see <a target="_blank" href=
 * "https://tools.ietf.org/html/rfc6749#section-4.1.3">Section 4.1.3 Access Token
 * Request</a>
 * @see <a target="_blank" href=
 * "https://tools.ietf.org/html/rfc6749#section-4.1.4">Section 4.1.4 Access Token
 * Response</a>
 */
public class OAuth2LoginReactiveAuthenticationManager implements ReactiveAuthenticationManager {

	private final ReactiveAuthenticationManager authorizationCodeManager;

	private final ReactiveOAuth2UserService<OAuth2UserRequest, OAuth2User> userService;

	private GrantedAuthoritiesMapper authoritiesMapper = ((authorities) -> authorities);

	public OAuth2LoginReactiveAuthenticationManager(
			ReactiveOAuth2AccessTokenResponseClient<OAuth2AuthorizationCodeGrantRequest> accessTokenResponseClient,
			ReactiveOAuth2UserService<OAuth2UserRequest, OAuth2User> userService) {
		Assert.notNull(accessTokenResponseClient, "accessTokenResponseClient cannot be null");
		Assert.notNull(userService, "userService cannot be null");
		this.authorizationCodeManager = new OAuth2AuthorizationCodeReactiveAuthenticationManager(
				accessTokenResponseClient);
		this.userService = userService;
	}

	@Override
	public Mono<Authentication> authenticate(Authentication authentication) {
		return Mono.defer(() -> {
			OAuth2AuthorizationCodeAuthenticationToken token = (OAuth2AuthorizationCodeAuthenticationToken) authentication;
			// Section 3.1.2.1 Authentication Request -
			// https://openid.net/specs/openid-connect-core-1_0.html#AuthRequest scope
			// REQUIRED. OpenID Connect requests MUST contain the "openid" scope value.
			if (token.getAuthorizationExchange().getAuthorizationRequest().getScopes().contains("openid")) {
				// This is an OpenID Connect Authentication Request so return null
				// and let OidcAuthorizationCodeReactiveAuthenticationManager handle it
				// instead once one is created
				return Mono.empty();
			}
			return this.authorizationCodeManager.authenticate(token)
					.onErrorMap(OAuth2AuthorizationException.class,
							(e) -> new OAuth2AuthenticationException(e.getError(), e.getError().toString(), e))
					.cast(OAuth2AuthorizationCodeAuthenticationToken.class).flatMap(this::onSuccess);
		});
	}

	/**
	 * Sets the {@link GrantedAuthoritiesMapper} used for mapping
	 * {@link OAuth2User#getAuthorities()} to a new set of authorities which will be
	 * associated to the {@link OAuth2LoginAuthenticationToken}.
	 * @param authoritiesMapper the {@link GrantedAuthoritiesMapper} used for mapping the
	 * user's authorities
	 * @since 5.4
	 */
	public final void setAuthoritiesMapper(GrantedAuthoritiesMapper authoritiesMapper) {
		Assert.notNull(authoritiesMapper, "authoritiesMapper cannot be null");
		this.authoritiesMapper = authoritiesMapper;
	}

	private Mono<OAuth2LoginAuthenticationToken> onSuccess(OAuth2AuthorizationCodeAuthenticationToken authentication) {
		OAuth2AccessToken accessToken = authentication.getAccessToken();
		Map<String, Object> additionalParameters = authentication.getAdditionalParameters();
		OAuth2UserRequest userRequest = new OAuth2UserRequest(authentication.getClientRegistration(), accessToken,
				additionalParameters);
		return this.userService.loadUser(userRequest).map((oauth2User) -> {
			Collection<? extends GrantedAuthority> mappedAuthorities = this.authoritiesMapper
					.mapAuthorities(oauth2User.getAuthorities());
			OAuth2LoginAuthenticationToken authenticationResult = new OAuth2LoginAuthenticationToken(
					authentication.getClientRegistration(), authentication.getAuthorizationExchange(), oauth2User,
					mappedAuthorities, accessToken, authentication.getRefreshToken());
			return authenticationResult;
		});
	}

}
