/*
 * Copyright 2020-2021 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.server.authorization.authentication;

import java.util.LinkedHashSet;
import java.util.Set;
import java.util.stream.Collectors;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.security.authentication.AuthenticationProvider;
import org.springframework.security.core.Authentication;
import org.springframework.security.core.AuthenticationException;
import org.springframework.security.oauth2.core.AuthorizationGrantType;
import org.springframework.security.oauth2.core.OAuth2AccessToken;
import org.springframework.security.oauth2.core.OAuth2AuthenticationException;
import org.springframework.security.oauth2.core.OAuth2Error;
import org.springframework.security.oauth2.core.OAuth2ErrorCodes;
import org.springframework.security.oauth2.core.OAuth2TokenType;
import org.springframework.security.oauth2.jwt.JoseHeader;
import org.springframework.security.oauth2.jwt.Jwt;
import org.springframework.security.oauth2.jwt.JwtClaimsSet;
import org.springframework.security.oauth2.jwt.JwtEncoder;
import org.springframework.security.oauth2.server.authorization.OAuth2Authorization;
import org.springframework.security.oauth2.server.authorization.OAuth2AuthorizationService;
import org.springframework.security.oauth2.server.authorization.client.RegisteredClient;
import org.springframework.security.oauth2.server.authorization.config.ProviderSettings;
import org.springframework.security.oauth2.server.authorization.JwtEncodingContext;
import org.springframework.security.oauth2.server.authorization.OAuth2TokenCustomizer;
import org.springframework.util.Assert;
import org.springframework.util.CollectionUtils;

import static org.springframework.security.oauth2.server.authorization.authentication.OAuth2AuthenticationProviderUtils.getAuthenticatedClientElseThrowInvalidClient;

/**
 * An {@link AuthenticationProvider} implementation for the OAuth 2.0 Client Credentials Grant.
 *
 * @author Alexey Nesterov
 * @author Joe Grandja
 * @since 0.0.1
 * @see OAuth2ClientCredentialsAuthenticationToken
 * @see OAuth2AccessTokenAuthenticationToken
 * @see OAuth2AuthorizationService
 * @see JwtEncoder
 * @see OAuth2TokenCustomizer
 * @see JwtEncodingContext
 * @see <a target="_blank" href="https://tools.ietf.org/html/rfc6749#section-4.4">Section 4.4 Client Credentials Grant</a>
 * @see <a target="_blank" href="https://tools.ietf.org/html/rfc6749#section-4.4.2">Section 4.4.2 Access Token Request</a>
 */
public class OAuth2ClientCredentialsAuthenticationProvider implements AuthenticationProvider {
	private final OAuth2AuthorizationService authorizationService;
	private final JwtEncoder jwtEncoder;
	private OAuth2TokenCustomizer<JwtEncodingContext> jwtCustomizer = (context) -> {};
	private ProviderSettings providerSettings;

	/**
	 * Constructs an {@code OAuth2ClientCredentialsAuthenticationProvider} using the provided parameters.
	 *
	 * @param authorizationService the authorization service
	 * @param jwtEncoder the jwt encoder
	 */
	public OAuth2ClientCredentialsAuthenticationProvider(OAuth2AuthorizationService authorizationService,
			JwtEncoder jwtEncoder) {
		Assert.notNull(authorizationService, "authorizationService cannot be null");
		Assert.notNull(jwtEncoder, "jwtEncoder cannot be null");
		this.authorizationService = authorizationService;
		this.jwtEncoder = jwtEncoder;
	}

	public final void setJwtCustomizer(OAuth2TokenCustomizer<JwtEncodingContext> jwtCustomizer) {
		Assert.notNull(jwtCustomizer, "jwtCustomizer cannot be null");
		this.jwtCustomizer = jwtCustomizer;
	}

	@Autowired(required = false)
	protected void setProviderSettings(ProviderSettings providerSettings) {
		this.providerSettings = providerSettings;
	}

	@Override
	public Authentication authenticate(Authentication authentication) throws AuthenticationException {
		OAuth2ClientCredentialsAuthenticationToken clientCredentialsAuthentication =
				(OAuth2ClientCredentialsAuthenticationToken) authentication;

		OAuth2ClientAuthenticationToken clientPrincipal =
				getAuthenticatedClientElseThrowInvalidClient(clientCredentialsAuthentication);
		RegisteredClient registeredClient = clientPrincipal.getRegisteredClient();

		if (!registeredClient.getAuthorizationGrantTypes().contains(AuthorizationGrantType.CLIENT_CREDENTIALS)) {
			throw new OAuth2AuthenticationException(new OAuth2Error(OAuth2ErrorCodes.UNAUTHORIZED_CLIENT));
		}

		Set<String> authorizedScopes = registeredClient.getScopes();		// Default to configured scopes
		if (!CollectionUtils.isEmpty(clientCredentialsAuthentication.getScopes())) {
			Set<String> unauthorizedScopes = clientCredentialsAuthentication.getScopes().stream()
					.filter(requestedScope -> !registeredClient.getScopes().contains(requestedScope))
					.collect(Collectors.toSet());
			if (!CollectionUtils.isEmpty(unauthorizedScopes)) {
				throw new OAuth2AuthenticationException(new OAuth2Error(OAuth2ErrorCodes.INVALID_SCOPE));
			}
			authorizedScopes = new LinkedHashSet<>(clientCredentialsAuthentication.getScopes());
		}

		String issuer = this.providerSettings != null ? this.providerSettings.issuer() : null;

		JoseHeader.Builder headersBuilder = JwtUtils.headers();
		JwtClaimsSet.Builder claimsBuilder = JwtUtils.accessTokenClaims(
				registeredClient, issuer, clientPrincipal.getName(), authorizedScopes);

		// @formatter:off
		JwtEncodingContext context = JwtEncodingContext.with(headersBuilder, claimsBuilder)
				.registeredClient(registeredClient)
				.principal(clientPrincipal)
				.authorizedScopes(authorizedScopes)
				.tokenType(OAuth2TokenType.ACCESS_TOKEN)
				.authorizationGrantType(AuthorizationGrantType.CLIENT_CREDENTIALS)
				.authorizationGrant(clientCredentialsAuthentication)
				.build();
		// @formatter:on

		this.jwtCustomizer.customize(context);

		JoseHeader headers = context.getHeaders().build();
		JwtClaimsSet claims = context.getClaims().build();
		Jwt jwtAccessToken = this.jwtEncoder.encode(headers, claims);

		OAuth2AccessToken accessToken = new OAuth2AccessToken(OAuth2AccessToken.TokenType.BEARER,
				jwtAccessToken.getTokenValue(), jwtAccessToken.getIssuedAt(),
				jwtAccessToken.getExpiresAt(), authorizedScopes);

		// @formatter:off
		OAuth2Authorization authorization = OAuth2Authorization.withRegisteredClient(registeredClient)
				.principalName(clientPrincipal.getName())
				.authorizationGrantType(AuthorizationGrantType.CLIENT_CREDENTIALS)
				.token(accessToken,
						(metadata) ->
								metadata.put(OAuth2Authorization.Token.CLAIMS_METADATA_NAME, jwtAccessToken.getClaims()))
				.attribute(OAuth2Authorization.AUTHORIZED_SCOPE_ATTRIBUTE_NAME, authorizedScopes)
				.build();
		// @formatter:on

		this.authorizationService.save(authorization);

		return new OAuth2AccessTokenAuthenticationToken(registeredClient, clientPrincipal, accessToken);
	}

	@Override
	public boolean supports(Class<?> authentication) {
		return OAuth2ClientCredentialsAuthenticationToken.class.isAssignableFrom(authentication);
	}
}