/*
 * Copyright 2020-2025 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 sample.extgrant;

import org.springframework.security.authentication.AuthenticationProvider;
import org.springframework.security.core.Authentication;
import org.springframework.security.core.AuthenticationException;
import org.springframework.security.oauth2.core.ClaimAccessor;
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.OAuth2Token;
import org.springframework.security.oauth2.server.authorization.OAuth2Authorization;
import org.springframework.security.oauth2.server.authorization.OAuth2AuthorizationService;
import org.springframework.security.oauth2.server.authorization.OAuth2TokenType;
import org.springframework.security.oauth2.server.authorization.authentication.OAuth2AccessTokenAuthenticationToken;
import org.springframework.security.oauth2.server.authorization.authentication.OAuth2ClientAuthenticationToken;
import org.springframework.security.oauth2.server.authorization.client.RegisteredClient;
import org.springframework.security.oauth2.server.authorization.context.AuthorizationServerContextHolder;
import org.springframework.security.oauth2.server.authorization.token.DefaultOAuth2TokenContext;
import org.springframework.security.oauth2.server.authorization.token.OAuth2TokenContext;
import org.springframework.security.oauth2.server.authorization.token.OAuth2TokenGenerator;
import org.springframework.util.Assert;

public class CustomCodeGrantAuthenticationProvider implements AuthenticationProvider {
	// @fold:on
	private final OAuth2AuthorizationService authorizationService;
	private final OAuth2TokenGenerator<? extends OAuth2Token> tokenGenerator;

	public CustomCodeGrantAuthenticationProvider(OAuth2AuthorizationService authorizationService,
			OAuth2TokenGenerator<? extends OAuth2Token> tokenGenerator) {
		Assert.notNull(authorizationService, "authorizationService cannot be null");
		Assert.notNull(tokenGenerator, "tokenGenerator cannot be null");
		this.authorizationService = authorizationService;
		this.tokenGenerator = tokenGenerator;
	}
	// @fold:off

	@Override
	public Authentication authenticate(Authentication authentication) throws AuthenticationException {
		CustomCodeGrantAuthenticationToken customCodeGrantAuthentication =
				(CustomCodeGrantAuthenticationToken) authentication;

		// Ensure the client is authenticated
		OAuth2ClientAuthenticationToken clientPrincipal =
				getAuthenticatedClientElseThrowInvalidClient(customCodeGrantAuthentication);
		RegisteredClient registeredClient = clientPrincipal.getRegisteredClient();

		// Ensure the client is configured to use this authorization grant type
		if (!registeredClient.getAuthorizationGrantTypes().contains(customCodeGrantAuthentication.getGrantType())) {
			throw new OAuth2AuthenticationException(OAuth2ErrorCodes.UNAUTHORIZED_CLIENT);
		}

		// TODO Validate the code parameter

		// Generate the access token
		OAuth2TokenContext tokenContext = DefaultOAuth2TokenContext.builder()
				.registeredClient(registeredClient)
				.principal(clientPrincipal)
				.authorizationServerContext(AuthorizationServerContextHolder.getContext())
				.tokenType(OAuth2TokenType.ACCESS_TOKEN)
				.authorizationGrantType(customCodeGrantAuthentication.getGrantType())
				.authorizationGrant(customCodeGrantAuthentication)
				.build();

		OAuth2Token generatedAccessToken = this.tokenGenerator.generate(tokenContext);
		if (generatedAccessToken == null) {
			OAuth2Error error = new OAuth2Error(OAuth2ErrorCodes.SERVER_ERROR,
					"The token generator failed to generate the access token.", null);
			throw new OAuth2AuthenticationException(error);
		}
		OAuth2AccessToken accessToken = new OAuth2AccessToken(OAuth2AccessToken.TokenType.BEARER,
				generatedAccessToken.getTokenValue(), generatedAccessToken.getIssuedAt(),
				generatedAccessToken.getExpiresAt(), null);

		// Initialize the OAuth2Authorization
		OAuth2Authorization.Builder authorizationBuilder = OAuth2Authorization.withRegisteredClient(registeredClient)
				.principalName(clientPrincipal.getName())
				.authorizationGrantType(customCodeGrantAuthentication.getGrantType());
		if (generatedAccessToken instanceof ClaimAccessor claimAccessor) {
			authorizationBuilder.token(accessToken, (metadata) ->
				metadata.put(
					OAuth2Authorization.Token.CLAIMS_METADATA_NAME,
					claimAccessor.getClaims())
			);
		} else {
			authorizationBuilder.accessToken(accessToken);
		}
		OAuth2Authorization authorization = authorizationBuilder.build();

		// Save the OAuth2Authorization
		this.authorizationService.save(authorization);

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

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

	// @fold:on
	private static OAuth2ClientAuthenticationToken getAuthenticatedClientElseThrowInvalidClient(Authentication authentication) {
		OAuth2ClientAuthenticationToken clientPrincipal = null;
		if (OAuth2ClientAuthenticationToken.class.isAssignableFrom(authentication.getPrincipal().getClass())) {
			clientPrincipal = (OAuth2ClientAuthenticationToken) authentication.getPrincipal();
		}
		if (clientPrincipal != null && clientPrincipal.isAuthenticated()) {
			return clientPrincipal;
		}
		throw new OAuth2AuthenticationException(OAuth2ErrorCodes.INVALID_CLIENT);
	}
	// @fold:off

}