/*
 * Copyright 2020-2023 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.security;

import java.io.IOException;

import jakarta.servlet.ServletException;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;

import org.springframework.http.server.ServletServerHttpRequest;
import org.springframework.security.core.AuthenticationException;
import org.springframework.security.oauth2.client.registration.ClientRegistration;
import org.springframework.security.oauth2.client.registration.ClientRegistrationRepository;
import org.springframework.security.oauth2.client.web.OAuth2AuthorizationRequestRedirectFilter;
import org.springframework.security.web.AuthenticationEntryPoint;
import org.springframework.security.web.DefaultRedirectStrategy;
import org.springframework.security.web.RedirectStrategy;
import org.springframework.security.web.authentication.LoginUrlAuthenticationEntryPoint;
import org.springframework.web.util.UriComponentsBuilder;

/**
 * An {@link AuthenticationEntryPoint} for initiating the login flow to an
 * external provider using the {@code idp} query parameter, which represents the
 * {@code registrationId} of the desired {@link ClientRegistration}.
 *
 * @author Steve Riesenberg
 * @since 1.1
 */
public final class FederatedIdentityAuthenticationEntryPoint implements AuthenticationEntryPoint {

	private final RedirectStrategy redirectStrategy = new DefaultRedirectStrategy();

	private String authorizationRequestUri = OAuth2AuthorizationRequestRedirectFilter.DEFAULT_AUTHORIZATION_REQUEST_BASE_URI
			+ "/{registrationId}";

	private final AuthenticationEntryPoint delegate;

	private final ClientRegistrationRepository clientRegistrationRepository;

	public FederatedIdentityAuthenticationEntryPoint(String loginPageUrl, ClientRegistrationRepository clientRegistrationRepository) {
		this.delegate = new LoginUrlAuthenticationEntryPoint(loginPageUrl);
		this.clientRegistrationRepository = clientRegistrationRepository;
	}

	@Override
	public void commence(HttpServletRequest request, HttpServletResponse response, AuthenticationException authenticationException) throws IOException, ServletException {
		String idp = request.getParameter("idp");
		if (idp != null) {
			ClientRegistration clientRegistration = this.clientRegistrationRepository.findByRegistrationId(idp);
			if (clientRegistration != null) {
				String redirectUri = UriComponentsBuilder.fromHttpRequest(new ServletServerHttpRequest(request))
						.replaceQuery(null)
						.replacePath(this.authorizationRequestUri)
						.buildAndExpand(clientRegistration.getRegistrationId())
						.toUriString();
				this.redirectStrategy.sendRedirect(request, response, redirectUri);
				return;
			}
		}

		this.delegate.commence(request, response, authenticationException);
	}

	public void setAuthorizationRequestUri(String authorizationRequestUri) {
		this.authorizationRequestUri = authorizationRequestUri;
	}

}