/*
    * Copyright 2006-2011 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.provider.error;
  
  import java.io.IOException;
  
  import javax.servlet.ServletException;
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpServletResponse;
  
  import org.springframework.http.HttpHeaders;
  import org.springframework.http.ResponseEntity;
  import org.springframework.security.core.AuthenticationException;
  import org.springframework.security.oauth2.common.OAuth2AccessToken;
  import org.springframework.security.web.AuthenticationEntryPoint;
  import org.springframework.util.StringUtils;
  
  /**
   * If authentication fails and the caller has asked for a specific content type response, this entry point can send one,
   * along with a standard 401 status. Add to the Spring Security configuration as an {@link AuthenticationEntryPoint} in
   * the usual way.
   * 
   * @author Dave Syer
   * 
   */
  public class OAuth2AuthenticationEntryPoint extends AbstractOAuth2SecurityExceptionHandler implements
  		AuthenticationEntryPoint {
  
  	private String typeName = OAuth2AccessToken.BEARER_TYPE;
  
  	private String realmName = "oauth";
  
  	public void setRealmName(String realmName) {
  		this.realmName = realmName;
  	}
  
  	public void setTypeName(String typeName) {
  		this.typeName = typeName;
  	}
  
  	public void commence(HttpServletRequest request, HttpServletResponse response, AuthenticationException authException)
  			throws IOException, ServletException {
  		doHandle(request, response, authException);
  	}
  
  	@Override
  	protected ResponseEntity<?> enhanceResponse(ResponseEntity<?> response, Exception exception) {
  		HttpHeaders headers = response.getHeaders();
  		String existing = null;
  		if (headers.containsKey("WWW-Authenticate")) {
  			existing = extractTypePrefix(headers.getFirst("WWW-Authenticate"));
  		}
  		StringBuilder builder = new StringBuilder();
  		builder.append(typeName+" ");
  		builder.append("realm=\"" + realmName + "\"");
  		if (existing!=null) {
  			builder.append(", "+existing);
  		}
  		HttpHeaders update = new HttpHeaders();
  		update.putAll(response.getHeaders());
  		update.set("WWW-Authenticate", builder.toString());
  		return new ResponseEntity<Object>(response.getBody(), update, response.getStatusCode());
  	}
  
  	private String extractTypePrefix(String header) {
  		String existing = header;
  		String[] tokens = existing.split(" +");
  		if (tokens.length > 1 && !tokens[0].endsWith(",")) {
  			existing = StringUtils.arrayToDelimitedString(tokens, " ").substring(existing.indexOf(" ") + 1);
  		}
  		return existing;
  	}
  
  }