package com.bookstore.microservice.gateway;

import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.cloud.gateway.filter.GatewayFilterChain;
import org.springframework.cloud.gateway.filter.GlobalFilter;
import org.springframework.cloud.gateway.filter.NettyWriteResponseFilter;
import org.springframework.core.Ordered;
import org.springframework.http.HttpHeaders;
import org.springframework.stereotype.Component;
import org.springframework.web.server.ServerWebExchange;
import reactor.core.publisher.Mono;

@Component
public class CorsResponseHeaderFilter implements GlobalFilter, Ordered {

  private static final Logger logger = LoggerFactory.getLogger(CorsResponseHeaderFilter.class);

  private static final String ANY = "*";

  @Override
  public int getOrder() {
    // 指定此过滤器位于NettyWriteResponseFilter之后
    // 即待处理完响应体后接着处理响应头
    return NettyWriteResponseFilter.WRITE_RESPONSE_FILTER_ORDER + 1;
  }

  @Override
  @SuppressWarnings("serial")
  public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
    return chain.filter(exchange).then(Mono.fromRunnable(() -> {
      exchange.getResponse().getHeaders().entrySet().stream()
          .filter(kv -> (kv.getValue() != null && kv.getValue().size() > 1))
          .filter(kv -> (kv.getKey().equals(HttpHeaders.ACCESS_CONTROL_ALLOW_ORIGIN)
              || kv.getKey().equals(HttpHeaders.ACCESS_CONTROL_ALLOW_CREDENTIALS)
              || kv.getKey().equals(HttpHeaders.VARY)))
          .forEach(kv ->
          {
            // Vary只需要去重即可
            if(kv.getKey().equals(HttpHeaders.VARY))
              kv.setValue(kv.getValue().stream().distinct().collect(Collectors.toList()));
            else{
              List<String> value = new ArrayList<>();
              if(kv.getValue().contains(ANY)){  //如果包含*，则取*
                value.add(ANY);
                kv.setValue(value);
              }else{
                value.add(kv.getValue().get(0)); // 否则默认取第一个
                kv.setValue(value);
              }
            }
          });
    }));
  }
}
