Add a hack to adjust Swagger UI to use reverse different URLs when behind proxy

Author: gavlyukovskiy

src/main/java/net/hackyourfuture/coursehub/SwaggerBehindReverseProxyConfig.java

@@ -1,19 +1,40 @@
 package net.hackyourfuture.coursehub;
 
 import org.springdoc.core.customizers.ServerBaseUrlCustomizer;
+import org.springdoc.core.properties.SpringDocConfigProperties;
+import org.springdoc.core.properties.SwaggerUiConfigProperties;
+import org.springdoc.core.providers.SpringWebProvider;
+import org.springdoc.webmvc.ui.SwaggerWelcomeWebMvc;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 
+/**
+ * This configuration adjusts Swagger URLs when the application is running behind a reverse proxy on Digital Ocean.
+ */
 @Configuration
 public class SwaggerBehindReverseProxyConfig {
 
+    @Bean
+    SwaggerWelcomeWebMvc swaggerWelcome(SwaggerUiConfigProperties swaggerUiConfig, SpringDocConfigProperties springDocConfigProperties, SpringWebProvider springWebProvider) {
+        if (isBehindDigitalOceanReverseProxy()) {
+            swaggerUiConfig.setUrl("/api/v3/api-docs");
+            swaggerUiConfig.setConfigUrl("/api/v3/api-docs/swagger-config");
+        }
+        return new SwaggerWelcomeWebMvc(swaggerUiConfig, springDocConfigProperties, springWebProvider);
+    }
+
     @Bean
     ServerBaseUrlCustomizer serverBaseUrlCustomizer() {
         return (serverBaseUrl, request) -> {
-            if (serverBaseUrl.contains("coursehub.hyf.dev")) {
+            if (isBehindDigitalOceanReverseProxy()) {
                 return serverBaseUrl + "/api";
             }
             return serverBaseUrl;
         };
     }
+
+    private boolean isBehindDigitalOceanReverseProxy() {
+        var appDomain = System.getenv("APP_DOMAIN");
+        return appDomain != null && appDomain.contains("coursehub.hyf.dev");
+    }
 }