Webapp cache control

webapp/src/main/java/info/teksol/mindcode/webapp/WebConfig.java

@@ -2,19 +2,48 @@
 
 import org.springframework.context.annotation.Configuration;
 import org.springframework.core.io.Resource;
+import org.springframework.http.CacheControl;
 import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
 import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
 import org.springframework.web.servlet.resource.PathResourceResolver;
 
 import java.io.IOException;
+import java.util.concurrent.TimeUnit;
 
 @Configuration
 public class WebConfig implements WebMvcConfigurer {
 
     @Override
     public void addResourceHandlers(ResourceHandlerRegistry registry) {
+        // cache page data for an hour, includes stuff like
+        // the list of samples and their source code
+        // Note: Spring's PathPatternParser strictly prohibits "**" in the middle of a pattern
+        // like "/**/__data.json". Instead, we provide patterns for different depth levels.
+        registry.addResourceHandler(
+                "/__data.json",
+                "/*/__data.json",
+                "/*/*/__data.json",
+                "/*/*/*/__data.json"
+        )
+                .addResourceLocations("classpath:/static/")
+                .setCacheControl(CacheControl.maxAge(1, TimeUnit.HOURS));
+
+        // never cache version.json since it can change with each
+        // deployment and is used to trigger client updates
+        registry.addResourceHandler("/_app/version.json")
+                .addResourceLocations("classpath:/static/")
+                .setCacheControl(CacheControl.noStore());
+
+        // cache immutable assets for a year since 
+        // they have content hashes in their names
+        registry.addResourceHandler("/_app/immutable/**")
+                .addResourceLocations("classpath:/static/_app/immutable/")
+                .setCacheControl(CacheControl.maxAge(365, TimeUnit.DAYS).cachePublic());
+
+        // cache html pages for an hour and handle SPA routing
         registry.addResourceHandler("/**")
                 .addResourceLocations("classpath:/static/")
+                .setCacheControl(CacheControl.maxAge(1, TimeUnit.HOURS))
                 .resourceChain(true)
                 .addResolver(new PathResourceResolver() {
                     @Override