feat: add system info getter for plugin

api/src/main/java/run/halo/app/infra/SystemInfoGetter.java

@@ -0,0 +1,45 @@
+package run.halo.app.infra;
+
+import com.github.zafarkhaja.semver.Version;
+import java.net.URL;
+import java.util.Locale;
+import java.util.TimeZone;
+import java.util.function.Supplier;
+import lombok.Data;
+import lombok.experimental.Accessors;
+import reactor.core.publisher.Mono;
+
+public interface SystemInfoGetter extends Supplier<Mono<SystemInfoGetter.SystemInfo>> {
+
+    @Data
+    @Accessors(chain = true)
+    class SystemInfo {
+        private String title;
+
+        private String subtitle;
+
+        private String logo;
+
+        private String favicon;
+
+        private URL url;
+
+        private Version version;
+
+        private SeoProp seo;
+
+        private Locale locale;
+
+        private TimeZone timeZone;
+
+        private String activatedThemeName;
+    }
+
+    @Data
+    @Accessors(chain = true)
+    class SeoProp {
+        private boolean blockSpiders;
+        private String keywords;
+        private String description;
+    }
+}

application/src/main/java/run/halo/app/infra/SystemInfoGetterImpl.java

@@ -0,0 +1,71 @@
+package run.halo.app.infra;
+
+import java.net.MalformedURLException;
+import java.net.URI;
+import java.net.URL;
+import java.util.Locale;
+import java.util.TimeZone;
+import lombok.RequiredArgsConstructor;
+import org.apache.commons.lang3.BooleanUtils;
+import org.apache.commons.lang3.StringUtils;
+import org.springframework.boot.autoconfigure.web.ServerProperties;
+import org.springframework.boot.autoconfigure.web.reactive.WebFluxProperties;
+import org.springframework.stereotype.Component;
+import reactor.core.publisher.Mono;
+
+@Component
+@RequiredArgsConstructor
+public class SystemInfoGetterImpl implements SystemInfoGetter {
+    private final SystemConfigurableEnvironmentFetcher environmentFetcher;
+    private final SystemVersionSupplier systemVersionSupplier;
+    private final ExternalUrlSupplier externalUrlSupplier;
+    private final ServerProperties serverProperties;
+    private final WebFluxProperties webFluxProperties;
+
+    @Override
+    public Mono<SystemInfo> get() {
+        var systemInfo = new SystemInfo()
+            .setVersion(systemVersionSupplier.get())
+            .setUrl(getExternalUrl())
+            // TODO populate locale and timezone from system settings in the future
+            .setLocale(Locale.getDefault())
+            .setTimeZone(TimeZone.getDefault());
+
+        var basicMono =
+            environmentFetcher.fetch(SystemSetting.Basic.GROUP, SystemSetting.Basic.class)
+                .doOnNext(basic -> systemInfo.setTitle(basic.getTitle())
+                    .setSubtitle(basic.getSubtitle())
+                    .setLogo(basic.getLogo())
+                    .setFavicon(basic.getFavicon())
+                );
+
+        var seoMono = environmentFetcher.fetch(SystemSetting.Seo.GROUP, SystemSetting.Seo.class)
+            .doOnNext(seo -> systemInfo.setSeo(new SeoProp()
+                .setBlockSpiders(BooleanUtils.isTrue(seo.blockSpiders))
+                .setKeywords(seo.getKeywords())
+                .setDescription(seo.getDescription())
+            ));
+
+        var themeMono =
+            environmentFetcher.fetch(SystemSetting.Theme.GROUP, SystemSetting.Theme.class)
+                .doOnNext(theme -> systemInfo.setActivatedThemeName(theme.getActive()));
+        return Mono.when(basicMono, seoMono, themeMono)
+            .thenReturn(systemInfo);
+    }
+
+    private URL getExternalUrl() {
+        var url = externalUrlSupplier.getRaw();
+        if (url != null) {
+            return url;
+        }
+        var port = serverProperties.getPort();
+        var basePath = StringUtils.defaultIfBlank(webFluxProperties.getBasePath(), "/");
+        try {
+            var uriStr = "http://localhost:" + port + basePath;
+            return URI.create(StringUtils.removeEnd(uriStr, "/")).toURL();
+        } catch (MalformedURLException e) {
+            // Should not happen
+            throw new RuntimeException("Cannot create URL from server properties.", e);
+        }
+    }
+}

application/src/main/java/run/halo/app/plugin/SharedApplicationContextFactory.java

@@ -17,6 +17,7 @@
 import run.halo.app.infra.BackupRootGetter;
 import run.halo.app.infra.ExternalLinkProcessor;
 import run.halo.app.infra.ExternalUrlSupplier;
+import run.halo.app.infra.SystemInfoGetter;
 import run.halo.app.notification.NotificationCenter;
 import run.halo.app.notification.NotificationReasonEmitter;
 import run.halo.app.plugin.extensionpoint.ExtensionGetter;
@@ -97,6 +98,10 @@ public static ApplicationContext create(ApplicationContext rootContext) {
             .ifUnique(userDetailsService ->
                 beanFactory.registerSingleton("userDetailsService", userDetailsService)
             );
+        rootContext.getBeanProvider(SystemInfoGetter.class)
+            .ifUnique(systemInfoGetter ->
+                beanFactory.registerSingleton("systemInfoGetter", systemInfoGetter)
+            );
         // TODO add more shared instance here
 
         sharedContext.refresh();