Use ElementTagPostProcessor to handle image replacement

build.gradle

@@ -16,7 +16,7 @@ repositories {
 }
 
 dependencies {
-    implementation platform('run.halo.tools.platform:plugin:2.17.0-SNAPSHOT')
+    implementation platform('run.halo.tools.platform:plugin:2.20.0-SNAPSHOT')
     compileOnly 'run.halo.app:api'
 
     testImplementation 'run.halo.app:api'

src/main/java/se/webp/plugin/ImageTagProcessor.java

@@ -0,0 +1,111 @@
+package se.webp.plugin;
+
+import static org.thymeleaf.templatemode.TemplateMode.HTML;
+import static se.webp.plugin.Settings.BasicConfig.GROUP;
+
+import java.net.URI;
+import java.net.URL;
+import java.util.Objects;
+import java.util.Optional;
+import org.apache.commons.lang3.ArrayUtils;
+import org.springframework.stereotype.Component;
+import org.springframework.util.StringUtils;
+import org.springframework.web.util.UriComponentsBuilder;
+import org.thymeleaf.context.ITemplateContext;
+import org.thymeleaf.engine.ElementNames;
+import org.thymeleaf.model.IAttribute;
+import org.thymeleaf.model.IProcessableElementTag;
+import org.thymeleaf.processor.element.MatchingElementName;
+import org.thymeleaf.spring6.context.SpringContextUtils;
+import org.thymeleaf.spring6.context.webflux.SpringWebFluxThymeleafRequestContext;
+import reactor.core.publisher.Flux;
+import reactor.core.publisher.Mono;
+import run.halo.app.infra.ExternalUrlSupplier;
+import run.halo.app.plugin.ReactiveSettingFetcher;
+import run.halo.app.theme.dialect.ElementTagPostProcessor;
+
+@Component
+public class ImageTagProcessor implements ElementTagPostProcessor {
+
+    private final MatchingElementName matchingElementName;
+
+    private final ReactiveSettingFetcher settingFetcher;
+
+    private final ExternalUrlSupplier externalUrlSupplier;
+
+    public ImageTagProcessor(ReactiveSettingFetcher settingFetcher,
+        ExternalUrlSupplier externalUrlSupplier) {
+        this.settingFetcher = settingFetcher;
+        this.externalUrlSupplier = externalUrlSupplier;
+        this.matchingElementName =
+            MatchingElementName.forElementName(HTML, ElementNames.forHTMLName("img"));
+    }
+
+    private static boolean urlMatches(URL firstUrl, URL secondUrl) {
+        return Objects.equals(firstUrl.getAuthority(), secondUrl.getAuthority());
+    }
+
+    @Override
+    public Mono<IProcessableElementTag> process(ITemplateContext context,
+        IProcessableElementTag tag) {
+        if (!matchingElementName.matches(tag.getElementDefinition().getElementName())) {
+            return Mono.empty();
+        }
+        var requestContext = SpringContextUtils.getRequestContext(context);
+        if (!(requestContext instanceof SpringWebFluxThymeleafRequestContext springWebContext)) {
+            return Mono.empty();
+        }
+        var srcValue = Optional.ofNullable(tag.getAttribute("src"))
+            .map(IAttribute::getValue)
+            .filter(StringUtils::hasText)
+            .map(URI::create);
+        if (srcValue.isEmpty()) {
+            return Mono.empty();
+        }
+        var exchange = springWebContext.getServerWebExchange();
+        var externalUrl = externalUrlSupplier.getURL(exchange.getRequest());
+
+        return settingFetcher.fetch(GROUP, Settings.BasicConfig.class)
+            .filter(config -> !ArrayUtils.isEmpty(config.getProxies()))
+            .flatMapMany(config -> Flux.fromArray(config.getProxies()))
+            .filter(proxy ->
+                Objects.nonNull(proxy.getProxyUrl()) && Objects.nonNull(proxy.getOriginUrl())
+            )
+            .filter(proxy -> urlMatches(externalUrl, proxy.getOriginUrl()))
+            .next()
+            .map(proxy -> {
+                var srcBuilder = UriComponentsBuilder.fromHttpUrl(proxy.getProxyUrl().toString())
+                    .path(srcValue.get().getPath())
+                    .query(srcValue.get().getQuery())
+                    .fragment(srcValue.get().getFragment());
+                var newSrc = srcBuilder.toUriString();
+                var modelFactory = context.getModelFactory();
+                var newTag = tag;
+                if (!tag.hasAttribute("srcset")) {
+                    // calculate srcset and sizes
+                    newTag = modelFactory.setAttribute(newTag, "sizes",
+                        """
+                            (max-width: 400px) 400px, (max-width: 800px) 800px, \
+                            (max-width: 1200px) 1200px, (max-width: 1600px) 1600px\
+                            """);
+                    var w400Src = srcBuilder.cloneBuilder().queryParam("width", 400)
+                        .toUriString();
+                    var w800Src = srcBuilder.cloneBuilder().queryParam("width", 800)
+                        .toUriString();
+                    var w1200Src = srcBuilder.cloneBuilder().queryParam("width", 1200)
+                        .toUriString();
+                    var w1600Src = srcBuilder.cloneBuilder().queryParam("width", 1600)
+                        .toUriString();
+                    newTag = modelFactory.setAttribute(newTag, "srcset",
+                        w400Src + " 400w, "
+                            + w800Src + " 800w, "
+                            + w1200Src + " 1200w, "
+                            + w1600Src + " 1600w"
+                    );
+                }
+                newTag = modelFactory.setAttribute(newTag, "src",
+                    newSrc);
+                return newTag;
+            });
+    }
+}

src/main/java/se/webp/plugin/Settings.java

@@ -1,28 +1,29 @@
 package se.webp.plugin;
 
+import com.fasterxml.jackson.annotation.JsonProperty;
+import java.net.URL;
 import lombok.Data;
-import reactor.core.publisher.Mono;
-import run.halo.app.plugin.ReactiveSettingFetcher;
 
 public class Settings {
 
-    public static Mono<BasicConfig> getBasicConfig(ReactiveSettingFetcher settingFetcher) {
-        return settingFetcher.fetch(BasicConfig.GROUP, BasicConfig.class);
-    }
-
     @Data
     public static class BasicConfig {
+
         public static final String GROUP = "basic";
 
         String apiKeySecret;
 
         Proxy[] proxies;
+
     }
 
     @Data
     public static class Proxy {
-        String origin_url;
 
-        String proxy_url;
+        @JsonProperty("origin_url")
+        URL originUrl;
+
+        @JsonProperty("proxy_url")
+        URL proxyUrl;
     }
 }

src/main/resources/plugin.yaml

@@ -4,7 +4,7 @@ metadata:
   name: plugin-webp-se-cloud
 spec:
   enabled: true
-  requires: ">=2.7.0"
+  requires: ">=2.20.0"
   author:
     name: WebP Cloud Services
     website: https://webp.se/