Add Open Graph and Twitter Card meta-tags for link previews

Replace PathResourceResolver SPA fallback with SpaController that injects OG/Twitter meta-tags into cached index.html template. Event pages get event-specific tags (title, date, location), all other pages get generic fete branding. Includes og-image.png brand asset and forward-headers-strategy for proxy support. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
2026-03-09 20:25:39 +01:00
parent fa34223c10
commit 751201617d
16 changed files with 1270 additions and 28 deletions
--- a/backend/src/main/java/de/fete/adapter/in/web/SpaController.java
+++ b/backend/src/main/java/de/fete/adapter/in/web/SpaController.java
@@ -0,0 +1,188 @@
+package de.fete.adapter.in.web;
+
+import de.fete.domain.model.Event;
+import de.fete.domain.model.EventToken;
+import de.fete.domain.port.in.GetEventUseCase;
+import jakarta.annotation.PostConstruct;
+import jakarta.servlet.http.HttpServletRequest;
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.time.ZonedDateTime;
+import java.time.format.DateTimeFormatter;
+import java.util.LinkedHashMap;
+import java.util.Locale;
+import java.util.Map;
+import java.util.Optional;
+import java.util.UUID;
+import org.springframework.core.io.ClassPathResource;
+import org.springframework.http.MediaType;
+import org.springframework.stereotype.Controller;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.PathVariable;
+import org.springframework.web.bind.annotation.ResponseBody;
+import org.springframework.web.servlet.support.ServletUriComponentsBuilder;
+
+/** Serves the SPA index.html with injected Open Graph and Twitter Card meta-tags. */
+@Controller
+public class SpaController {
+
+  private static final String PLACEHOLDER = "<!-- OG_META_TAGS -->";
+  private static final int MAX_TITLE_LENGTH = 70;
+  private static final int MAX_DESCRIPTION_LENGTH = 200;
+  private static final String GENERIC_TITLE = "fete";
+  private static final String GENERIC_DESCRIPTION =
+      "Privacy-focused event planning. Create and share events without accounts.";
+  private static final DateTimeFormatter DATE_FORMAT =
+      DateTimeFormatter.ofPattern("EEEE, MMMM d, yyyy 'at' h:mm a", Locale.ENGLISH);
+
+  private final GetEventUseCase getEventUseCase;
+  private String htmlTemplate;
+
+  /** Creates a new SpaController. */
+  public SpaController(GetEventUseCase getEventUseCase) {
+    this.getEventUseCase = getEventUseCase;
+  }
+
+  /** Loads and caches the index.html template at startup. */
+  @PostConstruct
+  void loadTemplate() throws IOException {
+    var resource = new ClassPathResource("/static/index.html");
+    if (resource.exists()) {
+      htmlTemplate = resource.getContentAsString(StandardCharsets.UTF_8);
+    }
+  }
+
+  /** Serves SPA HTML with generic meta-tags for non-event routes. */
+  @GetMapping(
+      value = {"/", "/create", "/events"},
+      produces = MediaType.TEXT_HTML_VALUE
+  )
+  @ResponseBody
+  public String serveGenericPage(HttpServletRequest request) {
+    if (htmlTemplate == null) {
+      return "";
+    }
+    String baseUrl = getBaseUrl(request);
+    return htmlTemplate.replace(PLACEHOLDER, renderTags(buildGenericMeta(baseUrl)));
+  }
+
+  /** Serves SPA HTML with event-specific meta-tags. */
+  @GetMapping(
+      value = "/events/{token}",
+      produces = MediaType.TEXT_HTML_VALUE
+  )
+  @ResponseBody
+  public String serveEventPage(@PathVariable String token,
+      HttpServletRequest request) {
+    if (htmlTemplate == null) {
+      return "";
+    }
+    String baseUrl = getBaseUrl(request);
+    Map<String, String> meta = resolveEventMeta(token, baseUrl);
+    return htmlTemplate.replace(PLACEHOLDER, renderTags(meta));
+  }
+
+  // --- Meta-tag composition ---
+
+  private Map<String, String> buildEventMeta(Event event, String baseUrl) {
+    var tags = new LinkedHashMap<String, String>();
+    String title = truncateTitle(event.getTitle());
+    String description = formatDescription(event);
+    tags.put("og:title", title);
+    tags.put("og:description", description);
+    tags.put("og:url", baseUrl + "/events/" + event.getEventToken().value());
+    tags.put("og:type", "website");
+    tags.put("og:site_name", GENERIC_TITLE);
+    tags.put("og:image", baseUrl + "/og-image.png");
+    tags.put("twitter:card", "summary");
+    tags.put("twitter:title", title);
+    tags.put("twitter:description", description);
+    return tags;
+  }
+
+  private Map<String, String> buildGenericMeta(String baseUrl) {
+    var tags = new LinkedHashMap<String, String>();
+    tags.put("og:title", GENERIC_TITLE);
+    tags.put("og:description", GENERIC_DESCRIPTION);
+    tags.put("og:url", baseUrl);
+    tags.put("og:type", "website");
+    tags.put("og:site_name", GENERIC_TITLE);
+    tags.put("og:image", baseUrl + "/og-image.png");
+    tags.put("twitter:card", "summary");
+    tags.put("twitter:title", GENERIC_TITLE);
+    tags.put("twitter:description", GENERIC_DESCRIPTION);
+    return tags;
+  }
+
+  private Map<String, String> resolveEventMeta(String token, String baseUrl) {
+    try {
+      UUID uuid = UUID.fromString(token);
+      Optional<Event> event =
+          getEventUseCase.getByEventToken(new EventToken(uuid));
+      if (event.isPresent()) {
+        return buildEventMeta(event.get(), baseUrl);
+      }
+    } catch (IllegalArgumentException ignored) {
+      // Invalid UUID — fall back to generic
+    }
+    return buildGenericMeta(baseUrl);
+  }
+
+  // --- Description formatting ---
+
+  private String truncateTitle(String title) {
+    if (title.length() <= MAX_TITLE_LENGTH) {
+      return title;
+    }
+    return title.substring(0, MAX_TITLE_LENGTH - 3) + "...";
+  }
+
+  private String formatDescription(Event event) {
+    ZonedDateTime zoned = event.getDateTime().atZoneSameInstant(event.getTimezone());
+    var sb = new StringBuilder();
+    sb.append("📅 ").append(zoned.format(DATE_FORMAT));
+
+    if (event.getLocation() != null && !event.getLocation().isBlank()) {
+      sb.append(" · 📍 ").append(event.getLocation());
+    }
+
+    if (event.getDescription() != null && !event.getDescription().isBlank()) {
+      sb.append(" — ").append(event.getDescription());
+    }
+
+    String result = sb.toString();
+    if (result.length() > MAX_DESCRIPTION_LENGTH) {
+      return result.substring(0, MAX_DESCRIPTION_LENGTH - 3) + "...";
+    }
+    return result;
+  }
+
+  // --- HTML rendering ---
+
+  private String renderTags(Map<String, String> tags) {
+    var sb = new StringBuilder();
+    for (var entry : tags.entrySet()) {
+      String key = entry.getKey();
+      String value = escapeHtml(entry.getValue());
+      String attr = key.startsWith("twitter:") ? "name" : "property";
+      sb.append("<meta ").append(attr).append("=\"").append(key)
+          .append("\" content=\"").append(value).append("\">\n");
+    }
+    return sb.toString().stripTrailing();
+  }
+
+  private String escapeHtml(String input) {
+    return input
+        .replace("&", "&amp;")
+        .replace("\"", "&quot;")
+        .replace("<", "&lt;")
+        .replace(">", "&gt;");
+  }
+
+  private String getBaseUrl(HttpServletRequest request) {
+    return ServletUriComponentsBuilder.fromRequestUri(request)
+        .replacePath("")
+        .build()
+        .toUriString();
+  }
+}
--- a/backend/src/main/java/de/fete/config/WebConfig.java
+++ b/backend/src/main/java/de/fete/config/WebConfig.java
@@ -1,21 +1,17 @@
 package de.fete.config;

-import java.io.IOException;
 import java.time.Clock;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
-import org.springframework.core.io.ClassPathResource;
-import org.springframework.core.io.Resource;
 import org.springframework.web.bind.annotation.RestController;
 import org.springframework.web.servlet.config.annotation.PathMatchConfigurer;
-import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
 import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
-import org.springframework.web.servlet.resource.PathResourceResolver;

-/** Configures API path prefix and SPA static resource serving. */
+/** Configures API path prefix. Static resources served by default Spring Boot handler. */
@Configuration
 public class WebConfig implements WebMvcConfigurer {

+  /** Provides a system clock bean for time-dependent services. */
  @Bean
  Clock clock() {
    return Clock.systemDefaultZone();
@@ -25,23 +21,4 @@ public class WebConfig implements WebMvcConfigurer {
  public void configurePathMatch(PathMatchConfigurer configurer) {
    configurer.addPathPrefix("/api", c -> c.isAnnotationPresent(RestController.class));
  }
-
-  @Override
-  public void addResourceHandlers(ResourceHandlerRegistry registry) {
-    registry.addResourceHandler("/**")
-        .addResourceLocations("classpath:/static/")
-        .resourceChain(true)
-        .addResolver(new PathResourceResolver() {
-          @Override
-          protected Resource getResource(String resourcePath,
-              Resource location) throws IOException {
-            Resource requested = location.createRelative(resourcePath);
-            if (requested.exists() && requested.isReadable()) {
-              return requested;
-            }
-            Resource index = new ClassPathResource("/static/index.html");
-            return (index.exists() && index.isReadable()) ? index : null;
-          }
-        });
-  }
 }
--- a/backend/src/main/resources/application.properties
+++ b/backend/src/main/resources/application.properties
@@ -7,6 +7,9 @@ spring.jpa.open-in-view=false
 # Liquibase
 spring.liquibase.change-log=classpath:db/changelog/db.changelog-master.xml

+# Proxy headers
+server.forward-headers-strategy=framework
+
 # Actuator
 management.endpoints.web.exposure.include=health
 management.endpoint.health.show-details=never
--- a/backend/src/test/java/de/fete/adapter/in/web/SpaControllerTest.java
+++ b/backend/src/test/java/de/fete/adapter/in/web/SpaControllerTest.java
@@ -0,0 +1,281 @@
+package de.fete.adapter.in.web;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.content;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
+
+import de.fete.TestcontainersConfig;
+import de.fete.adapter.out.persistence.EventJpaEntity;
+import de.fete.adapter.out.persistence.EventJpaRepository;
+import java.time.LocalDate;
+import java.time.OffsetDateTime;
+import java.time.ZoneOffset;
+import java.util.UUID;
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.autoconfigure.web.servlet.AutoConfigureMockMvc;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.context.annotation.Import;
+import org.springframework.http.MediaType;
+import org.springframework.test.web.servlet.MockMvc;
+
+@SpringBootTest
+@AutoConfigureMockMvc
+@Import(TestcontainersConfig.class)
+class SpaControllerTest {
+
+  @Autowired
+  private MockMvc mockMvc;
+
+  @Autowired
+  private EventJpaRepository eventJpaRepository;
+
+  // --- Phase 2: Base functionality ---
+
+  @Test
+  void rootServesHtml() throws Exception {
+    mockMvc.perform(get("/").accept(MediaType.TEXT_HTML))
+        .andExpect(status().isOk())
+        .andExpect(content().contentTypeCompatibleWith(MediaType.TEXT_HTML));
+  }
+
+  @Test
+  void rootHtmlDoesNotContainPlaceholder() throws Exception {
+    String html = mockMvc.perform(get("/").accept(MediaType.TEXT_HTML))
+        .andExpect(status().isOk())
+        .andReturn().getResponse().getContentAsString();
+
+    assertThat(html).doesNotContain("<!-- OG_META_TAGS -->");
+  }
+
+  @Test
+  void createRouteServesHtml() throws Exception {
+    mockMvc.perform(get("/create").accept(MediaType.TEXT_HTML))
+        .andExpect(status().isOk())
+        .andExpect(content().contentTypeCompatibleWith(MediaType.TEXT_HTML));
+  }
+
+  @Test
+  void eventsRouteServesHtml() throws Exception {
+    mockMvc.perform(get("/events").accept(MediaType.TEXT_HTML))
+        .andExpect(status().isOk())
+        .andExpect(content().contentTypeCompatibleWith(MediaType.TEXT_HTML));
+  }
+
+  // --- Phase 4 (US2): Generic OG meta-tags ---
+
+  @Test
+  void rootContainsGenericOgTitle() throws Exception {
+    String html = mockMvc.perform(get("/").accept(MediaType.TEXT_HTML))
+        .andExpect(status().isOk())
+        .andReturn().getResponse().getContentAsString();
+
+    assertThat(html).contains("og:title");
+    assertThat(html).contains("content=\"fete\"");
+  }
+
+  @Test
+  void createRouteContainsGenericOgDescription() throws Exception {
+    String html = mockMvc.perform(get("/create").accept(MediaType.TEXT_HTML))
+        .andExpect(status().isOk())
+        .andReturn().getResponse().getContentAsString();
+
+    assertThat(html).contains("og:description");
+    assertThat(html).contains("Privacy-focused event planning");
+  }
+
+  @Test
+  void unknownRouteReturns404() throws Exception {
+    mockMvc.perform(get("/unknown/path").accept(MediaType.TEXT_HTML))
+        .andExpect(status().isNotFound());
+  }
+
+  // --- Phase 5 (US3): Twitter Card meta-tags ---
+
+  @Test
+  void eventRouteContainsTwitterCardTags() throws Exception {
+    EventJpaEntity event = seedEvent(
+        "Twitter Test", "Testing cards",
+        "Europe/Berlin", "Berlin", LocalDate.now().plusDays(30));
+
+    String html = mockMvc.perform(
+            get("/events/" + event.getEventToken()).accept(MediaType.TEXT_HTML))
+        .andExpect(status().isOk())
+        .andReturn().getResponse().getContentAsString();
+
+    assertThat(html).contains("twitter:card");
+    assertThat(html).contains("twitter:title");
+    assertThat(html).contains("twitter:description");
+  }
+
+  @Test
+  void genericRouteContainsTwitterCardTags() throws Exception {
+    String html = mockMvc.perform(get("/").accept(MediaType.TEXT_HTML))
+        .andExpect(status().isOk())
+        .andReturn().getResponse().getContentAsString();
+
+    assertThat(html).contains("twitter:card");
+    assertThat(html).contains("content=\"summary\"");
+  }
+
+  // --- Phase 3 (US1): Event-specific OG meta-tags ---
+
+  @Test
+  void eventRouteContainsEventSpecificOgTitle() throws Exception {
+    EventJpaEntity event = seedEvent(
+        "Birthday Party", "Come celebrate!",
+        "Europe/Berlin", "Berlin", LocalDate.now().plusDays(30));
+
+    String html = mockMvc.perform(
+            get("/events/" + event.getEventToken()).accept(MediaType.TEXT_HTML))
+        .andExpect(status().isOk())
+        .andReturn().getResponse().getContentAsString();
+
+    assertThat(html).contains("og:title");
+    assertThat(html).contains("Birthday Party");
+  }
+
+  @Test
+  void eventRouteContainsOgDescription() throws Exception {
+    EventJpaEntity event = seedEvent(
+        "BBQ", "Bring drinks!",
+        "Europe/Berlin", "Central Park", LocalDate.now().plusDays(30));
+
+    String html = mockMvc.perform(
+            get("/events/" + event.getEventToken()).accept(MediaType.TEXT_HTML))
+        .andExpect(status().isOk())
+        .andReturn().getResponse().getContentAsString();
+
+    assertThat(html).contains("og:description");
+    assertThat(html).contains("Central Park");
+    assertThat(html).contains("Bring drinks!");
+  }
+
+  @Test
+  void eventRouteContainsOgUrl() throws Exception {
+    EventJpaEntity event = seedEvent(
+        "Party", null,
+        "Europe/Berlin", null, LocalDate.now().plusDays(30));
+
+    String html = mockMvc.perform(
+            get("/events/" + event.getEventToken()).accept(MediaType.TEXT_HTML))
+        .andExpect(status().isOk())
+        .andReturn().getResponse().getContentAsString();
+
+    assertThat(html).contains("og:url");
+    assertThat(html).contains("/events/" + event.getEventToken());
+  }
+
+  @Test
+  void eventRouteContainsOgImage() throws Exception {
+    EventJpaEntity event = seedEvent(
+        "Party", null,
+        "Europe/Berlin", null, LocalDate.now().plusDays(30));
+
+    String html = mockMvc.perform(
+            get("/events/" + event.getEventToken()).accept(MediaType.TEXT_HTML))
+        .andExpect(status().isOk())
+        .andReturn().getResponse().getContentAsString();
+
+    assertThat(html).contains("og:image");
+    assertThat(html).contains("/og-image.png");
+  }
+
+  @Test
+  void unknownEventTokenFallsBackToGenericMeta() throws Exception {
+    String html = mockMvc.perform(
+            get("/events/" + UUID.randomUUID()).accept(MediaType.TEXT_HTML))
+        .andExpect(status().isOk())
+        .andReturn().getResponse().getContentAsString();
+
+    assertThat(html).contains("og:title");
+    assertThat(html).contains("content=\"fete\"");
+  }
+
+  // --- HTML escaping ---
+
+  @Test
+  void specialCharactersAreHtmlEscaped() throws Exception {
+    EventJpaEntity event = seedEvent(
+        "Tom & Jerry's \"Party\"", "Fun <times> & more",
+        "Europe/Berlin", "O'Brien's Pub", LocalDate.now().plusDays(30));
+
+    String html = mockMvc.perform(
+            get("/events/" + event.getEventToken()).accept(MediaType.TEXT_HTML))
+        .andExpect(status().isOk())
+        .andReturn().getResponse().getContentAsString();
+
+    assertThat(html).contains("Tom &amp; Jerry");
+    assertThat(html).contains("&amp; more");
+    assertThat(html).contains("&lt;times&gt;");
+    assertThat(html).doesNotContain("content=\"Tom & Jerry");
+  }
+
+  // --- Title truncation ---
+
+  @Test
+  void longTitleIsTruncatedTo70Chars() throws Exception {
+    String longTitle = "A".repeat(80);
+    EventJpaEntity event = seedEvent(
+        longTitle, "Desc",
+        "Europe/Berlin", null, LocalDate.now().plusDays(30));
+
+    String html = mockMvc.perform(
+            get("/events/" + event.getEventToken()).accept(MediaType.TEXT_HTML))
+        .andExpect(status().isOk())
+        .andReturn().getResponse().getContentAsString();
+
+    assertThat(html).contains("A".repeat(67) + "...");
+    assertThat(html).doesNotContain("A".repeat(68));
+  }
+
+  // --- Description formatting ---
+
+  @Test
+  void eventWithoutLocationOmitsPinEmoji() throws Exception {
+    EventJpaEntity event = seedEvent(
+        "Online Meetup", "Virtual gathering",
+        "Europe/Berlin", null, LocalDate.now().plusDays(30));
+
+    String html = mockMvc.perform(
+            get("/events/" + event.getEventToken()).accept(MediaType.TEXT_HTML))
+        .andExpect(status().isOk())
+        .andReturn().getResponse().getContentAsString();
+
+    assertThat(html).doesNotContain("📍");
+  }
+
+  @Test
+  void eventWithoutDescriptionOmitsDash() throws Exception {
+    EventJpaEntity event = seedEvent(
+        "Silent Event", null,
+        "Europe/Berlin", "Berlin", LocalDate.now().plusDays(30));
+
+    String html = mockMvc.perform(
+            get("/events/" + event.getEventToken()).accept(MediaType.TEXT_HTML))
+        .andExpect(status().isOk())
+        .andReturn().getResponse().getContentAsString();
+
+    assertThat(html).contains("📅");
+    assertThat(html).contains("Berlin");
+    assertThat(html).doesNotContain(" — ");
+  }
+
+  private EventJpaEntity seedEvent(
+      String title, String description, String timezone,
+      String location, LocalDate expiryDate) {
+    var entity = new EventJpaEntity();
+    entity.setEventToken(UUID.randomUUID());
+    entity.setOrganizerToken(UUID.randomUUID());
+    entity.setTitle(title);
+    entity.setDescription(description);
+    entity.setDateTime(
+        OffsetDateTime.of(2026, 6, 15, 20, 0, 0, 0, ZoneOffset.ofHours(2)));
+    entity.setTimezone(timezone);
+    entity.setLocation(location);
+    entity.setExpiryDate(expiryDate);
+    entity.setCreatedAt(OffsetDateTime.now());
+    return eventJpaRepository.save(entity);
+  }
+}
--- a/backend/src/test/java/de/fete/config/WebConfigTest.java
+++ b/backend/src/test/java/de/fete/config/WebConfigTest.java
@@ -29,8 +29,10 @@ class WebConfigTest {

  @Test
  void apiPrefixNotAccessibleWithoutIt() throws Exception {
-    // /events without /api prefix should not resolve to the API endpoint
-    mockMvc.perform(get("/events"))
-        .andExpect(status().isNotFound());
+    // /events without /api prefix should not resolve to the REST API endpoint;
+    // it is served by SpaController as HTML instead
+    mockMvc.perform(get("/events")
+            .accept("text/html"))
+        .andExpect(status().isOk());
  }
 }
--- a/backend/src/test/resources/static/index.html
+++ b/backend/src/test/resources/static/index.html
@@ -0,0 +1,13 @@
+<!DOCTYPE html>
+<html lang="en">
+  <head>
+    <meta charset="UTF-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <link rel="icon" type="image/svg+xml" href="/favicon.svg">
+    <!-- OG_META_TAGS -->
+    <title>fete</title>
+  </head>
+  <body>
+    <div id="app"></div>
+  </body>
+</html>