ActivityPub: HTTP Signatures and autoaccept followers

17 files changed, 211 insertions, 116 deletions

diff --git a/juick-server/src/main/java/com/juick/server/api/activity/Profile.java b/juick-server/src/main/java/com/juick/server/api/activity/Profile.java
index 9f98b4ea..656d85dd 100644
--- a/juick-server/src/main/java/com/juick/server/api/activity/Profile.java
+++ b/juick-server/src/main/java/com/juick/server/api/activity/Profile.java
@@ -2,24 +2,33 @@ package com.juick.server.api.activity;
 
 import com.juick.User;
 import com.juick.server.KeystoreManager;
+import com.juick.server.SignatureManager;
 import com.juick.server.api.activity.model.*;
+import com.juick.server.api.activity.model.activities.Create;
+import com.juick.server.api.activity.model.activities.Follow;
+import com.juick.server.api.activity.model.activities.Undo;
 import com.juick.server.util.HttpNotFoundException;
 import com.juick.server.util.UserUtils;
 import com.juick.service.MessagesService;
 import com.juick.service.UserService;
+import com.juick.service.activities.FollowEvent;
 import com.juick.util.MessageUtils;
 import org.apache.commons.lang3.StringUtils;
 import org.springframework.beans.factory.annotation.Value;
-import org.springframework.web.bind.annotation.GetMapping;
-import org.springframework.web.bind.annotation.PathVariable;
-import org.springframework.web.bind.annotation.RequestParam;
-import org.springframework.web.bind.annotation.RestController;
+import org.springframework.context.ApplicationEventPublisher;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.*;
 import org.springframework.web.servlet.support.ServletUriComponentsBuilder;
+import org.springframework.web.util.UriComponents;
 import org.springframework.web.util.UriComponentsBuilder;
 
 import javax.inject.Inject;
+import java.net.URI;
 import java.util.Collections;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
@@ -31,6 +40,10 @@ public class Profile {
     private MessagesService messagesService;
     @Inject
     private KeystoreManager keystoreManager;
+    @Inject
+    private SignatureManager signatureManager;
+    @Inject
+    private ApplicationEventPublisher applicationEventPublisher;
     @Value("${web_domain:localhost}")
     private String domain;
     @Value("${ap_base_uri:http://localhost:8080/}")
@@ -38,7 +51,7 @@ public class Profile {
     @Value("${img_url:http://localhost:8080/i/}")
     private String baseImagesUri;
 
-    @GetMapping(value = "/u/{userName}", produces = { ActivityObject.LD_JSON_MEDIA_TYPE, ActivityObject.ACTIVITY_JSON_MEDIA_TYPE })
+    @GetMapping(value = "/u/{userName}", produces = { Context.LD_JSON_MEDIA_TYPE, Context.ACTIVITY_JSON_MEDIA_TYPE })
     public Person getUser(@PathVariable String userName) {
         User user = userService.getUserByName(userName);
         if (!user.isAnonymous()) {
@@ -52,9 +65,9 @@ public class Profile {
             Key publicKey = new Key();
             publicKey.setId(person.getId() + "#main-key");
             publicKey.setOwner(person.getId());
-            publicKey.setPublicKeyPem(keystoreManager.getPublicKey());
+            publicKey.setPublicKeyPem(keystoreManager.getPublicKeyPem());
             person.setPublicKey(publicKey);
-            uri.replacePath("/post");
+            uri.replacePath("/api/inbox");
             person.setInbox(uri.toUriString());
             person.setOutbox(uri.replacePath(String.format("/u/%s/blog/toc", userName)).toUriString());
             person.setFollowers(uri.replacePath(String.format("/u/%s/followers/toc", userName)).toUriString());
@@ -65,11 +78,11 @@ public class Profile {
             avatar.setUrl(image.toUriString());
             avatar.setMediaType("image/png");
             person.setIcon(avatar);
-            return (Person) ActivityObject.build(person);
+            return (Person) Context.build(person);
         }
         throw new HttpNotFoundException();
     }
-    @GetMapping(value = "/u/{userName}/blog/toc", produces = { ActivityObject.LD_JSON_MEDIA_TYPE, ActivityObject.ACTIVITY_JSON_MEDIA_TYPE })
+    @GetMapping(value = "/u/{userName}/blog/toc", produces = { Context.LD_JSON_MEDIA_TYPE, Context.ACTIVITY_JSON_MEDIA_TYPE })
     public OrderedCollection getOutbox(@PathVariable String userName) {
         User user = userService.getUserByName(userName);
         if (!user.isAnonymous()) {
@@ -78,11 +91,11 @@ public class Profile {
             blog.setId(ServletUriComponentsBuilder.fromCurrentRequestUri().toUriString());
             blog.setTotalItems(userService.getStatsMessages(user.getUid()));
             blog.setFirst(uriComponentsBuilder.path(String.format("/u/%s/blog", userName)).toUriString());
-            return (OrderedCollection) ActivityObject.build(blog);
+            return (OrderedCollection) Context.build(blog);
         }
         throw new HttpNotFoundException();
     }
-    @GetMapping(value = "/u/{userName}/blog", produces = { ActivityObject.LD_JSON_MEDIA_TYPE, ActivityObject.ACTIVITY_JSON_MEDIA_TYPE })
+    @GetMapping(value = "/u/{userName}/blog", produces = { Context.LD_JSON_MEDIA_TYPE, Context.ACTIVITY_JSON_MEDIA_TYPE })
     public OrderedCollectionPage getOutboxPage(@PathVariable String userName,
                                            @RequestParam(required = false, defaultValue = "0") int before) {
         User visitor = UserUtils.getCurrentUser();
@@ -127,11 +140,11 @@ public class Profile {
                 page.setNext(uri.queryParam("before", beforeNext).toUriString());
             }
             page.setLast(uri.replaceQueryParam("before", "1").toUriString());
-            return (OrderedCollectionPage) ActivityObject.build(page);
+            return (OrderedCollectionPage) Context.build(page);
         }
         throw new HttpNotFoundException();
     }
-    @GetMapping(value = "/u/{userName}/followers/toc", produces = { ActivityObject.LD_JSON_MEDIA_TYPE, ActivityObject.ACTIVITY_JSON_MEDIA_TYPE })
+    @GetMapping(value = "/u/{userName}/followers/toc", produces = { Context.LD_JSON_MEDIA_TYPE, Context.ACTIVITY_JSON_MEDIA_TYPE })
     public OrderedCollection getFollowers(@PathVariable String userName) {
         User user = userService.getUserByName(userName);
         if (!user.isAnonymous()) {
@@ -140,11 +153,11 @@ public class Profile {
             followers.setId(ServletUriComponentsBuilder.fromCurrentRequestUri().toUriString());
             followers.setTotalItems(userService.getStatsMyReaders(user.getUid()));
             followers.setFirst(uriComponentsBuilder.path(String.format("/u/%s/followers", userName)).toUriString());
-            return (OrderedCollection) ActivityObject.build(followers);
+            return (OrderedCollection) Context.build(followers);
         }
         throw new HttpNotFoundException();
     }
-    @GetMapping(value = "/u/{userName}/followers", produces = { ActivityObject.LD_JSON_MEDIA_TYPE, ActivityObject.ACTIVITY_JSON_MEDIA_TYPE })
+    @GetMapping(value = "/u/{userName}/followers", produces = { Context.LD_JSON_MEDIA_TYPE, Context.ACTIVITY_JSON_MEDIA_TYPE })
     public OrderedCollectionPage getFollowersPage(@PathVariable String userName,
                                                @RequestParam(required = false, defaultValue = "0") int page) {
         User user = userService.getUserByName(userName);
@@ -169,11 +182,11 @@ public class Profile {
             if (hasNext) {
                 result.setNext(uriComponentsBuilder.queryParam("page", page + 1).toUriString());
             }
-            return (OrderedCollectionPage) ActivityObject.build(result);
+            return (OrderedCollectionPage) Context.build(result);
         }
         throw new HttpNotFoundException();
     }
-    @GetMapping(value = "/u/{userName}/following/toc", produces = { ActivityObject.LD_JSON_MEDIA_TYPE, ActivityObject.ACTIVITY_JSON_MEDIA_TYPE })
+    @GetMapping(value = "/u/{userName}/following/toc", produces = { Context.LD_JSON_MEDIA_TYPE, Context.ACTIVITY_JSON_MEDIA_TYPE })
     public OrderedCollection getFollowing(@PathVariable String userName) {
         User user = userService.getUserByName(userName);
         if (!user.isAnonymous()) {
@@ -182,11 +195,11 @@ public class Profile {
             following.setId(ServletUriComponentsBuilder.fromCurrentRequestUri().toUriString());
             following.setTotalItems(userService.getUserFriends(user.getUid()).size());
             following.setFirst(uriComponentsBuilder.path(String.format("/u/%s/followers", userName)).toUriString());
-            return (OrderedCollection) ActivityObject.build(following);
+            return (OrderedCollection) Context.build(following);
         }
         throw new HttpNotFoundException();
     }
-    @GetMapping(value = "/u/{userName}/following", produces = { ActivityObject.LD_JSON_MEDIA_TYPE, ActivityObject.ACTIVITY_JSON_MEDIA_TYPE })
+    @GetMapping(value = "/u/{userName}/following", produces = { Context.LD_JSON_MEDIA_TYPE, Context.ACTIVITY_JSON_MEDIA_TYPE })
     public OrderedCollectionPage getFollowingPage(@PathVariable String userName,
                                                   @RequestParam(required = false, defaultValue = "0") int page) {
         User user = userService.getUserByName(userName);
@@ -211,8 +224,37 @@ public class Profile {
             if (hasNext) {
                 result.setNext(uriComponentsBuilder.queryParam("page", page + 1).toUriString());
             }
-            return (OrderedCollectionPage) ActivityObject.build(result);
+            return (OrderedCollectionPage) Context.build(result);
         }
         throw new HttpNotFoundException();
     }
+    @PostMapping(value = "/api/inbox", consumes = { Context.LD_JSON_MEDIA_TYPE, Context.ACTIVITY_JSON_MEDIA_TYPE })
+    public ResponseEntity<Void> processInbox(@RequestBody Context activity,
+                                             @RequestHeader(name = "Host") String host,
+                                             @RequestHeader(name = "Date") String date,
+                                             @RequestHeader(name = "Digest") String digest,
+                                             @RequestHeader(name = "Content-Type") String contentType,
+                                             @RequestHeader(name = "Signature") String signature) {
+        if (activity instanceof Follow) {
+            Follow followRequest = (Follow) activity;
+            UriComponents componentsBuilder = ServletUriComponentsBuilder.fromCurrentRequestUri().build();
+            Map<String, String> headers = new HashMap<>();
+            headers.put("host", host);
+            headers.put("date", date);
+            headers.put("digest", digest);
+            headers.put("content-type", contentType);
+            boolean valid = signatureManager.verifySignature(signature, URI.create(followRequest.getActor()), "POST",
+                    componentsBuilder.getPath(), headers);
+            if (valid) {
+                applicationEventPublisher.publishEvent(
+                        new FollowEvent(this, followRequest));
+                return new ResponseEntity<>(HttpStatus.ACCEPTED);
+            }
+            return new ResponseEntity<>(HttpStatus.UNAUTHORIZED);
+        }
+        if (activity instanceof Undo) {
+            return new ResponseEntity<>(HttpStatus.OK);
+        }
+        return new ResponseEntity<>(HttpStatus.BAD_REQUEST);
+    }
 }
diff --git a/juick-server/src/main/java/com/juick/server/api/activity/model/Activity.java b/juick-server/src/main/java/com/juick/server/api/activity/model/Activity.java
new file mode 100644
index 00000000..ec126b88
--- /dev/null
+++ b/juick-server/src/main/java/com/juick/server/api/activity/model/Activity.java
@@ -0,0 +1,23 @@
+package com.juick.server.api.activity.model;
+
+public abstract class Activity extends Context {
+
+    private String actor;
+    private Object object;
+
+    public String getActor() {
+        return actor;
+    }
+
+    public void setActor(String actor) {
+        this.actor = actor;
+    }
+
+    public Object getObject() {
+        return object;
+    }
+
+    public void setObject(Object object) {
+        this.object = object;
+    }
+}
diff --git a/juick-server/src/main/java/com/juick/server/api/activity/model/ActivityObject.java b/juick-server/src/main/java/com/juick/server/api/activity/model/ActivityObject.java
deleted file mode 100644
index fceb3612..00000000
--- a/juick-server/src/main/java/com/juick/server/api/activity/model/ActivityObject.java
+++ /dev/null
@@ -1,52 +0,0 @@
-package com.juick.server.api.activity.model;
-
-import com.fasterxml.jackson.annotation.JsonProperty;
-
-import java.time.Instant;
-import java.util.Arrays;
-import java.util.Collections;
-import java.util.List;
-
-public abstract class ActivityObject {
-
-    private List<String> context;
-
-    private String id;
-
-    private Instant published;
-
-    public String getId() {
-        return id;
-    }
-
-    public void setId(String id) {
-        this.id = id;
-    }
-
-    public String getType() {
-        return getClass().getSimpleName();
-    }
-
-    @JsonProperty("@context")
-    public List<String> getContext() {
-        return context;
-    }
-
-    public final static String ACTIVITY_STREAMS_URI = "https://www.w3.org/ns/activitystreams";
-    public final static String SECURITY_URI = "https://w3id.org/security/v1";
-    public final static String LD_JSON_MEDIA_TYPE = "application/ld+json; profile=\"https://www.w3.org/ns/activitystreams\"";
-    public final static String ACTIVITY_JSON_MEDIA_TYPE = "application/activity+json; profile=\"https://www.w3.org/ns/activitystreams\"";
-
-    public Instant getPublished() {
-        return published;
-    }
-
-    public void setPublished(Instant published) {
-        this.published = published;
-    }
-
-    public static ActivityObject build(ActivityObject response) {
-        response.context = Arrays.asList(ACTIVITY_STREAMS_URI, SECURITY_URI);
-        return response;
-    }
-}
diff --git a/juick-server/src/main/java/com/juick/server/api/activity/model/Context.java b/juick-server/src/main/java/com/juick/server/api/activity/model/Context.java
new file mode 100644
index 00000000..984eb2cd
--- /dev/null
+++ b/juick-server/src/main/java/com/juick/server/api/activity/model/Context.java
@@ -0,0 +1,82 @@
+package com.juick.server.api.activity.model;
+
+import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonSubTypes;
+import com.fasterxml.jackson.annotation.JsonTypeInfo;
+import com.juick.server.api.activity.model.activities.*;
+
+import java.time.Instant;
+import java.util.Arrays;
+import java.util.List;
+
+@JsonIgnoreProperties(ignoreUnknown = true)
+@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, property="type")
+@JsonSubTypes({
+        @JsonSubTypes.Type(value = Create.class, name = "Create"),
+        @JsonSubTypes.Type(value = Delete.class, name = "Delete"),
+        @JsonSubTypes.Type(value = Follow.class, name = "Follow"),
+        @JsonSubTypes.Type(value = Accept.class, name = "Accept"),
+        @JsonSubTypes.Type(value = Undo.class, name = "Undo"),
+        @JsonSubTypes.Type(value = Image.class, name = "Image"),
+        @JsonSubTypes.Type(value = Key.class, name = "Key"),
+        @JsonSubTypes.Type(value = Link.class, name = "Link"),
+        @JsonSubTypes.Type(value = Note.class, name = "Note"),
+        @JsonSubTypes.Type(value = OrderedCollection.class, name = "OrderedCollection"),
+        @JsonSubTypes.Type(value = OrderedCollectionPage.class, name = "OrderedCollectionPage"),
+        @JsonSubTypes.Type(value = Person.class, name = "Person")
+})
+public abstract class Context {
+
+    private List<Object> context;
+
+    private String id;
+
+    private Instant published;
+
+
+    private List<String> to;
+
+    public String getId() {
+        return id;
+    }
+
+    public void setId(String id) {
+        this.id = id;
+    }
+
+    public String getType() {
+        return getClass().getSimpleName();
+    }
+
+    @JsonProperty("@context")
+    public List<Object> getContext() {
+        return context;
+    }
+
+    public final static String ACTIVITY_STREAMS_URI = "https://www.w3.org/ns/activitystreams";
+    public final static String SECURITY_URI = "https://w3id.org/security/v1";
+    public final static String LD_JSON_MEDIA_TYPE = "application/ld+json; profile=\"https://www.w3.org/ns/activitystreams\"";
+    public final static String ACTIVITY_JSON_MEDIA_TYPE = "application/activity+json; profile=\"https://www.w3.org/ns/activitystreams\"";
+
+    public Instant getPublished() {
+        return published;
+    }
+
+    public void setPublished(Instant published) {
+        this.published = published;
+    }
+
+    public List<String> getTo() {
+        return to;
+    }
+
+    public void setTo(List<String> to) {
+        this.to = to;
+    }
+
+    public static Context build(Context response) {
+        response.context = Arrays.asList(ACTIVITY_STREAMS_URI, SECURITY_URI);
+        return response;
+    }
+}
diff --git a/juick-server/src/main/java/com/juick/server/api/activity/model/Create.java b/juick-server/src/main/java/com/juick/server/api/activity/model/Create.java
deleted file mode 100644
index 2acdd6a6..00000000
--- a/juick-server/src/main/java/com/juick/server/api/activity/model/Create.java
+++ /dev/null
@@ -1,34 +0,0 @@
-package com.juick.server.api.activity.model;
-
-import java.util.List;
-
-public class Create extends ActivityObject {
-
-    private String actor;
-    private Note object;
-    private List<String> to;
-
-    public String getActor() {
-        return actor;
-    }
-
-    public void setActor(String actor) {
-        this.actor = actor;
-    }
-
-    public Note getObject() {
-        return object;
-    }
-
-    public void setObject(Note object) {
-        this.object = object;
-    }
-
-    public List<String> getTo() {
-        return to;
-    }
-
-    public void setTo(List<String> to) {
-        this.to = to;
-    }
-}
diff --git a/juick-server/src/main/java/com/juick/server/api/activity/model/Image.java b/juick-server/src/main/java/com/juick/server/api/activity/model/Image.java
index 9a3b1659..c8f869a5 100644
--- a/juick-server/src/main/java/com/juick/server/api/activity/model/Image.java
+++ b/juick-server/src/main/java/com/juick/server/api/activity/model/Image.java
@@ -1,6 +1,6 @@
 package com.juick.server.api.activity.model;
 
-public class Image extends ActivityObject {
+public class Image extends Context {
     private String mediaType;
     private String url;
 
diff --git a/juick-server/src/main/java/com/juick/server/api/activity/model/Key.java b/juick-server/src/main/java/com/juick/server/api/activity/model/Key.java
index 32417778..bc41b460 100644
--- a/juick-server/src/main/java/com/juick/server/api/activity/model/Key.java
+++ b/juick-server/src/main/java/com/juick/server/api/activity/model/Key.java
@@ -1,6 +1,6 @@
 package com.juick.server.api.activity.model;
 
-public class Key extends ActivityObject {
+public class Key extends Context {
     private String owner;
     private String publicKeyPem;
 
diff --git a/juick-server/src/main/java/com/juick/server/api/activity/model/Link.java b/juick-server/src/main/java/com/juick/server/api/activity/model/Link.java
index b57dabbe..543b5f0c 100644
--- a/juick-server/src/main/java/com/juick/server/api/activity/model/Link.java
+++ b/juick-server/src/main/java/com/juick/server/api/activity/model/Link.java
@@ -1,6 +1,6 @@
 package com.juick.server.api.activity.model;
 
-public class Link extends ActivityObject {
+public class Link extends Context {
     private String href;
 
     public String getHref() {
diff --git a/juick-server/src/main/java/com/juick/server/api/activity/model/Note.java b/juick-server/src/main/java/com/juick/server/api/activity/model/Note.java
index ac58b033..ff64c4b9 100644
--- a/juick-server/src/main/java/com/juick/server/api/activity/model/Note.java
+++ b/juick-server/src/main/java/com/juick/server/api/activity/model/Note.java
@@ -2,7 +2,7 @@ package com.juick.server.api.activity.model;
 
 import java.util.List;
 
-public class Note extends ActivityObject {
+public class Note extends Context {
     private String content;
     private String attributedTo;
     private Link attachment;
diff --git a/juick-server/src/main/java/com/juick/server/api/activity/model/OrderedCollection.java b/juick-server/src/main/java/com/juick/server/api/activity/model/OrderedCollection.java
index 90f04de3..d66c55be 100644
--- a/juick-server/src/main/java/com/juick/server/api/activity/model/OrderedCollection.java
+++ b/juick-server/src/main/java/com/juick/server/api/activity/model/OrderedCollection.java
@@ -1,6 +1,6 @@
 package com.juick.server.api.activity.model;
 
-public class OrderedCollection extends ActivityObject {
+public class OrderedCollection extends Context {
 
     private int totalItems;
 
diff --git a/juick-server/src/main/java/com/juick/server/api/activity/model/OrderedCollectionPage.java b/juick-server/src/main/java/com/juick/server/api/activity/model/OrderedCollectionPage.java
index af7f2cec..bcae87d0 100644
--- a/juick-server/src/main/java/com/juick/server/api/activity/model/OrderedCollectionPage.java
+++ b/juick-server/src/main/java/com/juick/server/api/activity/model/OrderedCollectionPage.java
@@ -2,7 +2,7 @@ package com.juick.server.api.activity.model;
 
 import java.util.List;
 
-public class OrderedCollectionPage extends ActivityObject {
+public class OrderedCollectionPage extends Context {
 
     private String partOf;
 
@@ -12,7 +12,7 @@ public class OrderedCollectionPage extends ActivityObject {
 
     private String last;
 
-    private List<? extends ActivityObject> orderedItems;
+    private List<? extends Context> orderedItems;
 
     public String getNext() {
         return next;
@@ -22,11 +22,11 @@ public class OrderedCollectionPage extends ActivityObject {
         this.next = next;
     }
 
-    public List<? extends ActivityObject> getOrderedItems() {
+    public List<? extends Context> getOrderedItems() {
         return orderedItems;
     }
 
-    public void setOrderedItems(List<? extends ActivityObject> orderedItems) {
+    public void setOrderedItems(List<? extends Context> orderedItems) {
         this.orderedItems = orderedItems;
     }
 
diff --git a/juick-server/src/main/java/com/juick/server/api/activity/model/Person.java b/juick-server/src/main/java/com/juick/server/api/activity/model/Person.java
index e314624d..8a817c18 100644
--- a/juick-server/src/main/java/com/juick/server/api/activity/model/Person.java
+++ b/juick-server/src/main/java/com/juick/server/api/activity/model/Person.java
@@ -1,6 +1,8 @@
 package com.juick.server.api.activity.model;
 
-public class Person extends ActivityObject {
+import com.fasterxml.jackson.annotation.JsonTypeInfo;
+
+public class Person extends Context {
 
     private String name;
     private String preferredUsername;
@@ -25,6 +27,7 @@ public class Person extends ActivityObject {
         this.name = name;
     }
 
+    @JsonTypeInfo(use = JsonTypeInfo.Id.NONE)
     public Image getIcon() {
         return icon;
     }
@@ -73,6 +76,7 @@ public class Person extends ActivityObject {
         this.url = url;
     }
 
+    @JsonTypeInfo(use = JsonTypeInfo.Id.NONE)
     public Key getPublicKey() {
         return publicKey;
     }
diff --git a/juick-server/src/main/java/com/juick/server/api/activity/model/activities/Accept.java b/juick-server/src/main/java/com/juick/server/api/activity/model/activities/Accept.java
new file mode 100644
index 00000000..1e0a9968
--- /dev/null
+++ b/juick-server/src/main/java/com/juick/server/api/activity/model/activities/Accept.java
@@ -0,0 +1,6 @@
+package com.juick.server.api.activity.model.activities;
+
+import com.juick.server.api.activity.model.Activity;
+
+public class Accept extends Activity {
+}
diff --git a/juick-server/src/main/java/com/juick/server/api/activity/model/activities/Create.java b/juick-server/src/main/java/com/juick/server/api/activity/model/activities/Create.java
new file mode 100644
index 00000000..52507373
--- /dev/null
+++ b/juick-server/src/main/java/com/juick/server/api/activity/model/activities/Create.java
@@ -0,0 +1,6 @@
+package com.juick.server.api.activity.model.activities;
+
+import com.juick.server.api.activity.model.Activity;
+
+public class Create extends Activity {
+}
diff --git a/juick-server/src/main/java/com/juick/server/api/activity/model/activities/Delete.java b/juick-server/src/main/java/com/juick/server/api/activity/model/activities/Delete.java
new file mode 100644
index 00000000..f4392020
--- /dev/null
+++ b/juick-server/src/main/java/com/juick/server/api/activity/model/activities/Delete.java
@@ -0,0 +1,6 @@
+package com.juick.server.api.activity.model.activities;
+
+import com.juick.server.api.activity.model.Activity;
+
+public class Delete extends Activity {
+}
diff --git a/juick-server/src/main/java/com/juick/server/api/activity/model/activities/Follow.java b/juick-server/src/main/java/com/juick/server/api/activity/model/activities/Follow.java
new file mode 100644
index 00000000..573ecc6e
--- /dev/null
+++ b/juick-server/src/main/java/com/juick/server/api/activity/model/activities/Follow.java
@@ -0,0 +1,6 @@
+package com.juick.server.api.activity.model.activities;
+
+import com.juick.server.api.activity.model.Activity;
+
+public class Follow extends Activity {
+}
diff --git a/juick-server/src/main/java/com/juick/server/api/activity/model/activities/Undo.java b/juick-server/src/main/java/com/juick/server/api/activity/model/activities/Undo.java
new file mode 100644
index 00000000..4e87e9d0
--- /dev/null
+++ b/juick-server/src/main/java/com/juick/server/api/activity/model/activities/Undo.java
@@ -0,0 +1,6 @@
+package com.juick.server.api.activity.model.activities;
+
+import com.juick.server.api.activity.model.Activity;
+
+public class Undo extends Activity {
+}