Initial commit; nothing works yet

src/dog_and_duck/quack/quack.clj

@@ -0,0 +1,63 @@
+(ns dog-and-duck.quack.quack
+  "Validator for ActivityPub objects: if it walks like a duck, and it quacks like a duck..."
+  ;;(:require [clojure.spec.alpha as s])
+  (:import [java.net URI URISyntaxException]))
+
+(defn object?
+  "Return `true` iff `x` is recognisably an ActivityStreams object.
+   
+   **NOTE THAT** The ActivityStreams spec 
+   [says](https://www.w3.org/TR/activitystreams-core/#object):
+   
+   > All properties are optional (including the id and type)
+   
+   But we are *just not having that*, because otherwise we're flying blind.
+   We *shall* reject objects lacking at least `:type`. Missing `:id` keys are
+   tolerable because they represent transient objects, which we expect to 
+   handle."
+  [x]
+  (and (map? x) (:type x) true))
+
+(object? nil)
+(object? {:type "test"})
+
+(defn persistent-object?
+  "`true` iff `x` is a persistent object.
+
+   Transient objects in ActivityPub are not required to have an `id` key, but persistent
+   ones must have a key, and it must be an IRI (but normally a URI)."
+  [x]
+  (try
+    (and (object? x) (uri? (URI. (:id x))))
+    (catch URISyntaxException _ false)))
+
+(persistent-object? {:type "test" :id "https://mastodon.scot/@barfilfarm"})
+
+(defn actor?
+  "TODO!"
+  [x]
+  true)
+
+(def verb?
+  "The set of types we will accept as verbs.
+   
+   There's an [explicit set of allowed verbs]
+   (https://www.w3.org/TR/activitystreams-vocabulary/#activity-types)."
+  #{"Accept" "Add" "Announce" "Arrive" "Block" "Create" "Delete" "Dislike"
+    "Flag" "Follow" "Ignore" "Invite" "Join" "Leave" "Like" "Listen" "Move"
+    "Offer" "Question" "Reject" "Read" "Remove" "TentativeAccept"
+    "TentativeReject" "Travel" "Undo" "Update" "View"})
+
+(defn activity?
+  "`true` iff `x` is an activity, else false.
+
+  see "
+  [x]
+  (try
+    (and (object? x)
+         (uri? (URI. ((keyword "@context") x)))
+         (string? (:summary x))
+         (actor? (:actor x))
+         (verb? (:type x))
+         (or (object? (:object x)) (uri? (URI. x))))
+    (catch URISyntaxException _ false)))