Implement a "nearest time" function for timelines

src/hottub/timeline.clj

@@ -20,3 +20,22 @@
 
 (defn timeline-last-value [tln]
   (last (second (last tln))))
+
+(defn- distance [tln a b] 
+  (let [d (.compare (.comp tln) a b)]
+    (if (neg? d) (- d) d)))
+
+(defn time-nearest [tln clock]
+  (let [akv (first (rsubseq tln <= clock))
+        bkv (first (subseq tln >= clock))]
+    (if-not akv
+      (if-not bkv 
+        nil 
+        (key bkv))
+      (if-not bkv 
+        (key akv)
+        (let [a (key akv) 
+              b (key bkv)
+              da (distance tln clock a)
+              db (distance tln clock b)]
+          (if (<= da db) a b))))))