Use tree-based command dispatch (#110)

* Use print-error

* Move from table based dispatch to tree based dispatch

* Implement Did you mean? based on edit-distance

* Use babashka.cli :require and :validate everywhere

src/nextjournal/edit_distance.clj

@@ -0,0 +1,28 @@
+(ns nextjournal.edit-distance)
+
+(defn edit-distance [a b]
+  (let [alen (count a)
+        blen (count b)
+        [longlen shortlen a b] (if (> alen blen)
+                                 [alen blen a b]
+                                 [blen alen b a])
+        [a' & a-rest] a
+        [b' & b-rest] b]
+    (if (zero? shortlen)
+      longlen
+      (if (= a' b')
+        (edit-distance a-rest b-rest)
+        (+ 1 (min (edit-distance a-rest b-rest)
+                  (edit-distance a-rest b)))))))
+
+(def max-edit-distance 3)
+(def max-candidates 3)
+
+(defn candidates [input available-cmds]
+  (->> available-cmds
+       (map (fn [c] {:dist (edit-distance c input)
+                     :cmd c}))
+       (filter (fn [{:keys [dist]}] (<= dist max-edit-distance)))
+       (sort-by :dist)
+       (map :cmd)
+       (take max-candidates)))