Simplify terminals, move towards using tries for commands

src/SimpleTrie.hs

@@ -3,6 +3,7 @@
 
 module SimpleTrie where
 
+import Data.Monoid
 import Control.Lens
 import qualified Data.Map.Strict as M
 
@@ -30,6 +31,28 @@ lookupTrie :: Ord a => [a] -> Trie a b -> Maybe b
 lookupTrie (k : ks) t = _trieChildren t M.!? k >>= lookupTrie ks
 lookupTrie [] t = _trieMVal t
 
+--nextTrie :: Ord a => [a] -> Trie a b -> Maybe (b, Trie a b)
+nextTrie :: [a] -> Trie a b -> Maybe (b, Trie a b)
+nextTrie (k:ks) t = undefined
+nextTrie [] t = Nothing
+
+splitLookupTrie :: Ord a => [a] -> Trie a b -> (Trie a b,Maybe b,Trie a b)
+splitLookupTrie (k:ks) t@(Trie x xs) = case m of
+    Nothing -> (Trie x l,Nothing,Trie x r)
+    Just t' -> let (l',m',r') = splitLookupTrie ks t'
+        in (Trie x (M.insert k l' l),m', Trie x (M.insert k r' r))
+  where
+    (l,m,r) = M.splitLookup k xs
+splitLookupTrie [] t@(Trie x xs) = (Trie Nothing mempty,x, Trie Nothing xs)
+-- the above would be better if it removed empty trie strings; the left trie
+-- will always be empty and the right trie might be empty.
+-- I cannot think of a smart way to do this
+
+firstTrie :: Ord a => Trie a b -> Maybe b
+firstTrie t = case t ^. trieMVal of
+    Just x -> Just x
+    Nothing -> getFirst $ foldMap (First . firstTrie) (t ^. trieChildren)
+
 -- # OPTIONS -Wno-incomplete-uni-patterns #-}
 multiLookupTrie :: Ord a => [a] -> Trie a b -> [([a], b)]
 multiLookupTrie xs t@(Trie my ch)