From 5c110716cfda6e616a795edd12f2012b132dca9f Mon Sep 17 00:00:00 2001
From: Joris
Date: Sun, 2 Apr 2017 17:51:12 +0200
Subject: Add a chart on payments by month by categories

---
 src/client/Utils/List.elm  | 19 +++++++++++++++++++
 src/client/Utils/Maybe.elm | 34 ----------------------------------
 2 files changed, 19 insertions(+), 34 deletions(-)
 delete mode 100644 src/client/Utils/Maybe.elm

(limited to 'src/client/Utils')

diff --git a/src/client/Utils/List.elm b/src/client/Utils/List.elm
index cc57d9f..8e26e85 100644
--- a/src/client/Utils/List.elm
+++ b/src/client/Utils/List.elm
@@ -1,9 +1,11 @@
 module Utils.List exposing
   ( groupBy
   , mean
+  , links
   )
 
 import Dict
+import Maybe.Extra as Maybe
 
 groupBy : (a -> comparable) -> List a -> List (comparable, List a)
 groupBy f xs =
@@ -15,3 +17,20 @@ groupBy f xs =
 
 mean : List Int -> Int
 mean xs = (List.sum xs) // (List.length xs)
+
+links : List a -> List (a, a)
+links xs =
+  let reversed = List.reverse xs
+  in  List.foldr
+        (\x acc ->
+          case Maybe.map Tuple.first (List.head acc) of
+            Just y ->
+              (x, y) :: acc
+            _ ->
+              acc
+        )
+        (case reversed of
+          x :: y :: _ -> [(y, x)]
+          _ -> []
+        )
+        (List.reverse << List.drop 2 <| reversed)
diff --git a/src/client/Utils/Maybe.elm b/src/client/Utils/Maybe.elm
deleted file mode 100644
index 46456e1..0000000
--- a/src/client/Utils/Maybe.elm
+++ /dev/null
@@ -1,34 +0,0 @@
-module Utils.Maybe exposing
-  ( isJust
-  , cat
-  , toList
-  , orElse
-  )
-
-isJust : Maybe a -> Bool
-isJust maybe =
-  case maybe of
-    Just _  -> True
-    Nothing -> False
-
-cat : List (Maybe a) -> List a
-cat =
-  List.foldr
-    (\mb xs ->
-      case mb of
-        Just x  -> x :: xs
-        Nothing -> xs
-    )
-    []
-
-toList : Maybe a -> List a
-toList mb =
-  case mb of
-    Just a  -> [a]
-    Nothing -> []
-
-orElse : Maybe a -> Maybe a -> Maybe a
-orElse mb1 mb2 =
-  case mb1 of
-    Just x -> Just x
-    Nothing -> mb2
-- 
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