From 89879153de431ebdba1cedf7f2e638f1302953f1 Mon Sep 17 00:00:00 2001
From: Jonathan Lamothe <jonathan@jlamothe.net>
Date: Wed, 22 Sep 2021 20:54:09 -0400
Subject: [PATCH] implemented Handlers.incAnchorBy

---
 src/Helpers.hs      | 10 ++++++++++
 test/HelpersSpec.hs | 17 +++++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/src/Helpers.hs b/src/Helpers.hs
index 51ce991..0a8eac1 100644
--- a/src/Helpers.hs
+++ b/src/Helpers.hs
@@ -31,6 +31,7 @@ module Helpers (
   editParam,
   editAnchor,
   incParamBy,
+  incAnchorBy,
   incStrBy
   ) where
 
@@ -145,6 +146,15 @@ incParamBy
   -> Maybe Url
 incParamBy n p = editParam p $ incStrBy n
 
+-- | Increment an anchor by a given amount (if possible)
+incAnchorBy
+  :: Integer
+  -- ^ the amount to increment by
+  -> Url
+  -- ^ the 'Url' to edit
+  -> Maybe Url
+incAnchorBy n = editAnchor $ incStrBy n
+
 -- | Increment a 'String' representation of an 'Integer' by a given
 -- amount (if possible)
 incStrBy
diff --git a/test/HelpersSpec.hs b/test/HelpersSpec.hs
index 690023e..01d51d8 100644
--- a/test/HelpersSpec.hs
+++ b/test/HelpersSpec.hs
@@ -39,6 +39,7 @@ spec = do
   editParamSpec
   editAnchorSpec
   incParamBySpec
+  incAnchorBySpec
   incStrBySpec
 
 textToUrlSpec :: Spec
@@ -194,6 +195,22 @@ incParamBySpec = describe "incParamBy" $ mapM_
       , ( "c", Just "foo" )
       ]
 
+incAnchorBySpec :: Spec
+incAnchorBySpec = describe "incAnchorBy" $ mapM_
+  ( \(desc, n, url, expected) -> context desc $
+    it ("should be " ++ show expected) $
+      incAnchorBy n url `shouldBe` expected
+  )
+
+  --  description,   number, url,           expected
+  [ ( "+1",          1,      urlWith "1",   Just $ urlWith "2" )
+  , ( "+2",          2,      urlWith "1",   Just $ urlWith "3" )
+  , ( "empty",       1,      simpleUrl,     Just simpleUrl     )
+  , ( "non-numeric", 1,      urlWith "foo", Nothing            )
+  ]
+
+  where urlWith str = simpleUrl { anchor = Just str }
+
 incStrBySpec :: Spec
 incStrBySpec = describe "incStrBy" $ mapM_
   ( \(n, str, expected) ->