From 994e2777c34e68abef660a698116d4e733c6951c Mon Sep 17 00:00:00 2001
From: Jonathan Lamothe <jonathan@jlamothe.net>
Date: Wed, 22 Sep 2021 20:32:34 -0400
Subject: [PATCH] implemented editAnchor

---
 src/Helpers.hs      | 14 ++++++++++++++
 test/HelpersSpec.hs | 20 ++++++++++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/src/Helpers.hs b/src/Helpers.hs
index b98560f..51ce991 100644
--- a/src/Helpers.hs
+++ b/src/Helpers.hs
@@ -29,6 +29,7 @@ module Helpers (
   editHost,
   dropParam,
   editParam,
+  editAnchor,
   incParamBy,
   incStrBy
   ) where
@@ -120,6 +121,19 @@ editParam pName f url = do
     ) $ params url
   Just url { params = params' }
 
+-- | Edit an anchor
+editAnchor
+  :: (String -> Maybe String)
+  -- ^ the transformation function
+  -> Url
+  -- ^ the 'Url' being edited
+  -> Maybe Url
+editAnchor f url = case anchor url of
+  Just a -> do
+    a' <- f a
+    Just url { anchor = Just a' }
+  Nothing -> Just url
+
 -- | Increment a parameter of a 'Url' by a given amount (if possible)
 incParamBy
   :: Integer
diff --git a/test/HelpersSpec.hs b/test/HelpersSpec.hs
index 9f74a63..690023e 100644
--- a/test/HelpersSpec.hs
+++ b/test/HelpersSpec.hs
@@ -37,6 +37,7 @@ spec = do
   editHostSpec
   dropParamSpec
   editParamSpec
+  editAnchorSpec
   incParamBySpec
   incStrBySpec
 
@@ -151,6 +152,25 @@ editParamSpec = describe "editParam" $ mapM_
       , ( "c", Nothing    )
       ]
 
+editAnchorSpec :: Spec
+editAnchorSpec = describe "editAnchor" $ mapM_
+  ( \(desc, f, url, expected) -> context desc $
+    it ("should be " ++ show url) $
+      editAnchor f url `shouldBe` expected
+  )
+
+  --  description,     function,       url,       expected
+  [ ( "reverse",       Just . reverse, fooUrl,    Just reversedUrl )
+  , ( "fail",          const Nothing,  fooUrl,    Nothing          )
+  , ( "reverse empty", Just . reverse, simpleUrl, Just simpleUrl   )
+  , ( "fail empty",    const Nothing,  simpleUrl, Just simpleUrl   )
+  ]
+
+  where
+    fooUrl      = urlWith "foo"
+    reversedUrl = urlWith "oof"
+    urlWith a   = simpleUrl { anchor = Just a }
+
 incParamBySpec :: Spec
 incParamBySpec = describe "incParamBy" $ mapM_
   ( \(desc, n, pName, expected) -> context desc $