1 files changed, 60 insertions, 0 deletions
diff --git a/src/Model/Mail.hs b/src/Model/Mail.hs
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+++ b/src/Model/Mail.hs
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+{-# LANGUAGE OverloadedStrings #-}
+
+module Model.Mail
+  ( mailSubject
+  , mailBody
+  ) where
+
+import Data.Text (Text)
+import qualified Data.Text as T
+
+import Model.Date
+import Model.Birthdate
+
+mailSubject :: [Birthdate] -> Text
+mailSubject birthdates =
+  let count = length birthdates
+  in  T.concat
+        [ "Hey, "
+        , if count > 1 then "there are" else "there is"
+        , " "
+        , T.pack . show $ count
+        , " birthday"
+        , if count > 1 then "s" else ""
+        , " today!"
+        ]
+
+mailBody :: Date -> [Birthdate] -> Text
+mailBody currentDate birthdates =
+  T.concat $ map (mailLine currentDate) (attachLines birthdates)
+
+attachLines :: [Birthdate] -> [(Line, Birthdate)]
+attachLines birthdates =
+  let count = length birthdates
+      lineKind 1 = if count == 1 then SingleLine else FirstLine
+      lineKind line = if line == count then LastLine else MiddleLine
+      mapFst f (x, y) = (f x, y)
+  in  map (mapFst lineKind) . zip [1..] $ birthdates
+
+data Line =
+  SingleLine
+  | FirstLine
+  | MiddleLine
+  | LastLine
+  deriving (Eq, Show)
+
+mailLine :: Date -> (Line, Birthdate) -> Text
+mailLine currDate (line, birthdate) =
+  T.concat
+    [ case line of
+        MiddleLine -> ", "
+        LastLine -> " and "
+        _ -> ""
+    , fullname birthdate
+    , case line of
+        x | x `elem` [SingleLine, FirstLine] -> " is now "
+        _ -> " is "
+    , T.pack . show $ age currDate birthdate
+    , " years old"
+    , if line == LastLine then "." else ""
+    ]