Groundwork for new Criteria setup

1 files changed, 86 insertions, 0 deletions

diff --git a/src/Criteria.hs b/src/Criteria.hs
new file mode 100644
index 0000000..5df9cf1
--- /dev/null
+++ b/src/Criteria.hs
@@ -0,0 +1,86 @@
+module Criteria(
+    Criteria,
+    CTest,
+
+    evaluate,
+    matchID,
+    matchFromList,
+    many
+    ) where
+
+
+
+
+import qualified Control.Monad as Con
+import qualified Data.List as List
+import qualified Data.Either.Unwrap as Either
+import qualified Candidate as Typ
+import qualified Preferences as Pref
+
+
+
+
+type Criteria = [CTest]
+type CTest = CList -> Either CError CList
+type CList = [Typ.CandidateID]
+type CError = String
+
+
+
+
+evaluate :: Typ.BelowLineBallot -> [Pref.Preference] -> Criteria -> Bool
+evaluate ballot preferences criteria =
+    let clist = prefsToCList ballot preferences
+        parsed = Con.foldM (flip id) clist criteria
+        result = Either.isRight parsed
+    in if (isValidInput ballot preferences)
+        then result
+        else False
+
+
+
+
+isValidInput :: Typ.BelowLineBallot -> [Pref.Preference] -> Bool
+isValidInput ballot preferences =
+    all (\(x,y) -> x > 0 && x <= length ballot && y > 0 && y <= length ballot) preferences
+
+
+
+
+prefsToCList :: Typ.BelowLineBallot -> [Pref.Preference] -> CList
+prefsToCList ballot preferences =
+    let t0 = map (\(x,y) -> (ballot !! (x - 1), y)) preferences
+        t1 = List.sortBy (\x y -> compare (snd x) (snd y)) t0
+    in map fst t1
+
+
+
+
+matchID :: Typ.CandidateID -> CTest
+matchID candID = (\x ->
+    let r = (head x == candID)
+    in if (length x == 0 || not r)
+        then Left "Couldn't match candidate"
+        else Right (tail x))
+
+
+
+
+matchFromList :: [Typ.CandidateID] -> CTest
+matchFromList candList = (\x ->
+    let r = (head x) `elem` candList
+    in if (length x == 0 || not r)
+        then Left "Couldn't match candidate"
+        else Right (tail x))
+
+
+
+
+many :: CTest -> CTest
+many ct = (\x ->
+    let r = ct x
+    in if (Either.isRight r)
+        then many ct (Either.fromRight r)
+        else Right x)
+
+