30ec1adce8
In the end, it should be possible to write a single config which is pushed to the service to steer which emails arrive. This implements some helper functions and some more endpoints. We implement Semigroup/Monoid for labelled tuples. Change-Id: I48bfd311e4a7bba5bc08a9681d823a6a7d5175a8 Reviewed-on: https://cl.tvl.fyi/c/depot/+/7727 Reviewed-by: Profpatsch <mail@profpatsch.de> Autosubmit: Profpatsch <mail@profpatsch.de> Tested-by: BuildkiteCI
120 lines
3.8 KiB
Haskell
120 lines
3.8 KiB
Haskell
{-# LANGUAGE DataKinds #-}
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{-# LANGUAGE DerivingStrategies #-}
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{-# LANGUAGE GHC2021 #-}
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{-# LANGUAGE InstanceSigs #-}
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{-# LANGUAGE KindSignatures #-}
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{-# LANGUAGE RankNTypes #-}
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{-# LANGUAGE ScopedTypeVariables #-}
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{-# LANGUAGE TypeApplications #-}
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module Label
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( Label,
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label,
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label',
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getLabel,
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T2 (..),
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T3 (..),
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)
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where
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import Data.Data (Proxy (..))
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import Data.Function ((&))
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import Data.Typeable (Typeable)
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import GHC.Records (HasField (..))
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import GHC.TypeLits (KnownSymbol, Symbol, symbolVal)
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-- | A labelled value.
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--
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-- Use 'label'/'label'' to construct,
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-- then use dot-syntax to get the inner value.
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newtype Label (label :: Symbol) value = Label value
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deriving stock (Eq, Ord)
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deriving newtype (Typeable, Semigroup, Monoid)
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instance (KnownSymbol label, Show value) => Show (Label label value) where
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showsPrec d (Label val) =
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showParen (d > 10) $
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showString "Label @"
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. showsPrec 11 (symbolVal (Proxy @label))
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. showString " "
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. showsPrec 11 val
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-- | Attach a label to a value; should be used with a type application to name the label.
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--
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-- @@
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-- let f = label @"foo" 'f' :: Label "foo" Char
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-- in f.foo :: Char
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-- @@
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--
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-- Use dot-syntax to get the labelled value.
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label :: forall label value. value -> Label label value
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label value = Label value
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-- | Attach a label to a value; Pass it a proxy with the label name in the argument type.
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-- This is intended for passing through the label value;
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-- you can also use 'label'.
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--
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--
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-- @@
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-- let f = label' (Proxy @"foo") 'f' :: Label "foo" Char
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-- in f.foo :: Char
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-- @@
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--
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-- Use dot-syntax to get the labelled value.
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label' :: forall label value. (Proxy label) -> value -> Label label value
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label' Proxy value = Label value
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-- | Fetches the labelled value.
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instance HasField label (Label label value) value where
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getField :: (Label label value) -> value
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getField (Label value) = value
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-- | Fetch a value from a record, like 'getField', but also keep it wrapped by its label.
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getLabel :: forall label record a. HasField label record a => record -> Label label a
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getLabel rec = rec & getField @label & label @label
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-- | A named 2-element tuple. Since the elements are named, you can access them with `.`.
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--
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-- @@
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-- let t2 = T2 (label @"myfield" 'c') (label @"otherfield" True) :: T2 "myfield" Char "otherfield" Bool
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-- in (
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-- t2.myfield :: Char,
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-- t2.otherfield :: Bool
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-- )
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-- @@
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data T2 (l1 :: Symbol) t1 (l2 :: Symbol) t2 = T2 (Label l1 t1) (Label l2 t2)
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-- | Access the first field by label
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instance HasField l1 (T2 l1 t1 l2 t2) t1 where
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getField (T2 t1 _) = getField @l1 t1
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-- | Access the second field by label
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instance HasField l2 (T2 l1 t1 l2 t2) t2 where
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getField (T2 _ t2) = getField @l2 t2
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instance (Semigroup t1, Semigroup t2) => Semigroup (T2 l1 t1 l2 t2) where
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T2 t1 t2 <> T2 t1' t2' = T2 (t1 <> t1') (t2 <> t2')
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instance (Monoid t1, Monoid t2) => Monoid (T2 l1 t1 l2 t2) where
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mempty = T2 mempty mempty
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-- | A named 3-element tuple. Since the elements are named, you can access them with `.`. See 'T2' for an example.
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data T3 (l1 :: Symbol) t1 (l2 :: Symbol) t2 (l3 :: Symbol) t3 = T3 (Label l1 t1) (Label l2 t2) (Label l3 t3)
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-- | Access the first field by label
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instance HasField l1 (T3 l1 t1 l2 t2 l3 t3) t1 where
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getField (T3 t1 _ _) = getField @l1 t1
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-- | Access the second field by label
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instance HasField l2 (T3 l1 t1 l2 t2 l3 t3) t2 where
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getField (T3 _ t2 _) = getField @l2 t2
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-- | Access the third field by label
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instance HasField l3 (T3 l1 t1 l2 t2 l3 t3) t3 where
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getField (T3 _ _ t3) = getField @l3 t3
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instance (Semigroup t1, Semigroup t2, Semigroup t3) => Semigroup (T3 l1 t1 l2 t2 l3 t3) where
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T3 t1 t2 t3 <> T3 t1' t2' t3' = T3 (t1 <> t1') (t2 <> t2') (t3 <> t3')
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instance (Monoid t1, Monoid t2, Monoid t3) => Monoid (T3 l1 t1 l2 t2 l3 t3) where
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mempty = T3 mempty mempty mempty
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