{-# LANGUAGE TypeFamilies #-}

{-|
Copyright: © 2021-2023 IOHK, 2024 Cardano Foundation
License: Apache-2.0

Delta types for lists.
-}
module Data.Delta.List
    ( DeltaList (..)
    ) where

import Prelude

import Data.Delta.Core
    ( Delta (..)
    )

{-------------------------------------------------------------------------------
    Delta type for lists
-------------------------------------------------------------------------------}

-- | Delta type for lists where a list of elements is prepended.
newtype DeltaList a = Append [a]
    deriving (DeltaList a -> DeltaList a -> Bool
(DeltaList a -> DeltaList a -> Bool)
-> (DeltaList a -> DeltaList a -> Bool) -> Eq (DeltaList a)
forall a. Eq a => DeltaList a -> DeltaList a -> Bool
forall a. (a -> a -> Bool) -> (a -> a -> Bool) -> Eq a
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-> (DeltaList a -> DeltaList a -> Bool)
-> (DeltaList a -> DeltaList a -> DeltaList a)
-> (DeltaList a -> DeltaList a -> DeltaList a)
-> Ord (DeltaList a)
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DeltaList a -> DeltaList a -> Ordering
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forall a.
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$cmax :: forall a. Ord a => DeltaList a -> DeltaList a -> DeltaList a
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-- |
-- prop> apply (Append xs) ys = xs ++ ys
instance Delta (DeltaList a) where
    type Base (DeltaList a) = [a]
    apply :: DeltaList a -> Base (DeltaList a) -> Base (DeltaList a)
apply (Append [a]
xs) Base (DeltaList a)
ys = [a]
xs [a] -> [a] -> [a]
forall a. [a] -> [a] -> [a]
++ [a]
Base (DeltaList a)
ys

-- | Remember that the semigroup instance is required to satisfy
-- the following properties:
--
-- prop> apply mempty = id
-- prop> apply (d1 <> d2) = apply d1 . apply d2
instance Ord a => Semigroup (DeltaList a) where
    (Append [a]
xs) <> :: DeltaList a -> DeltaList a -> DeltaList a
<> (Append [a]
ys) = [a] -> DeltaList a
forall a. [a] -> DeltaList a
Append ([a]
xs [a] -> [a] -> [a]
forall a. [a] -> [a] -> [a]
++ [a]
ys)

instance Ord a => Monoid (DeltaList a) where
    mempty :: DeltaList a
mempty = [a] -> DeltaList a
forall a. [a] -> DeltaList a
Append []