{-# LANGUAGE DeriveFoldable      #-}
{-# LANGUAGE DeriveFunctor       #-}
{-# LANGUAGE DeriveTraversable   #-}

module Database.Persist.Pagination.Types where

import Control.Applicative (Alternative(..))
import           Database.Persist.Sql (Entity)

-- | The amount of records in a 'Page' of results.
--
-- @since 0.1.0.0
newtype PageSize = PageSize { PageSize -> Int
unPageSize :: Int }
    deriving (PageSize -> PageSize -> Bool
(PageSize -> PageSize -> Bool)
-> (PageSize -> PageSize -> Bool) -> Eq PageSize
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Eq, Int -> PageSize -> ShowS
[PageSize] -> ShowS
PageSize -> String
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-- | Whether to sort by @ASC@ or @DESC@ when you're paging over results.
--
-- @since 0.1.0.0
data SortOrder = Ascend | Descend
    deriving (SortOrder -> SortOrder -> Bool
(SortOrder -> SortOrder -> Bool)
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-- | A datatype describing the min and max value of the relevant field that
-- you are ranging over in a non-empty sequence of records.
--
-- @since 0.1.0.0
data Range t = Range { Range t -> t
rangeMin :: t, Range t -> t
rangeMax :: t }
    deriving (Range t -> Range t -> Bool
(Range t -> Range t -> Bool)
-> (Range t -> Range t -> Bool) -> Eq (Range t)
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instance Ord t => Semigroup (Range t) where
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h t
h')

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    mempty :: Range t
mempty = t -> t -> Range t
forall t. t -> t -> Range t
Range t
forall a. Bounded a => a
minBound t
forall a. Bounded a => a
maxBound
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mappend = Range t -> Range t -> Range t
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(<>)

-- | Users aren't required to put a value in for the range - a value of
-- 'Nothing' is equivalent to saying "unbounded from below."
--
-- @since 0.1.0.0
type DesiredRange t = Range (Maybe t)

-- | Modify the 'DesiredRange' according to the 'Range' that was provided
-- by the query and the 'SortOrder'.
--
-- @since 0.1.0.0
bumpPageRange
    :: Ord typ
    => SortOrder
    -> DesiredRange typ
    -> Range typ
    -> DesiredRange typ
bumpPageRange :: SortOrder -> DesiredRange typ -> Range typ -> DesiredRange typ
bumpPageRange SortOrder
sortOrder (Range Maybe typ
mmin Maybe typ
mmax) (Range typ
min' typ
max') =
    case SortOrder
sortOrder of
        SortOrder
Ascend ->
            Maybe typ -> Maybe typ -> DesiredRange typ
forall t. t -> t -> Range t
Range (Maybe typ
mmin Maybe typ -> Maybe typ -> Maybe typ
forall a. Ord a => a -> a -> a
`max` typ -> Maybe typ
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max') Maybe typ
mmax
        SortOrder
Descend ->
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