{-# language FlexibleContexts #-}
{-# language NamedFieldPuns #-}
{-# language ScopedTypeVariables #-}
{-# language TypeApplications #-}
{-# language TypeFamilies #-}
{-# language ViewPatterns #-}

module Rel8.Table.Aggregate
  ( groupBy, hgroupBy
  , listAgg, nonEmptyAgg
  )
where

-- base
import Data.Functor.Identity ( Identity( Identity ) )
import Prelude

-- rel8
import Rel8.Aggregate ( Aggregate, Aggregates )
import Rel8.Expr ( Expr )
import Rel8.Expr.Aggregate
  ( groupByExpr
  , slistAggExpr
  , snonEmptyAggExpr
  )
import Rel8.Schema.Dict ( Dict( Dict ) )
import Rel8.Schema.HTable ( HTable, hfield, htabulate )
import Rel8.Schema.HTable.Vectorize ( hvectorize )
import Rel8.Schema.Null ( Sql )
import Rel8.Schema.Spec ( Spec( Spec, info ) )
import Rel8.Table ( toColumns, fromColumns )
import Rel8.Table.Eq ( EqTable, eqTable )
import Rel8.Table.List ( ListTable )
import Rel8.Table.NonEmpty ( NonEmptyTable )
import Rel8.Type.Eq ( DBEq )


-- | Group equal tables together. This works by aggregating each column in the
-- given table with 'groupByExpr'.
groupBy :: forall exprs aggregates. (EqTable exprs, Aggregates aggregates exprs)
  => exprs -> aggregates
groupBy :: exprs -> aggregates
groupBy = Columns exprs Aggregate -> aggregates
forall (context :: Context) a.
Table context a =>
Columns a context -> a
fromColumns (Columns exprs Aggregate -> aggregates)
-> (exprs -> Columns exprs Aggregate) -> exprs -> aggregates
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Columns exprs (Dict (Sql DBEq))
-> Columns exprs Expr -> Columns exprs Aggregate
forall (t :: HTable).
HTable t =>
t (Dict (Sql DBEq)) -> t Expr -> t Aggregate
hgroupBy (EqTable exprs => Columns exprs (Dict (Sql DBEq))
forall a. EqTable a => Columns a (Dict (Sql DBEq))
eqTable @exprs) (Columns exprs Expr -> Columns exprs Aggregate)
-> (exprs -> Columns exprs Expr)
-> exprs
-> Columns exprs Aggregate
forall b c a. (b -> c) -> (a -> b) -> a -> c
. exprs -> Columns exprs Expr
forall (context :: Context) a.
Table context a =>
a -> Columns a context
toColumns


hgroupBy :: HTable t => t (Dict (Sql DBEq)) -> t Expr -> t Aggregate
hgroupBy :: t (Dict (Sql DBEq)) -> t Expr -> t Aggregate
hgroupBy t (Dict (Sql DBEq))
eqs t Expr
exprs = (forall a. HField t a -> Aggregate a) -> t Aggregate
forall (t :: HTable) (context :: Context).
HTable t =>
(forall a. HField t a -> context a) -> t context
htabulate ((forall a. HField t a -> Aggregate a) -> t Aggregate)
-> (forall a. HField t a -> Aggregate a) -> t Aggregate
forall a b. (a -> b) -> a -> b
$ \HField t a
field ->
  case t (Dict (Sql DBEq)) -> HField t a -> Dict (Sql DBEq) a
forall (t :: HTable) (context :: Context) a.
HTable t =>
t context -> HField t a -> context a
hfield t (Dict (Sql DBEq))
eqs HField t a
field of
    Dict (Sql DBEq) a
Dict -> case t Expr -> HField t a -> Expr a
forall (t :: HTable) (context :: Context) a.
HTable t =>
t context -> HField t a -> context a
hfield t Expr
exprs HField t a
field of
      Expr a
expr -> Expr a -> Aggregate a
forall a. Sql DBEq a => Expr a -> Aggregate a
groupByExpr Expr a
expr


-- | Aggregate rows into a single row containing an array of all aggregated
-- rows. This can be used to associate multiple rows with a single row, without
-- changing the over cardinality of the query. This allows you to essentially
-- return a tree-like structure from queries.
--
-- For example, if we have a table of orders and each orders contains multiple
-- items, we could aggregate the table of orders, pairing each order with its
-- items:
--
-- @
-- ordersWithItems :: Query (Order Expr, ListTable Expr (Item Expr))
-- ordersWithItems = do
--   order <- each orderSchema
--   items <- aggregate $ listAgg <$> itemsFromOrder order
--   return (order, items)
-- @
listAgg :: Aggregates aggregates exprs => exprs -> ListTable Aggregate aggregates
listAgg :: exprs -> ListTable Aggregate aggregates
listAgg (exprs -> Columns exprs Expr
forall (context :: Context) a.
Table context a =>
a -> Columns a context
toColumns -> Columns exprs Expr
exprs) = Columns (ListTable Aggregate aggregates) Aggregate
-> ListTable Aggregate aggregates
forall (context :: Context) a.
Table context a =>
Columns a context -> a
fromColumns (Columns (ListTable Aggregate aggregates) Aggregate
 -> ListTable Aggregate aggregates)
-> Columns (ListTable Aggregate aggregates) Aggregate
-> ListTable Aggregate aggregates
forall a b. (a -> b) -> a -> b
$
  (forall a. Spec a -> Identity (Expr a) -> Aggregate [a])
-> Identity (Columns exprs Expr)
-> HVectorize [] (Columns exprs) Aggregate
forall (t :: HTable) (f :: Context) (list :: Context)
       (context :: Context) (context' :: Context).
(HTable t, Unzip f, Vector list) =>
(forall a. Spec a -> f (context a) -> context' (list a))
-> f (t context) -> HVectorize list t context'
hvectorize
    (\Spec {TypeInformation (Unnullify a)
info :: TypeInformation (Unnullify a)
info :: forall a. Spec a -> TypeInformation (Unnullify a)
info} (Identity a) -> TypeInformation (Unnullify a) -> Expr a -> Aggregate [a]
forall a. TypeInformation (Unnullify a) -> Expr a -> Aggregate [a]
slistAggExpr TypeInformation (Unnullify a)
info Expr a
a)
    (Columns exprs Expr -> Identity (Columns exprs Expr)
forall (f :: Context) a. Applicative f => a -> f a
pure Columns exprs Expr
exprs)


-- | Like 'listAgg', but the result is guaranteed to be a non-empty list.
nonEmptyAgg :: Aggregates aggregates exprs => exprs -> NonEmptyTable Aggregate aggregates
nonEmptyAgg :: exprs -> NonEmptyTable Aggregate aggregates
nonEmptyAgg (exprs -> Columns exprs Expr
forall (context :: Context) a.
Table context a =>
a -> Columns a context
toColumns -> Columns exprs Expr
exprs) = Columns (NonEmptyTable Aggregate aggregates) Aggregate
-> NonEmptyTable Aggregate aggregates
forall (context :: Context) a.
Table context a =>
Columns a context -> a
fromColumns (Columns (NonEmptyTable Aggregate aggregates) Aggregate
 -> NonEmptyTable Aggregate aggregates)
-> Columns (NonEmptyTable Aggregate aggregates) Aggregate
-> NonEmptyTable Aggregate aggregates
forall a b. (a -> b) -> a -> b
$
  (forall a. Spec a -> Identity (Expr a) -> Aggregate (NonEmpty a))
-> Identity (Columns exprs Expr)
-> HVectorize NonEmpty (Columns exprs) Aggregate
forall (t :: HTable) (f :: Context) (list :: Context)
       (context :: Context) (context' :: Context).
(HTable t, Unzip f, Vector list) =>
(forall a. Spec a -> f (context a) -> context' (list a))
-> f (t context) -> HVectorize list t context'
hvectorize
    (\Spec {TypeInformation (Unnullify a)
info :: TypeInformation (Unnullify a)
info :: forall a. Spec a -> TypeInformation (Unnullify a)
info} (Identity a) -> TypeInformation (Unnullify a) -> Expr a -> Aggregate (NonEmpty a)
forall a.
TypeInformation (Unnullify a) -> Expr a -> Aggregate (NonEmpty a)
snonEmptyAggExpr TypeInformation (Unnullify a)
info Expr a
a)
    (Columns exprs Expr -> Identity (Columns exprs Expr)
forall (f :: Context) a. Applicative f => a -> f a
pure Columns exprs Expr
exprs)