{-# LANGUAGE FlexibleContexts #-}

module Opaleye.Values(
  values,
  -- * Explicit versions
  valuesExplicit,
  -- * Adaptors
  V.Valuesspec,
  V.valuesspecField,
  ) where

import qualified Opaleye.Internal.Values as V
import qualified Opaleye.Select              as S

import qualified Data.List.NonEmpty as NEL
import           Data.Profunctor.Product.Default (Default, def)

-- | 'values' implements Postgres's @VALUES@ construct and allows you
-- to create a @SELECT@ that consists of the given rows.
--
-- Example type specialization:
--
-- @
-- values :: [(Field a, Field b)] -> Select (Field a, Field b)
-- @
--
-- Assuming the @makeAdaptorAndInstance@ splice has been run for the
-- product type @Foo@:
--
-- @
-- values :: [Foo (Field a) (Field b) (Field c)] -> S.Select (Foo (Field a) (Field b) (Field c))
-- @
values :: Default V.Valuesspec fields fields
       => [fields] -> S.Select fields
values :: forall fields.
Default Valuesspec fields fields =>
[fields] -> Select fields
values = forall fields fields'.
Valuesspec fields fields' -> [fields] -> Select fields'
valuesExplicit forall (p :: * -> * -> *) a b. Default p a b => p a b
def

valuesExplicit :: V.Valuesspec fields fields'
               -> [fields] -> S.Select fields'
valuesExplicit :: forall fields fields'.
Valuesspec fields fields' -> [fields] -> Select fields'
valuesExplicit (V.ValuesspecSafe Nullspec fields fields'
nullspec Rowspec fields fields'
rowspec) [fields]
fields = case forall a. [a] -> Maybe (NonEmpty a)
NEL.nonEmpty [fields]
fields of
  Maybe (NonEmpty fields)
Nothing -> forall columns a. Nullspec columns a -> Select a
V.emptySelectExplicit Nullspec fields fields'
nullspec
  Just NonEmpty fields
rows -> forall columns columns'.
Rowspec columns columns' -> NonEmpty columns -> Select columns'
V.nonEmptyValues Rowspec fields fields'
rowspec NonEmpty fields
rows