{-# LANGUAGE CPP #-}
{-# LANGUAGE LambdaCase #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE RecordWildCards #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE TypeApplications #-}
{-# LANGUAGE ViewPatterns #-}

module Database.Esqueleto.Record
  ( deriveEsqueletoRecord
  , deriveEsqueletoRecordWith

  , DeriveEsqueletoRecordSettings(..)
  , defaultDeriveEsqueletoRecordSettings
  ) where

import Control.Monad.Trans.State.Strict (StateT(..), evalStateT)
import Data.Proxy (Proxy(..))
import Database.Esqueleto.Experimental
       (Entity, PersistValue, SqlExpr, Value(..), (:&)(..))
import Database.Esqueleto.Experimental.ToAlias (ToAlias(..))
import Database.Esqueleto.Experimental.ToAliasReference (ToAliasReference(..))
import Database.Esqueleto.Internal.Internal (SqlSelect(..))
import Language.Haskell.TH
import Language.Haskell.TH.Syntax
import Data.Bifunctor (first)
import Data.Text (Text)
import Control.Monad (forM)
import Data.Foldable (foldl')
import GHC.Exts (IsString(fromString))
import Data.Maybe (mapMaybe, fromMaybe, listToMaybe)

-- | Takes the name of a Haskell record type and creates a variant of that
-- record prefixed with @Sql@ which can be used in esqueleto expressions. This
-- reduces the amount of pattern matching on large tuples required to interact
-- with data extracted with esqueleto.
--
-- Note that because the input record and the @Sql@-prefixed record share field
-- names, the @{-\# LANGUAGE DuplicateRecordFields \#-}@ extension is required in
-- modules that use `deriveEsqueletoRecord`. Additionally, the @{-\# LANGUAGE
-- TypeApplications \#-}@ extension is required for some of the generated code.
--
-- Given the following record:
--
-- @
-- data MyRecord = MyRecord
--   { myName    :: 'Text'
--   , myAge     :: 'Maybe' 'Int'
--   , myUser    :: 'Entity' User
--   , myAddress :: 'Maybe' ('Entity' Address)
--   }
-- @
--
-- @$('deriveEsqueletoRecord' ''MyRecord)@ will generate roughly the following code:
--
-- @
-- data SqlMyRecord =
--   SqlMyRecord { myName    :: 'SqlExpr' ('Value' Text)
--               , myAge     :: 'SqlExpr' ('Value' ('Maybe' Int))
--               , myUser    :: 'SqlExpr' ('Entity' User)
--               , myAddress :: 'SqlExpr' ('Maybe' ('Entity' Address))
--               }
--
-- instance 'SqlSelect' SqlMyRecord MyRecord where
--   'sqlSelectCols'
--     identInfo
--     SqlMyRecord { myName    = myName
--                 , myAge     = myAge
--                 , myUser    = myUser
--                 , myAddress = myAddress
--                 } =
--     'sqlSelectCols' identInfo (myName :& myAge :& myUser :& myAddress)
--
--   'sqlSelectColCount' _ =
--     'sqlSelectColCount'
--       ('Proxy' \@(   ('SqlExpr' ('Value' Text))
--                :& ('SqlExpr' ('Value' ('Maybe' Int)))
--                :& ('SqlExpr' ('Entity' User))
--                :& ('SqlExpr' ('Maybe' ('Entity' Address)))))
--
--   'sqlSelectProcessRow' columns =
--     'first' (('fromString' "Failed to parse MyRecord: ") <>)
--           ('evalStateT' process columns)
--     where
--       process = do
--         'Value' myName <- 'takeColumns' \@('SqlExpr' ('Value' Text))
--         'Value' myAge  <- 'takeColumns' \@('SqlExpr' ('Value' ('Maybe' Int)))
--         myUser       <- 'takeColumns' \@('SqlExpr' ('Entity' User))
--         myAddress    <- 'takeColumns' \@('SqlExpr' ('Maybe' ('Entity' Address)))
--         'pure' MyRecord { myName = myName
--                       , myAge = myAge
--                       , myUser = myUser
--                       , myAddress = myAddress
--                       }
-- @
--
-- Then, we could write a selection function to use the record in queries:
--
-- @
-- getMyRecord :: 'Database.Esqueleto.SqlPersistT' 'IO' [MyRecord]
-- getMyRecord = 'Database.Esqueleto.Experimental.select' myRecordQuery
--
-- myRecordQuery :: 'Database.Esqueleto.SqlQuery' SqlMyRecord
-- myRecordQuery = do
--   user ':&' address <- 'Database.Esqueleto.Experimental.from' '$'
--     'Database.Esqueleto.Experimental.table' \@User
--       \`'Database.Esqueleto.Experimental.leftJoin'\`
--       'Database.Esqueleto.Experimental.table' \@Address
--       \`'Database.Esqueleto.Experimental.on'\` (do \\(user ':&' address) -> user 'Database.Esqueleto.Experimental.^.' #address 'Database.Esqueleto.Experimental.==.' address 'Database.Esqueleto.Experimental.?.' #id)
--   'pure'
--     SqlMyRecord
--       { myName = 'Database.Esqueleto.Experimental.castString' '$' user 'Database.Esqueleto.Experimental.^.' #firstName
--       , myAge = 'Database.Esqueleto.Experimental.val' 10
--       , myUser = user
--       , myAddress = address
--       }
-- @
--
-- @since 3.5.6.0
deriveEsqueletoRecord :: Name -> Q [Dec]
deriveEsqueletoRecord :: Name -> Q [Dec]
deriveEsqueletoRecord = DeriveEsqueletoRecordSettings -> Name -> Q [Dec]
deriveEsqueletoRecordWith DeriveEsqueletoRecordSettings
defaultDeriveEsqueletoRecordSettings

-- | Codegen settings for 'deriveEsqueletoRecordWith'.
--
-- @since 3.5.8.0
data DeriveEsqueletoRecordSettings = DeriveEsqueletoRecordSettings
  { DeriveEsqueletoRecordSettings -> String -> String
sqlNameModifier :: String -> String
    -- ^ Function applied to the Haskell record's type name and constructor
    -- name to produce the SQL record's type name and constructor name.
    --
    -- @since 3.5.8.0
  , DeriveEsqueletoRecordSettings -> String -> String
sqlFieldModifier :: String -> String
    -- ^ Function applied to the Haskell record's field names to produce the
    -- SQL record's field names.
    --
    -- @since 3.5.8.0
  }

-- | The default codegen settings for 'deriveEsqueletoRecord'.
--
-- These defaults will cause you to require @{-# LANGUAGE DuplicateRecordFields #-}@
-- in certain cases (see 'deriveEsqueletoRecord'.) If you don't want to do this,
-- change the value of 'sqlFieldModifier' so the field names of the generated SQL
-- record different from those of the Haskell record.
--
-- @since 3.5.8.0
defaultDeriveEsqueletoRecordSettings :: DeriveEsqueletoRecordSettings
defaultDeriveEsqueletoRecordSettings :: DeriveEsqueletoRecordSettings
defaultDeriveEsqueletoRecordSettings = DeriveEsqueletoRecordSettings
  { sqlNameModifier :: String -> String
sqlNameModifier = (String
"Sql" forall a. [a] -> [a] -> [a]
++)
  , sqlFieldModifier :: String -> String
sqlFieldModifier = forall a. a -> a
id
  }

-- | Takes the name of a Haskell record type and creates a variant of that
-- record based on the supplied settings which can be used in esqueleto
-- expressions. This reduces the amount of pattern matching on large tuples
-- required to interact with data extracted with esqueleto.
--
-- This is a variant of 'deriveEsqueletoRecord' which allows you to avoid the
-- use of @{-# LANGUAGE DuplicateRecordFields #-}@, by configuring the
-- 'DeriveEsqueletoRecordSettings' used to generate the SQL record.
--
-- @since 3.5.8.0
deriveEsqueletoRecordWith :: DeriveEsqueletoRecordSettings -> Name -> Q [Dec]
deriveEsqueletoRecordWith :: DeriveEsqueletoRecordSettings -> Name -> Q [Dec]
deriveEsqueletoRecordWith DeriveEsqueletoRecordSettings
settings Name
originalName = do
  RecordInfo
info <- DeriveEsqueletoRecordSettings -> Name -> Q RecordInfo
getRecordInfo DeriveEsqueletoRecordSettings
settings Name
originalName
  -- It would be nicer to use `mconcat` here but I don't think the right
  -- instance is available in GHC 8.
  Dec
recordDec <- RecordInfo -> Q Dec
makeSqlRecord RecordInfo
info
  Dec
sqlSelectInstanceDec <- RecordInfo -> Q Dec
makeSqlSelectInstance RecordInfo
info
  Dec
toAliasInstanceDec <- RecordInfo -> Q Dec
makeToAliasInstance RecordInfo
info
  Dec
toAliasReferenceInstanceDec <- RecordInfo -> Q Dec
makeToAliasReferenceInstance RecordInfo
info
  forall (f :: * -> *) a. Applicative f => a -> f a
pure
    [ Dec
recordDec
    , Dec
sqlSelectInstanceDec
    , Dec
toAliasInstanceDec
    , Dec
toAliasReferenceInstanceDec
    ]

-- | Information about a record we need to generate the declarations.
-- We compute this once and then pass it around to save on complexity /
-- repeated work.
data RecordInfo = RecordInfo
  { -- | The original record's name.
    RecordInfo -> Name
name :: Name
  , -- | The generated SQL record's name.
    RecordInfo -> Name
sqlName :: Name
  , -- | The original record's constraints. If this isn't empty it'll probably
    -- cause problems, but it's easy to pass around so might as well.
    RecordInfo -> Cxt
constraints :: Cxt
  , -- | The original record's type-variable-binders.
#if MIN_VERSION_template_haskell(2,17,0)
    RecordInfo -> [TyVarBndr ()]
typeVarBinders :: [TyVarBndr ()]
#else
    typeVarBinders :: [TyVarBndr]
#endif
  , -- | The original record's kind, I think.
    RecordInfo -> Maybe Type
kind :: Maybe Kind
  , -- | The original record's constructor name.
    RecordInfo -> Name
constructorName :: Name
  , -- | The generated SQL record's constructor name.
    RecordInfo -> Name
sqlConstructorName :: Name
  , -- | The original record's field names and types, derived from the
    -- constructors.
    RecordInfo -> [(Name, Type)]
fields :: [(Name, Type)]
  , -- | The generated SQL record's field names and types, computed
    -- with 'sqlFieldType'.
    RecordInfo -> [(Name, Type)]
sqlFields :: [(Name, Type)]
  }

-- | Get a `RecordInfo` instance for the given record name.
getRecordInfo :: DeriveEsqueletoRecordSettings -> Name -> Q RecordInfo
getRecordInfo :: DeriveEsqueletoRecordSettings -> Name -> Q RecordInfo
getRecordInfo DeriveEsqueletoRecordSettings
settings Name
name = do
  TyConI Dec
dec <- Name -> Q Info
reify Name
name
  (Cxt
constraints, [TyVarBndr ()]
typeVarBinders, Maybe Type
kind, [Con]
constructors) <-
        case Dec
dec of
          DataD Cxt
constraints' Name
_name [TyVarBndr ()]
typeVarBinders' Maybe Type
kind' [Con]
constructors' [DerivClause]
_derivingClauses ->
            forall (f :: * -> *) a. Applicative f => a -> f a
pure (Cxt
constraints', [TyVarBndr ()]
typeVarBinders', Maybe Type
kind', [Con]
constructors')
          NewtypeD Cxt
constraints' Name
_name [TyVarBndr ()]
typeVarBinders' Maybe Type
kind' Con
constructor' [DerivClause]
_derivingClauses ->
            forall (f :: * -> *) a. Applicative f => a -> f a
pure (Cxt
constraints', [TyVarBndr ()]
typeVarBinders', Maybe Type
kind', [Con
constructor'])
          Dec
_ -> forall (m :: * -> *) a. MonadFail m => String -> m a
fail forall a b. (a -> b) -> a -> b
$ String
"Esqueleto records can only be derived for records and newtypes, but " forall a. [a] -> [a] -> [a]
++ forall a. Show a => a -> String
show Name
name forall a. [a] -> [a] -> [a]
++ String
" is neither"
  Con
constructor <- case [Con]
constructors of
                  (Con
c : [Con]
_) -> forall (f :: * -> *) a. Applicative f => a -> f a
pure Con
c
                  [] -> forall (m :: * -> *) a. MonadFail m => String -> m a
fail forall a b. (a -> b) -> a -> b
$ String
"Cannot derive Esqueleto record for a type with no constructors: " forall a. [a] -> [a] -> [a]
++ forall a. Show a => a -> String
show Name
name
  let constructorName :: Name
constructorName =
        case forall a. [a] -> a
head [Con]
constructors of
          RecC Name
name' [VarBangType]
_fields -> Name
name'
          Con
con -> forall a. HasCallStack => String -> a
error forall a b. (a -> b) -> a -> b
$ Con -> String
nonRecordConstructorMessage Con
con
      fields :: [(Name, Type)]
fields = Con -> [(Name, Type)]
getFields Con
constructor
      sqlName :: Name
sqlName = DeriveEsqueletoRecordSettings -> Name -> Name
makeSqlName DeriveEsqueletoRecordSettings
settings Name
name
      sqlConstructorName :: Name
sqlConstructorName = DeriveEsqueletoRecordSettings -> Name -> Name
makeSqlName DeriveEsqueletoRecordSettings
settings Name
constructorName

  [(Name, Type)]
sqlFields <- forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM (Name, Type) -> Q (Name, Type)
toSqlField [(Name, Type)]
fields

  forall (f :: * -> *) a. Applicative f => a -> f a
pure RecordInfo {Cxt
[(Name, Type)]
[TyVarBndr ()]
Maybe Type
Name
sqlFields :: [(Name, Type)]
sqlConstructorName :: Name
sqlName :: Name
fields :: [(Name, Type)]
constructorName :: Name
kind :: Maybe Type
typeVarBinders :: [TyVarBndr ()]
constraints :: Cxt
name :: Name
sqlFields :: [(Name, Type)]
fields :: [(Name, Type)]
sqlConstructorName :: Name
constructorName :: Name
kind :: Maybe Type
typeVarBinders :: [TyVarBndr ()]
constraints :: Cxt
sqlName :: Name
name :: Name
..}
  where
    getFields :: Con -> [(Name, Type)]
    getFields :: Con -> [(Name, Type)]
getFields (RecC Name
_name [VarBangType]
fields) = [(Name
fieldName', Type
fieldType') | (Name
fieldName', Bang
_bang, Type
fieldType') <- [VarBangType]
fields]
    getFields Con
con = forall a. HasCallStack => String -> a
error forall a b. (a -> b) -> a -> b
$ Con -> String
nonRecordConstructorMessage Con
con

    toSqlField :: (Name, Type) -> Q (Name, Type)
toSqlField (Name
fieldName', Type
ty) = do
      let modifier :: Name -> Name
modifier = String -> Name
mkName forall b c a. (b -> c) -> (a -> b) -> a -> c
. DeriveEsqueletoRecordSettings -> String -> String
sqlFieldModifier DeriveEsqueletoRecordSettings
settings forall b c a. (b -> c) -> (a -> b) -> a -> c
. Name -> String
nameBase
      Type
sqlTy <- Type -> Q Type
sqlFieldType Type
ty
      forall (f :: * -> *) a. Applicative f => a -> f a
pure (Name -> Name
modifier Name
fieldName', Type
sqlTy)

-- | Create a new name by prefixing @Sql@ to a given name.
makeSqlName :: DeriveEsqueletoRecordSettings -> Name -> Name
makeSqlName :: DeriveEsqueletoRecordSettings -> Name -> Name
makeSqlName DeriveEsqueletoRecordSettings
settings Name
name = String -> Name
mkName forall a b. (a -> b) -> a -> b
$ DeriveEsqueletoRecordSettings -> String -> String
sqlNameModifier DeriveEsqueletoRecordSettings
settings forall a b. (a -> b) -> a -> b
$ Name -> String
nameBase Name
name

-- | Transforms a record field type into a corresponding `SqlExpr` type.
--
-- * @'Entity' x@ is transformed into @'SqlExpr' ('Entity' x)@.
-- * @'Maybe' ('Entity' x)@ is transformed into @'SqlExpr' ('Maybe' ('Entity' x))@.
-- * @x@ is transformed into @'SqlExpr' ('Value' x)@.
-- * If there exists an instance @'SqlSelect' sql x@, then @x@ is transformed into @sql@.
--
-- This function should match `sqlSelectProcessRowPat`.
sqlFieldType :: Type -> Q Type
sqlFieldType :: Type -> Q Type
sqlFieldType Type
fieldType = do
  Maybe Type
maybeSqlType <- Type -> Q (Maybe Type)
reifySqlSelectType Type
fieldType

  forall (f :: * -> *) a. Applicative f => a -> f a
pure forall a b. (a -> b) -> a -> b
$
    forall a b c. (a -> b -> c) -> b -> a -> c
flip forall a. a -> Maybe a -> a
fromMaybe Maybe Type
maybeSqlType forall a b. (a -> b) -> a -> b
$
      case Type
fieldType of
        -- Entity x -> SqlExpr (Entity x)
        AppT (ConT (forall a. Eq a => a -> a -> Bool
(==) ''Entity -> Bool
True)) Type
_innerType -> Type -> Type -> Type
AppT (Name -> Type
ConT ''SqlExpr) Type
fieldType

        -- Maybe (Entity x) -> SqlExpr (Maybe (Entity x))
        (ConT (forall a. Eq a => a -> a -> Bool
(==) ''Maybe -> Bool
True))
          `AppT` ((ConT (forall a. Eq a => a -> a -> Bool
(==) ''Entity -> Bool
True))
                  `AppT` Type
_innerType) -> Type -> Type -> Type
AppT (Name -> Type
ConT ''SqlExpr) Type
fieldType

        -- x -> SqlExpr (Value x)
        Type
_ -> (Name -> Type
ConT ''SqlExpr)
                Type -> Type -> Type
`AppT` ((Name -> Type
ConT ''Value)
                        Type -> Type -> Type
`AppT` Type
fieldType)

-- | Generates the declaration for an @Sql@-prefixed record, given the original
-- record's information.
makeSqlRecord :: RecordInfo -> Q Dec
makeSqlRecord :: RecordInfo -> Q Dec
makeSqlRecord RecordInfo {Cxt
[(Name, Type)]
[TyVarBndr ()]
Maybe Type
Name
sqlFields :: [(Name, Type)]
fields :: [(Name, Type)]
sqlConstructorName :: Name
constructorName :: Name
kind :: Maybe Type
typeVarBinders :: [TyVarBndr ()]
constraints :: Cxt
sqlName :: Name
name :: Name
sqlFields :: RecordInfo -> [(Name, Type)]
fields :: RecordInfo -> [(Name, Type)]
sqlConstructorName :: RecordInfo -> Name
constructorName :: RecordInfo -> Name
kind :: RecordInfo -> Maybe Type
typeVarBinders :: RecordInfo -> [TyVarBndr ()]
constraints :: RecordInfo -> Cxt
sqlName :: RecordInfo -> Name
name :: RecordInfo -> Name
..} = do
  let newConstructor :: Con
newConstructor = Name -> [VarBangType] -> Con
RecC Name
sqlConstructorName (forall {a} {c}. (a, c) -> (a, Bang, c)
makeField forall a b. (a -> b) -> [a] -> [b]
`map` [(Name, Type)]
sqlFields)
      derivingClauses :: [a]
derivingClauses = []
  forall (f :: * -> *) a. Applicative f => a -> f a
pure forall a b. (a -> b) -> a -> b
$ Cxt
-> Name
-> [TyVarBndr ()]
-> Maybe Type
-> [Con]
-> [DerivClause]
-> Dec
DataD Cxt
constraints Name
sqlName [TyVarBndr ()]
typeVarBinders Maybe Type
kind [Con
newConstructor] forall a. [a]
derivingClauses
  where
    makeField :: (a, c) -> (a, Bang, c)
makeField (a
fieldName', c
fieldType) =
      (a
fieldName', SourceUnpackedness -> SourceStrictness -> Bang
Bang SourceUnpackedness
NoSourceUnpackedness SourceStrictness
NoSourceStrictness, c
fieldType)

-- | Generates an `SqlSelect` instance for the given record and its
-- @Sql@-prefixed variant.
makeSqlSelectInstance :: RecordInfo -> Q Dec
makeSqlSelectInstance :: RecordInfo -> Q Dec
makeSqlSelectInstance info :: RecordInfo
info@RecordInfo {Cxt
[(Name, Type)]
[TyVarBndr ()]
Maybe Type
Name
sqlFields :: [(Name, Type)]
fields :: [(Name, Type)]
sqlConstructorName :: Name
constructorName :: Name
kind :: Maybe Type
typeVarBinders :: [TyVarBndr ()]
constraints :: Cxt
sqlName :: Name
name :: Name
sqlFields :: RecordInfo -> [(Name, Type)]
fields :: RecordInfo -> [(Name, Type)]
sqlConstructorName :: RecordInfo -> Name
constructorName :: RecordInfo -> Name
kind :: RecordInfo -> Maybe Type
typeVarBinders :: RecordInfo -> [TyVarBndr ()]
constraints :: RecordInfo -> Cxt
sqlName :: RecordInfo -> Name
name :: RecordInfo -> Name
..} = do
  Dec
sqlSelectColsDec' <- RecordInfo -> Q Dec
sqlSelectColsDec RecordInfo
info
  Dec
sqlSelectColCountDec' <- RecordInfo -> Q Dec
sqlSelectColCountDec RecordInfo
info
  Dec
sqlSelectProcessRowDec' <- RecordInfo -> Q Dec
sqlSelectProcessRowDec RecordInfo
info
  let overlap :: Maybe a
overlap = forall a. Maybe a
Nothing
      instanceConstraints :: [a]
instanceConstraints = []
      instanceType :: Type
instanceType =
        (Name -> Type
ConT ''SqlSelect)
          Type -> Type -> Type
`AppT` (Name -> Type
ConT Name
sqlName)
          Type -> Type -> Type
`AppT` (Name -> Type
ConT Name
name)

  forall (f :: * -> *) a. Applicative f => a -> f a
pure forall a b. (a -> b) -> a -> b
$ Maybe Overlap -> Cxt -> Type -> [Dec] -> Dec
InstanceD forall a. Maybe a
overlap forall a. [a]
instanceConstraints Type
instanceType [Dec
sqlSelectColsDec', Dec
sqlSelectColCountDec', Dec
sqlSelectProcessRowDec']

-- | Generates the `sqlSelectCols` declaration for an `SqlSelect` instance.
sqlSelectColsDec :: RecordInfo -> Q Dec
sqlSelectColsDec :: RecordInfo -> Q Dec
sqlSelectColsDec RecordInfo {Cxt
[(Name, Type)]
[TyVarBndr ()]
Maybe Type
Name
sqlFields :: [(Name, Type)]
fields :: [(Name, Type)]
sqlConstructorName :: Name
constructorName :: Name
kind :: Maybe Type
typeVarBinders :: [TyVarBndr ()]
constraints :: Cxt
sqlName :: Name
name :: Name
sqlFields :: RecordInfo -> [(Name, Type)]
fields :: RecordInfo -> [(Name, Type)]
sqlConstructorName :: RecordInfo -> Name
constructorName :: RecordInfo -> Name
kind :: RecordInfo -> Maybe Type
typeVarBinders :: RecordInfo -> [TyVarBndr ()]
constraints :: RecordInfo -> Cxt
sqlName :: RecordInfo -> Name
name :: RecordInfo -> Name
..} = do
  -- Pairs of record field names and local variable names.
  [(Name, Name)]
fieldNames <- forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
t a -> (a -> m b) -> m (t b)
forM [(Name, Type)]
sqlFields (\(Name
name', Type
_type) -> do
    Name
var <- forall (m :: * -> *). Quote m => String -> m Name
newName forall a b. (a -> b) -> a -> b
$ Name -> String
nameBase Name
name'
    forall (f :: * -> *) a. Applicative f => a -> f a
pure (Name
name', Name
var))

  -- Patterns binding record fields to local variables.
  let fieldPatterns :: [FieldPat]
      fieldPatterns :: [FieldPat]
fieldPatterns = [(Name
name', Name -> Pat
VarP Name
var) | (Name
name', Name
var) <- [(Name, Name)]
fieldNames]

      -- Local variables for fields joined with `:&` in a single expression.
      joinedFields :: Exp
      joinedFields :: Exp
joinedFields =
        case forall a b. (a, b) -> b
snd forall a b. (a -> b) -> [a] -> [b]
`map` [(Name, Name)]
fieldNames of
          [] -> [Maybe Exp] -> Exp
TupE []
          [Name
f1] -> Name -> Exp
VarE Name
f1
          Name
f1 : [Name]
rest ->
            let helper :: Exp -> Name -> Exp
helper Exp
lhs Name
field =
                  Maybe Exp -> Exp -> Maybe Exp -> Exp
InfixE
                    (forall a. a -> Maybe a
Just Exp
lhs)
                    (Name -> Exp
ConE '(:&))
                    (forall a. a -> Maybe a
Just forall a b. (a -> b) -> a -> b
$ Name -> Exp
VarE Name
field)
             in forall (t :: * -> *) b a.
Foldable t =>
(b -> a -> b) -> b -> t a -> b
foldl' Exp -> Name -> Exp
helper (Name -> Exp
VarE Name
f1) [Name]
rest

  Name
identInfo <- forall (m :: * -> *). Quote m => String -> m Name
newName String
"identInfo"
  -- Roughly:
  -- sqlSelectCols $identInfo SqlFoo{..} = sqlSelectCols $identInfo $joinedFields
  forall (f :: * -> *) a. Applicative f => a -> f a
pure forall a b. (a -> b) -> a -> b
$
    Name -> [Clause] -> Dec
FunD
      'sqlSelectCols
      [ [Pat] -> Body -> [Dec] -> Clause
Clause
          [ Name -> Pat
VarP Name
identInfo
          , Name -> [FieldPat] -> Pat
RecP Name
sqlName [FieldPat]
fieldPatterns
          ]
          ( Exp -> Body
NormalB forall a b. (a -> b) -> a -> b
$
              (Name -> Exp
VarE 'sqlSelectCols)
                Exp -> Exp -> Exp
`AppE` (Name -> Exp
VarE Name
identInfo)
                Exp -> Exp -> Exp
`AppE` (Exp -> Exp
ParensE Exp
joinedFields)
          )
          -- `where` clause.
          []
      ]

-- | Generates the `sqlSelectColCount` declaration for an `SqlSelect` instance.
sqlSelectColCountDec :: RecordInfo -> Q Dec
sqlSelectColCountDec :: RecordInfo -> Q Dec
sqlSelectColCountDec RecordInfo {Cxt
[(Name, Type)]
[TyVarBndr ()]
Maybe Type
Name
sqlFields :: [(Name, Type)]
fields :: [(Name, Type)]
sqlConstructorName :: Name
constructorName :: Name
kind :: Maybe Type
typeVarBinders :: [TyVarBndr ()]
constraints :: Cxt
sqlName :: Name
name :: Name
sqlFields :: RecordInfo -> [(Name, Type)]
fields :: RecordInfo -> [(Name, Type)]
sqlConstructorName :: RecordInfo -> Name
constructorName :: RecordInfo -> Name
kind :: RecordInfo -> Maybe Type
typeVarBinders :: RecordInfo -> [TyVarBndr ()]
constraints :: RecordInfo -> Cxt
sqlName :: RecordInfo -> Name
name :: RecordInfo -> Name
..} = do
  let joinedTypes :: Type
joinedTypes =
        case forall a b. (a, b) -> b
snd forall a b. (a -> b) -> [a] -> [b]
`map` [(Name, Type)]
sqlFields of
          [] -> Int -> Type
TupleT Int
0
          Type
t1 : Cxt
rest ->
            let helper :: Type -> Type -> Type
helper Type
lhs Type
ty =
                  Type -> Name -> Type -> Type
InfixT Type
lhs ''(:&) Type
ty
             in forall (t :: * -> *) b a.
Foldable t =>
(b -> a -> b) -> b -> t a -> b
foldl' Type -> Type -> Type
helper Type
t1 Cxt
rest

  -- Roughly:
  -- sqlSelectColCount _ = sqlSelectColCount (Proxy @($joinedTypes))
  forall (f :: * -> *) a. Applicative f => a -> f a
pure forall a b. (a -> b) -> a -> b
$
    Name -> [Clause] -> Dec
FunD
      'sqlSelectColCount
      [ [Pat] -> Body -> [Dec] -> Clause
Clause
          [Pat
WildP]
          ( Exp -> Body
NormalB forall a b. (a -> b) -> a -> b
$
              Exp -> Exp -> Exp
AppE (Name -> Exp
VarE 'sqlSelectColCount) forall a b. (a -> b) -> a -> b
$
                Exp -> Exp
ParensE forall a b. (a -> b) -> a -> b
$
                  Exp -> Type -> Exp
AppTypeE
                    (Name -> Exp
ConE 'Proxy)
                    Type
joinedTypes
          )
          -- `where` clause.
          []
      ]

-- | Generates the `sqlSelectProcessRow` declaration for an `SqlSelect`
-- instance.
sqlSelectProcessRowDec :: RecordInfo -> Q Dec
sqlSelectProcessRowDec :: RecordInfo -> Q Dec
sqlSelectProcessRowDec RecordInfo {Cxt
[(Name, Type)]
[TyVarBndr ()]
Maybe Type
Name
sqlFields :: [(Name, Type)]
fields :: [(Name, Type)]
sqlConstructorName :: Name
constructorName :: Name
kind :: Maybe Type
typeVarBinders :: [TyVarBndr ()]
constraints :: Cxt
sqlName :: Name
name :: Name
sqlFields :: RecordInfo -> [(Name, Type)]
fields :: RecordInfo -> [(Name, Type)]
sqlConstructorName :: RecordInfo -> Name
constructorName :: RecordInfo -> Name
kind :: RecordInfo -> Maybe Type
typeVarBinders :: RecordInfo -> [TyVarBndr ()]
constraints :: RecordInfo -> Cxt
sqlName :: RecordInfo -> Name
name :: RecordInfo -> Name
..} = do
  -- Binding statements and field expressions (used in record construction) to
  -- fill out the body of the main generated `do` expression.
  --
  -- Each statement is like:
  --     Value fooName' <- takeColumns @(SqlExpr (Value Text))
  -- A corresponding field expression would be:
  --     fooName = fooName'
  --
  -- See `sqlSelectProcessRowPat` for the left-hand side of the patterns.
  ([Stmt]
statements, [(Name, Exp)]
fieldExps) <-
    forall a b. [(a, b)] -> ([a], [b])
unzip forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
t a -> (a -> m b) -> m (t b)
forM (forall a b. [a] -> [b] -> [(a, b)]
zip [(Name, Type)]
fields [(Name, Type)]
sqlFields) (\((Name
fieldName', Type
fieldType), (Name
_, Type
sqlType')) -> do
      Name
valueName <- forall (m :: * -> *). Quote m => String -> m Name
newName (Name -> String
nameBase Name
fieldName')
      Pat
pattern <- Type -> Name -> Q Pat
sqlSelectProcessRowPat Type
fieldType Name
valueName
      forall (f :: * -> *) a. Applicative f => a -> f a
pure
        ( Pat -> Exp -> Stmt
BindS
            Pat
pattern
            (Exp -> Type -> Exp
AppTypeE (Name -> Exp
VarE 'takeColumns) Type
sqlType')
        , (String -> Name
mkName forall a b. (a -> b) -> a -> b
$ Name -> String
nameBase Name
fieldName', Name -> Exp
VarE Name
valueName)
        ))

  Name
colsName <- forall (m :: * -> *). Quote m => String -> m Name
newName String
"columns"
  Name
processName <- forall (m :: * -> *). Quote m => String -> m Name
newName String
"process"

  -- Roughly:
  -- sqlSelectProcessRow $colsName =
  --   first ((fromString "Failed to parse $name: ") <>)
  --         (evalStateT $processName $colsName)
  --   where $processName = do $statements
  --                           pure $name {$fieldExps}
  Exp
bodyExp <- [e|
    first (fromString ("Failed to parse " ++ $(lift $ nameBase name) ++ ": ") <>)
          (evalStateT $(varE processName) $(varE colsName))
    |]

  forall (f :: * -> *) a. Applicative f => a -> f a
pure forall a b. (a -> b) -> a -> b
$
    Name -> [Clause] -> Dec
FunD
      'sqlSelectProcessRow
      [ [Pat] -> Body -> [Dec] -> Clause
Clause
          [Name -> Pat
VarP Name
colsName]
          (Exp -> Body
NormalB Exp
bodyExp)
          -- `where` clause
          [ Pat -> Body -> [Dec] -> Dec
ValD
              (Name -> Pat
VarP Name
processName)
              ( Exp -> Body
NormalB forall a b. (a -> b) -> a -> b
$
                  Maybe ModName -> [Stmt] -> Exp
DoE
#if MIN_VERSION_template_haskell(2,17,0)
                    forall a. Maybe a
Nothing
#endif
                    ([Stmt]
statements forall a. [a] -> [a] -> [a]
++ [Exp -> Stmt
NoBindS forall a b. (a -> b) -> a -> b
$ Exp -> Exp -> Exp
AppE (Name -> Exp
VarE 'pure) (Name -> [(Name, Exp)] -> Exp
RecConE Name
constructorName [(Name, Exp)]
fieldExps)])
              )
              []
          ]
      ]

-- | Get the left-hand side pattern of a statement in a @do@ block for binding
-- to the result of `sqlSelectProcessRow`.
--
-- * A type of @'Entity' x@ gives a pattern of @var@.
-- * A type of @'Maybe' ('Entity' x)@ gives a pattern of @var@.
-- * A type of @x@ gives a pattern of @'Value' var@.
-- * If there exists an instance @'SqlSelect' sql x@, then a type of @x@ gives a pattern of @var@.
--
-- This function should match `sqlFieldType`.
sqlSelectProcessRowPat :: Type -> Name -> Q Pat
sqlSelectProcessRowPat :: Type -> Name -> Q Pat
sqlSelectProcessRowPat Type
fieldType Name
var = do
  Maybe Type
maybeSqlType <- Type -> Q (Maybe Type)
reifySqlSelectType Type
fieldType

  case Maybe Type
maybeSqlType of
    Just Type
_ -> forall (f :: * -> *) a. Applicative f => a -> f a
pure forall a b. (a -> b) -> a -> b
$ Name -> Pat
VarP Name
var
    Maybe Type
Nothing -> case Type
fieldType of
        -- Entity x -> var
        AppT (ConT (forall a. Eq a => a -> a -> Bool
(==) ''Entity -> Bool
True)) Type
_innerType -> forall (f :: * -> *) a. Applicative f => a -> f a
pure forall a b. (a -> b) -> a -> b
$ Name -> Pat
VarP Name
var
        -- Maybe (Entity x) -> var
        (ConT (forall a. Eq a => a -> a -> Bool
(==) ''Maybe -> Bool
True))
          `AppT` ((ConT (forall a. Eq a => a -> a -> Bool
(==) ''Entity -> Bool
True))
                  `AppT` Type
_innerType) -> forall (f :: * -> *) a. Applicative f => a -> f a
pure forall a b. (a -> b) -> a -> b
$ Name -> Pat
VarP Name
var
        -- x -> Value var
#if MIN_VERSION_template_haskell(2,18,0)
        Type
_ -> forall (f :: * -> *) a. Applicative f => a -> f a
pure forall a b. (a -> b) -> a -> b
$ Name -> Cxt -> [Pat] -> Pat
ConP 'Value [] [Name -> Pat
VarP Name
var]
#else
        _ -> pure $ ConP 'Value [VarP var]
#endif

-- Given a type, find the corresponding SQL type.
--
-- If there exists an instance `SqlSelect sql ty`, then the SQL type for `ty`
-- is `sql`.
--
-- This function definitely works for records and instances generated by this
-- module, and might work for instances outside of it.
reifySqlSelectType :: Type -> Q (Maybe Type)
reifySqlSelectType :: Type -> Q (Maybe Type)
reifySqlSelectType Type
originalType = do
  -- Here we query the compiler for Instances of `SqlSelect a $(originalType)`;
  -- the API for this is super weird, it interprets a list of types as being
  -- applied as successive arguments to the typeclass name.
  --
  -- See: https://gitlab.haskell.org/ghc/ghc/-/issues/21825
  --
  -- >>> reifyInstances ''SqlSelect [VarT (mkName "a"), ConT ''MyRecord]
  -- [ InstanceD Nothing
  --             []
  --             (AppT (AppT (ConT Database.Esqueleto.Internal.Internal.SqlSelect)
  --                         (ConT Ghci3.SqlMyRecord))
  --                   (ConT Ghci3.MyRecord))
  --             []
  -- ]
  Name
tyVarName <- forall (m :: * -> *). Quote m => String -> m Name
newName String
"a"
  [Dec]
instances <- Name -> Cxt -> Q [Dec]
reifyInstances ''SqlSelect [Name -> Type
VarT Name
tyVarName, Type
originalType]

  -- Given the original type (`originalType`) and an instance type for a
  -- `SqlSelect` instance, get the SQL type which corresponds to the original
  -- type.
  let extractSqlRecord :: Type -> Type -> Maybe Type
      extractSqlRecord :: Type -> Type -> Maybe Type
extractSqlRecord Type
originalTy Type
instanceTy =
        case Type
instanceTy of
          (ConT (forall a. Eq a => a -> a -> Bool
(==) ''SqlSelect -> Bool
True))
            `AppT` Type
sqlTy
            `AppT` (forall a. Eq a => a -> a -> Bool
(==) Type
originalTy -> Bool
True) -> forall a. a -> Maybe a
Just Type
sqlTy
          Type
_ -> forall a. Maybe a
Nothing

      -- Filter `instances` to the instances which match `originalType`.
      filteredInstances :: [Type]
      filteredInstances :: Cxt
filteredInstances =
        forall a b c. (a -> b -> c) -> b -> a -> c
flip forall a b. (a -> Maybe b) -> [a] -> [b]
mapMaybe [Dec]
instances
          (\case InstanceD Maybe Overlap
_overlap
                           Cxt
_constraints
                           (Type -> Type -> Maybe Type
extractSqlRecord Type
originalType -> Just Type
sqlRecord)
                           [Dec]
_decs ->
                             forall a. a -> Maybe a
Just Type
sqlRecord
                 Dec
_ -> forall a. Maybe a
Nothing)

  forall (f :: * -> *) a. Applicative f => a -> f a
pure forall a b. (a -> b) -> a -> b
$ forall a. [a] -> Maybe a
listToMaybe Cxt
filteredInstances

-- | Statefully parse some number of columns from a list of `PersistValue`s,
-- where the number of columns to parse is determined by `sqlSelectColCount`
-- for @a@.
--
-- This is used to implement `sqlSelectProcessRow` for records created with
-- `deriveEsqueletoRecord`.
takeColumns ::
  forall a b.
  SqlSelect a b =>
  StateT [PersistValue] (Either Text) b
takeColumns :: forall a b. SqlSelect a b => StateT [PersistValue] (Either Text) b
takeColumns = forall s (m :: * -> *) a. (s -> m (a, s)) -> StateT s m a
StateT (\[PersistValue]
pvs ->
  let targetColCount :: Int
targetColCount =
        forall a r. SqlSelect a r => Proxy a -> Int
sqlSelectColCount (forall {k} (t :: k). Proxy t
Proxy @a)
      ([PersistValue]
target, [PersistValue]
other) =
        forall a. Int -> [a] -> ([a], [a])
splitAt Int
targetColCount [PersistValue]
pvs
   in if forall (t :: * -> *) a. Foldable t => t a -> Int
length [PersistValue]
target forall a. Eq a => a -> a -> Bool
== Int
targetColCount
        then do
          b
value <- forall a r. SqlSelect a r => [PersistValue] -> Either Text r
sqlSelectProcessRow [PersistValue]
target
          forall a b. b -> Either a b
Right (b
value, [PersistValue]
other)
        else forall a b. a -> Either a b
Left Text
"Insufficient columns when trying to parse a column")

-- | Get an error message for a non-record constructor.
-- This module does not yet support non-record constructors, so we'll tell the
-- user what sort of constructor they provided that we can't use, along with
-- the name of that constructor. This turns out to require recursion, but you
-- can't win every battle.
nonRecordConstructorMessage :: Con -> String
nonRecordConstructorMessage :: Con -> String
nonRecordConstructorMessage Con
con =
  case Con
con of
    (RecC {}) -> forall a. HasCallStack => String -> a
error String
"Record constructors are not an error"
    (NormalC {}) -> String -> String
helper String
"non-record data constructor"
    (InfixC {}) -> String -> String
helper String
"infix constructor"
    (ForallC {}) -> String -> String
helper String
"constructor qualified by type variables / class contexts"
    (GadtC {}) -> String -> String
helper String
"GADT constructor"
    (RecGadtC {}) -> String -> String
helper String
"record GADT constructor"
  where
    helper :: String -> String
helper String
constructorType =
      String
"Esqueleto records can only be derived for record constructors, but "
        forall a. [a] -> [a] -> [a]
++ forall a. Show a => a -> String
show (Con -> Name
constructorName Con
con)
        forall a. [a] -> [a] -> [a]
++ String
" is a "
        forall a. [a] -> [a] -> [a]
++ String
constructorType

    constructorName :: Con -> Name
constructorName Con
constructor =
      case Con
constructor of
        (RecC Name
name [VarBangType]
_) -> Name
name
        (NormalC Name
name [BangType]
_fields) -> Name
name
        (InfixC BangType
_ty1 Name
name BangType
_ty2) -> Name
name
        (ForallC [TyVarBndr Specificity]
_vars Cxt
_constraints Con
innerConstructor) -> Con -> Name
constructorName Con
innerConstructor
        -- If there's GADTs where multiple constructors are declared with the
        -- same type signature you're evil and furthermore this diagnostic will
        -- only show you the first name.
        (GadtC [Name]
names [BangType]
_fields Type
_ret) -> forall a. [a] -> a
head [Name]
names
        (RecGadtC [Name]
names [VarBangType]
_fields Type
_ret) -> forall a. [a] -> a
head [Name]
names

makeToAliasInstance :: RecordInfo -> Q Dec
makeToAliasInstance :: RecordInfo -> Q Dec
makeToAliasInstance info :: RecordInfo
info@RecordInfo {Cxt
[(Name, Type)]
[TyVarBndr ()]
Maybe Type
Name
sqlFields :: [(Name, Type)]
fields :: [(Name, Type)]
sqlConstructorName :: Name
constructorName :: Name
kind :: Maybe Type
typeVarBinders :: [TyVarBndr ()]
constraints :: Cxt
sqlName :: Name
name :: Name
sqlFields :: RecordInfo -> [(Name, Type)]
fields :: RecordInfo -> [(Name, Type)]
sqlConstructorName :: RecordInfo -> Name
constructorName :: RecordInfo -> Name
kind :: RecordInfo -> Maybe Type
typeVarBinders :: RecordInfo -> [TyVarBndr ()]
constraints :: RecordInfo -> Cxt
sqlName :: RecordInfo -> Name
name :: RecordInfo -> Name
..} = do
  Dec
toAliasDec' <- RecordInfo -> Q Dec
toAliasDec RecordInfo
info
  let overlap :: Maybe a
overlap = forall a. Maybe a
Nothing
      instanceConstraints :: [a]
instanceConstraints = []
      instanceType :: Type
instanceType =
        (Name -> Type
ConT ''ToAlias)
          Type -> Type -> Type
`AppT` (Name -> Type
ConT Name
sqlName)
  forall (f :: * -> *) a. Applicative f => a -> f a
pure forall a b. (a -> b) -> a -> b
$ Maybe Overlap -> Cxt -> Type -> [Dec] -> Dec
InstanceD forall a. Maybe a
overlap forall a. [a]
instanceConstraints Type
instanceType [Dec
toAliasDec']

toAliasDec :: RecordInfo -> Q Dec
toAliasDec :: RecordInfo -> Q Dec
toAliasDec RecordInfo {Cxt
[(Name, Type)]
[TyVarBndr ()]
Maybe Type
Name
sqlFields :: [(Name, Type)]
fields :: [(Name, Type)]
sqlConstructorName :: Name
constructorName :: Name
kind :: Maybe Type
typeVarBinders :: [TyVarBndr ()]
constraints :: Cxt
sqlName :: Name
name :: Name
sqlFields :: RecordInfo -> [(Name, Type)]
fields :: RecordInfo -> [(Name, Type)]
sqlConstructorName :: RecordInfo -> Name
constructorName :: RecordInfo -> Name
kind :: RecordInfo -> Maybe Type
typeVarBinders :: RecordInfo -> [TyVarBndr ()]
constraints :: RecordInfo -> Cxt
sqlName :: RecordInfo -> Name
name :: RecordInfo -> Name
..} = do
  ([Stmt]
statements, [FieldPat]
fieldPatterns, [(Name, Exp)]
fieldExps) <-
    forall a b c. [(a, b, c)] -> ([a], [b], [c])
unzip3 forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
t a -> (a -> m b) -> m (t b)
forM [(Name, Type)]
sqlFields (\(Name
fieldName', Type
_) -> do
      Name
fieldPatternName <- forall (m :: * -> *). Quote m => String -> m Name
newName (Name -> String
nameBase Name
fieldName')
      Name
boundValueName <- forall (m :: * -> *). Quote m => String -> m Name
newName (Name -> String
nameBase Name
fieldName')
      forall (f :: * -> *) a. Applicative f => a -> f a
pure
        ( Pat -> Exp -> Stmt
BindS
            (Name -> Pat
VarP Name
boundValueName)
            (Name -> Exp
VarE 'toAlias Exp -> Exp -> Exp
`AppE` Name -> Exp
VarE Name
fieldPatternName)
        , (Name
fieldName', Name -> Pat
VarP Name
fieldPatternName)
        , (Name
fieldName', Name -> Exp
VarE Name
boundValueName)
        ))

  forall (f :: * -> *) a. Applicative f => a -> f a
pure forall a b. (a -> b) -> a -> b
$
    Name -> [Clause] -> Dec
FunD
      'toAlias
      [ [Pat] -> Body -> [Dec] -> Clause
Clause
          [ Name -> [FieldPat] -> Pat
RecP Name
sqlName [FieldPat]
fieldPatterns
          ]
          ( Exp -> Body
NormalB forall a b. (a -> b) -> a -> b
$
              Maybe ModName -> [Stmt] -> Exp
DoE
#if MIN_VERSION_template_haskell(2,17,0)
                forall a. Maybe a
Nothing
#endif
                ([Stmt]
statements forall a. [a] -> [a] -> [a]
++ [Exp -> Stmt
NoBindS forall a b. (a -> b) -> a -> b
$ Exp -> Exp -> Exp
AppE (Name -> Exp
VarE 'pure) (Name -> [(Name, Exp)] -> Exp
RecConE Name
sqlName [(Name, Exp)]
fieldExps)])
          )
          -- `where` clause.
          []
      ]

makeToAliasReferenceInstance :: RecordInfo -> Q Dec
makeToAliasReferenceInstance :: RecordInfo -> Q Dec
makeToAliasReferenceInstance info :: RecordInfo
info@RecordInfo {Cxt
[(Name, Type)]
[TyVarBndr ()]
Maybe Type
Name
sqlFields :: [(Name, Type)]
fields :: [(Name, Type)]
sqlConstructorName :: Name
constructorName :: Name
kind :: Maybe Type
typeVarBinders :: [TyVarBndr ()]
constraints :: Cxt
sqlName :: Name
name :: Name
sqlFields :: RecordInfo -> [(Name, Type)]
fields :: RecordInfo -> [(Name, Type)]
sqlConstructorName :: RecordInfo -> Name
constructorName :: RecordInfo -> Name
kind :: RecordInfo -> Maybe Type
typeVarBinders :: RecordInfo -> [TyVarBndr ()]
constraints :: RecordInfo -> Cxt
sqlName :: RecordInfo -> Name
name :: RecordInfo -> Name
..} = do
  Dec
toAliasReferenceDec' <- RecordInfo -> Q Dec
toAliasReferenceDec RecordInfo
info
  let overlap :: Maybe a
overlap = forall a. Maybe a
Nothing
      instanceConstraints :: [a]
instanceConstraints = []
      instanceType :: Type
instanceType =
        (Name -> Type
ConT ''ToAliasReference)
          Type -> Type -> Type
`AppT` (Name -> Type
ConT Name
sqlName)
  forall (f :: * -> *) a. Applicative f => a -> f a
pure forall a b. (a -> b) -> a -> b
$ Maybe Overlap -> Cxt -> Type -> [Dec] -> Dec
InstanceD forall a. Maybe a
overlap forall a. [a]
instanceConstraints Type
instanceType [Dec
toAliasReferenceDec']

toAliasReferenceDec :: RecordInfo -> Q Dec
toAliasReferenceDec :: RecordInfo -> Q Dec
toAliasReferenceDec RecordInfo {Cxt
[(Name, Type)]
[TyVarBndr ()]
Maybe Type
Name
sqlFields :: [(Name, Type)]
fields :: [(Name, Type)]
sqlConstructorName :: Name
constructorName :: Name
kind :: Maybe Type
typeVarBinders :: [TyVarBndr ()]
constraints :: Cxt
sqlName :: Name
name :: Name
sqlFields :: RecordInfo -> [(Name, Type)]
fields :: RecordInfo -> [(Name, Type)]
sqlConstructorName :: RecordInfo -> Name
constructorName :: RecordInfo -> Name
kind :: RecordInfo -> Maybe Type
typeVarBinders :: RecordInfo -> [TyVarBndr ()]
constraints :: RecordInfo -> Cxt
sqlName :: RecordInfo -> Name
name :: RecordInfo -> Name
..} = do
  Name
identInfo <- forall (m :: * -> *). Quote m => String -> m Name
newName String
"identInfo"

  ([Stmt]
statements, [FieldPat]
fieldPatterns, [(Name, Exp)]
fieldExps) <-
    forall a b c. [(a, b, c)] -> ([a], [b], [c])
unzip3 forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
t a -> (a -> m b) -> m (t b)
forM [(Name, Type)]
sqlFields (\(Name
fieldName', Type
_) -> do
      Name
fieldPatternName <- forall (m :: * -> *). Quote m => String -> m Name
newName (Name -> String
nameBase Name
fieldName')
      Name
boundValueName <- forall (m :: * -> *). Quote m => String -> m Name
newName (Name -> String
nameBase Name
fieldName')
      forall (f :: * -> *) a. Applicative f => a -> f a
pure
        ( Pat -> Exp -> Stmt
BindS
            (Name -> Pat
VarP Name
boundValueName)
            (Name -> Exp
VarE 'toAliasReference Exp -> Exp -> Exp
`AppE` Name -> Exp
VarE Name
identInfo Exp -> Exp -> Exp
`AppE` Name -> Exp
VarE Name
fieldPatternName)
        , (Name
fieldName', Name -> Pat
VarP Name
fieldPatternName)
        , (Name
fieldName', Name -> Exp
VarE Name
boundValueName)
        ))

  forall (f :: * -> *) a. Applicative f => a -> f a
pure forall a b. (a -> b) -> a -> b
$
    Name -> [Clause] -> Dec
FunD
      'toAliasReference
      [ [Pat] -> Body -> [Dec] -> Clause
Clause
          [ Name -> Pat
VarP Name
identInfo
          , Name -> [FieldPat] -> Pat
RecP Name
sqlName [FieldPat]
fieldPatterns
          ]
          ( Exp -> Body
NormalB forall a b. (a -> b) -> a -> b
$
              Maybe ModName -> [Stmt] -> Exp
DoE
#if MIN_VERSION_template_haskell(2,17,0)
                forall a. Maybe a
Nothing
#endif
                ([Stmt]
statements forall a. [a] -> [a] -> [a]
++ [Exp -> Stmt
NoBindS forall a b. (a -> b) -> a -> b
$ Exp -> Exp -> Exp
AppE (Name -> Exp
VarE 'pure) (Name -> [(Name, Exp)] -> Exp
RecConE Name
sqlName [(Name, Exp)]
fieldExps)])
          )
          -- `where` clause.
          []
      ]