{-# LANGUAGE AllowAmbiguousTypes #-}
{-# LANGUAGE DataKinds #-}
{-# LANGUAGE LambdaCase #-}
{-# LANGUAGE PolyKinds #-}
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE TypeApplications #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE TypeOperators #-}
{-# LANGUAGE UndecidableInstances #-}

module Text.Regex.Pcre2.TH where

import           Control.Applicative        (Alternative(..))
import           Data.IORef
import           Data.List.NonEmpty         (NonEmpty(..))
import           Data.Map.Lazy              (Map)
import qualified Data.Map.Lazy              as Map
import           Data.Proxy                 (Proxy(..))
import           Data.Text                  (Text)
import qualified Data.Text                  as Text
import           Data.Type.Bool             (type (||), If)
import           Data.Type.Equality         (type (==))
import           GHC.TypeLits               hiding (Text)
import qualified GHC.TypeLits               as TypeLits
import           Language.Haskell.TH
import           Language.Haskell.TH.Quote
import           Language.Haskell.TH.Syntax
import           Lens.Micro
import           Lens.Micro.Extras          (view)
import           System.IO.Unsafe           (unsafePerformIO)
import           Text.Regex.Pcre2.Internal

-- | A wrapper around a list of captures that carries additional type-level
-- information about the number and names of those captures.
--
-- This type is only intended to be created by `regex`\/`_regex` and consumed by
-- `capture`\/`_capture`, relying on type inference.  Specifying the @info@
-- explicitly in a type signature is not supported—the definition of
-- `CapturesInfo` is not part of the public API and may change without warning.
--
-- After obtaining `Captures` it\'s recommended to immediately consume them and
-- transform them into application-level data, to avoid leaking the types to top
-- level and having to write signatures.  In times of need, \"@Captures _@\" may
-- be written with the help of @{-\# LANGUAGE PartialTypeSignatures \#-}@.
newtype Captures (info :: CapturesInfo) = Captures (NonEmpty Text)

-- | The kind of `Captures`\'s @info@.  The first number is the total number of
-- parenthesized captures, and the list is a lookup table from capture names to
-- numbers.
type CapturesInfo = (Nat, [(Symbol, Nat)])

-- | Helper for constructing an empty lookup table.  If we splice `promotedNilT`
-- directly, we would have to require the user to turn on either
-- @KindSignatures@ or @PolyKinds@; GHC seems to monokind @'[]@ as @[*]@,
-- instead of unifying it with the list inside `CapturesInfo`.
type NoNamedCaptures = '[] :: [(Symbol, Nat)]

-- | Look up the number of a capture at compile time, either by number or by
-- name.  Throw a helpful 'TypeError' if the index doesn\'t exist.
type family CaptNum (i :: k) (info :: CapturesInfo) :: Nat where
    CaptNum (num :: Nat) '(hi, _) =
        If (CmpNat num 0 == 'LT || CmpNat num hi == 'GT)
            -- then
            (TypeError (TypeLits.Text "No capture numbered " :<>: ShowType num))
            -- else
            num

    CaptNum (name :: Symbol) '(_, '(name, num) ': _) = num
    CaptNum (name :: Symbol) '(hi, _ ': kvs) = CaptNum name '(hi, kvs)
    CaptNum (name :: Symbol) _ = TypeError
        (TypeLits.Text "No capture named " :<>: ShowType name)

    CaptNum _ _ = TypeError
        (TypeLits.Text "Capture index must be a number (Nat) or name (Symbol)")

-- | Safely lookup a capture in a `Captures` result obtained from a Template
-- Haskell-generated matching function.
--
-- The ugly type signature may be interpreted like this:  /Given some capture/
-- /group index @i@ and some @info@ about a regex, ensure that index exists and/
-- /is resolved to the number @num@ at compile time.  Then, at runtime, get a/
-- /capture group from a list of captures./
--
-- In practice the variable @i@ is specified by type application and the other
-- variables are inferred.
--
-- > capture @3
-- > capture @"bar"
--
-- Specifying a nonexistent number or name will result in a type error.
capture :: forall i info num. (CaptNum i info ~ num, KnownNat num) =>
    Captures info -> Text
capture :: Captures info -> Text
capture = Getting Text (Captures info) Text -> Captures info -> Text
forall a s. Getting a s a -> s -> a
view (Getting Text (Captures info) Text -> Captures info -> Text)
-> Getting Text (Captures info) Text -> Captures info -> Text
forall a b. (a -> b) -> a -> b
$ forall k (i :: k) (info :: CapturesInfo) (num :: Nat).
(CaptNum i info ~ num, KnownNat num) =>
Lens' (Captures info) Text
forall (info :: CapturesInfo) (num :: Nat).
(CaptNum i info ~ num, KnownNat num) =>
Lens' (Captures info) Text
_capture @i

-- | Like `capture` but focus from a `Captures` to a capture.
_capture :: forall i info num. (CaptNum i info ~ num, KnownNat num) =>
    Lens' (Captures info) Text
_capture :: Lens' (Captures info) Text
_capture = (NonEmpty Text -> f (NonEmpty Text))
-> Captures info -> f (Captures info)
forall (f :: * -> *) (info :: CapturesInfo) (info :: CapturesInfo).
Functor f =>
(NonEmpty Text -> f (NonEmpty Text))
-> Captures info -> f (Captures info)
_Captures ((NonEmpty Text -> f (NonEmpty Text))
 -> Captures info -> f (Captures info))
-> ((Text -> f Text) -> NonEmpty Text -> f (NonEmpty Text))
-> (Text -> f Text)
-> Captures info
-> f (Captures info)
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Traversal (NonEmpty Text) (NonEmpty Text) Text Text
-> Lens (NonEmpty Text) (NonEmpty Text) Text Text
forall s t a. HasCallStack => Traversal s t a a -> Lens s t a a
singular (Index (NonEmpty Text)
-> Traversal' (NonEmpty Text) (IxValue (NonEmpty Text))
forall m. Ixed m => Index m -> Traversal' m (IxValue m)
ix (Index (NonEmpty Text)
 -> Traversal' (NonEmpty Text) (IxValue (NonEmpty Text)))
-> Index (NonEmpty Text)
-> Traversal' (NonEmpty Text) (IxValue (NonEmpty Text))
forall a b. (a -> b) -> a -> b
$ Integer -> Int
forall a. Num a => Integer -> a
fromInteger (Integer -> Int) -> Integer -> Int
forall a b. (a -> b) -> a -> b
$ Proxy num -> Integer
forall (n :: Nat) (proxy :: Nat -> *).
KnownNat n =>
proxy n -> Integer
natVal @num Proxy num
forall k (t :: k). Proxy t
Proxy) where
    _Captures :: (NonEmpty Text -> f (NonEmpty Text))
-> Captures info -> f (Captures info)
_Captures NonEmpty Text -> f (NonEmpty Text)
f (Captures NonEmpty Text
cs) = NonEmpty Text -> Captures info
forall (info :: CapturesInfo). NonEmpty Text -> Captures info
Captures (NonEmpty Text -> Captures info)
-> f (NonEmpty Text) -> f (Captures info)
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> NonEmpty Text -> f (NonEmpty Text)
f NonEmpty Text
cs

-- | Unexported, top-level `IORef` that\'s created upon the first runtime
-- evaluation of a Template Haskell `Matcher`.
globalMatcherCache :: IORef (Map Text Matcher)
globalMatcherCache :: IORef (Map Text Matcher)
globalMatcherCache = IO (IORef (Map Text Matcher)) -> IORef (Map Text Matcher)
forall a. IO a -> a
unsafePerformIO (IO (IORef (Map Text Matcher)) -> IORef (Map Text Matcher))
-> IO (IORef (Map Text Matcher)) -> IORef (Map Text Matcher)
forall a b. (a -> b) -> a -> b
$ Map Text Matcher -> IO (IORef (Map Text Matcher))
forall a. a -> IO (IORef a)
newIORef Map Text Matcher
forall k a. Map k a
Map.empty
{-# NOINLINE globalMatcherCache #-}

-- | Given a pattern, create or retrieve a `Matcher` from the global cache.
memoMatcher :: Text -> Matcher
memoMatcher :: Text -> Matcher
memoMatcher Text
patt = IO Matcher -> Matcher
forall a. IO a -> a
unsafePerformIO (IO Matcher -> Matcher) -> IO Matcher -> Matcher
forall a b. (a -> b) -> a -> b
$ do
    Map Text Matcher
cache <- IORef (Map Text Matcher) -> IO (Map Text Matcher)
forall a. IORef a -> IO a
readIORef IORef (Map Text Matcher)
globalMatcherCache
    case Text -> Map Text Matcher -> Maybe Matcher
forall k a. Ord k => k -> Map k a -> Maybe a
Map.lookup Text
patt Map Text Matcher
cache of
        Just Matcher
matcher -> Matcher -> IO Matcher
forall (m :: * -> *) a. Monad m => a -> m a
return Matcher
matcher
        Maybe Matcher
Nothing      -> IORef (Map Text Matcher)
-> (Map Text Matcher -> (Map Text Matcher, Matcher)) -> IO Matcher
forall a b. IORef a -> (a -> (a, b)) -> IO b
atomicModifyIORef' IORef (Map Text Matcher)
globalMatcherCache ((Map Text Matcher -> (Map Text Matcher, Matcher)) -> IO Matcher)
-> (Map Text Matcher -> (Map Text Matcher, Matcher)) -> IO Matcher
forall a b. (a -> b) -> a -> b
$ \Map Text Matcher
cache ->
            let matcher :: Matcher
matcher = Option -> Text -> Matcher
pureUserMatcher Option
forall a. Monoid a => a
mempty Text
patt
            in (Text -> Matcher -> Map Text Matcher -> Map Text Matcher
forall k a. Ord k => k -> a -> Map k a -> Map k a
Map.insert Text
patt Matcher
matcher Map Text Matcher
cache, Matcher
matcher)

-- | Predict parenthesized captures \(maybe named\) of a pattern at splice time.
predictCaptureNamesQ :: String -> Q [Maybe Text]
predictCaptureNamesQ :: String -> Q [Maybe Text]
predictCaptureNamesQ = IO [Maybe Text] -> Q [Maybe Text]
forall a. IO a -> Q a
runIO (IO [Maybe Text] -> Q [Maybe Text])
-> (String -> IO [Maybe Text]) -> String -> Q [Maybe Text]
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Option -> Text -> IO [Maybe Text]
predictCaptureNames Option
forall a. Monoid a => a
mempty (Text -> IO [Maybe Text])
-> (String -> Text) -> String -> IO [Maybe Text]
forall b c a. (b -> c) -> (a -> b) -> a -> c
. String -> Text
Text.pack

-- | Get the indexes of `Just` the named captures.
toKVs :: [Maybe Text] -> [(Int, Text)]
toKVs :: [Maybe Text] -> [(Int, Text)]
toKVs [Maybe Text]
names = [(Int
number, Text
name) | (Int
number, Just Text
name) <- [Int] -> [Maybe Text] -> [(Int, Maybe Text)]
forall a b. [a] -> [b] -> [(a, b)]
zip [Int
1 ..] [Maybe Text]
names]

-- | Generate the data-kinded phantom type parameter of `Captures` of a pattern,
-- if needed.
capturesInfoQ :: String -> Q (Maybe Type)
capturesInfoQ :: String -> Q (Maybe Type)
capturesInfoQ String
s = String -> Q [Maybe Text]
predictCaptureNamesQ String
s Q [Maybe Text]
-> ([Maybe Text] -> Q (Maybe Type)) -> Q (Maybe Type)
forall (m :: * -> *) a b. Monad m => m a -> (a -> m b) -> m b
>>= \case
    -- No parenthesized captures, so need for Captures, so no info.
    [] -> Maybe Type -> Q (Maybe Type)
forall (m :: * -> *) a. Monad m => a -> m a
return Maybe Type
forall a. Maybe a
Nothing

    -- One or more parenthesized captures.  Present
    --     [Just "foo", Nothing, Nothing, Just "bar", Nothing]
    -- as
    --     '(5, '[ '("foo", 1), '("bar", 4)]).
    [Maybe Text]
captureNames -> Type -> Maybe Type
forall a. a -> Maybe a
Just (Type -> Maybe Type) -> Q Type -> Q (Maybe Type)
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> Int -> Q Type
promotedTupleT Int
2 Q Type -> Q Type -> Q Type
`appT` Q Type
hiQ Q Type -> Q Type -> Q Type
`appT` Q Type
kvsQ where
        -- 5
        hiQ :: Q Type
hiQ = TyLitQ -> Q Type
litT (TyLitQ -> Q Type) -> TyLitQ -> Q Type
forall a b. (a -> b) -> a -> b
$ Integer -> TyLitQ
numTyLit (Integer -> TyLitQ) -> Integer -> TyLitQ
forall a b. (a -> b) -> a -> b
$ Int -> Integer
forall a b. (Integral a, Num b) => a -> b
fromIntegral (Int -> Integer) -> Int -> Integer
forall a b. (a -> b) -> a -> b
$ [Maybe Text] -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
length [Maybe Text]
captureNames
        -- '[ '("foo", 1), '("bar", 4)]
        kvsQ :: Q Type
kvsQ = case [Maybe Text] -> [(Int, Text)]
toKVs [Maybe Text]
captureNames of
            -- We can't splice '[] because it doesn't kind-check.  See above.
            []  -> [t| NoNamedCaptures |]
            [(Int, Text)]
kvs -> ((Int, Text) -> Q Type -> Q Type)
-> Q Type -> [(Int, Text)] -> Q Type
forall (t :: * -> *) a b.
Foldable t =>
(a -> b -> b) -> b -> t a -> b
foldr (Int, Text) -> Q Type -> Q Type
forall a. Integral a => (a, Text) -> Q Type -> Q Type
f Q Type
promotedNilT [(Int, Text)]
kvs
        -- '("foo", 1) ': ...
        f :: (a, Text) -> Q Type -> Q Type
f (a
number, Text
name) Q Type
r = Q Type
promotedConsT Q Type -> Q Type -> Q Type
`appT` Q Type
kvQ Q Type -> Q Type -> Q Type
`appT` Q Type
r where
            kvQ :: Q Type
kvQ = Int -> Q Type
promotedTupleT Int
2                           -- '(,)
                Q Type -> Q Type -> Q Type
`appT` TyLitQ -> Q Type
litT (String -> TyLitQ
strTyLit (String -> TyLitQ) -> String -> TyLitQ
forall a b. (a -> b) -> a -> b
$ Text -> String
Text.unpack Text
name)    -- "foo"
                Q Type -> Q Type -> Q Type
`appT` TyLitQ -> Q Type
litT (Integer -> TyLitQ
numTyLit (Integer -> TyLitQ) -> Integer -> TyLitQ
forall a b. (a -> b) -> a -> b
$ a -> Integer
forall a b. (Integral a, Num b) => a -> b
fromIntegral a
number) -- 1

-- | Helper for `regex` with no parenthesized captures.
matchTH :: (Alternative f) => Text -> Text -> f Text
matchTH :: Text -> Text -> f Text
matchTH Text
patt = Getting (Alt f Text) Text Text -> Text -> f Text
forall (f :: * -> *) a s.
Alternative f =>
Getting (Alt f a) s a -> s -> f a
toAlternativeOf (Getting (Alt f Text) Text Text -> Text -> f Text)
-> Getting (Alt f Text) Text Text -> Text -> f Text
forall a b. (a -> b) -> a -> b
$ Text -> Traversal' Text Text
_matchTH Text
patt

-- | Helper for `regex` with parenthesized captures.
capturesTH :: (Alternative f) => Text -> Proxy info -> Text -> f (Captures info)
capturesTH :: Text -> Proxy info -> Text -> f (Captures info)
capturesTH Text
patt Proxy info
proxy = Getting (Alt f (Captures info)) Text (Captures info)
-> Text -> f (Captures info)
forall (f :: * -> *) a s.
Alternative f =>
Getting (Alt f a) s a -> s -> f a
toAlternativeOf (Getting (Alt f (Captures info)) Text (Captures info)
 -> Text -> f (Captures info))
-> Getting (Alt f (Captures info)) Text (Captures info)
-> Text
-> f (Captures info)
forall a b. (a -> b) -> a -> b
$ Text -> Proxy info -> Traversal' Text (Captures info)
forall (info :: CapturesInfo).
Text -> Proxy info -> Traversal' Text (Captures info)
_capturesTH Text
patt Proxy info
proxy

-- | Helper for `regex` as a guard pattern.
matchesTH :: Text -> Text -> Bool
matchesTH :: Text -> Text -> Bool
matchesTH Text
patt = Getting Any Text (Proxy Text) -> Text -> Bool
forall s a. Getting Any s a -> s -> Bool
has (Getting Any Text (Proxy Text) -> Text -> Bool)
-> Getting Any Text (Proxy Text) -> Text -> Bool
forall a b. (a -> b) -> a -> b
$ Matcher -> FromMatch Proxy -> Traversal' Text (Proxy Text)
forall (t :: * -> *).
Traversable t =>
Matcher -> FromMatch t -> Traversal' Text (t Text)
_gcaptures (Text -> Matcher
memoMatcher Text
patt) FromMatch Proxy
getNoSlices

-- | Helper for `regex` as a pattern that binds local variables.
capturesNumberedTH :: Text -> [Int] -> Text -> [Text]
capturesNumberedTH :: Text -> [Int] -> Text -> [Text]
capturesNumberedTH Text
patt [Int]
numbers = Getting [Text] Text [Text] -> Text -> [Text]
forall a s. Getting a s a -> s -> a
view (Getting [Text] Text [Text] -> Text -> [Text])
-> Getting [Text] Text [Text] -> Text -> [Text]
forall a b. (a -> b) -> a -> b
$
    Matcher -> FromMatch [] -> Traversal' Text [Text]
forall (t :: * -> *).
Traversable t =>
Matcher -> FromMatch t -> Traversal' Text (t Text)
_gcaptures (Text -> Matcher
memoMatcher Text
patt) ([Int] -> FromMatch []
forall (t :: * -> *). Traversable t => t Int -> FromMatch t
getWhitelistedSlices [Int]
numbers)

-- | Helper for `_regex` with no parenthesized captures.
_matchTH :: Text -> Traversal' Text Text
_matchTH :: Text -> Traversal' Text Text
_matchTH Text
patt = Matcher -> FromMatch Identity -> Traversal' Text (Identity Text)
forall (t :: * -> *).
Traversable t =>
Matcher -> FromMatch t -> Traversal' Text (t Text)
_gcaptures (Text -> Matcher
memoMatcher Text
patt) FromMatch Identity
get0thSlice ((Identity Text -> f (Identity Text)) -> Text -> f Text)
-> ((Text -> f Text) -> Identity Text -> f (Identity Text))
-> (Text -> f Text)
-> Text
-> f Text
forall b c a. (b -> c) -> (a -> b) -> a -> c
. (Text -> f Text) -> Identity Text -> f (Identity Text)
forall a. Lens' (Identity a) a
_Identity

-- | Helper for `_regex` with parenthesized captures.
_capturesTH :: Text -> Proxy info -> Traversal' Text (Captures info)
_capturesTH :: Text -> Proxy info -> Traversal' Text (Captures info)
_capturesTH Text
patt Proxy info
_ = Matcher -> FromMatch NonEmpty -> Traversal' Text (NonEmpty Text)
forall (t :: * -> *).
Traversable t =>
Matcher -> FromMatch t -> Traversal' Text (t Text)
_gcaptures (Text -> Matcher
memoMatcher Text
patt) FromMatch NonEmpty
getAllSlices ((NonEmpty Text -> f (NonEmpty Text)) -> Text -> f Text)
-> ((Captures info -> f (Captures info))
    -> NonEmpty Text -> f (NonEmpty Text))
-> (Captures info -> f (Captures info))
-> Text
-> f Text
forall b c a. (b -> c) -> (a -> b) -> a -> c
. (Captures info -> f (Captures info))
-> NonEmpty Text -> f (NonEmpty Text)
forall (f :: * -> *) (info :: CapturesInfo) (info :: CapturesInfo).
Functor f =>
(Captures info -> f (Captures info))
-> NonEmpty Text -> f (NonEmpty Text)
captured where
    captured :: (Captures info -> f (Captures info))
-> NonEmpty Text -> f (NonEmpty Text)
captured Captures info -> f (Captures info)
f NonEmpty Text
cs = Captures info -> f (Captures info)
f (NonEmpty Text -> Captures info
forall (info :: CapturesInfo). NonEmpty Text -> Captures info
Captures NonEmpty Text
cs) f (Captures info)
-> (Captures info -> NonEmpty Text) -> f (NonEmpty Text)
forall (f :: * -> *) a b. Functor f => f a -> (a -> b) -> f b
<&> \(Captures NonEmpty Text
cs') -> NonEmpty Text
cs'

-- | === As an expression
--
-- @
-- regex :: (`Alternative` f) => String -> Text -> f (`Captures` info)
-- @
--
-- in the presence of parenthesized captures, or
--
-- > regex :: (Alternative f) => String -> Text -> f Text
--
-- if there are none.  In other words, if there is more than the 0th capture,
-- this behaves like `captures` (except returning an opaque `Captures` instead
-- of a `NonEmpty` list), otherwise it behaves like `match`.
--
-- To retrieve an individual capture from a `Captures`, use `capture`.
--
-- > case [regex|(?<y>\d{4})-(?<m>\d{2})-(?<d>\d{2})|] "submitted 2020-10-20" of
-- >     Just cs ->
-- >         let date = capture @0 cs
-- >             year = read @Int $ Text.unpack $ capture @"y" cs
-- >             ...
--
-- > forM_ ([regex|\s+$|] line :: Maybe Text) $ \spaces -> error $
-- >     "line has trailing spaces (" ++ show (Text.length spaces) ++ " characters)"
--
-- === As a pattern
--
-- This matches when the regex first matches, whereupon any named captures are
-- bound to variables of the same names.
--
-- > case "submitted 2020-10-20" of
-- >     [regex|(?<y>\d{4})-(?<m>\d{2})-(?<d>\d{2})|] ->
-- >         let year = read @Int $ Text.unpack y
-- >             ...
--
-- Note that it is not possible to access the 0th capture this way.  As a
-- workaround, explicitly capture the whole pattern and name it.
--
-- If there are no named captures, this simply acts as a guard.
regex :: QuasiQuoter
regex :: QuasiQuoter
regex = QuasiQuoter :: (String -> Q Exp)
-> (String -> Q Pat)
-> (String -> Q Type)
-> (String -> Q [Dec])
-> QuasiQuoter
QuasiQuoter{
    quoteExp :: String -> Q Exp
quoteExp = \String
s -> String -> Q (Maybe Type)
capturesInfoQ String
s Q (Maybe Type) -> (Maybe Type -> Q Exp) -> Q Exp
forall (m :: * -> *) a b. Monad m => m a -> (a -> m b) -> m b
>>= \case
        Maybe Type
Nothing   -> [e| matchTH (Text.pack $(stringE s)) |]
        Just Type
info -> [e| capturesTH
            (Text.pack $(stringE s))
            (Proxy :: Proxy $(return info)) |],

    quotePat :: String -> Q Pat
quotePat = \String
s -> do
        [Maybe Text]
captureNames <- String -> Q [Maybe Text]
predictCaptureNamesQ String
s

        case [Maybe Text] -> [(Int, Text)]
toKVs [Maybe Text]
captureNames of
            -- No named captures.  Test whether the string matches without
            -- creating any new Text values.
            [] -> Q Exp -> Q Pat -> Q Pat
viewP
                [e| matchesTH (Text.pack $(stringE s)) |]
                [p| True |]

            -- One or more named captures.  Attempt to bind only those to local
            -- variables of the same names.
            [(Int, Text)]
numberedNames -> Q Exp -> Q Pat -> Q Pat
viewP Q Exp
e Q Pat
p where
                ([Int]
numbers, [Text]
names) = [(Int, Text)] -> ([Int], [Text])
forall a b. [(a, b)] -> ([a], [b])
unzip [(Int, Text)]
numberedNames
                e :: Q Exp
e = [e| capturesNumberedTH
                    (Text.pack $(stringE s))
                    $(liftData numbers) |]
                p :: Q Pat
p = (Text -> Q Pat -> Q Pat) -> Q Pat -> [Text] -> Q Pat
forall (t :: * -> *) a b.
Foldable t =>
(a -> b -> b) -> b -> t a -> b
foldr Text -> Q Pat -> Q Pat
f Q Pat
wildP [Text]
names
                f :: Text -> Q Pat -> Q Pat
f Text
name Q Pat
r = Name -> [Q Pat] -> Q Pat
conP '(:) [Name -> Q Pat
varP (Name -> Q Pat) -> Name -> Q Pat
forall a b. (a -> b) -> a -> b
$ String -> Name
mkName (String -> Name) -> String -> Name
forall a b. (a -> b) -> a -> b
$ Text -> String
Text.unpack Text
name, Q Pat
r],

    quoteType :: String -> Q Type
quoteType = Q Type -> String -> Q Type
forall a b. a -> b -> a
const (Q Type -> String -> Q Type) -> Q Type -> String -> Q Type
forall a b. (a -> b) -> a -> b
$ String -> Q Type
forall (m :: * -> *) a. MonadFail m => String -> m a
fail String
"regex: cannot produce a type",

    quoteDec :: String -> Q [Dec]
quoteDec = Q [Dec] -> String -> Q [Dec]
forall a b. a -> b -> a
const (Q [Dec] -> String -> Q [Dec]) -> Q [Dec] -> String -> Q [Dec]
forall a b. (a -> b) -> a -> b
$ String -> Q [Dec]
forall (m :: * -> *) a. MonadFail m => String -> m a
fail String
"regex: cannot produce declarations"}

-- | An optical variant of `regex`.  Can only be used as an expression.
--
-- @
-- _regex :: String -> `Traversal'` Text (`Captures` info)
-- _regex :: String -> Traversal' Text Text
-- @
--
-- > import Control.Lens
-- > import Data.Text.Lens
-- >
-- > embeddedNumbers :: Traversal' String Int
-- > embeddedNumbers = packed . [_regex|\d+|] . unpacked . _Show
-- >
-- > main :: IO ()
-- > main = putStrLn $ "There are 14 competing standards" & embeddedNumbers %~ (+ 1)
-- >
-- > -- There are 15 competing standards
_regex :: QuasiQuoter
_regex :: QuasiQuoter
_regex = QuasiQuoter :: (String -> Q Exp)
-> (String -> Q Pat)
-> (String -> Q Type)
-> (String -> Q [Dec])
-> QuasiQuoter
QuasiQuoter{
    quoteExp :: String -> Q Exp
quoteExp = \String
s -> String -> Q (Maybe Type)
capturesInfoQ String
s Q (Maybe Type) -> (Maybe Type -> Q Exp) -> Q Exp
forall (m :: * -> *) a b. Monad m => m a -> (a -> m b) -> m b
>>= \case
        Maybe Type
Nothing   -> [e| _matchTH (Text.pack $(stringE s)) |]
        Just Type
info -> [e| _capturesTH
            (Text.pack $(stringE s))
            (Proxy :: Proxy $(return info)) |],

    quotePat :: String -> Q Pat
quotePat = Q Pat -> String -> Q Pat
forall a b. a -> b -> a
const (Q Pat -> String -> Q Pat) -> Q Pat -> String -> Q Pat
forall a b. (a -> b) -> a -> b
$ String -> Q Pat
forall (m :: * -> *) a. MonadFail m => String -> m a
fail String
"_regex: cannot produce a pattern",

    quoteType :: String -> Q Type
quoteType = Q Type -> String -> Q Type
forall a b. a -> b -> a
const (Q Type -> String -> Q Type) -> Q Type -> String -> Q Type
forall a b. (a -> b) -> a -> b
$ String -> Q Type
forall (m :: * -> *) a. MonadFail m => String -> m a
fail String
"_regex: cannot produce a type",

    quoteDec :: String -> Q [Dec]
quoteDec = Q [Dec] -> String -> Q [Dec]
forall a b. a -> b -> a
const (Q [Dec] -> String -> Q [Dec]) -> Q [Dec] -> String -> Q [Dec]
forall a b. (a -> b) -> a -> b
$ String -> Q [Dec]
forall (m :: * -> *) a. MonadFail m => String -> m a
fail String
"_regex: cannot produce declarations"}