-- |
-- Module      : Amazonka.Data.Query
-- Copyright   : (c) 2013-2023 Brendan Hay
-- License     : Mozilla Public License, v. 2.0.
-- Maintainer  : Brendan Hay <brendan.g.hay+amazonka@gmail.com>
-- Stability   : provisional
-- Portability : non-portable (GHC extensions)
module Amazonka.Data.Query where

import Amazonka.Data.ByteString
import Amazonka.Data.Text
import Amazonka.Prelude
import qualified Data.ByteString.Builder as Build
import qualified Data.ByteString.Char8 as BS8
import qualified Data.ByteString.Lazy as LBS
import qualified Data.HashMap.Strict as HashMap
import qualified Data.List as List
import qualified Data.Text.Encoding as Text
import qualified Network.HTTP.Types.URI as URI

-- | Structured representation of a query string.
--
-- Some operations (e.g., [sqs:CreateQueue](https://docs.aws.amazon.com/AWSSimpleQueueService/latest/APIReference/API_CreateQueue.html))
-- use query parameters to pass structured data like lists and maps,
-- which is why this type is more complicatated than the
-- @[(ByteString, Maybe ByteString)]@ from @http-types@ that you may
-- have expected here.
data QueryString
  = QList [QueryString]
  | QPair ByteString QueryString
  | QValue (Maybe ByteString)
  deriving stock (Eq, Show)

instance Semigroup QueryString where
  a <> b = case (a, b) of
    (QList l, QList r) -> QList (l ++ r)
    (QList l, r) -> QList (r : l)
    (l, QList r) -> QList (l : r)
    (l, r) -> QList [l, r]

instance Monoid QueryString where
  mempty = QList []
  mappend = (<>)

instance IsString QueryString where
  fromString = parseQueryString . fromString
  {-# INLINE fromString #-}

parseQueryString :: ByteString -> QueryString
parseQueryString bs
  | BS8.null bs = mempty
  | otherwise =
      QList (map breakPair . filter (not . BS8.null) $ BS8.split '&' bs)
  where
    breakPair x =
      case BS8.break (== '=') x of
        ("", "") -> mempty
        ("", v) -> stripValue v
        (k, v) -> QPair (URI.urlDecode True k) (stripValue v)

    stripValue :: ByteString -> QueryString
    stripValue x =
      case x of
        "" -> QValue Nothing
        "=" -> QValue Nothing
        _ -> QValue (Just (URI.urlDecode True $ BS8.drop 1 x))

-- FIXME: use Builder
instance ToByteString QueryString where
  toBS = LBS.toStrict . Build.toLazyByteString . cat . List.sort . enc Nothing
    where
      enc :: Maybe ByteString -> QueryString -> [ByteString]
      enc p = \case
        QList xs -> concatMap (enc p) xs
        QPair (URI.urlEncode True -> k) x
          | Just n <- p -> enc (Just (n <> kdelim <> k)) x -- <prev>.key <recur>
          | otherwise -> enc (Just k) x -- key <recur>
        QValue (Just (URI.urlEncode True -> v))
          | Just n <- p -> [n <> vsep <> v] -- key=value
          | otherwise -> [v <> vsep] -- value= -- note: required for signing.
        _
          | Just n <- p -> [n <> vsep] -- key=
          -- note: this case required for request signing
          | otherwise -> []

      cat :: [ByteString] -> ByteStringBuilder
      cat [] = mempty
      cat [x] = Build.byteString x
      cat (x : xs) = Build.byteString x <> ksep <> cat xs

      kdelim = "."
      ksep = "&"
      vsep = "="

pair :: ToQuery a => ByteString -> a -> QueryString -> QueryString
pair k v = mappend (QPair k (toQuery v))

infixr 7 =:

(=:) :: ToQuery a => ByteString -> a -> QueryString
k =: v = QPair k (toQuery v)

toQueryList ::
  (IsList a, ToQuery (Item a)) =>
  ByteString ->
  a ->
  QueryString
toQueryList k = QPair k . QList . zipWith f [1 ..] . toList
  where
    f :: ToQuery a => Int -> a -> QueryString
    f n v = toBS n =: toQuery v

toQueryMap ::
  (ToQuery k, ToQuery v) =>
  ByteString ->
  ByteString ->
  ByteString ->
  HashMap k v ->
  QueryString
toQueryMap e k v = toQueryList e . map f . HashMap.toList
  where
    f (x, y) = QList [k =: toQuery x, v =: toQuery y]

class ToQuery a where
  toQuery :: a -> QueryString
  default toQuery :: ToText a => a -> QueryString
  toQuery = toQuery . toText

instance ToQuery QueryString where
  toQuery = id

instance (ToByteString k, ToQuery v) => ToQuery (k, v) where
  toQuery (k, v) = QPair (toBS k) (toQuery v)

instance ToQuery Char where
  toQuery = toQuery . BS8.singleton

instance ToQuery ByteString where
  toQuery "" = QValue Nothing
  toQuery bs = QValue (Just bs)

instance ToQuery Text where toQuery = toQuery . Text.encodeUtf8

instance ToQuery Int where toQuery = toQuery . toBS

instance ToQuery Integer where toQuery = toQuery . toBS

instance ToQuery Double where toQuery = toQuery . toBS

instance ToQuery Natural where toQuery = toQuery . toBS

instance ToQuery a => ToQuery (Maybe a) where
  toQuery (Just x) = toQuery x
  toQuery Nothing = mempty

instance ToQuery Bool where
  toQuery True = toQuery ("true" :: ByteString)
  toQuery False = toQuery ("false" :: ByteString)