{-# LANGUAGE DataKinds #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE KindSignatures #-}
{-# LANGUAGE LambdaCase #-}
{-# LANGUAGE NamedFieldPuns #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE UnicodeSyntax #-}
{-# LANGUAGE ViewPatterns #-}
-- | StackExchange API request manipulation routines
module Network.StackExchange.Request
  ( -- * Type
    Request, R(..), Auth(..), SE(..), Object(..)
    -- * Constructing requests
  , host, path, method, parse
  , query, token, key, site, filter, state, Scope(..), scope
  , client, redirectURI, secret, code
    -- * Internal wrapping/unwrapping
  , wrap, unwrap
    -- * Rendering
  , render
  ) where

import Data.Monoid
import GHC.TypeLits (Symbol)
import Prelude hiding (filter)
import Unsafe.Coerce (unsafeCoerce)

import           Data.ByteString.Lazy (ByteString)
import           Data.Aeson (FromJSON)
import           Data.Aeson.Types (Value)
import           Data.Default (Default(..))
import           Data.Map (Map)
import qualified Data.Map as M
import           Data.Text.Lazy (Text)
import qualified Data.Text.Lazy as T
import           Data.Text.Lazy.Builder (toLazyText)
import           Data.Text.Lazy.Builder.Int (decimal)


-- | Authentication
data Auth =
    RequireToken -- ^ Request requires auth_token
  | Ready -- ^ Request may be sent without auth_token


-- | SE response type
data Object =
    AccessToken -- ^ <https://api.stackexchange.com/docs/types/access-token>
  | AccountMerge -- ^ <https://api.stackexchange.com/docs/types/account-merge>
  | Answer -- ^ <https://api.stackexchange.com/docs/types/answer>
  | Badge -- ^  <https://api.stackexchange.com/docs/types/badge>
  | Comment -- ^ <https://api.stackexchange.com/docs/types/comment>
  | Error -- ^ <https://api.stackexchange.com/docs/types/error>
  | Event -- ^ <https://api.stackexchange.com/docs/types/event>
  | Filter -- ^ <https://api.stackexchange.com/docs/types/filter>
  | InboxItem -- ^ <https://api.stackexchange.com/docs/types/inbox-item>
  | Info -- ^ <https://api.stackexchange.com/docs/types/info>
  | NetworkUser -- ^ <https://api.stackexchange.com/docs/types/network-user>
  | Notification -- ^ <https://api.stackexchange.com/docs/types/notification>
  | Post -- ^ <https://api.stackexchange.com/docs/types/post>
  | Privilege -- ^ <https://api.stackexchange.com/docs/types/privilege>
  | Question -- ^ <https://api.stackexchange.com/docs/types/question>
  | QuestionTimeline -- ^ <https://api.stackexchange.com/docs/types/question-timeline>
  | Reputation -- ^ <https://api.stackexchange.com/docs/types/reputation>
  | ReputationHistory -- ^ <https://api.stackexchange.com/docs/types/reputation-history>
  | Revision -- ^ <https://api.stackexchange.com/docs/types/revision>
  | Site -- ^ <https://api.stackexchange.com/docs/types/site>
  | SuggestedEdit -- ^ <https://api.stackexchange.com/docs/types/suggested-edit>
  | Tag -- ^ <https://api.stackexchange.com/docs/types/tag>
  | TagScore -- ^ <https://api.stackexchange.com/docs/types/tag-score>
  | TagSynonym -- ^ <https://api.stackexchange.com/docs/types/tag-synonym>
  | TagWiki -- ^ <https://api.stackexchange.com/docs/types/tag-wiki>
  | TopTag -- ^ <https://api.stackexchange.com/docs/types/top-tag>
  | User -- ^ <https://api.stackexchange.com/docs/types/user>
  | UserTimeline -- ^ <https://api.stackexchange.com/docs/types/user-timeline>
  | WritePermission -- ^ <https://api.stackexchange.com/docs/types/write-permission>


-- | SE response value wrapper
newtype SE (a ∷ Object) = SE { unSE ∷ Value } deriving (Show, FromJSON)


-- | StackExchange API Request data type.
--
-- @a@ is a phantom type showing whether authentication is enabled
--
-- @n@ is a phantom type dissallowing combination of
-- different API calls in one request
--
-- @r@ is a type of parsed API call result
data R (a ∷ Auth) (n ∷ Symbol) r = R
  { _host ∷ Text -- ^ API host link
  , _path ∷ Text -- ^ API call link
  , _method ∷ Text -- ^ API call method (GET/POST)
  , _query ∷ Map Text Text -- ^ API call query parameters
  , _parse ∷ Maybe (ByteString → r) -- ^ API call result parsing function
  }


type Request a n r = Dual (Endo (R a n r))


-- | Default StackExchange API request, defines only host link
instance Default (R a n r) where
  def = R
    { _host = "https://api.stackexchange.com/2.1"
    , _path = mempty
    , _method = "GET"
    , _query = mempty
    , _parse = Nothing
    }
  {-# INLINE def #-}


-- | Request defining only API call host
--
-- Primarily used in Auth, not intended for usage by library user
host ∷ Text → Request a n r
host h = wrap $ \r -> r { _host = h }
{-# INLINE host #-}


-- | Request defining only API call path
--
-- Primarily used in API call wrappers, not intended for usage by library user
path ∷ Text → Request a n r
path p = wrap $ \r -> r { _path = p }
{-# INLINE path #-}


-- | Request defining only call method
--
-- Primarily used in API call wrappers, not intended for usage by library user
method ∷ Text → Request a n r
method m = wrap $ \r -> r { _method = m }
{-# INLINE method #-}


-- | Request defining only API call result parsing function
--
-- Primarily used in API call wrappers, not intended for usage by library user
parse ∷ (ByteString → r) → Request a n r
parse f = wrap $ \r -> r { _parse = Just f }
{-# INLINE parse #-}


-- | Request defining only API call query parameters
--
-- Rather low level interface. For more specific usage 'site',
-- 'filter', etc calls may be more convenient
--
--
-- Takes a list of (key, value) parameters such as @[(\"order\", \"asc\"), (\"sort\", \"rank\")]@
query ∷ [(Text, Text)] → Request a n r
query q = wrap $ __query (M.fromList q <>)
{-# INLINE query #-}


-- | Convert token requiring Request into ready one
token ∷ Text → Request RequireToken n r → Request Ready n r
token t = unsafeCoerce . mappend (wrap (__query (M.insert "access_token" t)))
{-# INLINE token #-}


-- | Request defining only App key
key ∷ Text → Request a n r
key k = wrap $ __query (M.insert "key" k)
{-# INLINE key #-}


-- | Request defining only API call site query parameter
site ∷ Text → Request a n r
site s = wrap $ __query (M.insert "site" s)
{-# INLINE site #-}


-- | Request defining only API call filter query parameter
filter ∷ Text → Request a n r
filter f = wrap $ __query (M.insert "filter" f)
{-# INLINE filter #-}


-- | Request defining only API call state query parameter
state ∷ Text → Request a n r
state s = wrap $ __query (M.insert "state" s)
{-# INLINE state #-}


-- | Scope defines permission granted for application by user
data Scope = ReadInbox | NoExpiry | WriteAccess | PrivateInfo


-- | Request defining only API call scope query parameter
scope ∷ [Scope] → Request a n r
scope ss = wrap $ __query (M.insert "scope" $ scopie ss)
 where
  scopie xs = T.intercalate "," . flip map xs $ \case
    ReadInbox   → "read_inbox"
    NoExpiry    → "no_expiry"
    WriteAccess → "write_access"
    PrivateInfo → "private_info"


-- | Request defining only Authentication API call application id
--
-- Primarily used in Authentication API call wrappers, not intended for usage by library user
client ∷ Int → Request a n r
client (toLazyText . decimal → c) = wrap $ __query (M.insert "client_id" c)
{-# INLINE client #-}


-- | Request defining only Authentication API call redirect url
--
-- Primarily used in Authentication API call wrappers, not intended for usage by library user
redirectURI ∷ Text → Request a n r
redirectURI r = wrap $ __query (M.insert "redirect_uri" r)
{-# INLINE redirectURI #-}


-- | Request defining only Authentication API call application secret
--
-- Primarily used in Authentication API call wrappers, not intended for usage by library user
secret ∷ Text → Request a n r
secret c = wrap $ __query (M.insert "client_secret" c)
{-# INLINE secret #-}


-- | Request defining only Authentication API call code
--
-- Primarily used in Authentication API call wrappers, not intended for usage by library user
code ∷ Text → Request a n r
code c = wrap $ __query (M.insert "code" c)
{-# INLINE code #-}


-- | Wrapping to interesting 'Monoid' ('R' -> 'R') instance
wrap ∷ (R a n r → R a n r) → Request a n r
wrap = Dual . Endo


-- | Unwrapping from interesting 'Monoid' ('R' -> 'R') instance
unwrap ∷ Request a n r → (R a n r → R a n r)
unwrap = appEndo . getDual


-- | Render 'R' as URI string for networking
render ∷ Request a n r → String
render (($ def) . unwrap → R {_host, _path, _query}) =
  T.unpack $ mconcat [_host, "/", _path, "?", argie _query]
 where
  argie = T.intercalate "&" . M.foldrWithKey (\k v m → T.concat [k, "=", v] : m) mempty


__query :: (Map Text Text -> Map Text Text) -> R a n r -> R a n r
__query f = \r -> r { _query  = f (_query r) }