{-# LANGUAGE CPP #-}

{-|
Module      :  GitHub.REST
Maintainer  :  Brandon Chinn <brandonchinn178@gmail.com>
Stability   :  experimental
Portability :  portable

Definitions for querying the GitHub REST API. See README.md for an example.
-}
module GitHub.REST (
  -- * Monad transformer and type-class for querying the GitHub REST API
  MonadGitHubREST (..),
  GitHubT,
  GitHubSettings (..),
  runGitHubT,

  -- * GitHub authentication
  Token (..),

  -- * GitHub Endpoints
  GHEndpoint (..),
  GitHubData,
  EndpointVals,

  -- * KeyValue pairs
  KeyValue (..),

  -- * Helpers
  githubTry,
  githubTry',
  (.:),

  -- * Re-exports
  StdMethod (..),
) where

import Control.Monad.IO.Unlift (MonadUnliftIO)
import Data.Aeson (FromJSON, Value (..), decode, withObject)
import Data.Aeson.Types (parseEither, parseField)
import qualified Data.ByteString.Lazy as ByteStringL
import Data.Text (Text)
import Network.HTTP.Client (
  HttpException (..),
  HttpExceptionContent (..),
  Response (..),
 )
import Network.HTTP.Types (Status, StdMethod (..), status422)
import UnliftIO.Exception (handleJust)

#if MIN_VERSION_aeson(2,0,0)
import Data.Aeson.Key (fromText)
#endif

import GitHub.REST.Auth
import GitHub.REST.Endpoint
import GitHub.REST.KeyValue
import GitHub.REST.Monad

{- HTTP exception handling -}

-- | Handle 422 exceptions thrown by the GitHub REST API.
--
--  Most client errors are 422, since we should always be sending valid JSON. If an endpoint
--  throws different error codes, use githubTry'.
--
--  https://developer.github.com/v3/#client-errors
githubTry :: (MonadUnliftIO m) => m a -> m (Either Value a)
githubTry = githubTry' status422

-- | Handle the given exception thrown by the GitHub REST API.
githubTry' :: (MonadUnliftIO m) => Status -> m a -> m (Either Value a)
githubTry' status = handleJust statusException (return . Left) . fmap Right
  where
    statusException (HttpExceptionRequest _ (StatusCodeException r body))
      | responseStatus r == status = decode $ ByteStringL.fromStrict body
    statusException _ = Nothing

{- Aeson helpers -}

-- | Get the given key from the Value, erroring if it doesn't exist.
(.:) :: (FromJSON a) => Value -> Text -> a
(.:) v key = either error id $ parseEither parseObject v
  where
    parseObject = withObject "parseObject" (`parseField` fromText key)

#if !MIN_VERSION_aeson(2,0,0)
fromText :: Text -> Text
fromText = id
#endif