-- | Helpers for dealing with HTTP requests.
module Strive.Internal.HTTP
  ( delete
  , get
  , post
  , put
  , buildRequest
  , performRequest
  , handleResponse
  , decodeValue
  ) where

import Data.Aeson (FromJSON, eitherDecode)
import Data.ByteString.Char8 (unpack)
import Data.ByteString.Lazy (ByteString)
import Network.HTTP.Client
  (Request, Response, method, parseRequest, responseBody)
import Network.HTTP.Types
  ( Method
  , Query
  , QueryLike
  , methodDelete
  , methodGet
  , methodPost
  , methodPut
  , renderQuery
  , toQuery
  )
import Strive.Aliases (Result)
import Strive.Client (Client(client_accessToken, client_requester))

-- | Perform an HTTP DELETE request.
delete :: (QueryLike q, FromJSON j) => Client -> String -> q -> IO (Result j)
delete = http methodDelete

-- | Perform an HTTP GET request.
get :: (QueryLike q, FromJSON j) => Client -> String -> q -> IO (Result j)
get = http methodGet

-- | Perform an HTTP POST request.
post :: (QueryLike q, FromJSON j) => Client -> String -> q -> IO (Result j)
post = http methodPost

-- | Perform an HTTP PUT request.
put :: (QueryLike q, FromJSON j) => Client -> String -> q -> IO (Result j)
put = http methodPut

-- | Perform an HTTP request.
http
  :: (QueryLike q, FromJSON j)
  => Method
  -> Client
  -> String
  -> q
  -> IO (Result j)
http httpMethod client resource query = do
  request <- buildRequest httpMethod client resource query
  response <- performRequest client request
  return (handleResponse response)

-- | Build a request.
buildRequest :: QueryLike q => Method -> Client -> String -> q -> IO Request
buildRequest httpMethod client resource query = do
  request <- parseRequest (buildUrl client resource query)
  return request { method = httpMethod }

-- | Build a URL.
buildUrl :: QueryLike q => Client -> String -> q -> String
buildUrl client resource query = concat
  [ "https://www.strava.com/"
  , resource
  , unpack (renderQuery True (buildQuery client <> toQuery query))
  ]

-- | Build a query.
buildQuery :: Client -> Query
buildQuery client = toQuery [("access_token", client_accessToken client)]

-- | Actually perform an HTTP request.
performRequest :: Client -> Request -> IO (Response ByteString)
performRequest = client_requester

-- | Handle decoding a potentially failed response.
handleResponse :: FromJSON j => Response ByteString -> Result j
handleResponse response = case decodeValue response of
  Left message -> Left (response, message)
  Right value -> Right value

-- | Decode a response body as JSON.
decodeValue :: FromJSON j => Response ByteString -> Either String j
decodeValue response = eitherDecode (responseBody response)