module Utils.Http exposing
  ( post
  , delete
  , decodeHttpValue
  , errorKey
  )

import Http exposing (..)
import Task exposing (..)
import Json.Decode as Json exposing (Decoder)

post : String -> Task Error Value
post = request "POST"

delete : String -> Task Error Value
delete = request "DELETE"

request : String -> String -> Task Error Value
request method url =
  { verb = method
  , headers = []
  , url = url
  , body = empty
  }
    |> Http.send defaultSettings
    |> mapError promoteError
    |> flip Task.andThen handleResponse

promoteError : RawError -> Error
promoteError rawError =
  case rawError of
    RawTimeout -> Timeout
    RawNetworkError -> NetworkError

handleResponse : Response -> Task Error Value
handleResponse response =
  if 200 <= response.status && response.status < 300
    then Task.succeed response.value
    else fail (BadResponse response.status (responseString response.value))

responseString : Value -> String
responseString value =
  case value of
    Text str -> str
    _ -> ""

decodeHttpValue : Decoder a -> Value -> Task Error a
decodeHttpValue decoder value =
  case value of
    Text str ->
      case Json.decodeString decoder str of
        Ok v -> succeed v
        Err msg -> fail (UnexpectedPayload msg)
    _ ->
      fail (UnexpectedPayload "Response body is a blob, expecting a string.")

errorKey : Error -> String
errorKey error =
  case error of
    Timeout -> "Timeout"
    NetworkError -> "NetworkError"
    UnexpectedPayload _ -> "UnexpectedPayload"
    BadResponse _ key -> key