module ServerCommunication
  ( Communication(..)
  , sendRequest
  , serverCommunications
  ) where

import Signal
import Task as Task exposing (Task)
import Http
import Json.Decode exposing (..)
import Date

import Model.Message exposing (messageDecoder)
import Model.Payment exposing (PaymentId, perPage, paymentsDecoder)

import Update as U
import Update.SignIn exposing (..)
import Update.Payment as UP

type Communication =
  NoCommunication
  | SignIn String
  | AddPayment String Int
  | DeletePayment PaymentId
  | UpdatePage Int
  | SignOut

serverCommunications : Signal.Mailbox Communication
serverCommunications = Signal.mailbox NoCommunication

sendRequest : Communication -> Task Http.RawError U.Action
sendRequest communication =
  case getRequest communication of
    Nothing ->
      Task.succeed U.NoOp
    Just request ->
      Http.send Http.defaultSettings request
        |> Task.map (communicationToAction communication)

getRequest : Communication -> Maybe Http.Request
getRequest communication =
  case communication of
    NoCommunication ->
      Nothing
    SignIn login ->
      Just (simple "post" ("/signIn?login=" ++ login))
    AddPayment name cost ->
      Just (simple "post" ("/payment/add?name=" ++ name ++ "&cost=" ++ (toString cost)))
    DeletePayment paymentId ->
      Just (simple "post" ("payment/delete?id=" ++ paymentId))
    UpdatePage page ->
      Just (simple "get" ("payments?page=" ++ toString page ++ "&perPage=" ++ toString perPage))
    SignOut ->
      Just (simple "post"  "/signOut")

simple : String -> String -> Http.Request
simple method url =
  { verb = method
  , headers = []
  , url = url
  , body = Http.empty
  }

communicationToAction : Communication -> Http.Response -> U.Action
communicationToAction communication response =
  if response.status == 200
    then
      case communication of
        NoCommunication ->
          U.NoOp
        SignIn login ->
          U.UpdateSignIn (ValidLogin login)
        AddPayment name cost ->
          decodeResponse
            response
            messageDecoder
            (\id -> U.UpdatePayment (UP.AddPayment id name cost))
        DeletePayment id ->
          U.UpdatePayment (UP.Remove id)
        UpdatePage page ->
          decodeResponse
            response
            paymentsDecoder
            (\payments -> U.UpdatePayment (UP.UpdatePage page payments))
        SignOut ->
          U.GoSignInView
    else
      decodeResponse
        response
        messageDecoder
        (\error ->
          case communication of
            SignIn _ ->
              U.UpdateSignIn (ErrorLogin error)
            _ ->
              U.NoOp
        )

decodeResponse : Http.Response -> Decoder a -> (a -> U.Action) -> U.Action
decodeResponse response decoder responseToAction =
  case response.value of
    Http.Text text ->
      case decodeString decoder text of
        Ok x ->
          responseToAction x
        Err _ ->
          U.NoOp
    Http.Blob _ ->
      U.NoOp