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 String Int
  | DeletePayment PaymentId String Int Int
  | 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.andThen` (serverResult communication)

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

updatePageRequest : Int -> Http.Request
updatePageRequest page =
  simple "get" ("payments?page=" ++ toString page ++ "&perPage=" ++ toString perPage)

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

serverResult : Communication -> Http.Response -> Task Http.RawError U.Action
serverResult communication response =
  if response.status == 200
    then
      case communication of
        NoCommunication ->
          Task.succeed U.NoOp
        SignIn login ->
          Task.succeed (U.UpdateSignIn (ValidLogin login))
        AddPayment userName paymentName cost ->
          Http.send Http.defaultSettings (updatePageRequest 1)
            |> Task.map (\response ->
                 if response.status == 200
                   then
                     decodeResponse
                       response
                       paymentsDecoder
                       (\payments -> U.UpdatePayment (UP.AddPayment userName cost payments))
                   else
                     U.NoOp
               )
        DeletePayment id userName cost currentPage ->
          Http.send Http.defaultSettings (updatePageRequest currentPage)
            |> Task.map (\response ->
                 if response.status == 200
                   then
                     decodeResponse
                       response
                       paymentsDecoder
                       (\payments -> U.UpdatePayment (UP.Remove userName cost payments))
                   else
                     U.NoOp
               )
        UpdatePage page ->
          decodeResponse
            response
            paymentsDecoder
            (\payments -> U.UpdatePayment (UP.UpdatePage page payments))
          |> Task.succeed
        SignOut ->
          Task.succeed (U.GoSignInView)
    else
      decodeResponse
        response
        messageDecoder
        (\error ->
          case communication of
            SignIn _ ->
              U.UpdateSignIn (ErrorLogin error)
            _ ->
              U.NoOp
        )
      |> Task.succeed

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