{-# LANGUAGE OverloadedStrings #-}

module AdListener
  ( listenToNewAds
  ) where

import Data.List (intersperse)
import Data.Text (Text)
import qualified Data.Text as T
import qualified Data.Text.IO as T

import Control.Concurrent (threadDelay)

import Fetch (fetchResumes, fetchAds)

import Model.Ad
import Model.URL
import Model.Resume

import View.Ad (renderAds)

import Page
import Parser.Detail

import Mail (sendMail)

import Config (Config)
import qualified Config as C

import Time (getCurrentFormattedTime)

listenToNewAds :: Config -> IO ()
listenToNewAds config = do
  eitherResumes <- fetchResumes (C.url config)
  case eitherResumes of
    Left error ->
      listenError config [] error
    Right resumes ->
      let newURLs = map url resumes
      in  do
            putStrLn "Listening for new ads…"
            listenToNewAdsWithViewedURLs config newURLs

listenToNewAdsWithViewedURLs :: Config -> [URL] -> IO ()
listenToNewAdsWithViewedURLs config viewedURLs = do
  eitherResumes <- fetchResumes (C.url config)
  case eitherResumes of
    Left error ->
      listenError config viewedURLs error
    Right resumes ->
      listenToNewAdsWithResumes config viewedURLs resumes

listenToNewAdsWithResumes :: Config -> [URL] -> [Resume] -> IO ()
listenToNewAdsWithResumes config viewedURLs resumes =
  let (newURLs, newResumes) = getNewResumes viewedURLs resumes
  in  do
        eitherNewAds <- fetchAds newResumes
        case eitherNewAds of
          Left error ->
            listenError config viewedURLs error
          Right newAds ->
            do
              time <- getCurrentFormattedTime
              if not (null newAds)
                then
                  let message = newAdsMessage time newAds
                  in  do
                        T.putStrLn message
                        trySendMail config message
                else
                  return ()
              waitOneMinute
              listenToNewAdsWithViewedURLs config (viewedURLs ++ newURLs)

trySendMail :: Config -> Text -> IO ()
trySendMail config message =
  case C.mailTo config of
    Just mailTo ->
      do
        eitherMailSuccess <- sendMail mailTo message
        case eitherMailSuccess of
          Right () ->
            putStrLn "Mail sent."
          Left error ->
            T.putStrLn . T.concat $
              [ "Error sending mail: "
              , error
              ]
    Nothing ->
      return ()

newAdsMessage :: Text -> [Ad] -> Text
newAdsMessage time newAds =
  let newAdsMessage =
        T.concat
          [ "\nAt "
          , time
          , ", got "
          , T.pack . show . length $ newAds
          , " new ad"
          , if length newAds > 1 then "s" else ""
          ]
      line = T.map (\_ -> '-') newAdsMessage
  in  T.intercalate
        "\n"
        [ newAdsMessage
        , T.concat [line, "\n"]
        , renderAds newAds
        ]

listenError :: Config -> [URL] -> Text -> IO ()
listenError config viewedURLs error = do
  T.putStrLn error
  waitOneMinute
  listenToNewAdsWithViewedURLs config viewedURLs

waitOneMinute :: IO ()
waitOneMinute = threadDelay (1000 * 1000 * 60)