{-# LANGUAGE OverloadedStrings #-}

module Main where

import           Control.Concurrent
import           Control.Monad        (forM_)
import qualified Data.Text.Lazy       as Txt
import qualified Data.Text.Lazy.IO    as TxtI
import qualified Network.HTTP.Client  as HTTP
import           System.Environment   (getArgs)

import           Hash2Pub.PostService (Hashtag, clientPublishPost)

-- configuration constants
timelineFile = "../simulationData/inputs/generated/timeline_sample.csv"

main :: IO ()
main = do
    -- read CLI parameters
    speedupStr : _ <- getArgs
    -- read and parse timeline schedule
    -- relying on lazyness of HaskellIO, hoping it does not introduce too strong delays
    postEvents <- parseSchedule <$> TxtI.readFile timelineFile
    -- actually schedule and send the post events
    executeSchedule (read speedupStr) postEvents
    pure ()



parseSchedule :: Txt.Text
              -> [(Int, Hashtag, (String, Int))] -- ^ [(delay in microseconds, hashtag, (hostname, port))]
parseSchedule = fmap (parseEntry . Txt.split (== ';')) . Txt.lines
  where
      parseEntry [delayT, contactT, tag] =
          (read $ Txt.unpack delayT, tag, read $ Txt.unpack contactT)
      parseEntry entry = error $ "invalid schedule input format: " <> show entry

executeSchedule :: Int  -- ^ speedup factor
                -> [(Int, Hashtag, (String, Int))] -- ^ [(delay in microseconds, hashtag, (hostname, port))]
                -> IO ()
executeSchedule speedup events = do
    -- initialise HTTP manager
    httpMan <- HTTP.newManager HTTP.defaultManagerSettings
    forM_ events $ \(delay, tag, (pubHost, pubPort)) -> do
        _ <- forkIO $
            clientPublishPost httpMan pubHost pubPort ("foobar #" <> tag)
            >>= either putStrLn (const $ pure ())
        -- while threadDelay gives only minimum delay guarantees, let's hope the
        -- additional delays are negligible
        -- otherwise: evaluate usage of https://hackage.haskell.org/package/schedule-0.3.0.0/docs/Data-Schedule.html
        threadDelay $ delay `div` speedup