module Main where

import Data.Char          (isDigit)
import Data.List          (intersect)
import Data.Version       (showVersion)
import Paths_Monadoro     (version)
import System.Environment (getArgs)
import Control.Monad      (void)

import CountdownLoop      (countdown)
import Pomodoro           (session)

main :: IO ()
main = monadoro

monadoro :: IO ()
monadoro = getArgs >>= parseArgs

parseArgs :: [String] -> IO ()
parseArgs xs
  | xs `containsEither` ["--help", "-h"]    = putStrLn usage
  | xs `containsEither` ["--version", "-v"] = putStrLn . showVersion $ version
  | xs `containsEither` ["--session", "-s"] = session
  | otherwise = do
    warnAboutErrorsIfAny invalidIntervals
    runTimer validIntervals
    where (validIntervals, invalidIntervals) = checkInput xs

warnAboutErrorsIfAny :: [String] -> IO ()
warnAboutErrorsIfAny [] = return ()
warnAboutErrorsIfAny errors =
  putStrLn $ "Unable to parse as interval: " ++ show errors

{-| checkInput
 
Returns valid entries (first list) and invalid entries (second list).

>>> checkInput []
([],[])

>>> checkInput ["x"]
([],["x"])

>>> checkInput ["00:00"]
(["00:00"],[])

>>> checkInput ["00:00", "x"]
(["00:00"],["x"])

>>> checkInput ["00:00", "x"]
(["00:00"],["x"])

>>> checkInput ["00:00", "00:01", "x"]
(["00:00","00:01"],["x"])

-}

checkInput :: [String] -> ([String], [String])
checkInput [] = ([], [])
checkInput [x]
  | isValidTimeInterval x = ([x], [])
  | otherwise = ([], [x])
checkInput (x:xs) = (validEntries, invalidEntries)
  where
    validEntries =
      fst (checkInput [x]) ++ fst (checkInput xs)
    invalidEntries =
      snd (checkInput [x]) ++ snd (checkInput xs)

{-| isValidTimeInterval

>>> isValidTimeInterval "x"
False

>>> isValidTimeInterval "00:00"
True

-}

isValidTimeInterval :: String -> Bool
isValidTimeInterval (m1:m2:':':s1:[s2])
  | all isDigit [m1, m2, s1, s2] = True
isValidTimeInterval _ = False

containsEither :: (Eq a) => [a] -> [a] -> Bool
containsEither a = not . null . intersect a

usage :: String
usage = "Usage: monadoro [-vh] [--session] [INTERVAL [...]]"

runTimer :: [String] -> IO ()
runTimer []     = void (countdown "25:00")
runTimer [t]    = void (countdown t)
runTimer (t:ts) = parseArgs [t] >> parseArgs ts