{-# LANGUAGE DeriveGeneric #-}
{-# LANGUAGE DerivingVia #-}
{-# LANGUAGE GADTs #-}
{-# LANGUAGE OverloadedStrings #-}

{- |
Module      : System.MemInfo.Choices
Copyright   : (c) 2022 Tim Emiola
Maintainer  : Tim Emiola <adetokunbo@emio.la>
SPDX-License-Identifier: BSD3

This module defines the command line flags used to control the behavior of the
__printmem__ command
-}
module System.MemInfo.Choices (
  Choices (..),
  Style (..),
  PrintOrder (..),
  cmdInfo,
  getChoices,
) where

import qualified Data.Text as Text
import GHC.Generics (Generic)
import Options.Applicative (
  Parser,
  ParserInfo,
  ReadM,
  eitherReader,
  execParser,
  help,
  helper,
  info,
  long,
  metavar,
  option,
  optional,
  readerError,
  short,
  switch,
 )
import Options.Applicative.NonEmpty (some1)
import System.MemInfo.Prelude


-- | Parses the command line arguments.
getChoices :: IO Choices
getChoices = execParser cmdInfo


-- | Represents the user-specified choices extracted from the command line
data Choices = Choices
  { choiceSplitArgs :: !Bool
  , choiceOnlyTotal :: !Bool
  , choiceByPid :: !Bool
  , choiceShowSwap :: !Bool
  , choiceReversed :: !Bool
  , choiceWatchSecs :: !(Maybe Natural)
  , choicePidsToShow :: !(Maybe (NonEmpty ProcessID))
  , choicePrintOrder :: !(Maybe PrintOrder)
  , choiceStyle :: !(Maybe Style)
  }
  deriving (Eq, Show, Generic)


-- | Specifies a command line that when parsed will provide 'Choices'
cmdInfo :: ParserInfo Choices
cmdInfo = info (helper <*> parseChoices) mempty


parseChoices :: Parser Choices
parseChoices =
  Choices
    <$> parseSplitArgs
    <*> parseOnlyTotal
    <*> parseDiscriminateByPid
    <*> parseShowSwap
    <*> parseReversed
    <*> optional parseWatchPeriodSecs
    <*> optional parseChoicesPidsToShow
    <*> optional parsePrintOrder
    <*> optional parseStyle


parseChoicesPidsToShow :: Parser (NonEmpty ProcessID)
parseChoicesPidsToShow =
  some1
    $ option positiveNum
    $ short 'p'
    <> long "pids"
    <> metavar "<pid1> [ -p pid2 ... -p pidN ]"
    <> help "Only show memory usage of the specified PIDs"


parseSplitArgs :: Parser Bool
parseSplitArgs =
  switch
    $ short 's'
    <> long "split-args"
    <> help "Show and separate by all command line arguments"


parseOnlyTotal :: Parser Bool
parseOnlyTotal =
  switch
    $ short 't'
    <> long "total"
    <> help "Only show the total value"


parseReversed :: Parser Bool
parseReversed =
  switch
    $ short 'r'
    <> long "reverse"
    <> help "Reverses the output order so that output descends on the sorting field"


parseDiscriminateByPid :: Parser Bool
parseDiscriminateByPid =
  switch
    $ short 'd'
    <> long "discriminate-by-pid"
    <> help "Show by process rather than by program"


parseShowSwap :: Parser Bool
parseShowSwap =
  switch
    $ short 'S'
    <> long "show_swap"
    <> help "Show swap information"


parseWatchPeriodSecs :: Parser Natural
parseWatchPeriodSecs =
  option positiveNum
    $ short 'w'
    <> long "watch"
    <> metavar "N"
    <> help "Measure and show memory every N seconds (N > 0)"


positiveNum :: (Read a, Ord a, Num a) => ReadM a
positiveNum =
  let
    checkPositive i
      | i > 0 = pure i
      | otherwise = readerError "Value must be greater than 0"
   in
    autoOrNotAllowed >>= checkPositive


parsePrintOrder :: Parser PrintOrder
parsePrintOrder =
  option autoIgnoreCase
    $ short 'b'
    <> long "order-by"
    <> metavar "< private | swap | shared | count >"
    <> help "Orders the output by ascending values of the given field"


-- | Determines the order in which @MemUsages@ in a report are printed out
data PrintOrder
  = Swap
  | Private
  | Shared
  | Count
  deriving (Eq, Show, Read, Generic)


parseStyle :: Parser Style
parseStyle =
  option autoIgnoreCase
    $ short 'y'
    <> long "output-style"
    <> metavar "< [normal] | csv >"
    <> help (Text.unpack styleHelp)


styleHelp :: Text
styleHelp =
  Text.unlines
    [ "Determines how the output report is presented;"
    , "'normal' is the default and is the same as if this option was omitted;"
    , "'csv' outputs the usage and header rows in csv format, with all values in KiB and no 'total' row."
    , "With 'csv', the --total (-t) flag is ignored"
    ]


-- | Determines the format style of the output
data Style
  = Csv
  | Normal
  deriving (Eq, Show, Read, Generic)


autoIgnoreCase :: (Read a) => ReadM a
autoIgnoreCase =
  let toTitle' = Text.unpack . Text.toTitle . Text.pack
   in eitherReader $ readOrNotAllowed toTitle'


autoOrNotAllowed :: (Read a) => ReadM a
autoOrNotAllowed = eitherReader $ readOrNotAllowed id


readOrNotAllowed :: (Read a) => (String -> String) -> String -> Either String a
readOrNotAllowed f x = case readEither $ f x of
  Left _ -> Left $ "value '" ++ x ++ "' is not permitted"
  right -> right