Color.hs

{-|
  Module containing color definitions, mappings between @Priority@ and color,
  and code to apply color to the terminal.
-}
module System.Log.Color
  ( ColorMap

  , colorize

  , black, red, green, yellow, blue, magenta, cyan, white
  , grey, bred, bgreen , byellow, bblue, bmagenta, bcyan, bwhite
  , colors16, colors256, noColor
  )
  where

import Data.List (find)
import Data.Word (Word8)
import System.Console.ANSI (ConsoleLayer (Foreground), SGR (..), setSGRCode)
import System.Log.Logger (Priority (..))


colorize :: ColorMap -> Priority -> String -> String
colorize colorMap prio str = case priorityColor of
  (Just (swapColors, color)) ->
       setSGRCode [SetPaletteColor Foreground color]
    <> setSGRCode [SetSwapForegroundBackground swapColors]
    <> str
    <> setSGRCode [Reset]
  Nothing -> str

  where
    priorityColor = snd <$> find ((== prio) . fst) colorMap


-- | These correspond to the basic 16 ANSI term color values
black, red, green, yellow, blue, magenta, cyan, white, grey, bred, bgreen,
  byellow, bblue, bmagenta, bcyan, bwhite :: Word8
black = 0
red = 1
green = 2
yellow = 3
blue = 4
magenta = 5
cyan = 6
white = 7
grey = 8
bred = 9
bgreen = 10
byellow = 11
bblue = 12
bmagenta = 13
bcyan = 14
bwhite = 15


-- | This type maps a logging Priority to a pair indicating if the output
--   should be inverted (foreground and background swapped) and the color value
--   as a @Word8@ (an index into the 256 color palette)
type ColorMap = [(Priority, (Bool, Word8))]


-- | Use this @ColorMap@ to disable color entirely
noColor :: ColorMap
noColor = []


-- | Basic colors. Good when the term doesn't support 256.
colors16 :: ColorMap
colors16 =
  [ (DEBUG    , (False, bcyan))
  , (INFO     , (False, bgreen))
  , (NOTICE   , (False, bwhite))
  , (WARNING  , (False, byellow))
  , (ERROR    , (False, bred))
  , (CRITICAL , (False, magenta))
  , (ALERT    , (False, bblue))
  , (EMERGENCY, (True,  bred))
  ]


-- | Some decent colors
colors256 :: ColorMap
colors256 =
  [ (DEBUG    , (False, 75))      -- Easier-to-read blue
  , (INFO     , (False, 156))     -- Minty green
  , (NOTICE   , (False, bwhite))  -- White
  , (WARNING  , (False, byellow)) -- Bright yellow
  , (ERROR    , (False, bred))    -- Bright red
  , (CRITICAL , (False, 161))     -- Dull red
  , (ALERT    , (False, 206))     -- Brighter magenta
  , (EMERGENCY, (True,  bred))    -- Inverted bright red
  ]