{-# Language RankNTypes, OverloadedStrings #-}
{-|
Module      : Client.EventLoop.Actions
Description : Programmable keyboard actions
Copyright   : (c) Eric Mertens, 2016
License     : ISC
Maintainer  : emertens@gmail.com

-}

module Client.EventLoop.Actions
  ( Action(..)
  , KeyMap
  , keyToAction
  , initialKeyMap
  , addKeyBinding
  , removeKeyBinding
  , keyMapEntries

  -- * Keys as text
  , parseKey
  , prettyModifierKey
  , actionName
  ) where

import           Graphics.Vty.Input.Events
import           Config.Schema.Spec
import           Control.Applicative
import           Control.Lens
import           Data.Char (showLitChar)
import           Data.Functor.Compose
import           Data.List
import           Data.Map (Map)
import qualified Data.Map as Map
import           Data.HashMap.Lazy (HashMap)
import qualified Data.HashMap.Lazy as HashMap
import           Data.Semigroup ((<>))
import           Data.Text (Text)
import qualified Data.Text as Text
import           Text.Read

-- | Actions that can be invoked using the keyboard.
data Action

  = ActBackspace
  | ActDelete
  | ActLeft
  | ActRight
  | ActHome
  | ActEnd
  | ActOlderLine
  | ActNewerLine
  | ActScrollUp
  | ActScrollDown
  | ActBackWord
  | ActForwardWord

  | ActYank
  | ActKillHome
  | ActKillEnd
  | ActKillWordBack
  | ActKillWordForward
  | ActToggle

  | ActBold
  | ActColor
  | ActItalic
  | ActUnderline
  | ActReverseVideo
  | ActClearFormat
  | ActInsertEnter
  | ActDigraph

  | ActRetreatFocus
  | ActAdvanceFocus
  | ActAdvanceNetwork
  | ActJumpToActivity
  | ActJumpPrevious
  | ActJump Int

  | ActTabComplete
  | ActTabCompleteBack

  | ActEnter
  | ActReset
  | ActRefresh
  | ActCommand Text
  | ActInsert Char
  | ActIgnored
  deriving (Eq, Ord, Read, Show)

-- | Lookup table for keyboard events to actions. Use with
-- keyToAction.
newtype KeyMap = KeyMap (Map [Modifier] (Map Key Action))
  deriving (Show)

keyMapEntries :: KeyMap -> [([Modifier], Key, Action)]
keyMapEntries (KeyMap m) =
  [ (mods, k, a)
     | (mods, m1) <- Map.toList m
     , (k,a) <- Map.toList m1
     ]

instance Spec Action where
  valuesSpec = customSpec "action" anyAtomSpec $ \a ->
                fst <$> HashMap.lookup a actionInfos


-- | Names and default key bindings for each action.
--
-- Note that Jump, Insert and Ignored are excluded. These will
-- be computed on demand by keyToAction.
actionInfos :: HashMap Text (Action, [([Modifier],Key)])
actionInfos =
  let norm = (,) [     ]
      ctrl = (,) [MCtrl]
      meta = (,) [MMeta] in

  HashMap.fromList

  [("delete"            , (ActDelete           , [ctrl (KChar 'd'), norm KDel]))
  ,("backspace"         , (ActBackspace        , [norm KBS]))
  ,("home"              , (ActHome             , [norm KHome, ctrl (KChar 'a')]))
  ,("end"               , (ActEnd              , [norm KEnd , ctrl (KChar 'e')]))
  ,("kill-home"         , (ActKillHome         , [ctrl (KChar 'u')]))
  ,("kill-end"          , (ActKillEnd          , [ctrl (KChar 'k')]))
  ,("yank"              , (ActYank             , [ctrl (KChar 'y')]))
  ,("toggle"            , (ActToggle           , [ctrl (KChar 't')]))
  ,("kill-word-left"    , (ActKillWordBack     , [ctrl (KChar 'w'), meta KBS]))
  ,("kill-word-right"   , (ActKillWordForward  , [meta (KChar 'd')]))

  ,("bold"              , (ActBold             , [ctrl (KChar 'b')]))
  ,("color"             , (ActColor            , [ctrl (KChar 'c')]))
  ,("italic"            , (ActItalic           , [ctrl (KChar ']')]))
  ,("underline"         , (ActUnderline        , [ctrl (KChar '_')]))
  ,("clear-format"      , (ActClearFormat      , [ctrl (KChar 'o')]))
  ,("reverse-video"     , (ActReverseVideo     , [ctrl (KChar 'v')]))

  ,("insert-newline"    , (ActInsertEnter      , [meta KEnter]))
  ,("insert-digraph"    , (ActDigraph          , [meta (KChar 'k')]))

  ,("next-window"       , (ActAdvanceFocus     , [ctrl (KChar 'n')]))
  ,("prev-window"       , (ActRetreatFocus     , [ctrl (KChar 'p')]))
  ,("next-network"      , (ActAdvanceNetwork   , [ctrl (KChar 'x')]))
  ,("refresh"           , (ActRefresh          , [ctrl (KChar 'l')]))
  ,("jump-to-activity"  , (ActJumpToActivity   , [meta (KChar 'a')]))
  ,("jump-to-previous"  , (ActJumpPrevious     , [meta (KChar 's')]))

  ,("reset"             , (ActReset            , [norm KEsc]))

  ,("left-word"         , (ActBackWord         , [meta KLeft, meta (KChar 'b')]))
  ,("right-word"        , (ActForwardWord      , [meta KRight, meta (KChar 'f')]))
  ,("left"              , (ActLeft             , [norm KLeft]))
  ,("right"             , (ActRight            , [norm KRight]))
  ,("up"                , (ActOlderLine        , [norm KUp]))
  ,("down"              , (ActNewerLine        , [norm KDown]))
  ,("scroll-up"         , (ActScrollUp         , [norm KPageUp]))
  ,("scroll-down"       , (ActScrollDown       , [norm KPageDown]))
  ,("enter"             , (ActEnter            , [norm KEnter]))
  ,("word-complete-back", (ActTabCompleteBack  , [norm KBackTab]))
  ,("word-complete"     , (ActTabComplete      , [norm (KChar '\t')]))
  ]


actionNames :: Map Action Text
actionNames = Map.fromList
  [ (action, name) | (name, (action,_)) <- HashMap.toList actionInfos ]


-- | Render action as human-readable text.
actionName :: Action -> Text
actionName (ActCommand txt) = "command: " <> txt
actionName a = Map.findWithDefault (Text.pack (show a)) a actionNames


keyMapLens :: [Modifier] -> Key -> Lens' KeyMap (Maybe Action)
keyMapLens mods key f (KeyMap m) =
  KeyMap <$> (at (normalizeModifiers mods) . non' _Empty . at key) f m


-- | Lookup the action to perform in response to a particular key event.
keyToAction ::
  KeyMap     {- ^ actions         -} ->
  [Modifier] {- ^ jump modifier   -} ->
  Text       {- ^ window names    -} ->
  [Modifier] {- ^ actual modifier -} ->
  Key        {- ^ key             -} ->
  Action     {- ^ action          -}
keyToAction _ jumpMods names mods (KChar c)
  | normalizeModifiers jumpMods == normalizeModifiers mods
  , Just i <- Text.findIndex (c==) names = ActJump i
keyToAction m _ _ modifier key =
  case m ^. keyMapLens modifier key of
    Just a -> a
    Nothing | KChar c <- key, null modifier -> ActInsert c
            | otherwise                     -> ActIgnored


-- | Bind a keypress event to a new action.
addKeyBinding ::
  [Modifier] {- ^ modifiers -} ->
  Key        {- ^ key       -} ->
  Action     {- ^ action    -} ->
  KeyMap     {- ^ actions   -} ->
  KeyMap
addKeyBinding mods k a = keyMapLens mods k ?~ a

-- | Unbind the action associated with a key.
removeKeyBinding ::
  [Modifier] {- ^ modifiers -} ->
  Key        {- ^ key       -} ->
  KeyMap     {- ^ actions   -} ->
  KeyMap
removeKeyBinding mods k = set (keyMapLens mods k) Nothing


normalizeModifiers :: [Modifier] -> [Modifier]
normalizeModifiers = nub . sort


-- | Default key bindings
initialKeyMap :: KeyMap
initialKeyMap = KeyMap $
  Map.fromListWith Map.union $

   ([], Map.fromList
          [ (KFun 2, ActCommand "toggle-detail")
          , (KFun 3, ActCommand "toggle-activity-bar")
          , (KFun 4, ActCommand "toggle-metadata")
          , (KFun 5, ActCommand "toggle-layout")
          ])
    :

    [ (mods, Map.singleton k act)
      | (act, mks) <- HashMap.elems actionInfos
      , (mods, k)  <- mks
      ]


parseKey :: String -> Maybe ([Modifier], Key)
parseKey = getCompose . go
  where
    modifier x   = Compose (Just ([x], ()))
    liftMaybe mb = Compose ((,)[] <$> mb)
    go str =
      case str of
        "Space"     -> pure (KChar ' ')
        "Tab"       -> pure (KChar '\t')
        "BackTab"   -> pure KBackTab
        "Enter"     -> pure KEnter
        "Home"      -> pure KHome
        "End"       -> pure KEnd
        "Esc"       -> pure KEsc
        "PageUp"    -> pure KPageUp
        "PageDown"  -> pure KPageDown
        "Backspace" -> pure KBS
        "Delete"    -> pure KDel
        "Left"      -> pure KLeft
        "Right"     -> pure KRight
        [c]         -> pure (KChar c)
        'F':xs      -> KFun <$> liftMaybe (readMaybe xs)
        'C':'-':xs  -> modifier MCtrl  *> go xs
        'M':'-':xs  -> modifier MMeta  *> go xs
        'S':'-':xs  -> modifier MShift *> go xs
        'A':'-':xs  -> modifier MAlt   *> go xs
        _           -> empty


prettyModifierKey :: [Modifier] -> Key -> String
prettyModifierKey mods k
  = foldr prettyModifier (prettyKey k) mods

prettyModifier :: Modifier -> ShowS
prettyModifier MCtrl  = showString "C-"
prettyModifier MMeta  = showString "M-"
prettyModifier MShift = showString "S-"
prettyModifier MAlt   = showString "A-"

prettyKey :: Key -> String
prettyKey (KChar ' ') = "Space"
prettyKey (KChar '\t') = "Tab"
prettyKey (KChar c) = showLitChar c "" -- escapes anything non-ascii
prettyKey (KFun n)  = 'F' : show n
prettyKey KBackTab  = "BackTab"
prettyKey KEnter    = "Enter"
prettyKey KEsc      = "Esc"
prettyKey KHome     = "Home"
prettyKey KEnd      = "End"
prettyKey KPageUp   = "PageUp"
prettyKey KPageDown = "PageDn"
prettyKey KDel      = "Delete"
prettyKey KBS       = "Backspace"
prettyKey KLeft     = "Left"
prettyKey KRight    = "Right"
prettyKey k         = show k
