{-# LANGUAGE LambdaCase #-}
{-
	Copyright (C) 2018 Dr. Alistair Ward

	This file is part of BishBosh.

	BishBosh is free software: you can redistribute it and/or modify
	it under the terms of the GNU General Public License as published by
	the Free Software Foundation, either version 3 of the License, or
	(at your option) any later version.

	BishBosh is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
	GNU General Public License for more details.

	You should have received a copy of the GNU General Public License
	along with BishBosh.  If not, see <http://www.gnu.org/licenses/>.
-}
{- |
 [@AUTHOR@]	Dr. Alistair Ward

 [@DESCRIPTION@]	Defines the commands a user can issue.
-}

module BishBosh.UI.Command (
-- * Types
-- ** Data-types
	Command(..),
-- * Constants
--	commandPrefix,
--	hintTag,
	printTag,
--	quitTag,
--	reportTag,
--	resignTag,
--	restartTag,
--	rollBackTag,
--	saveTag,
	setTag,
--	swapTag,
--	alternationTag,
--	printArgs,
--	reportArgs,
--	setArgs,
--	commands,
	usageMessage,
-- * Functions
	readsCommand,
	showsCommand,
	issueCommand,
	autoComplete
 ) where

import qualified	BishBosh.Data.List
import qualified	BishBosh.Input.Options				as Input.Options
import qualified	BishBosh.Property.ExtendedPositionDescription	as Property.ExtendedPositionDescription
import qualified	BishBosh.Text.AutoComplete			as Text.AutoComplete
import qualified	BishBosh.Type.Count				as Type.Count
import qualified	BishBosh.UI.PrintObject				as UI.PrintObject
import qualified	BishBosh.UI.ReportObject			as UI.ReportObject
import qualified	BishBosh.UI.SetObject				as UI.SetObject
import qualified	Control.Arrow
import qualified	Control.DeepSeq
import qualified	Data.List
import qualified	Data.List.Extra
import qualified	Data.Maybe
import qualified	Text.Printf

-- | Used to distinguish a command from a move.
commandPrefix :: Char
commandPrefix	= ':'

-- | Input-format.
hintTag :: String
hintTag		= "hint"

-- | Input-format.
printTag :: String
printTag	= "print"

-- | Input-format.
quitTag :: String
quitTag		= "quit"

-- | Input-format.
reportTag :: String
reportTag	= "report"

-- | Input-format.
resignTag :: String
resignTag	= "resign"

-- | Input-format.
restartTag :: String
restartTag	= "restart"

-- | Input-format.
rollBackTag :: String
rollBackTag	= "rollBack"

-- | Input-format.
saveTag :: String
saveTag		= "save"

-- | Input-format.
setTag :: String
setTag		= "set"

-- | Input-format.
swapTag :: String
swapTag		= "swap"

-- | The symbol used to denote alternation.
alternationTag :: String
alternationTag	= "|"

-- | Show the arguments of a command.
printArgs :: String
printArgs	= Data.List.intercalate alternationTag $ map show UI.PrintObject.range

-- | Show the arguments of a command.
reportArgs :: String
reportArgs	= Data.List.intercalate alternationTag $ map show UI.ReportObject.range

-- | The format of the argument to the runtime-command /set/.
setArgs :: String
setArgs	= Data.List.intercalate alternationTag [
	showString Property.ExtendedPositionDescription.tag " <EPD>",
	showString UI.SetObject.searchDepthTag " <Int>"
 ]

-- | The sum-type of commands that a user may issue.
data Command
	= Hint					-- ^ Request a move-suggestion.
	| Print UI.PrintObject.PrintObject	-- ^ Print the requested static data.
	| Quit					-- ^ Terminate this application.
	| Report UI.ReportObject.ReportObject	-- ^ Report on the requested dynamic data.
	| Resign				-- ^ Admit defeat.
	| Restart				-- ^ Abandon the current game, & start afresh.
	| RollBack (Maybe Type.Count.NPlies)	-- ^ Roll-back the optionally specified number of plies.
	| Save					-- ^ Persist the current game-state.
	| Set UI.SetObject.SetObject		-- ^ I.E. mutate something.
	| Swap					-- ^ Swap options between the two sides; which causes the players to swap sides.
	deriving (Eq, Show)

instance Control.DeepSeq.NFData Command where
	rnf (Print printObject)	= Control.DeepSeq.rnf printObject
	rnf (Set setObject)	= Control.DeepSeq.rnf setObject
	rnf _			= ()

-- | The data required to compose the usage-message for the available /command/s.
commands :: [(String, Maybe String, String)]
commands	= [
	(
		hintTag,
		Nothing,
		"Request a move-suggestion"
	), (
		printTag,
		Just printArgs,
		"Print the specified static data"
	), (
		quitTag,
		Nothing,
		"Terminate this application"
	), (
		reportTag,
		Just reportArgs,
		"Report on the specified dynamic data"
	), (
		resignTag,
		Nothing,
		"Admit defeat"
	), (
		restartTag,
		Nothing,
		"Restart the game, preserving the current configuration"
	), (
		rollBackTag,
		Just "[<Int>]",
		"The optionally specified number of plies to roll-back"
	), (
		saveTag,
		Nothing,
		"Persist the current game-state"
	), (
		setTag,
		Just setArgs,
		"Mutate something"
	), (
		swapTag,
		Nothing,
		showString "Swap " $ shows Input.Options.tag " between the two sides"
	)
 ]

-- | A message defining the syntax of the available /command/s.
usageMessage :: String
usageMessage	= showString (
	Text.Printf.printf (showString indent $ showChar ' ' format) commandFieldWidth "Command" objectFieldWidth "Object" "Definition"
 ) $ concatMap (
	\(command, maybeArg, definition)	-> Text.Printf.printf (
		showChar '\n' . showString indent . showChar commandPrefix $ showString format "."
	) commandFieldWidth command objectFieldWidth (
		Data.Maybe.fromMaybe "" maybeArg
	) definition
 ) commands where
	indent, format :: String
	indent	= replicate 2 ' '
	format	= "%-*s%-*s%s"

	commandFieldWidth, objectFieldWidth :: Int
	commandFieldWidth	= succ . maximum $ map (\(tag, _, _) -> length tag) commands
	objectFieldWidth	= succ $ maximum [length arg | (_, Just arg, _) <- commands]

-- | Reads a /command/.
readsCommand :: String -> Either String (Command, String)
readsCommand []	= Left . showString "null command received; specify one of " . show $ map (\(tag, _, _) -> tag) commands
readsCommand s	= case Control.Arrow.first Data.List.Extra.lower `map` lex s of
	[("hint", s')]		-> Right (Hint, s')
	[("help", s')]		-> Right (Print UI.PrintObject.Help, s')	-- Include a specific abbreviation.
	[("print", s')]		-> case reads $ UI.PrintObject.autoComplete s' of
		[pair]	-> Right $ Control.Arrow.first Print pair
		_	-> Left . showString "failed to read the object to " . showString printTag . showString " from " . shows s' . showString ". Usage: \"" . showChar commandPrefix . showString printTag . showChar ' ' $ showString printArgs "\""
	[("quit", s')]		-> Right (Quit, s')
	[("report", s')]	-> case reads $ UI.ReportObject.autoComplete s' of
		[pair]	-> Right $ Control.Arrow.first Report pair
		_	-> Left . showString "failed to read the object to " . showString reportTag . showString " from " . shows s' . showString ". Usage: \"" . showChar commandPrefix . showString reportTag . showChar ' ' $ showString reportArgs "\""
	[("resign", s')]	-> Right (Resign, s')
	[("restart", s')]	-> Right (Restart, s')
	[("save", s')]		-> Right (Save, s')
	[("set", s')]		-> case reads $ UI.SetObject.autoComplete s' of
		[pair]	-> Right $ Control.Arrow.first Set pair
		_	-> Left . showString "failed to read the object to " . showString setTag . showString " from " . shows s' . showString ". Usage: \"" . showChar commandPrefix . showString setTag . showString " (" $ showString setArgs ")\""
	[("rollback", s')]	-> case Data.List.Extra.trimStart s' of
		[]	-> Right (RollBack Nothing, s')
		s''	-> case reads s'' of
			[(nPlies, s''')]
				| nPlies <= 0	-> Left . showString "the specified number of plies (" $ shows nPlies ") must exceed zero"
				| otherwise	-> Right (RollBack (Just $ fromInteger nPlies), s''')
			_			-> Left . showString "failed to read the integral number of plies to " . showString rollBackTag . showString " from " $ show s''
	[("swap", s')]		-> Right (Swap, s')
	(command, _) : _	-> Left . showString "failed to read a command from " . shows s . showString "; did you mean " . show . BishBosh.Data.List.findClosest command $ map (\(tag, _, _) -> tag) commands
	_			-> Left "no command received"

-- | Shows a /command/.
showsCommand :: Command -> ShowS
showsCommand	= \case
	Hint			-> showString hintTag
	Print printObject	-> showString printTag . showChar ' ' . shows printObject
	Quit			-> showString quitTag
	Report reportObject	-> showString reportTag . showChar ' ' . shows reportObject
	Resign			-> showString resignTag
	Restart			-> showString restartTag
	RollBack maybeNPlies	-> showString rollBackTag . Data.Maybe.maybe id (\nPlies -> showChar ' ' . shows nPlies) maybeNPlies
	Save			-> showString saveTag
	Set setObject		-> showString setTag . showChar ' ' . shows setObject
	Swap			-> showString swapTag

-- | Show the specified command in the format required by this application's parser.
issueCommand :: Command -> ShowS
issueCommand command	= showChar commandPrefix . shows command

-- | Replace the first word of the specified string with the name of a command of which it is an unambiguous case-insensitive prefix.
autoComplete :: ShowS
autoComplete	= Text.AutoComplete.autoComplete $ "help" : map (
	\(tag, _, _) -> tag
 ) commands