--- Operations for game settings / stats.
-- @module Noble.Settings
--
Noble.Settings = {}				-- This is the "class" that holds methods.
local settings = nil			-- This is the actual settings object. We keep it local to avoid direct tampering.
local settingsDefault = nil		-- We keep track of default values so they can be reset.

local function keyChange(__dataDefault, __data)
	local defaultKeys = {}
	local keys = {}
	for key, value in pairs(__dataDefault) do	table.insert(defaultKeys, key) end
	for key, value in pairs(__data) do table.insert(keys, key) end
	for i = 1, #keys, 1 do
		if (defaultKeys[i] ~= keys[i]) then return true end
	end
	return false
end

local function settingExists(__key)
	-- Check for valid data item.
	for key, value in pairs(settings) do
		if __key == key then
			return true
		end
	end
	error("BONK: Setting \'" .. __key .. "\' does not exist. Maybe you spellet ti wronlgly.", 3)
	return false
end

local settingsHaveBeenSetup = false

--- Sets up the settings for your game. You can only run this once, and you must run it before using other `Noble.Settings` functions. It is recommended to place it in your main.lua, before `Noble.new()`.
--
-- <strong>NOTE:</strong> You will *not* be able to add new keys via the `Noble.Settings.set` method. This means you need to specify the keys and default values of all of the settings in your game at setup.
-- If you need to add keys that are not known during setup, it is probably not a setting and you should consider using `Noble.GameData` instead.
-- @tparam table __keyValuePairs table. Your game's settings, and thier default values, as key/value pairs. <strong>NOTE:</strong> Do not use "nil" as a value.
-- @bool[opt=true] __saveToDisk Saves your default values immediatly to disk.
-- @bool[opt=true] __modifyExistingOnKeyChange Updates the existing settings object on disk if you make changes to your settings keys (not values) during development or when updating your game.
-- @usage
--	Noble.Settings.setup({
--		difficulty = "normal",
--		music = true,
--		sfx = true,
--		players = 2,
--		highScore = 0	-- You can store persistant stats here, too!
--	})
function Noble.Settings.setup(__keyValuePairs, __saveToDisk, __modifyExistingOnKeyChange)
	if (settingsHaveBeenSetup) then
		error("BONK: You can only run Noble.Settings.setup() once.")
		return
	else
		settingsHaveBeenSetup = true
	end

	-- Prevent using the setup() method if there are no settings to register
	if (__keyValuePairs == nil or table.getSize(__keyValuePairs) == 0) then
		error("BONK: Do not use Noble.Settings.setup if you do not have any settings to register. New settings cannot be added via Noble.Settings.set and must be all declared upfront in the Noble.Settings.setup method.")
		return
	end

	local saveToDisk = Utilities.handleOptionalBoolean(__saveToDisk, true)
	local modifyExistingOnKeyChange = Utilities.handleOptionalBoolean(__modifyExistingOnKeyChange, true)
	settingsDefault = __keyValuePairs

	-- Get existing settings from disk, if any.
	settings = Datastore.read("Settings")

	if (settings == nil) then
		-- No settings on disk, so we create a new settings object using default values.
		settings = table.deepcopy(settingsDefault)
	elseif (modifyExistingOnKeyChange and keyChange(settingsDefault, settings)) then
		-- Found settings on disk, but key changes have been made...
		-- ...so we start with a new default settings object...
		local existingSettings = table.deepcopy(settings)
		settings = table.deepcopy(settingsDefault)
		for key, value in pairs(settings) do
			-- ...then copy settings with unchanged keys to the new settings object,
			-- naturally discarding keys that don't exist anymore.
			if (existingSettings[key] ~= nil) then settings[key] = existingSettings[key] end
		end

	end

	if (saveToDisk) then
		Noble.Settings.save()
	end
end

--- Get the value of a setting.
-- @string __settingName The name of the setting.
-- @treturn any The value of the requested setting.
-- @see set
function Noble.Settings.get(__settingName)
	if (settingExists(__settingName)) then
		return settings[__settingName]
	end
end

--- Set the value of a setting.
--
-- <strong>NOTE:</strong> If __settingName is not a key in the __keyValuePairs dictionary given to the `setup` method it will not be added to the Settings.
-- @string __settingName The name of the setting.
-- @tparam any __value The setting's new value
-- @bool[opt=true] __saveToDisk Saves to disk immediately. Set to false if you prefer to manually save (via a confirm button, etc).
-- @see setup
-- @see get
-- @see save
function Noble.Settings.set(__settingName, __value, __saveToDisk)
	if (settingExists(__settingName)) then
		settings[__settingName] = __value
		local saveToDisk = Utilities.handleOptionalBoolean(__saveToDisk, true)
		if (saveToDisk) then Noble.Settings.save() end
	end
end

--- Resets the value of a setting to its default value defined in `setup()`.
-- @string __settingName The name of the setting.
-- @bool[opt=true] __saveToDisk Saves to disk immediately. Set to false if you prefer to manually save (via a confirm button, etc).
-- @see resetSome
-- @see resetAll
-- @see save
function Noble.Settings.reset(__settingName, __saveToDisk)
	if (settingExists(__settingName)) then
		settings[__settingName] = settingsDefault[__settingName]
		local saveToDisk = Utilities.handleOptionalBoolean(__saveToDisk, true)
		if (saveToDisk) then Noble.Settings.save() end
	end
end

--- Resets the value of multiple settings to thier default value defined in `setup()`. This is useful if you are storing persistant stats like high scores in `Settings` and want the player to be able to reset them seperately.
-- @tparam table __settingNames The names of the settings, in an array-style table.
-- @bool[opt=true] __saveToDisk Saves to disk immediately. Set to false if you prefer to manually save (via a confirm button, etc).
-- @see resetAll
-- @see save
function Noble.Settings.resetSome(__settingNames, __saveToDisk)
	for i = 1, #__settingNames, 1 do
		Noble.Settings.reset(__settingNames[i], __saveToDisk)
	end
end

--- Resets all settings to thier default values defined in `setup()`.
-- @bool[opt=true] __saveToDisk Saves to disk immediately. Set to false if you prefer to manually save (via a confirm button, etc).
-- @see resetSome
-- @see save
function Noble.Settings.resetAll(__saveToDisk)
	settings = table.deepcopy(settingsDefault)
	local saveToDisk = Utilities.handleOptionalBoolean(__saveToDisk, true)
	if (saveToDisk) then Noble.Settings.save() end
end

--- Saves settings to disk.
-- You don't need to call this unless you set `__saveToDisk` as false when setting or resetting a setting (say that five times fast!).
-- @see set
-- @see reset
-- @see resetAll
function Noble.Settings.save()
	Datastore.write(settings, "Settings")
end