--- ubiquitousse.signal

let registry_mt = {
	--- Map of signals to list of listeners.
	-- @impl ubiquitousse
	signals = {},

	--- Bind one or several functions to a signal name.
	-- @impl ubiquitousse
	bind = :(name, fn, ...)
		if not @signals[name] then
			@signals[name] = {}
		end
		table.insert(@signals[name], fn)
		if ... then
			return @bind(name, ...)
		end
	end,

	--- Unbind one or several functions to a signal name.
	-- @impl ubiquitousse
	unbind = :(name, fn, ...)
		if not @signals[name] then
			return
		end
		for i=#@signals[name], 1, -1 do
			if @signals[name] == fn then
				table.remove(@signals[name], i)
			end
		end
		if ... then
			return @unbind(name, ...)
		end
	end,

	--- Remove every bound function to a signal name.
	-- @impl ubiquitousse
	unbindAll = :(name)
		@signals[name] = nil
	end,

	--- Replace a bound function with another function.
	-- @impl ubiquitousse
	replace = :(name, sourceFn, destFn)
		if not @signals[name] then
			@signals[name] = {}
		end
		for i, fn in ipairs(@signals[name]) do
			if fn == sourceFn then
				@signals[name][i] = destFn
				break
			end
		end
	end,

	--- Remove every bound function to every signal.
	-- @impl ubiquitousse
	clear = :()
		@signals = {}
	end,

	--- Emit a signal, i.e. call every function bound to it, with the given arguments.
	-- @impl ubiquitousse
	emit = :(name, ...)
		if @signals[name] then
			for _, fn in ipairs(@signals[name]) do
				fn(...)
			end
		end
	end
}
registry_mt.__index = registry_mt

let signal = {
	--- Creates and return a new SignalRegistry.
	-- A SignalRegistry is a separate ubiquitousse.signal instance: its signals will be independant from other registries.
	-- @impl ubiquitousse
	new = ()
		return setmetatable({ signals = {} }, registry_mt)
	end,
	
	--- Global SignalRegistry.
	-- @impl ubiquitousse
	signals = {},
	bind = (...)
		return registry_mt.bind(signal, ...)
	end,
	unbind = (...)
		return registry_mt.unbind(signal, ...)
	end,
	clear = (...)
		return registry_mt.clear(signal, ...)
	end,
	emit = (...)
		return registry_mt.emit(signal, ...)
	end,

	--- SignalRegistry which will be used to bind signals that need to be called on game engine event.
	-- For example, every ubiquitousse module with a "update" function will bind it to the "update" signal in the registry;
	-- you can then call this signal on each game update to update every ubiquitousse module easily.
	-- Provided signals:
	-- * update, should be called on every game update
	-- * draw, should be called on every game draw
	-- * for LÖVE, there are callbacks for every LÖVE callback function that need to be called on their corresponding LÖVE callback
	-- @impl mixed
	event = nil,

	--- Call this function to hook signal.event signals to the current backend.
	-- For LÖVE, this means overriding every existing LÖVE callback. If a callback is already defined, the new one will call the old function along with the signal:emit.
	-- @impl backend
	registerEvents = () end
}

signal.event = signal.new()

return signal