-- map a value from one range to another
local function map(x: number, inMin: number, inMax: number, outMin: number, outMax: number): number
	return (x - inMin)*(outMax - outMin)/(inMax - inMin) + outMin
end

local function playSound(sound: Sound)
	sound.TimePosition = 0
	sound.Playing = true
end

local function shallowCopy(t)
	local out = {}
	for k, v in pairs(t) do
		out[k] = v
	end
	return out
end

local function initializeSoundSystem(instances)
	local player = instances.player
	local humanoid = instances.humanoid
	local rootPart = instances.rootPart

	local sounds: {[string]: Sound} = {}

	-- initialize sounds
	for name: string, props: {[string]: any} in pairs(SOUND_DATA) do
		local sound: Sound = Instance.new("Sound")
		sound.Name = name

		-- set default values
		sound.Archivable = false
		sound.RollOffMinDistance = 5
		sound.RollOffMaxDistance = 150
		sound.Volume = 0.65

		for propName, propValue: any in pairs(props) do
			(sound :: any)[propName] = propValue
		end

		sound.Parent = rootPart
		sounds[name] = sound
	end

	local playingLoopedSounds: {[Sound]: boolean?} = {}

	local function stopPlayingLoopedSounds(except: Sound?)
		for sound in pairs(shallowCopy(playingLoopedSounds)) do
			if sound ~= except then
				sound.Playing = false
				playingLoopedSounds[sound] = nil
			end
		end
	end

	-- state transition callbacks.
	local stateTransitions: {[Enum.HumanoidStateType]: () -> ()} = {
		[Enum.HumanoidStateType.FallingDown] = function()
			stopPlayingLoopedSounds()
		end,

		[Enum.HumanoidStateType.GettingUp] = function()
			stopPlayingLoopedSounds()
			playSound(sounds.GettingUp)
		end,

		[Enum.HumanoidStateType.Jumping] = function()
			stopPlayingLoopedSounds()
			playSound(sounds.Jumping)
		end,

		[Enum.HumanoidStateType.Swimming] = function()
			local verticalSpeed = math.abs(rootPart.AssemblyLinearVelocity.Y)
			if verticalSpeed > 0.1 then
				sounds.Splash.Volume = math.clamp(map(verticalSpeed, 100, 350, 0.28, 1), 0, 1)
				playSound(sounds.Splash)
			end
			stopPlayingLoopedSounds(sounds.Swimming)
			sounds.Swimming.Playing = true
			playingLoopedSounds[sounds.Swimming] = true
		end,

		[Enum.HumanoidStateType.Freefall] = function()
			sounds.FreeFalling.Volume = 0
			stopPlayingLoopedSounds(sounds.FreeFalling)
			playingLoopedSounds[sounds.FreeFalling] = true
		end,

		[Enum.HumanoidStateType.Landed] = function()
			stopPlayingLoopedSounds()
			local verticalSpeed = math.abs(rootPart.AssemblyLinearVelocity.Y)
			if verticalSpeed > 75 then
				sounds.Landing.Volume = math.clamp(map(verticalSpeed, 50, 100, 0, 1), 0, 1)
				playSound(sounds.Landing)
			end
		end,

		[Enum.HumanoidStateType.Running] = function()
			stopPlayingLoopedSounds(sounds.Running)
			sounds.Running.Playing = true
			playingLoopedSounds[sounds.Running] = true
		end,

		[Enum.HumanoidStateType.Climbing] = function()
			local sound = sounds.Climbing
			if math.abs(rootPart.AssemblyLinearVelocity.Y) > 0.1 then
				sound.Playing = true
				stopPlayingLoopedSounds(sound)
			else
				stopPlayingLoopedSounds()
			end
			playingLoopedSounds[sound] = true
		end,

		[Enum.HumanoidStateType.Seated] = function()
			stopPlayingLoopedSounds()
		end,

		[Enum.HumanoidStateType.Dead] = function()
			stopPlayingLoopedSounds()
			playSound(sounds.Died)
		end,
		
		[Enum.HumanoidStateType.Physics] = function()
			stopPlayingLoopedSounds()
		end,
	}

	-- updaters for looped sounds
	local loopedSoundUpdaters: {[Sound]: (number, Sound, Vector3) -> ()} = {
		[sounds.Climbing] = function(dt: number, sound: Sound, vel: Vector3)
			sound.Playing = vel.Magnitude > 0.1
		end,

		[sounds.FreeFalling] = function(dt: number, sound: Sound, vel: Vector3): ()
			if vel.Magnitude > 75 then
				sound.Volume = math.clamp(sound.Volume + 0.9*dt, 0, 1)
			else
				sound.Volume = 0
			end
		end,

		[sounds.Running] = function(dt: number, sound: Sound, vel: Vector3)
			sound.Playing = vel.Magnitude > 0.5 and humanoid.MoveDirection.Magnitude > 0.5
		end,
	}

	-- state substitutions to avoid duplicating entries in the state table
	local stateRemap: {[Enum.HumanoidStateType]: Enum.HumanoidStateType} = {
		[Enum.HumanoidStateType.RunningNoPhysics] = Enum.HumanoidStateType.Running,
	}

	local activeState: Enum.HumanoidStateType = stateRemap[humanoid:GetState()] or humanoid:GetState()

	local stateChangedConn = humanoid.StateChanged:Connect(function(_, state)
		state = stateRemap[state] or state

		if state ~= activeState then
			local transitionFunc: () -> () = stateTransitions[state]

			if transitionFunc then
				transitionFunc()
			end

			activeState = state
		end
	end)

	local steppedConn = RunService.Stepped:Connect(function(_, worldDt: number)
		-- update looped sounds on stepped
		for sound in pairs(playingLoopedSounds) do
			local updater: (number, Sound, Vector3) -> () = loopedSoundUpdaters[sound]

			if updater then
				updater(worldDt, sound, rootPart.AssemblyLinearVelocity)
			end
		end
	end)

	local function terminate()
		stateChangedConn:Disconnect()
		steppedConn:Disconnect()

		if FFlagUserAtomicCharacterSoundsUnparent then
			-- Unparent all sounds and empty sounds table
			-- This is needed in order to support the case where initializeSoundSystem might be called more than once for the same player,
			-- which might happen in case player character is unparented and parented back on server and reset-children mechanism is active.
			for name: string, sound: Sound in pairs(sounds) do
				sound:Destroy()
			end
			table.clear(sounds)
		end
	end

	return terminate
end

local binding = AtomicBinding.new({
	humanoid = "Humanoid",
	rootPart = "HumanoidRootPart",
}, initializeSoundSystem)

local playerConnections = {}

local function characterAdded(character)
	binding:bindRoot(character)
end

local function characterRemoving(character)
	binding:unbindRoot(character)
end

local function playerAdded(player: Player)
	local connections = playerConnections[player]
	if not connections then
		connections = {}
		playerConnections[player] = connections
	end

	if player.Character then
		characterAdded(player.Character)
	end
	table.insert(connections, player.CharacterAdded:Connect(characterAdded))
	table.insert(connections, player.CharacterRemoving:Connect(characterRemoving))
end

local function playerRemoving(player: Player)
	local connections = playerConnections[player]
	if connections then
		for _, conn in ipairs(connections) do
			conn:Disconnect()
		end
		playerConnections[player] = nil
	end

	if player.Character then
		characterRemoving(player.Character)
	end
end

for _, player in ipairs(Players:GetPlayers()) do
	task.spawn(playerAdded, player)
end
Players.PlayerAdded:Connect(playerAdded)
Players.PlayerRemoving:Connect(playerRemoving)