--[[
	Provides an API to use when referencing a Player's character
	to make sure it is "Fully loaded", which is defined as:
		1) Character is a descendant of workspace
		2) Character has a PrimaryPart set
		3) Character contains a child which is a Humanoid
		4) The Humanoid's RootPart property is not nil

	This differs from Player.CharacterAdded and Player.CharacterAppearanceLoaded which fire
	before a character is parented to workspace and does not guarantee these other conditions.

	This loaded event won't be necessary once the Player.CharacterAdded is moved to the end of the event
	call stack, per https://devforum.roblox.com/t/avatar-loading-event-ordering-improvements/269607

	This wrapper provides a died event when the first of the following happens:

	1) Humanoid's .Died event fires
	2) Character is removed

	We need this because there are some cases where a character can be removed without the humanoid dying,
	such as if :LoadCharacter() is called before a character dies. Cleanup code often needs to run when a
	character's "lifespan" is over, whether it be because the humanoid died or because the character is removed.
	To avoid having to connect to both events in multiple places, this wrapper moves both events into one.
--]]


local ReplicatedStorage = game:GetService("ReplicatedStorage")
local Workspace = game:GetService("Workspace")

local Signal = require(ReplicatedStorage.Source.Signal)
local Connections = require(ReplicatedStorage.Source.Connections)
local waitForChildOfClassAsync = require(ReplicatedStorage.Source.Utility.waitForChildOfClassAsync)

local function isPrimaryPartSet(character: Model)
	return if character.PrimaryPart then true else false
end

local function isHumanoidRootPartSet(humanoid: Humanoid)
	return if humanoid.RootPart then true else false
end

local function getHumanoid(character: Model)
	return character:FindFirstChildOfClass("Humanoid")
end

local function isHumanoidAlive(character: Model)
	local humanoidMaybe = getHumanoid(character)
	if not humanoidMaybe then
		return false
	end

	local humanoid = humanoidMaybe :: Humanoid
	return isHumanoidRootPartSet(humanoid) and humanoid.Health > 0
end

local CharacterLoadedWrapper = {}
CharacterLoadedWrapper.__index = CharacterLoadedWrapper

export type ClassType = typeof(setmetatable(
	{} :: {
		loaded: Signal.ClassType,
		died: Signal.ClassType,
		_player: Player,
		_destroyed: boolean,
		_connections: Connections.ClassType,
	},
	CharacterLoadedWrapper
))

function CharacterLoadedWrapper.new(player: Player): ClassType
	local self = {
		loaded = Signal.new(),
		died = Signal.new(),
		_player = player,
		_destroyed = false,
		_connections = Connections.new(),
	}
	setmetatable(self, CharacterLoadedWrapper)

	self:_listenForCharacterAdded()

	return self
end

function CharacterLoadedWrapper.isLoaded(self: ClassType, optionalCharacter: Model?)
	-- Character can be passed in to check if a specific character model is
	-- the currently loaded character model. Useful if you are maintaining a reference
	-- to a specific character model, you want to verify that :isLoaded() is true, but
	-- you also want to make sure your current character reference isn't out of date.
	local characterMaybe = optionalCharacter or self._player.Character
	if not characterMaybe then
		return false
	end

	local character = characterMaybe :: Model

	return isPrimaryPartSet(character) and isHumanoidAlive(character) and character:IsDescendantOf(Workspace)
end

function CharacterLoadedWrapper._listenForCharacterAdded(self: ClassType)
	task.spawn(function()
		local character = self._player.Character

		-- Avoids firing .loaded event when the character is already loaded
		if character then
			if self:isLoaded() then
				self:_listenForDeath(character)
			else
				self:_waitForLoadedAsync(character)
			end
		end

		local characterAddedConnection = self._player.CharacterAdded:Connect(function(newCharacter: Model)
			self:_waitForLoadedAsync(newCharacter)
		end)

		self._connections:add(characterAddedConnection)
	end)
end
