---@module ChessDuels.Main
-- Singleton guard that works whether or not the executor exposes `shared`.
local globalEnv = getgenv and getgenv() or _G

local ChessDuels = {}

-- Services.
local playersService = game:GetService("Players")
local replicatedStorage = game:GetService("ReplicatedStorage")
local userInputService = game:GetService("UserInputService")
local virtualUser = game:GetService("VirtualUser")

-- Constants.
local DEPTH_OPTIONS = { 2, 3, 4, 5, 6, 7, 8 }
local TIME_OPTIONS = { 0.3, 0.6, 1, 2, 3 }
local DELAY_OPTIONS = { 0, 0.4, 1, 2, 3.5 }
local POLL_INTERVAL = 0.25
local RETRY_AFTER = 3

-- State.
local localPlayer = playersService.LocalPlayer
local connections = {}
local guiRoot = nil
local running = true
local flags = {
	autoPlay = false,
	autoRematch = false,
	autoClaim = true,
	antiAfk = true,
}
local depthIndex = 5
local timeIndex = 3
local delayIndex = 2

local Engine = nil
local Bot = nil
local actionRemote = nil
local updateRemote = nil
local currentGetter = nil
local lastGame = nil
local lastKey = nil
local lastSentAt = 0
local suggestion = nil
local statusLabel = nil
local hintLabel = nil
local analysing = false

---Require a game module under identity 2 and restore identity 8.
---@param module ModuleScript
---@return any
local function safeRequire(module)
	setthreadidentity(2)
	local ok, result = pcall(require, module)
	setthreadidentity(8)
	return ok and result or nil
end

---Resolve the game's engine, bot and remotes.
local function loadGame()
	local chessFolder = replicatedStorage:WaitForChild("Chess", 10)
	if chessFolder then
		Engine = safeRequire(chessFolder:WaitForChild("Engine"))
		Bot = safeRequire(chessFolder:WaitForChild("Bot"))
	end

	local remotes = replicatedStorage:WaitForChild("ChessRemotes", 10)
	if remotes then
		actionRemote = remotes:WaitForChild("Action")
		updateRemote = remotes:WaitForChild("Update")
	end
end

---Find GameView.current through the GC so joining mid-game still works.
local function findCurrentGetter()
	if not getgc then return end
	for _, fn in ipairs(getgc(false)) do
		if typeof(fn) == "function" and not (isexecutorclosure and isexecutorclosure(fn)) then
			local okName, name = pcall(debug.info, fn, "n")
			local okSrc, source = pcall(debug.info, fn, "s")
			if okName and okSrc and name == "current" and type(source) == "string" and source:find("GameView") then
				currentGetter = fn
				return
			end
		end
	end
end

---Return the newest known game payload.
---@return table?
local function getGame()
	if currentGetter then
		local ok, game = pcall(currentGetter)
		if ok and type(game) == "table" and game.state then
			lastGame = game
		end
	end
	return lastGame
end

---Set the status text in the HUD.
---@param text string
local function setStatus(text)
	if statusLabel then statusLabel.Text = text end
end

---Format a move as coordinate notation.
---@param move table
---@return string
local function formatMove(move)
	return Engine.uci(move)
end

---Search the current position and return the best move.
---@param game table
---@return table?, number?, number?
local function searchBest(game)
	local state = Engine.deserialize(game.state)
	if #Engine.legalMoves(state) == 0 then return nil end

	local score, move, reached = Bot.analyze(state, DEPTH_OPTIONS[depthIndex], TIME_OPTIONS[timeIndex])
	if not move then
		move = Engine.legalMoves(state)[1]
	end
	return move, score, reached
end

---Send a move to the server exactly like the client does.
---@param move table
local function playMove(move)
	if not actionRemote then return end
	actionRemote:FireServer("move", {
		from = move.from,
		to = move.to,
		promo = move.promo,
	})
	lastSentAt = os.clock()
end

---Process the current game once per poll tick.
local function step()
	local game = getGame()
	if not game then
		setStatus("Waiting for a game...")
		return
	end

	if game.over then
		suggestion = nil
		lastKey = nil
		setStatus("Game over")
		if hintLabel then hintLabel.Text = "Best: -" end
		if flags.autoRematch and actionRemote and game.you ~= 0 then
			actionRemote:FireServer("rematch")
		end
		if flags.autoClaim and actionRemote then
			actionRemote:FireServer("claimReward")
		end
		return
	end

	if game.you == 0 then
		setStatus("Spectating")
		return
	end

	local state = Engine.deserialize(game.state)
	if state.turn ~= game.you then
		setStatus("Opponent thinking...")
		return
	end

	local key = tostring(game.id) .. ":" .. tostring(game.ply)
	if key == lastKey then
		-- Server may have rejected the move; retry after a grace period.
		if flags.autoPlay and suggestion and os.clock() - lastSentAt > RETRY_AFTER then
			playMove(suggestion)
		end
		return
	end

	if analysing then return end
	analysing = true
	lastKey = key
	setStatus("Calculating...")

	local move, score, reached = searchBest(game)
	analysing = false
	suggestion = move
	if not move then return end

	local shown = string.format("Best: %s  (%+.2f, d%d)", formatMove(move), (score or 0) / 100, reached or 0)
	if hintLabel then hintLabel.Text = shown end
	setStatus("Your move")

	if flags.autoPlay then
		task.wait(DELAY_OPTIONS[delayIndex])
		local fresh = getGame()
		if fresh and fresh.id == game.id and fresh.ply == game.ply and not fresh.over then
			playMove(move)
		end
	end
end

---Poll loop.
local function pollLoop()
	while running do
		local ok, err = pcall(step)
		if not ok then
			analysing = false
			warn("[ChessDuels] " .. tostring(err))
		end
		task.wait(POLL_INTERVAL)
	end
end

---Return a safe GUI parent.
---@return Instance
local function getGuiParent()
	if gethui then
		local ok, hui = pcall(gethui)
		if ok and hui then return hui end
	end
	return localPlayer:WaitForChild("PlayerGui")
end

---Build the native GUI.
function ChessDuels.buildGui()
	local screenGui = Instance.new("ScreenGui")
	screenGui.Name = "ChessDuels_Menu"
	screenGui.ResetOnSpawn = false
	screenGui.Parent = getGuiParent()
	guiRoot = screenGui

	local frame = Instance.new("Frame")
	frame.Size = UDim2.fromOffset(270, 0)
	frame.AutomaticSize = Enum.AutomaticSize.Y
	frame.Position = UDim2.fromOffset(25, 100)
	frame.BackgroundColor3 = Color3.fromRGB(18, 20, 24)
	frame.BorderSizePixel = 0
	frame.Parent = screenGui

	local stroke = Instance.new("UIStroke")
	stroke.Color = Color3.fromRGB(50, 56, 68)
	stroke.Parent = frame

	local corner = Instance.new("UICorner")
	corner.CornerRadius = UDim.new(0, 8)
	corner.Parent = frame

	local padding = Instance.new("UIPadding")
	padding.PaddingTop = UDim.new(0, 10)
	padding.PaddingBottom = UDim.new(0, 10)
	padding.PaddingLeft = UDim.new(0, 10)
	padding.PaddingRight = UDim.new(0, 10)
	padding.Parent = frame

	local layout = Instance.new("UIListLayout")
	layout.Padding = UDim.new(0, 4)
	layout.SortOrder = Enum.SortOrder.LayoutOrder
	layout.Parent = frame

	local order = 0

	local function makeButton(text)
		order += 1
		local button = Instance.new("TextButton")
		button.LayoutOrder = order
		button.Size = UDim2.new(1, 0, 0, 26)
		button.BackgroundColor3 = Color3.fromRGB(34, 38, 44)
		button.BorderSizePixel = 0
		button.TextColor3 = Color3.fromRGB(230, 230, 230)
		button.Font = Enum.Font.GothamMedium
		button.TextSize = 12
		button.Text = text
		button.Parent = frame

		local btnCorner = Instance.new("UICorner")
		btnCorner.CornerRadius = UDim.new(0, 4)
		btnCorner.Parent = button
		return button
	end

	local function makeLabel(text, size)
		order += 1
		local label = Instance.new("TextLabel")
		label.LayoutOrder = order
		label.Size = UDim2.new(1, 0, 0, size or 18)
		label.BackgroundTransparency = 1
		label.TextColor3 = Color3.fromRGB(160, 170, 185)
		label.Font = Enum.Font.GothamBold
		label.TextSize = 11
		label.TextXAlignment = Enum.TextXAlignment.Left
		label.Text = text
		label.Parent = frame
		return label
	end

	local function addToggle(text, name)
		local button = makeButton("")
		local function refresh()
			local on = flags[name]
			button.Text = text .. ": " .. (on and "ON" or "OFF")
			button.BackgroundColor3 = on and Color3.fromRGB(35, 140, 75) or Color3.fromRGB(34, 38, 44)
		end
		button.MouseButton1Click:Connect(function()
			flags[name] = not flags[name]
			refresh()
		end)
		refresh()
	end

	local function addCycler(text, options, getIndex, setIndex, suffix)
		local button = makeButton("")
		local function refresh()
			button.Text = text .. ": " .. tostring(options[getIndex()]) .. (suffix or "")
		end
		button.MouseButton1Click:Connect(function()
			setIndex(getIndex() % #options + 1)
			refresh()
		end)
		refresh()
	end

	makeLabel("CHESS DUELS (OP) | RightShift").TextColor3 = Color3.new(1, 1, 1)

	statusLabel = makeLabel("Waiting for a game...")
	hintLabel = makeLabel("Best: -", 22)
	hintLabel.TextColor3 = Color3.fromRGB(120, 255, 160)
	hintLabel.TextSize = 14

	makeLabel("ENGINE")
	addToggle("Auto-Play Best Move", "autoPlay")
	addCycler("Search Depth", DEPTH_OPTIONS, function() return depthIndex end, function(v) depthIndex = v end)
	addCycler("Think Time", TIME_OPTIONS, function() return timeIndex end, function(v) timeIndex = v end, "s")
	addCycler("Move Delay", DELAY_OPTIONS, function() return delayIndex end, function(v) delayIndex = v end, "s")

	makeButton("Play Best Move Now").MouseButton1Click:Connect(function()
		if suggestion then playMove(suggestion) end
	end)

	makeLabel("MATCH")
	addToggle("Auto Rematch", "autoRematch")
	addToggle("Auto Claim Rewards", "autoClaim")
	makeButton("Resign").MouseButton1Click:Connect(function()
		if actionRemote then actionRemote:FireServer("resign") end
	end)

	makeLabel("UTILITY")
	addToggle("Anti-AFK", "antiAfk")
	makeButton("Detach / Unload").MouseButton1Click:Connect(ChessDuels.detach)

	local dragging, dragStart, startPosition = false, nil, nil

	table.insert(connections, frame.InputBegan:Connect(function(input)
		if input.UserInputType ~= Enum.UserInputType.MouseButton1 then return end
		dragging = true
		dragStart = input.Position
		startPosition = frame.Position
	end))

	table.insert(connections, userInputService.InputChanged:Connect(function(input)
		if not dragging or input.UserInputType ~= Enum.UserInputType.MouseMovement then return end
		local delta = input.Position - dragStart
		frame.Position = UDim2.new(startPosition.X.Scale, startPosition.X.Offset + delta.X, startPosition.Y.Scale, startPosition.Y.Offset + delta.Y)
	end))

	table.insert(connections, userInputService.InputEnded:Connect(function(input)
		if input.UserInputType == Enum.UserInputType.MouseButton1 then dragging = false end
	end))

	table.insert(connections, userInputService.InputBegan:Connect(function(input)
		if input.KeyCode == Enum.KeyCode.RightShift then
			frame.Visible = not frame.Visible
		end
	end))
end

---Clean up everything.
function ChessDuels.detach()
	running = false
	for _, connection in ipairs(connections) do connection:Disconnect() end
	table.clear(connections)
	if guiRoot then guiRoot:Destroy() guiRoot = nil end
	globalEnv.ChessDuels = nil
	warn("[ChessDuels] Detached.")
end

---Initialize.
function ChessDuels.init()
	loadGame()
	if not (Engine and Bot and actionRemote) then
		error("Chess modules or remotes not found")
	end

	findCurrentGetter()

	-- Capture every game payload the server pushes.
	table.insert(connections, updateRemote.OnClientEvent:Connect(function(payload)
		if type(payload) == "table" and payload.state and payload.you ~= nil then
			lastGame = payload
		end
	end))

	table.insert(connections, localPlayer.Idled:Connect(function()
		if not flags.antiAfk then return end
		virtualUser:CaptureController()
		virtualUser:ClickButton2(Vector2.zero)
	end))

	ChessDuels.buildGui()
	task.spawn(pollLoop)
	warn("[ChessDuels] Loaded. Press RightShift to hide/show GUI.")
end

if globalEnv.ChessDuels then globalEnv.ChessDuels.detach() end
globalEnv.ChessDuels = ChessDuels

---@param err string
local function onInitializeError(err)
	warn("Failed to initialize.")
	warn(err)
	warn(debug.traceback())
	ChessDuels.detach()
end

xpcall(ChessDuels.init, onInitializeError)