--!optimize 2
--!native
--!strict

--Weird type hack for allowing more than 1 property to be defined inside a tween
--Couldnt get type packs working
type TweenAnimation<T,U> = {
    [string]: T | U --I hate "any"
}

type ClassConstructor<T,U> = typeof(setmetatable({} :: Constructor_Return_Props<T,U>, {} :: Impl_Constructor))
type Impl_Constructor = {
	__index: Impl_Constructor,
	constructor: Constructor_Fun,
	--Class functions
	Start: <T,U>(self: ClassConstructor<T,U>, PostInstance: Instance?, PostProperties: TweenAnimation<T,U>?, PostTweenSettings: TweenInfo?) -> Tween,
}

type Constructor_Fun = <T,U>(TweenSettings: TweenInfo?, Object: Instance?, PreProperties: TweenAnimation<T,U>?) -> ClassConstructor<T,U>
type Constructor_Return_Props<T,U> = {
	TweenInfo:     TweenInfo?,
	Instance:      Instance?,
	PreProperties: TweenAnimation<T,U>?,
}

export type TweenClass<T,U> = ClassConstructor<T,U>
export type TweenConstructor = Impl_Constructor

local Tween = {} :: Impl_Constructor
Tween.__index = Tween

local TS = game:GetService("TweenService")

function Tween.constructor(TweenSettings, Object, PreProperties)
    return setmetatable({
        TweenInfo     = TweenSettings,
        Instance      = Object,
        PreProperties = PreProperties
    }, Tween)
end

function Tween:Start<T,U>(PostInstance, PostProperties, PostTweenSettings)
    local Props         = self.PreProperties
    local Object        = self.Instance
    local TweenSettings = self.TweenInfo

    if PostProperties then
        if self.PreProperties then
            if Props then
                warn("Tween library: Combining PostProperties and PreProperties together", debug.traceback())
                for tween_prop, tween_value in PostProperties do
                    Props[tween_prop] = tween_value
                end
            end
        else
            Props = PostProperties
        end
    end
    if PostInstance then
        if Object then
            warn("Tween library: Overwriting an already defined animating object old=", Object, "new=", PostInstance, debug.traceback())
        end
        Object = PostInstance
    end
    if PostTweenSettings then
        if TweenSettings then
            warn("Tween library: Overwriting already defined Tween settings", debug.traceback())
        end
        TweenSettings = PostTweenSettings
    end

    local Animation = TS:Create(Object, TweenSettings, Props)
    Animation:Play()

    return Animation
end

return Tween