local module = {}

function module.Main(a1, a3, tooldebug, m)
    local primaryregionpart = Instance.new("Part", game.Lighting) -- make the box that will determine the region3
    primaryregionpart.Transparency = 1
    if tooldebug then primaryregionpart.Transparency = 0.5 end
    primaryregionpart.CanCollide = false
    primaryregionpart.Anchored = true
    primaryregionpart.CastShadow = false
    primaryregionpart.Parent = game.Workspace -- prepare this
    local cam = workspace.CurrentCamera -- make sure our camera is up to date
    local camcf = cam.CFrame -- save this before calculations to prevent bad stuff

    -- documentation for the questionable mental state code below if you want to understand it:
    --[[
    a1, a2, a3, a4 are the corners of the selection gui when the player started and ended holding left mouse button
    r means that it is the ray casted from the camera for that location
    s means that it is the on screen position, aka the vector3 of the vector2 of the camera
    d = distance
    m = midpoint
    p = prime (this means it was farther away)
    tmp = temp, as in it's only going to be used once and i couldn't be asked to make another letter for it
    a letter added on means its one of those things above
    for example
    a123ms would be the midpoint of a1, a2, and a3 at the player's coordinates (the corners of the gui they dragged)
    ]]
    local a2 = Vector2.new(a1.X, a3.Y) -- make a vector2 for a2
    local a4 = Vector2.new(a3.X, a1.Y)
    if tooldebug then print("All points:", a1, a2, a3) end
    local a1r = cam:ScreenPointToRay(a1.X, a1.Y) -- get the thing from lego game
    local a2r = cam:ScreenPointToRay(a2.X, a2.Y)
    local a3r = cam:ScreenPointToRay(a3.X, a3.Y)
    local a4r = cam:ScreenPointToRay(a4.X, a4.Y)
    local a1r = Ray.new(a1r.Origin, a1r.Direction * 0) -- make the rays
    local a2r = Ray.new(a2r.Origin, a2r.Direction * 0)
    local a3r = Ray.new(a3r.Origin, a3r.Direction * 0)
    local a4r = Ray.new(a4r.Origin, a4r.Direction * 0)
    local _, a1s = workspace:FindPartOnRay(a1r, cam) -- get the position, we don't actually care about the part xd
    local _, a2s = workspace:FindPartOnRay(a2r, cam)
    local _, a3s = workspace:FindPartOnRay(a3r, cam)
    local _, a4s = workspace:FindPartOnRay(a4r, cam)
    local a1p = (CFrame.new(a1s, camcf.p) * CFrame.new(0, 0, 300)).p -- get our prime values
    local a2p = (CFrame.new(a2s, camcf.p) * CFrame.new(0, 0, 300)).p
    local a3p = (CFrame.new(a3s, camcf.p) * CFrame.new(0, 0, 300)).p
    local a4p = (CFrame.new(a4s, camcf.p) * CFrame.new(0, 0, 300)).p

    local function makepointparts(x) -- debug function
        print("Creating debug parts.")
        for i, v in pairs(x) do
            local p = Instance.new("Part", game.Workspace)
            p.Anchored = true
            p.CanCollide = false
            p.CastShadow = false
            p.BrickColor = BrickColor.new("Storm blue")
            p.Material = Enum.Material.Neon
            p.Size = Vector3.new(0.05, 0.05, 0.05)
            p.Position = v
            p.Name = "dbgpart"
            if i > 4 then p.Size = Vector3.new(10, 10, 10) end
        end
    end

    local a1234pm = (a1p + a2p + a3p + a4p) / 4
    local a1234sm = (a1s + a2s + a3s + a4s) / 4
    local a1234spm = (a1234pm + a1234sm) / 2
    local a1234dspm = (a1234pm - a1234sm).magnitude
    local a12pd = (a1p - a2p).magnitude -- used to be height
    local a14pd = (a1p - a4p).magnitude -- used to be thick

    local function calcpoints(a1s, a2s, a1p, a2p, mod1, mod2) -- function works in terms of a1 and a2 but really takes any two points
        -- still requries thick and height though
        local removebox = Instance.new("Part") -- make the removebox, and set basic properties
        removebox.Anchored = true
        removebox.CanCollide = false
        removebox.CastShadow = false
        removebox.Transparency = 1
        removebox.BrickColor = BrickColor.new("Really red")
        removebox.Size = Vector3.new(1, 1, 1)
        removebox.Locked = true
        if tooldebug then removebox.Transparency = 0.5 end -- debugging
        removebox.Parent = game.Workspace
        local a12sm = (a1s + a2s) / 2
        local a12pm = (a1p + a2p) / 2 -- get the mid between the two points given
        local a12dpsm = (a12sm - a12pm).magnitude -- get the magnitude between those
        removebox.Size = Vector3.new(a14pd, a12pd, a12dpsm) -- set the size
        local a14pdtmp
        local a12pdtmp
        if mod2 then -- determines what changes to the operation need to be made based off of orientation
            a14pdtmp = a14pd / mod1
            a12pdtmp = 1
        else
            a14pdtmp = 1
            a12pdtmp = a12pd / mod1
        end
        removebox.CFrame = (CFrame.new(a12sm, a12pm) * CFrame.new(a14pdtmp, a12pdtmp, a1234dspm / -2)) -- set the cframe
        return removebox
    end

    local bp1 = calcpoints(a1s, a2s, a1p, a2p, 2, true)
    local bp2 = calcpoints(a2s, a3s, a2p, a3p, -2, false) -- inv
    local bp3 = calcpoints(a3s, a4s, a3p, a4p, -2, true)
    local bp4 = calcpoints(a4s, a1s, a4p, a1p, 2, false) -- inv

    primaryregionpart.Position = a1234spm
    primaryregionpart.Size = Vector3.new(a12pd, a14pd, a1234dspm)
    primaryregionpart.CFrame = CFrame.new(primaryregionpart.Position, a1234pm)

    if tooldebug then makepointparts({a1s, a2s, a3s, a4s, a1p, a2p, a3p, a4p}) end
    return primaryregionpart, bp1, bp2, bp3, bp4
end

return module