local Vector2D = {
    Zero = {X = 0, Y = 0}
}
function Vector2D.New(x, y)
    return {X = x or 0, Y = y or 0}
end

function Vector2D.Add(a, b)
    return Vector2D.New(a.X + b.X, a.Y + b.Y)
end

function Vector2D.Sub(a, b)
    return Vector2D.New(a.X - b.X, a.Y - b.Y)
end

function Vector2D.Mul(v, s)
    return Vector2D.New(v.X * s, v.Y * s)
end

function Vector2D.Div(v, s)
    return Vector2D.New(v.X / s, v.Y / s)
end

function Vector2D.Magnitude(v)
    return math.sqrt(v.X * v.X + v.Y * v.Y)
end

function Vector2D.Normalize(v)
    local mag = Vector2D.Magnitude(v)
    return mag > 0 and Vector2D.Div(v, mag) or Vector2D.New()
end

function Vector2D.Dot(a, b)
    return a.X * b.X + a.Y * b.Y
end

-- 2D 叉积（返回标量）
function Vector2D.Cross(a, b)
    return a.X * b.Y - a.Y * b.X
end

function Vector2D.ToUnrealEngine3D(vector, z)
    local FVector = import("Vector")
    local new_vector = FVector()
    new_vector.Z = z
    new_vector.X = vector.X
    new_vector.Y = vector.Y
    return new_vector
end

function Vector2D.Equals(a, b, tolerance)
    local tol = tolerance or 0.001
    print(tol, a.X-b.X, a.Y-b.Y)
    return math.abs(a.X - b.X) < tol and math.abs(a.Y - b.Y) < tol
end

return Vector2D