local InitialDelay, RegenTimers, PreviousHealth, RegenAmount = 3, {}, {}, {
--	[HP Band (%)] = HP/s
	[0] = -0,
	[5] = 0.85,
	[10] = 1.60,
	[15] = 2.20,
	[20] = 2.65,
	[25] = 3.00,
	[30] = 3.25,
	[35] = 3.40,
	[40] = 3.45,
	[45] = 3.40,
	[50] = 3.25,
	[55] = 3.00,
	[60] = 2.70,
	[65] = 2.35,
	[70] = 2.00,
	[75] = 1.65,
	[80] = 1.35,
	[85] = 1.10,
	[90] = 0.75,
	[95] = 0.40,
	[100] = 1,
}

local GetRegenPercent do
	local sorted_amounts = {} do
		for k, v in pairs(RegenAmount) do
			table.insert(sorted_amounts, {k / 100, v})
		end

		table.sort(sorted_amounts, function(a, b)
			return a[1] < b[1]
		end)
	end

	function GetRegenPercent(health_frac)
		for i, v in ipairs(sorted_amounts) do
			if health_frac < v[1] then
				return v[2]
			end
		end

		return 0
	end
end

hook.Add("PlayerTick", "Health Regen", function(ply)
	local regen_timer = RegenTimers[ply]
	if not regen_timer then
		regen_timer = util.Timer()
		RegenTimers[ply] = regen_timer
	end

	local health = ply:Health()
	local max_health = ply:GetMaxHealth()
	local health_frac = health / max_health

	if regen_timer:Started() and (health_frac <= 0 or health_frac >= 1) then
		regen_timer:Reset()
	elseif health_frac > 0 and health_frac < 1 then
		if (PreviousHealth[ply] or health) > health then
			regen_timer:Start(InitialDelay)
		end

		if regen_timer:Elapsed() then
			regen_timer:Start(1 / GetRegenPercent(health_frac))
			ply:SetHealth(math.min(max_health, health + 1))
		end
	end

	PreviousHealth[ply] = health
end)