local enabled = CreateClientConVar("fpsoptimizer_enable", "1", true)
local distance = CreateClientConVar("fpsoptimizer_distance", "1000", true)

local max_distance = 100

local emptyfunc = function() end

local function StoreHooks(entity)
    entity.__FPSOptimizerOldThink = entity.Think
    --entity.__FPSOptimizerOldDraw = entity.Draw
    --entity.__FPSOptimizerOldDrawTranslucent = entity.DrawTranslucent
end

local function EnableHooks(entity)
    if not entity.__fpsoptimizer_enabled then return end

    entity.__fpsoptimizer_enabled = false

    entity.Think = entity.__FPSOptimizerOldThink
    --entity.Draw = entity.__FPSOptimizerOldDraw
    --entity.DrawTranslucent = entity.__FPSOptimizerOldDrawTranslucent

    entity.__oldnodraw = entity.__nodraw
    entity:SetNoDraw(false)
end

local function DisableHooks(entity)
    if entity.__fpsoptimizer_enabled then return end

    entity.__fpsoptimizer_enabled = true

    StoreHooks(entity)

    entity.Think = emptyfunc
    --entity.Draw = emptyfunc
    --entity.DrawTranslucent = emptyfunc

    entity:SetNoDraw(entity.__oldnodraw or true)
end

_R.Entity.OldDrawModel = _R.Entity.OldDrawModel or _R.Entity.DrawModel

function _R.Entity:DrawModel()
    if not self.__fpsoptimizer_enabled then
        self:OldDrawModel(self)
    end
end

_R.Entity.OldSetNoDraw = _R.Entity.OldSetNoDraw or _R.Entity.SetNoDraw

function _R.Entity:SetNoDraw(bool)
    self.__nodraw = bool
    self:OldSetNoDraw(bool)
end

--[[ cam.OldStart3D2D = cam.OldStart3D2D or cam.Start3D2D
cam.OldEnd3D2D = cam.OldEnd3D2D or cam.End3D2D

function cam.Start3D2D(point, ...)
    if point:Distance(EyePos()) > distance:GetInt() then
        DONT_START3D2D = true
    return end
    cam.Start3D2D(point, ...)
end

function cam.End3D2D()
    if DONT_START3D2D then DONT_START3D2D = false return end
    cam.End3D2D()
end ]]

hook.Add("OnEntityCreated", "FPSOptimizer_OnEntityCreated", function(entity)
    StoreHooks(entity)
end)

-- I could just use the global EyePos(), which is supposed to do this (I think)
-- but it doesn't seem reliable and it jumps to random positions etc
-- And LocalPlayer():EyePos() is where the player's head is
-- So I'll just use this

local eyepos = vector_origin

hook.Add("CalcView", "FPSOptimizer_CalcView", function(_,point)
    eyepos = point
end)

local disabled = false

local function Think()
    if disabled and not enabled:GetBool() then return end

    disabled = false

    for key, entity in pairs(ents.GetAll()) do
        if not entity:IsPlayer() then
            local distant = entity:GetPos():Distance(eyepos)

            if distant > distance:GetInt() then
                DisableHooks(entity)
            elseif distant < distance:GetInt() then
                EnableHooks(entity)
            end
        end
    end

    if not enabled:GetBool() then
        for key, entity in pairs(ents.GetAll()) do
            if not entity:IsPlayer() then
                EnableHooks(entity)
            end
        end
        disabled = true
    end
end

timer.Create("FPSOptimizer", 0.3, 0, Think)