Crosshair spread indicator code

crosshair.lua

crosshair = {}

function crosshair:set_meta(meta)
    return setmetatable(self, {__index = function(self, index)
        if crosshair[index] ~= nil then
            return crosshair[index]
        end
        if meta[index] ~= nil then
            return meta[index]
        end
        return rawget(self, index)
    end})
end

function crosshair.new(meta, player)
    return crosshair.set_meta({player = player}, meta)
end

local function xy(x)
    return {x = x, y = x}
end

local function calculate_position(direction, spread)
    return modlib.vector.add(xy(0.5), modlib.vector.multiply_scalar(direction, spread / 2))
end

function crosshair:add(spread)
    spread = spread or 0
    local type, indicator_type, player = self.type, self.indicator_type, self.player
    if type ~= "default" then
        player:hud_set_flags{crosshair = false}
        self.crosshair = player:hud_add{
            hud_elem_type = "image",
            position = xy(0.5),
            alignment = xy(0),
            scale = xy(1),
            text = self.texture,
            name = "adv_weapons_crosshair",
            z_index = 1
        }
    end
    if indicator_type == "scale" then
        self.scale = player:hud_add{
            hud_elem_type = "image",
            position = xy(0.5),
            alignment = xy(0),
            scale = xy(-100 * spread),
            text = assert(self.indicator_texture),
            name = "adv_weapons_crosshair_scale",
            z_index = 0
        }
    elseif indicator_type == "axes" then
        self.axes = {}
        for rotation = 0, 270, 90 do
            local radians = math.rad(rotation)
            local direction = {x = modlib.number.round(math.cos(radians)), y = modlib.number.round(-math.sin(radians))}
            self.axes[player:hud_add{
                hud_elem_type = "image",
                position = calculate_position(direction, spread),
                -- TODO fix edge case of spread > 0.9... with indicators not on screen anymore
                offset = modlib.vector.multiply_scalar(direction, (self.size or 0) / 2),
                alignment = direction,
                scale = xy(1),
                text = assert(self.indicator_texture) .. "^[transformR" .. rotation,
                name = "adv_weapons_crosshair_axis_" .. rotation,
                z_index = 2
            }] = direction
        end
    end
end

function crosshair:update(spread)
    assert(spread >= 0 and spread <= 1)
    local indicator_type, player = self.indicator_type, self.player
    if indicator_type == "scale" then
        player:hud_change(self.scale, "scale", xy(-100 * spread))
    elseif indicator_type == "axes" then
        for id, direction in pairs(self.axes) do
            player:hud_change(id, "position", calculate_position(direction, spread))
        end
    end
end

function crosshair:remove()
    local type, indicator_type, player = self.type, self.indicator_type, self.player
    if type ~= "default" then
        player:hud_remove(self.crosshair)
        player:hud_set_flags{crosshair = true}
    end
    if indicator_type == "scale" then
        player:hud_remove(self.scale)
    elseif indicator_type == "axes" then
        for id in pairs(self.axes) do
            player:hud_remove(id)
        end
    end
end