local options = {
    reverse_projection = false,
    hpbar = {
        bg = 0x13131355,
        fg = 0xef787878,
        txt = 0xffffffff
    }
}

local function entityBox(ent)
    local cube = canvas3d.addBox(ent.x - 0.25, ent.y - 0.25, ent.z - 0.25)
    local hpbar = canvas3d.addFrame({ ent.x - 0.25, ent.y + 0.25, ent.z - 0.25 })

    cube.setAlpha(0x20)
    cube.setDepthTested(false)
    hpbar.setDepthTested(false)

    local hp_rect_bg, hp_rect_fg
    if ent.health ~= nil then
        hp_rect_bg = hpbar.addRectangle(0, 0, 100, 15, options.hpbar.bg)
        hp_rect_fg = hpbar.addRectangle(0, 0, 0, 15, options.hpbar.fg)
    end
    local hp_txt = hpbar.addText({ 0, 2 }, ent.name, options.hpbar.txt)

    return {
        _cube = cube,
        _hpbar = hpbar,
        _hp_rect_bg = hp_rect_bg,
        _hp_rect_fg = hp_rect_fg,
        _hp_txt = hp_txt,
        update = function(self, entity)
            self._cube.setPosition(entity.x - 0.25, entity.y - 0.25, entity.z - 0.25)
            self._hpbar.setPosition(entity.x, entity.y + 0.5, entity.z)
            if self._hp_rect_fg ~= nil then
                self._hp_rect_fg.setSize(100 * entity.health / entity.maxHealth, 15)
            end
            if entity.health ~= nil then
                self._hp_txt.setText(string.format("%s (%.1f/%.1f)", entity.name, entity.health, entity.maxHealth))
            else
                self._hp_txt.setText(string.format("%s", entity.name))
            end
        end,
        destroy = function(self)
            self._cube.remove()
            self._hpbar.remove()
        end
    }
end

return function()
    local cache = {}
    while _G._running do
        for uuid in table.keys(cache) do
            if surroundings.entitiesByUUID[uuid] == nil then
                cache[uuid]:destroy()
                cache[uuid] = nil
            end
        end

        for uuid, entity in pairs(surroundings.entitiesByUUID) do
            if uuid == player.id then
                -- nothing
            elseif cache[uuid] == nil then
                cache[uuid] = entityBox(entity)
            else
                cache[uuid]:update(entity)
            end
        end
        os.sleep(0.05)
    end

    for uuid in table.keys(cache) do
        cache[uuid]:destroy()
    end
end