feat: replaced python scripts with lua

- using lua scripts where we previously used python for lower resource
  consumption

1 files changed, 826 insertions, 0 deletions

diff --git a/modules/desktop/eww/system-stats.lua b/modules/desktop/eww/system-stats.lua
new file mode 100644
index 0000000..514647f
--- /dev/null
+++ b/modules/desktop/eww/system-stats.lua
@@ -0,0 +1,826 @@
+#!/usr/bin/env luajit
+-- system-stats: emit {cpu, ram, net, sound} as JSON.
+--
+-- Single-threaded LuaJIT port of the original Python script. Instead of
+-- OS threads, a single supervisor loop schedules the periodic cpu/ram and
+-- sound refreshes and polls an inotifywait child for link-state changes.
+local cjson = require("cjson")
+local posix = require("posix")
+local unistd = require("posix.unistd")
+local gettimeofday = require("posix.sys.time").gettimeofday
+local poll = require("posix.poll").poll
+
+local NULL = cjson.null
+
+local function nonnull(v)
+  if v == nil then
+    return NULL
+  end
+  return v
+end
+
+-- Throughput deltas between cpu/ram refreshes
+local net_last_time = nil
+local net_last_bytes = {}
+
+-- ------------------------------------------------ time
+local function mono_sec()
+  local g = gettimeofday()
+  return g.tv_sec + g.tv_usec / 1e6
+end
+
+-- ------------------------------------------------ process helpers
+local function sh(cmd)
+  local h = io.popen(cmd)
+  if not h then
+    return nil
+  end
+  local out = h:read("*a")
+  h:close()
+  return out
+end
+
+-- ------------------------------------------------ formatting
+local function format_rate(bytes_per_sec)
+  if bytes_per_sec == nil or bytes_per_sec < 0 then
+    return "0B"
+  end
+  local units = { "B", "K", "M", "G", "T" }
+  local val = bytes_per_sec
+  local unit_idx = 1
+  while val >= 1024 and unit_idx < #units do
+    val = val / 1024.0
+    unit_idx = unit_idx + 1
+  end
+  local unit = units[unit_idx]
+  if val >= 100 or unit == "B" then
+    return string.format("%d%s", math.floor(val + 0.5), unit)
+  end
+  return string.format("%.1f%s", val, unit)
+end
+
+local function format_bytes(kib)
+  if kib == nil or kib < 0 then
+    return "0B"
+  end
+  local units = { "K", "M", "G", "T" }
+  local val = kib
+  local unit_idx = 1
+  while val >= 1024 and unit_idx < #units do
+    val = val / 1024.0
+    unit_idx = unit_idx + 1
+  end
+  local unit = units[unit_idx]
+  if val >= 100 or unit == "K" then
+    return string.format("%d%s", math.floor(val + 0.5), unit)
+  end
+  return string.format("%.1f%s", val, unit)
+end
+
+-- ------------------------------------------------ /proc readers
+local function read_cpu_times()
+  local times = {}
+  local f = io.open("/proc/stat")
+  if not f then
+    return times
+  end
+  for line in f:lines() do
+    if not line:match("^cpu") then
+      break
+    end
+    local parts = {}
+    for w in line:gmatch("%S+") do
+      parts[#parts + 1] = w
+    end
+    local label = parts[1]
+    local total, idle = 0, 0
+    for j = 2, #parts do
+      local v = tonumber(parts[j]) or 0
+      total = total + v
+      if j == 4 or j == 5 then
+        idle = idle + v
+      end
+    end
+    times[label] = { idle = idle, total = total }
+  end
+  f:close()
+  return times
+end
+
+local function get_cpu_freq_mhz()
+  local count, sum, ok = 0, 0, false
+  local f = io.open("/proc/cpuinfo")
+  if not f then
+    return nil
+  end
+  for line in f:lines() do
+    local low = line:lower()
+    if low:find("^cpu mhz") then
+      local val = line:match(":%s*([%d%.]+)")
+      if val then
+        sum = sum + tonumber(val)
+        count = count + 1
+        ok = true
+      end
+    end
+  end
+  f:close()
+  if not ok then
+    return nil
+  end
+  return math.floor(sum / count + 0.5)
+end
+
+local function get_load_avg()
+  local f = io.open("/proc/loadavg")
+  if not f then
+    return nil
+  end
+  local line = f:read("*l")
+  f:close()
+  if not line then
+    return nil
+  end
+  local a, b, c = line:match("^([%d%.]+)%s+([%d%.]+)%s+([%d%.]+)")
+  if not a then
+    return nil
+  end
+  return { tonumber(a), tonumber(b), tonumber(c) }
+end
+
+local function get_ram_speed_mhz()
+  local out = sh("dmidecode -t 17 2>/dev/null")
+  if not out then
+    return nil
+  end
+  local speeds = {}
+  for line in out:gmatch("[^\n]+") do
+    local s = line:match("^%s*Configured Memory Speed:%s*(.-)%s*$")
+    if s then
+      local low = s:lower()
+      if low ~= "unknown" and low ~= "no module installed" then
+        local num = s:match("^(%d+)")
+        if num then
+          speeds[#speeds + 1] = tonumber(num)
+        end
+      end
+    end
+  end
+  if #speeds == 0 then
+    for line in out:gmatch("[^\n]+") do
+      local s = line:match("^%s*Speed:%s*(.-)%s*$")
+      if s then
+        local low = s:lower()
+        if low ~= "unknown" and low ~= "no module installed" then
+          local num = s:match("^(%d+)")
+          if num then
+            speeds[#speeds + 1] = tonumber(num)
+          end
+        end
+      end
+    end
+  end
+  if #speeds == 0 then
+    return nil
+  end
+  local mx = speeds[1]
+  for j = 2, #speeds do
+    if speeds[j] > mx then
+      mx = speeds[j]
+    end
+  end
+  return mx
+end
+
+-- ------------------------------------------------ network helpers
+local function get_all_default_ifaces()
+  local out = sh("ip -o route show default 2>/dev/null")
+  if not out then
+    return {}
+  end
+  local ifaces = {}
+  local seen = {}
+  for line in out:gmatch("[^\n]+") do
+    local iface = line:match("dev (%S+)")
+    if iface and not seen[iface] then
+      seen[iface] = true
+      ifaces[#ifaces + 1] = iface
+    end
+  end
+  return ifaces
+end
+
+local function get_iface_ip(iface)
+  if not iface or iface == "" then
+    return nil
+  end
+  local out = sh("ip -o -4 addr show dev " .. iface .. " 2>/dev/null")
+  if not out then
+    return nil
+  end
+  local ip = out:match("inet (%d+%.%d+%.%d+%.%d+)")
+  return ip
+end
+
+local function get_operstate(iface)
+  local f = io.open("/sys/class/net/" .. iface .. "/operstate")
+  if not f then
+    return "down"
+  end
+  local s = f:read("*l")
+  f:close()
+  return (s and s:match("^%s*(.-)%s*$")) or "down"
+end
+
+local function get_iface_type(iface)
+  if posix.stat("/sys/class/net/" .. iface .. "/wireless") then
+    return "wifi"
+  end
+  local st = posix.stat("/sys/class/net/" .. iface .. "/bridge")
+  if st and st.type == "directory" then
+    return "bridge"
+  end
+  if posix.stat("/sys/class/net/" .. iface .. "/tun_flags") then
+    return "tun"
+  end
+  return "ethernet"
+end
+
+local function get_speed_mbps(iface, iftype)
+  if iftype == "ethernet" then
+    local f = io.open("/sys/class/net/" .. iface .. "/speed")
+    if f then
+      local s = f:read("*l")
+      f:close()
+      local num = s and tonumber(s:match("^%s*(-?%d+)"))
+      if num and num >= 0 then
+        return num
+      end
+    end
+    return nil
+  end
+  if iftype == "wifi" then
+    local out = sh("iw dev " .. iface .. " link 2>/dev/null")
+    if not out then
+      return nil
+    end
+    for line in out:gmatch("[^\n]+") do
+      local l = line:match("^%s*tx bitrate:%s*(.-)%s*$")
+      if l then
+        local num = tonumber(l:match("^([%d%.]+)"))
+        if num then
+          return math.floor(num + 0.5)
+        end
+      end
+    end
+  end
+  return nil
+end
+
+local function get_iface_io_bytes(iface)
+  if not iface or iface == "" then
+    return nil, nil
+  end
+  local f = io.open("/proc/net/dev")
+  if not f then
+    return nil, nil
+  end
+  local rx, tx
+  for line in f:lines() do
+    local colon = line:find(":")
+    if colon then
+      local dev = line:sub(1, colon - 1):match("^%s*(.-)%s*$")
+      if dev == iface then
+        local fields = {}
+        for w in line:sub(colon + 1):gmatch("%S+") do
+          fields[#fields + 1] = w
+        end
+        rx = tonumber(fields[1]) or nil
+        tx = tonumber(fields[9]) or nil
+        break
+      end
+    end
+  end
+  f:close()
+  return rx, tx
+end
+
+-- ------------------------------------------------ tooltips
+local function build_cpu_tooltip(overall_pct, per_core_list, freq_mhz, load_avg)
+  local lines = { string.format("CPU: %d%%", overall_pct) }
+  if freq_mhz ~= nil then
+    lines[#lines + 1] = string.format("Freq: %d MHz", freq_mhz)
+  end
+  if load_avg ~= nil then
+    lines[#lines + 1] = string.format(
+      "Load: %.2f %.2f %.2f",
+      load_avg[1],
+      load_avg[2],
+      load_avg[3]
+    )
+  end
+  for i, pct in ipairs(per_core_list) do
+    lines[#lines + 1] = string.format("Core %d: %d%%", i - 1, pct)
+  end
+  return table.concat(lines, "\n")
+end
+
+local function build_ram_tooltip(ram_pct, used, total, available, swap_pct, swap_used, swap_total, speed_mhz)
+  local lines = { string.format("RAM: %d%% (%s / %s)", ram_pct, used, total) }
+  lines[#lines + 1] = "Available: " .. available
+  lines[#lines + 1] = string.format("Swap: %d%% (%s / %s)", swap_pct, swap_used, swap_total)
+  if speed_mhz ~= nil then
+    lines[#lines + 1] = string.format("Speed: %d MHz", speed_mhz)
+  else
+    lines[#lines + 1] = "Speed: unknown"
+  end
+  return table.concat(lines, "\n")
+end
+
+local function build_sound_tooltip(percent, mute, sink)
+  local vol = tostring(percent) .. "%"
+  local lines = {}
+  if mute then
+    lines[#lines + 1] = string.format("Muted (%s)", vol)
+  else
+    lines[#lines + 1] = "Volume: " .. vol
+  end
+  if sink then
+    lines[#lines + 1] = "Sink: " .. sink
+  end
+  return table.concat(lines, "\n")
+end
+
+-- ------------------------------------------------ state collectors
+-- get_all_default_ifaces (`ip route`), get_iface_ip (`ip addr`), and the
+-- wifi branch of get_speed_mbps (`iw dev link`) each spawn a subprocess.
+-- Those three rarely change second-to-second, so they're only re-probed
+-- every NET_SLOW_REFRESH_INTERVAL instead of on every check_net_status()
+-- call. operstate, iface type, ethernet speed, and rx/tx byte counters are
+-- all plain sysfs/proc reads with no subprocess involved, so they stay
+-- live on every call regardless -- rx/tx throughput in particular needs
+-- to stay frequent to be useful.
+local NET_SLOW_REFRESH_INTERVAL = 15.0
+local net_slow_ifaces = nil
+local net_slow_ip = {}
+local net_slow_wifi_speed = {}
+local net_slow_expires_at = 0
+
+local function refresh_net_slow_cache(now)
+  net_slow_ifaces = get_all_default_ifaces()
+  local ip_cache, wifi_speed_cache = {}, {}
+  for _, iface in ipairs(net_slow_ifaces) do
+    ip_cache[iface] = get_iface_ip(iface)
+    if get_iface_type(iface) == "wifi" then
+      wifi_speed_cache[iface] = get_speed_mbps(iface, "wifi")
+    end
+  end
+  net_slow_ip = ip_cache
+  net_slow_wifi_speed = wifi_speed_cache
+  net_slow_expires_at = now + NET_SLOW_REFRESH_INTERVAL
+end
+
+-- Pass force=true to bypass the timer and re-probe immediately (used for
+-- the initial call and whenever inotify reports an actual link change).
+local function check_net_status(force)
+  local now = mono_sec()
+  if force or net_slow_ifaces == nil or now >= net_slow_expires_at then
+    refresh_net_slow_cache(now)
+  end
+
+  local ifaces = net_slow_ifaces
+
+  if #ifaces == 0 then
+    return { status = "down", tooltip = "Network Offline", routes = {} }
+  end
+
+  local routes = {}
+  local any_up = false
+  local any_limited = false
+
+  for _, iface in ipairs(ifaces) do
+    local oper = get_operstate(iface)
+    if oper == "up" then
+      any_up = true
+    elseif oper == "dormant" then
+      any_limited = true
+    end
+
+    local iftype = get_iface_type(iface)
+    local ip_addr = net_slow_ip[iface]
+    local speed
+    if oper == "up" then
+      if iftype == "wifi" then
+        speed = net_slow_wifi_speed[iface]
+      else
+        -- Ethernet speed is a plain sysfs read (no subprocess), so it
+        -- stays live every call rather than going through the slow cache.
+        speed = get_speed_mbps(iface, iftype)
+      end
+    end
+
+    local rx_bytes, tx_bytes = get_iface_io_bytes(iface)
+    local rx_str, tx_str = nil, nil
+
+    if oper ~= "down" and rx_bytes ~= nil and tx_bytes ~= nil then
+      if net_last_time ~= nil and net_last_bytes[iface] then
+        local dt = now - net_last_time
+        if dt > 0 then
+          local prev = net_last_bytes[iface]
+          local rx_rate = math.max(0, (rx_bytes - prev[1]) / dt)
+          local tx_rate = math.max(0, (tx_bytes - prev[2]) / dt)
+          rx_str = format_rate(rx_rate)
+          tx_str = format_rate(tx_rate)
+        end
+      end
+      net_last_bytes[iface] = { rx_bytes, tx_bytes }
+    else
+      rx_str, tx_str = nil, nil
+    end
+
+    routes[#routes + 1] = {
+      iface = iface,
+      ip = nonnull(ip_addr),
+      ["type"] = iftype,
+      speed = nonnull(speed),
+      rx = nonnull(rx_str),
+      tx = nonnull(tx_str),
+    }
+  end
+
+  net_last_time = now
+
+  local overall_status
+  if any_up then
+    overall_status = "up"
+  elseif any_limited then
+    overall_status = "limited"
+  else
+    overall_status = "down"
+  end
+
+  local tooltip
+  if overall_status == "down" or #routes == 0 then
+    tooltip = "Network Offline"
+  else
+    local first = routes[1]
+    local rx = first.rx
+    local tx = first.tx
+    if rx == NULL or rx == nil then
+      rx = "-"
+    end
+    if tx == NULL or tx == nil then
+      tx = "-"
+    end
+    tooltip = string.format("\u{2193}%s \u{2191}%s", rx, tx)
+    for _, r in ipairs(routes) do
+      local iface = r.iface or "unknown"
+      local ip = r.ip
+      if ip == NULL or ip == nil then
+        ip = "no ip"
+      end
+      tooltip = tooltip .. "\n" .. iface .. ": " .. ip
+    end
+  end
+
+  return { status = overall_status, tooltip = tooltip, routes = routes }
+end
+
+local function get_sound_state()
+  local function pamixer_flag(flag)
+    local out = sh("pamixer " .. flag .. " 2>/dev/null")
+    if not out then
+      return nil
+    end
+    return out:gsub("^%s+", ""):gsub("%s+$", "")
+  end
+
+  local percent, mute, sink = nil, nil, nil
+
+  local pout = pamixer_flag("--get-volume")
+  if pout then
+    local num = tonumber(pout:match("^(%-?%d+)"))
+    if num then
+      percent = math.max(0, math.min(100, num))
+    end
+  end
+
+  local mout = pamixer_flag("--get-mute")
+  if mout ~= nil then
+    mute = (mout:lower() == "true")
+  end
+
+  local sout = pamixer_flag("--get-default-sink")
+  if sout then
+    -- Output ends with: INDEX "name" "description"
+    local names = {}
+    for q in sout:gmatch('"([^"]*)"') do
+      names[#names + 1] = q
+    end
+    if #names > 0 then
+      sink = names[#names]
+    else
+      local last = sout:match("([^\n]+)$")
+      sink = last or sout
+    end
+  end
+
+  local vol = tostring(percent) .. "%"
+  local supp = {}
+  if mute then
+    supp[#supp + 1] = string.format("Muted (%s)", vol)
+  else
+    supp[#supp + 1] = "Volume: " .. vol
+  end
+  if sink then
+    supp[#supp + 1] = "Sink: " .. sink
+  end
+
+  return {
+    percent = nonnull(percent),
+    mute = mute or false,
+    sink = nonnull(sink),
+    tooltip = table.concat(supp, "\n"),
+  }
+end
+
+-- ------------------------------------------------ state + emit
+local state = {
+  cpu = {
+    percent = 0,
+    per_core = {},
+    freq_mhz = NULL,
+    load_avg = NULL,
+    tooltip = "CPU: 0%",
+  },
+  ram = {
+    percent = 0,
+    used = "0B",
+    total = "0B",
+    available = "0B",
+    swap_percent = 0,
+    swap_used = "0B",
+    swap_total = "0B",
+    speed_mhz = NULL,
+    tooltip = "RAM: 0%",
+  },
+  net = {
+    status = "down",
+    tooltip = "Network Offline",
+    routes = {},
+  },
+  sound = {
+    percent = NULL,
+    mute = false,
+    sink = NULL,
+    tooltip = "Volume: unknown",
+  },
+}
+
+local function emit()
+  io.write(cjson.encode(state) .. "\n")
+  io.stdout:flush()
+end
+
+local CPU_INTERVAL = 2.0
+local SOUND_INTERVAL = 1.0
+local INOTIFY_RETRY_INTERVAL = 30.0 -- backoff between (re)spawn attempts
+
+-- ------------------------------------------------ inotifywait child
+-- Returns pid, read_fd on success, or nil, nil if the fork/exec setup
+-- itself failed outright (pipe/fork syscall failure, not inotifywait
+-- failing later).
+local function spawn_inotify()
+  local r, w = posix.pipe()
+  if not r or not w then
+    return nil, nil
+  end
+  local pid = posix.fork()
+  if pid == nil then
+    posix.close(r)
+    posix.close(w)
+    return nil, nil
+  end
+  if pid == 0 then
+    posix.dup2(w, unistd.STDOUT_FILENO)
+    local nullfd = posix.open("/dev/null", posix.O_WRONLY)
+    if nullfd then
+      posix.dup2(nullfd, unistd.STDERR_FILENO)
+      posix.close(nullfd)
+    end
+    posix.close(r)
+    posix.close(w)
+    local ok, err = posix.execp(
+      "inotifywait",
+      { "inotifywait", "-m", "-e", "modify", "/run/systemd/netif/state" }
+    )
+    if not ok then
+      io.stderr:write("inotifywait: " .. tostring(err) .. "\n")
+      os.exit(1)
+    end
+  end
+  posix.close(w)
+  return pid, r
+end
+
+-- ------------------------------------------------ main loop
+local function main()
+  local ram_speed_mhz = get_ram_speed_mhz()
+
+  -- seed global state copy with all keys (null defaults)
+  local prev_cpu_times = read_cpu_times()
+
+  -- initial emission
+  state.net = check_net_status(true)
+  emit()
+
+  -- net_fd is nil whenever we have no live inotifywait child to poll on.
+  -- We (re)spawn opportunistically, but never more often than
+  -- INOTIFY_RETRY_INTERVAL, so a persistently-failing child (missing
+  -- binary, watched path doesn't exist, permissions, ...) can never turn
+  -- into a tight loop -- it just falls back to picking up network
+  -- changes on the regular CPU_INTERVAL cadence below instead.
+  local inotify_pid = nil
+  local net_fd = nil
+  local next_inotify_attempt = 0 -- attempt immediately on first iteration
+
+  local next_cpu = mono_sec() + CPU_INTERVAL
+  local next_sound = mono_sec() + SOUND_INTERVAL
+
+  while true do
+    local now = mono_sec()
+
+    if net_fd == nil and now >= next_inotify_attempt then
+      inotify_pid, net_fd = spawn_inotify()
+      -- Whether this attempt succeeded or not, don't try again for a
+      -- while: a child that exits immediately (e.g. because the watched
+      -- path doesn't exist) would otherwise cause an attempt-per-loop
+      -- storm identical to the original bug.
+      next_inotify_attempt = mono_sec() + INOTIFY_RETRY_INTERVAL
+    end
+
+    if now >= next_cpu then
+      local cur_times = read_cpu_times()
+      local overall_pct = 0
+      local per_core = {}
+      for label, cur in pairs(cur_times) do
+        local prev = prev_cpu_times[label] or cur
+        local d_idle = cur.idle - prev.idle
+        local d_total = cur.total - prev.total
+        local pct = 0
+        if d_total > 0 then
+          pct = math.floor((1 - d_idle / d_total) * 100 + 0.5)
+        end
+        if label == "cpu" then
+          overall_pct = pct
+        else
+          per_core[tonumber(label:match("^cpu(.*)$")) or -1] = pct
+        end
+      end
+      prev_cpu_times = cur_times
+
+      local keys = {}
+      for k in pairs(per_core) do
+        keys[#keys + 1] = k
+      end
+      table.sort(keys)
+      local per_core_list = {}
+      for _, k in ipairs(keys) do
+        per_core_list[#per_core_list + 1] = per_core[k]
+      end
+
+      local freq_mhz = get_cpu_freq_mhz()
+      local load_avg = get_load_avg()
+
+      local cpu_state = {
+        percent = overall_pct,
+        per_core = per_core_list,
+        freq_mhz = nonnull(freq_mhz),
+        load_avg = nonnull(load_avg),
+        tooltip = build_cpu_tooltip(overall_pct, per_core_list, freq_mhz, load_avg),
+      }
+
+      -- RAM
+      local meminfo = {}
+      local f = io.open("/proc/meminfo")
+      if f then
+        for line in f:lines() do
+          local k, v = line:match("^([^:]+):%s*(%d+)")
+          if k and v then
+            meminfo[k] = tonumber(v)
+          end
+        end
+        f:close()
+      end
+
+      local total_kb = meminfo.MemTotal or 0
+      local avail_kb = meminfo.MemAvailable or 0
+      local used_kb = math.max(0, total_kb - avail_kb)
+      local ram_pct = 0
+      if total_kb > 0 then
+        ram_pct = math.floor((1 - avail_kb / total_kb) * 100 + 0.5)
+      end
+
+      local swap_total_kb = meminfo.SwapTotal or 0
+      local swap_free_kb = meminfo.SwapFree or 0
+      local swap_used_kb = math.max(0, swap_total_kb - swap_free_kb)
+      local swap_pct = 0
+      if swap_total_kb > 0 then
+        swap_pct = math.floor(swap_used_kb / swap_total_kb * 100 + 0.5)
+      end
+
+      local used_fmt = format_bytes(used_kb)
+      local total_fmt = format_bytes(total_kb)
+      local avail_fmt = format_bytes(avail_kb)
+      local swap_used_fmt = format_bytes(swap_used_kb)
+      local swap_total_fmt = format_bytes(swap_total_kb)
+
+      local ram_state = {
+        percent = ram_pct,
+        used = used_fmt,
+        total = total_fmt,
+        available = avail_fmt,
+        swap_percent = swap_pct,
+        swap_used = swap_used_fmt,
+        swap_total = swap_total_fmt,
+        speed_mhz = nonnull(ram_speed_mhz),
+        tooltip = build_ram_tooltip(
+          ram_pct,
+          used_fmt,
+          total_fmt,
+          avail_fmt,
+          swap_pct,
+          swap_used_fmt,
+          swap_total_fmt,
+          ram_speed_mhz
+        ),
+      }
+
+      state.cpu = cpu_state
+      state.ram = ram_state
+      -- Net status is always refreshed here too, so even with inotify
+      -- permanently unavailable we still pick up link changes within
+      -- CPU_INTERVAL seconds.
+      state.net = check_net_status()
+      emit()
+      next_cpu = mono_sec() + CPU_INTERVAL
+    end
+
+    if now >= next_sound then
+      state.sound = get_sound_state()
+      emit()
+      next_sound = mono_sec() + SOUND_INTERVAL
+    end
+
+    -- Poll inotifywait for link-state changes (timeout in ms). If we
+    -- have no live child right now, still sleep until the next
+    -- scheduled piece of work (or the next respawn attempt) instead of
+    -- busy-looping.
+    local wake_at = math.min(next_cpu, next_sound)
+    if net_fd == nil then
+      wake_at = math.min(wake_at, next_inotify_attempt)
+    end
+    local until_next = wake_at - mono_sec()
+    if until_next < 0 then
+      until_next = 0
+    end
+    local timeout_ms = math.floor(until_next * 1000 + 0.5)
+
+    local fds = {}
+    if net_fd ~= nil then
+      fds[net_fd] = { events = { IN = true } }
+    end
+
+    local nready = poll(fds, timeout_ms)
+    if net_fd ~= nil and nready and nready > 0 then
+      local revents = fds[net_fd].revents
+      if revents and (revents.IN or revents.HUP or revents.ERR) then
+        local data = unistd.read(net_fd, 8192)
+        if data and #data > 0 then
+          -- An actual link-state change: force a full re-probe rather
+          -- than waiting out the slow-refresh timer, since this is
+          -- exactly the moment the cached IP/speed could be stale.
+          state.net = check_net_status(true)
+          emit()
+        else
+          -- Empty read on a "ready" fd means the write end closed, i.e.
+          -- the inotifywait child exited (crashed, watched path missing,
+          -- binary not found, etc). Reap it, drop the fd, and don't
+          -- touch it again until the next backed-off retry -- this is
+          -- the fix for the tight busy-loop: without this branch, poll()
+          -- would report this dead fd as "ready" forever, on every
+          -- single iteration, with an effectively-zero timeout.
+          unistd.close(net_fd)
+          if inotify_pid then
+            pcall(posix.wait, inotify_pid)
+          end
+          net_fd = nil
+          inotify_pid = nil
+          next_inotify_attempt = mono_sec() + INOTIFY_RETRY_INTERVAL
+        end
+      end
+    end
+  end
+end
+
+main()