feat: add percent-based delta option

scripts/ac-power.lua

@@ -3,7 +3,7 @@
 
   Features:
     * Polls `/api/states/<sensor_id>` via curl with a long-lived token and trims the base URL to avoid duplicate slashes.
-    * Debounces HUD spam by only re-rendering when watt deltas exceed `min_delta_watts` or when `force_refresh_interval` elapses.
+    * Debounces HUD spam by only re-rendering when watt deltas exceed `min_delta_watts` (or `min_delta_percent`) or when `force_refresh_interval` elapses.
     * Survives flaky networks with capped exponential backoff, optional HUD error messages, and redraws of the last known value after OSD clears.
 
   Configuration:
@@ -16,6 +16,7 @@ local CONFIG = {
   ha_token = "REPLACE_WITH_LONG_LIVED_TOKEN",
   poll_interval = 3, -- seconds between successful polls
   min_delta_watts = 5, -- only show when change ≥ delta
+  min_delta_percent = 0, -- optional % change relative to last reading
   force_refresh_interval = 30, -- seconds, even if delta small
   display_label = "AC Power",
   units_label = "W",
@@ -123,6 +124,36 @@ local function ensure_poll_timer(delay, fn)
   end)
 end
 
+local function meets_delta_threshold(value)
+  if not value then
+    return false
+  end
+  if not last_watts then
+    return true
+  end
+
+  local delta = math.abs(value - last_watts)
+  if delta >= CONFIG.min_delta_watts then
+    return true
+  end
+
+  if CONFIG.min_delta_percent > 0 then
+    local baseline = math.abs(last_watts)
+    if baseline < 1e-6 then
+      baseline = math.abs(value)
+    end
+    if baseline < 1e-6 then
+      baseline = 1
+    end
+    local percent_delta = (delta / baseline) * 100
+    if percent_delta >= CONFIG.min_delta_percent then
+      return true
+    end
+  end
+
+  return false
+end
+
 local function handle_success(value, payload)
   backoff_failures = 0
   local now = mp.get_time()
@@ -130,8 +161,7 @@ local function handle_success(value, payload)
   local unit = sensor_units(payload)
   local force_due = CONFIG.force_refresh_interval > 0
     and (now - last_display_ts) >= CONFIG.force_refresh_interval
-  local significant_change = value
-    and (not last_watts or math.abs(value - last_watts) >= CONFIG.min_delta_watts)
+  local significant_change = meets_delta_threshold(value)
 
   if significant_change or force_due or last_watts == nil then
     show_value(printable, unit)