feat: implement multidistance rssi->distance model parameter estimation

lib/localiser/web/channels/calibration_channel.ex

@@ -0,0 +1,53 @@
+defmodule Localiser.Web.Channels.CalibrationChannel do
+  use Phoenix.Channel
+
+  alias Localiser.Domain.Sensors
+  alias Localiser.Localisation.Sensor.Server, as: SensorServer
+
+  @impl true
+  def join("calibration:" <> sensor_id, _params, socket) do
+    case Sensors.get_sensor_by_sensor_id(sensor_id) do
+      nil ->
+        {:error, %{reason: "sensor not found"}}
+
+      _sensor ->
+        Phoenix.PubSub.subscribe(Localiser.PubSub, "calibration:#{sensor_id}")
+        state = SensorServer.calibration_state(sensor_id)
+        {:ok, state, assign(socket, :sensor_id, sensor_id)}
+    end
+  end
+
+  @impl true
+  def handle_info({:calibration_mode_entered, _sensor_id, samples_needed}, socket) do
+    push(socket, "mode_entered", %{samples_needed: samples_needed})
+    {:noreply, socket}
+  end
+
+  def handle_info({:stage_started, _sensor_id, distance, completed_count}, socket) do
+    push(socket, "stage_started", %{distance: distance, completed_stages: completed_count})
+    {:noreply, socket}
+  end
+
+  def handle_info({:calibration_reading, _sensor_id, rssi, is_outlier, %{stage: {cur, total}}}, socket) do
+    push(socket, "reading", %{rssi: rssi, outlier: is_outlier, stage_progress: %{current: cur, total: total}})
+    {:noreply, socket}
+  end
+
+  def handle_info({:stage_complete, _sensor_id, distance, readings, mean_rssi}, socket) do
+    rendered = Enum.map(readings, fn {rssi, outlier} -> %{rssi: rssi, outlier: outlier} end)
+    push(socket, "stage_complete", %{distance: distance, readings: rendered, mean_rssi: mean_rssi})
+    {:noreply, socket}
+  end
+
+  def handle_info({:calibration_finished, _sensor_id, rssi_ref, path_loss_exp}, socket) do
+    push(socket, "finished", %{rssi_ref: rssi_ref, path_loss_exp: path_loss_exp})
+    {:noreply, socket}
+  end
+
+  def handle_info({:calibration_cancelled, _sensor_id}, socket) do
+    push(socket, "cancelled", %{})
+    {:noreply, socket}
+  end
+
+  def handle_info(_msg, socket), do: {:noreply, socket}
+end