add set mode option

pkg/econet/econetclient/client.go

@@ -113,6 +113,53 @@ func (c *Client) Refresh(ctx context.Context) error {
 	return nil
 }
 
+// SetMode changes a device's operating mode. It resolves the normalized mode
+// slug to the device's @MODE enum index and publishes a desired-state message
+// to the EcoNet cloud over ClearBlade's REST publish endpoint (the HTTP
+// equivalent of the app's MQTT publish). The change is applied asynchronously;
+// the new mode is only reflected after a subsequent Refresh.
+func (c *Client) SetMode(ctx context.Context, serial, mode string) error {
+	c.mu.RLock()
+	d, account := c.devices[serial], c.accountID
+	c.mu.RUnlock()
+	if d == nil {
+		return fmt.Errorf("econet: unknown device %q", serial)
+	}
+	idx, ok := d.modeIndex(mode)
+	if !ok {
+		return fmt.Errorf("econet: device %q does not support mode %q (supported: %s)",
+			serial, mode, strings.Join(d.SupportedModes(), ", "))
+	}
+
+	if err := c.ensureAuth(ctx); err != nil {
+		return err
+	}
+
+	desired, err := json.Marshal(map[string]any{
+		"transactionId": transactionID(),
+		"device_name":   d.DeviceID,
+		"serial_number": d.SerialNumber,
+		"@MODE":         idx,
+	})
+	if err != nil {
+		return err
+	}
+	publish := map[string]any{
+		"topic": "user/" + account + "/device/desired",
+		"body":  string(desired),
+		"qos":   1,
+	}
+
+	path := "/message/" + clearBladeSystemKey + "/publish"
+	if err := c.do(ctx, path, c.userToken(), publish, nil); err != nil {
+		c.clearToken() // token may have expired; re-auth next call
+		return fmt.Errorf("econet: set mode: %w", err)
+	}
+	c.log.Info().Str("serial", serial).Str("mode", mode).Int("modeIndex", idx).
+		Msg("econet: published mode change")
+	return nil
+}
+
 func (c *Client) clearToken() {
 	c.mu.Lock()
 	c.token = ""
@@ -274,6 +321,11 @@ func (c *Client) do(ctx context.Context, path, token string, body, out any) erro
 	if resp.StatusCode != http.StatusOK {
 		return fmt.Errorf("HTTP %d: %s", resp.StatusCode, bytes.TrimSpace(raw))
 	}
+	// The publish endpoint replies 200 with an empty (or non-JSON) body; callers
+	// that don't need the response pass out == nil.
+	if out == nil || len(bytes.TrimSpace(raw)) == 0 {
+		return nil
+	}
 	return json.Unmarshal(raw, out)
 }
 
@@ -285,6 +337,12 @@ func (c *Client) userToken() string {
 
 // --- usage helpers -------------------------------------------------------
 
+// transactionID mirrors the identifier the Rheem Android app stamps on each
+// desired-state publish: "ANDROID_" + a local second-resolution timestamp.
+func transactionID() string {
+	return "ANDROID_" + time.Now().Format("2006-01-02T15:04:05")
+}
+
 // dayWindow returns ISO-8601 start/end strings covering the current local day,
 // matching pyeconet's formats: energy includes the timezone offset, water does
 // not (the upstream parser is picky).