[cervantes] wifi: try to connect to known network before listing (#4462)

Defines new function reconnectOrShowNetworkMenu(), which iterates over
available networks ordered by signal power, and check if we can connect
to saved SSIDs. If we can, then skip network list dialog.

frontend/device/cervantes/device.lua

@@ -160,7 +160,7 @@ function Cervantes:initNetworkManager(NetworkMgr)
     function NetworkMgr:turnOnWifi(complete_callback)
         logger.info("Cervantes: enabling WiFi")
         os.execute("./enable-wifi.sh")
-        self:showNetworkMenu(complete_callback)
+        self:reconnectOrShowNetworkMenu(complete_callback)
     end
     NetworkMgr:setWirelessBackend("wpa_supplicant", {ctrl_interface = "/var/run/wpa_supplicant/eth0"})
     function NetworkMgr:obtainIP()

frontend/ui/network/manager.lua

@@ -280,6 +280,45 @@ function NetworkMgr:showNetworkMenu(complete_callback)
     end)
 end
 
+function NetworkMgr:reconnectOrShowNetworkMenu(complete_callback)
+    local info = InfoMessage:new{text = _("Scanning…")}
+    UIManager:show(info)
+    UIManager:nextTick(function()
+        local network_list, err = self:getNetworkList()
+        UIManager:close(info)
+        if network_list == nil then
+            UIManager:show(InfoMessage:new{text = err})
+            return
+        end
+        table.sort(network_list,
+           function(l, r) return l.signal_quality > r.signal_quality end)
+        local success = false
+        table.foreach(network_list,
+           function(idx, network)
+               if network.password then
+                   success = NetworkMgr:authenticateNetwork(network)
+                   if success then
+                       NetworkMgr:obtainIP()
+                       if complete_callback then
+                           complete_callback()
+                       end
+                       UIManager:show(InfoMessage:new{
+                           text = T(_("Connected to network %1"), network.ssid),
+                           timeout = 3,
+                       })
+                       return
+                   end
+               end
+           end)
+        if not success then
+            UIManager:show(require("ui/widget/networksetting"):new{
+                network_list = network_list,
+                connect_callback = complete_callback,
+            })
+        end
+    end)
+end
+
 function NetworkMgr:saveNetwork(setting)
     if not self.nw_settings then self:readNWSettings() end