fix: reordered button numbers to match the actual wiring

.gitignore

@@ -3,3 +3,4 @@
 .vscode/c_cpp_properties.json
 .vscode/launch.json
 .vscode/ipch
+include/wifi_credentials.h

include/internet_time.h

@@ -0,0 +1,36 @@
+#ifndef INTERNET_TIME_H
+#define INTERNET_TIME_H
+
+#include <Arduino.h>
+
+struct InternetTimeInfo
+{
+  bool valid;
+  uint16_t year;
+  uint8_t month;
+  uint8_t day;
+  uint8_t hour;
+  uint8_t minute;
+};
+
+class InternetTime
+{
+public:
+  InternetTime();
+  void update(unsigned long now, bool wifiConnected);
+  InternetTimeInfo info() const;
+  bool consumeDirty();
+
+private:
+  void fetch(unsigned long now);
+  void updateCurrentTime(unsigned long now);
+  InternetTimeInfo infoFromEpoch(unsigned long epoch) const;
+
+  unsigned long lastEpoch_;
+  unsigned long lastSyncMillis_;
+  unsigned long nextAttempt_;
+  InternetTimeInfo current_;
+  bool dirty_;
+};
+
+#endif

include/menu.h

@@ -0,0 +1,29 @@
+#ifndef MENU_H
+#define MENU_H
+
+#include <Arduino.h>
+#include <U8g2lib.h>
+
+enum class MenuAction
+{
+  ShowInternetDetails,
+  ShowHelloWorld,
+  BackToCarousel
+};
+
+class Menu
+{
+public:
+  Menu();
+  void draw(U8G2 &u8g2);
+  void nextOption();
+  MenuAction select();
+  bool consumeDirty();
+  void requestRedraw();
+
+private:
+  size_t selectedIndex_;
+  bool dirty_;
+};
+
+#endif

include/screens.h

@@ -4,10 +4,17 @@
 #include <U8g2lib.h>
 
 #include "am2302_sensor.h"
+#include "internet_time.h"
+#include "weather_forecast.h"
+#include "wifi_connection.h"
 
-void drawScreen1(U8G2 &u8g2);
+void setInternetTimeInfo(InternetTimeInfo timeInfo);
+void drawTimeScreen(U8G2 &u8g2);
+void drawHelloWorldScreen(U8G2 &u8g2);
+void drawInternetConnectionScreen(U8G2 &u8g2, WifiConnectionInfo wifiInfo);
 void setEnvironmentReading(Am2302Reading reading);
 void drawEnvironmentScreen(U8G2 &u8g2);
-void drawWeatherIconScreen(U8G2 &u8g2);
+void setWeatherForecastInfo(WeatherForecastInfo forecastInfo);
+void drawWeatherForecastScreen(U8G2 &u8g2);
 
 #endif

include/weather_forecast.h

@@ -0,0 +1,37 @@
+#ifndef WEATHER_FORECAST_H
+#define WEATHER_FORECAST_H
+
+#include <Arduino.h>
+
+struct WeatherForecastInfo
+{
+  bool valid;
+  float currentTemperatureC;
+  float minTemperatureC;
+  float maxTemperatureC;
+  float precipitationMm;
+  uint8_t precipitationProbabilityPercent;
+  int weatherCode;
+};
+
+class WeatherForecast
+{
+public:
+  WeatherForecast();
+  void update(unsigned long now, bool wifiConnected);
+  WeatherForecastInfo info() const;
+  bool consumeDirty();
+
+private:
+  void fetch(unsigned long now);
+  bool readResponse(String &body);
+  bool parseForecast(const String &body, WeatherForecastInfo &forecast) const;
+  bool parseFloatArray(const String &body, const char *name, float *values, size_t maxCount, size_t &count) const;
+  bool parseIntArray(const String &body, const char *name, int *values, size_t maxCount, size_t &count) const;
+
+  WeatherForecastInfo current_;
+  unsigned long nextAttempt_;
+  bool dirty_;
+};
+
+#endif

include/wifi_connection.h

@@ -0,0 +1,34 @@
+#ifndef WIFI_CONNECTION_H
+#define WIFI_CONNECTION_H
+
+#include <Arduino.h>
+#include <IPAddress.h>
+
+struct WifiConnectionInfo
+{
+  bool shieldAvailable;
+  bool connected;
+  IPAddress ipAddress;
+};
+
+class WifiConnection
+{
+public:
+  WifiConnection();
+  void begin(unsigned long now);
+  void update(unsigned long now);
+  WifiConnectionInfo info() const;
+  bool consumeDirty();
+
+private:
+  void connect(unsigned long now);
+  void recordStatus();
+
+  unsigned long nextAttempt_;
+  bool shieldAvailable_;
+  bool connected_;
+  IPAddress ipAddress_;
+  bool dirty_;
+};
+
+#endif

include/wifi_credentials.example.h

@@ -0,0 +1,14 @@
+#ifndef WIFI_CREDENTIALS_H
+#define WIFI_CREDENTIALS_H
+
+const char WIFI_SSID[] = "your-wifi-name";
+const char WIFI_PASSWORD[] = "your-wifi-password";
+
+// Offset from UTC in seconds. Examples: Finland winter 7200, Finland summer 10800.
+#define TIME_UTC_OFFSET_SECONDS 0
+
+// Coordinates used for the weather forecast.
+#define WEATHER_LATITUDE 60.1699
+#define WEATHER_LONGITUDE 24.9384
+
+#endif

src/carousel.cpp

@@ -1,6 +1,6 @@
 #include "carousel.h"
 
-const unsigned long pageInterval = 5000;
+const unsigned long pageInterval = 30000;
 
 Carousel::Carousel(Screen *screens, size_t screenCount)
     : screens_(screens),

src/internet_time.cpp

@@ -0,0 +1,142 @@
+#include "internet_time.h"
+
+#include <WiFi101.h>
+
+#include "wifi_credentials.h"
+
+#ifndef TIME_UTC_OFFSET_SECONDS
+#define TIME_UTC_OFFSET_SECONDS 0
+#endif
+
+namespace
+{
+const unsigned long retryInterval = 15000;
+const unsigned long refreshInterval = 3600000;
+const unsigned long secondsPerDay = 86400;
+
+bool isLeapYear(uint16_t year)
+{
+  return (year % 4 == 0 && year % 100 != 0) || year % 400 == 0;
+}
+
+uint8_t daysInMonth(uint16_t year, uint8_t month)
+{
+  const uint8_t days[] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
+  if (month == 2 && isLeapYear(year)) {
+    return 29;
+  }
+  return days[month - 1];
+}
+
+unsigned long applyTimeOffset(unsigned long epoch)
+{
+  if (TIME_UTC_OFFSET_SECONDS >= 0) {
+    return epoch + TIME_UTC_OFFSET_SECONDS;
+  }
+
+  const unsigned long offset = static_cast<unsigned long>(-TIME_UTC_OFFSET_SECONDS);
+  return epoch > offset ? epoch - offset : 0;
+}
+}
+
+InternetTime::InternetTime()
+    : lastEpoch_(0),
+      lastSyncMillis_(0),
+      nextAttempt_(0),
+      current_({false, 0, 0, 0, 0, 0}),
+      dirty_(true) {}
+
+void InternetTime::update(unsigned long now, bool wifiConnected)
+{
+  if (current_.valid) {
+    updateCurrentTime(now);
+  }
+
+  if (!wifiConnected) {
+    return;
+  }
+
+  if (now >= nextAttempt_) {
+    fetch(now);
+  }
+}
+
+InternetTimeInfo InternetTime::info() const
+{
+  return current_;
+}
+
+bool InternetTime::consumeDirty()
+{
+  const bool d = dirty_;
+  dirty_ = false;
+  return d;
+}
+
+void InternetTime::fetch(unsigned long now)
+{
+  const unsigned long epoch = WiFi.getTime();
+  nextAttempt_ = now + retryInterval;
+
+  if (epoch == 0) {
+    return;
+  }
+
+  lastEpoch_ = epoch;
+  lastSyncMillis_ = now;
+  nextAttempt_ = now + refreshInterval;
+  updateCurrentTime(now);
+}
+
+void InternetTime::updateCurrentTime(unsigned long now)
+{
+  const unsigned long elapsedSeconds = (now - lastSyncMillis_) / 1000;
+  const InternetTimeInfo updated = infoFromEpoch(lastEpoch_ + elapsedSeconds);
+
+  if (!current_.valid ||
+      current_.year != updated.year ||
+      current_.month != updated.month ||
+      current_.day != updated.day ||
+      current_.hour != updated.hour ||
+      current_.minute != updated.minute) {
+    current_ = updated;
+    dirty_ = true;
+  }
+}
+
+InternetTimeInfo InternetTime::infoFromEpoch(unsigned long epoch) const
+{
+  unsigned long adjustedEpoch = applyTimeOffset(epoch);
+  unsigned long days = adjustedEpoch / secondsPerDay;
+  unsigned long secondsToday = adjustedEpoch % secondsPerDay;
+
+  uint16_t year = 1970;
+  while (true) {
+    const uint16_t yearDays = isLeapYear(year) ? 366 : 365;
+    if (days < yearDays) {
+      break;
+    }
+    days -= yearDays;
+    year++;
+  }
+
+  uint8_t month = 1;
+  while (true) {
+    const uint8_t monthDays = daysInMonth(year, month);
+    if (days < monthDays) {
+      break;
+    }
+    days -= monthDays;
+    month++;
+  }
+
+  InternetTimeInfo info = {
+    true,
+    year,
+    month,
+    static_cast<uint8_t>(days + 1),
+    static_cast<uint8_t>(secondsToday / 3600),
+    static_cast<uint8_t>((secondsToday % 3600) / 60)
+  };
+  return info;
+}

src/main.cpp

@@ -4,48 +4,191 @@
 
 #include "am2302_sensor.h"
 #include "carousel.h"
+#include "internet_time.h"
+#include "menu.h"
 #include "screens.h"
+#include "weather_forecast.h"
+#include "wifi_connection.h"
 
 U8G2_SH1106_128X64_NONAME_F_HW_I2C u8g2(U8G2_R2, U8X8_PIN_NONE);
 
 int lastButtonNextState = LOW;
-uint8_t buttonNext = A4;
+int lastButtonSelectState = LOW;
-Am2302Sensor am2302(A3);
+uint8_t buttonNext = A3;
+uint8_t buttonSelect = A4;
+Am2302Sensor am2302(A5);
+WifiConnection wifiConnection;
+InternetTime internetTime;
+WeatherForecast weatherForecast;
+
+enum class AppMode
+{
+  Carousel,
+  Menu,
+  InternetDetails,
+  HelloWorld
+};
 
 Screen screens[] = {
-  { drawScreen1 },
+  { drawTimeScreen },
   { drawEnvironmentScreen },
-  { drawWeatherIconScreen }
+  { drawWeatherForecastScreen }
 };
 Carousel carousel(screens, sizeof(screens) / sizeof(screens[0]));
+Menu menu;
+AppMode appMode = AppMode::Carousel;
+bool appDirty = true;
 
 void setup() {
   pinMode(buttonNext, INPUT);
+  pinMode(buttonSelect, INPUT);
   am2302.begin();
+  wifiConnection.begin(millis());
 
   u8g2.begin();
   u8g2.clearBuffer();
   u8g2.sendBuffer();
 }
 
+void openMenu()
+{
+  appMode = AppMode::Menu;
+  menu.requestRedraw();
+  appDirty = true;
+}
+
+void selectMenuOption()
+{
+  switch (menu.select()) {
+    case MenuAction::ShowInternetDetails:
+      appMode = AppMode::InternetDetails;
+      break;
+    case MenuAction::ShowHelloWorld:
+      appMode = AppMode::HelloWorld;
+      break;
+    case MenuAction::BackToCarousel:
+      appMode = AppMode::Carousel;
+      carousel.requestRedraw();
+      break;
+  }
+
+  appDirty = true;
+}
+
+void handleNextButton()
+{
+  switch (appMode) {
+    case AppMode::Carousel:
+      carousel.nextScreen();
+      break;
+    case AppMode::Menu:
+      menu.nextOption();
+      break;
+    case AppMode::InternetDetails:
+    case AppMode::HelloWorld:
+      break;
+  }
+}
+
+void handleSelectButton()
+{
+  switch (appMode) {
+    case AppMode::Carousel:
+    case AppMode::InternetDetails:
+    case AppMode::HelloWorld:
+      openMenu();
+      break;
+    case AppMode::Menu:
+      selectMenuOption();
+      break;
+  }
+}
+
+bool displayNeedsRedraw()
+{
+  if (appDirty) {
+    appDirty = false;
+    return true;
+  }
+
+  switch (appMode) {
+    case AppMode::Carousel:
+      return carousel.consumeDirty();
+    case AppMode::Menu:
+      return menu.consumeDirty();
+    case AppMode::InternetDetails:
+      return wifiConnection.consumeDirty();
+    case AppMode::HelloWorld:
+      return false;
+  }
+
+  return false;
+}
+
+void drawActiveView()
+{
+  switch (appMode) {
+    case AppMode::Carousel:
+      carousel.draw(u8g2);
+      break;
+    case AppMode::Menu:
+      menu.draw(u8g2);
+      break;
+    case AppMode::InternetDetails:
+      drawInternetConnectionScreen(u8g2, wifiConnection.info());
+      break;
+    case AppMode::HelloWorld:
+      drawHelloWorldScreen(u8g2);
+      break;
+  }
+}
+
 void loop(){
   const unsigned long now = millis();
+  wifiConnection.update(now);
+  internetTime.update(now, wifiConnection.info().connected);
+  weatherForecast.update(now, wifiConnection.info().connected);
+
+  if (internetTime.consumeDirty()) {
+    setInternetTimeInfo(internetTime.info());
+    if (appMode == AppMode::Carousel) {
+      carousel.requestRedraw();
+    }
+  }
+
+  if (weatherForecast.consumeDirty()) {
+    setWeatherForecastInfo(weatherForecast.info());
+    if (appMode == AppMode::Carousel) {
+      carousel.requestRedraw();
+    }
+  }
+
+  if (appMode == AppMode::Carousel) {
     carousel.update(now);
+  }
 
   if (am2302.update(now)) {
     setEnvironmentReading(am2302.reading());
+    if (appMode == AppMode::Carousel) {
       carousel.requestRedraw();
     }
-
-  const int currentButtonState = digitalRead(buttonNext);
-  if (lastButtonNextState == LOW && currentButtonState == HIGH) {
-      carousel.nextScreen();
   }
-  lastButtonNextState = currentButtonState;
 
-  if (carousel.consumeDirty()) {
+  const int currentButtonNextState = digitalRead(buttonNext);
+  if (lastButtonNextState == LOW && currentButtonNextState == HIGH) {
+      handleNextButton();
+  }
+  lastButtonNextState = currentButtonNextState;
+
+  const int currentButtonSelectState = digitalRead(buttonSelect);
+  if (lastButtonSelectState == LOW && currentButtonSelectState == HIGH) {
+      handleSelectButton();
+  }
+  lastButtonSelectState = currentButtonSelectState;
+
+  if (displayNeedsRedraw()) {
     u8g2.clearBuffer();
-    carousel.draw(u8g2);
+    drawActiveView();
     u8g2.sendBuffer();
   }
 

src/menu.cpp

@@ -0,0 +1,67 @@
+#include "menu.h"
+
+namespace
+{
+const char *menuOptions[] = {
+  "Internet",
+  "Hello world",
+  "Back"
+};
+
+const size_t menuOptionCount = sizeof(menuOptions) / sizeof(menuOptions[0]);
+
+MenuAction actionForIndex(size_t index)
+{
+  switch (index) {
+    case 0:
+      return MenuAction::ShowInternetDetails;
+    case 1:
+      return MenuAction::ShowHelloWorld;
+    default:
+      return MenuAction::BackToCarousel;
+  }
+}
+}
+
+Menu::Menu()
+    : selectedIndex_(0),
+      dirty_(true) {}
+
+void Menu::draw(U8G2 &u8g2)
+{
+  u8g2.setFont(u8g2_font_6x12_tr);
+  u8g2.drawStr(0, 12, "Menu");
+
+  for (size_t i = 0; i < menuOptionCount; i++) {
+    const uint8_t y = 28 + (i * 14);
+    if (i == selectedIndex_) {
+      u8g2.drawStr(0, y, ">");
+    }
+    u8g2.drawStr(12, y, menuOptions[i]);
+  }
+
+  dirty_ = false;
+}
+
+void Menu::nextOption()
+{
+  selectedIndex_ = (selectedIndex_ + 1) % menuOptionCount;
+  dirty_ = true;
+}
+
+MenuAction Menu::select()
+{
+  return actionForIndex(selectedIndex_);
+}
+
+bool Menu::consumeDirty()
+{
+  const bool d = dirty_;
+  dirty_ = false;
+  return d;
+}
+
+void Menu::requestRedraw()
+{
+  dirty_ = true;
+}

src/screens.cpp

@@ -3,34 +3,120 @@
 namespace
 {
 Am2302Reading environmentReading = {0.0F, 0.0F, false};
+InternetTimeInfo internetTimeInfo = {false, 0, 0, 0, 0, 0};
+WeatherForecastInfo weatherForecastInfo = {false, 0.0F, 0.0F, 0.0F, 0.0F, 0, 0};
 
-void drawSun(U8G2 &u8g2, uint8_t x, uint8_t y)
+void printTwoDigits(U8G2 &u8g2, uint8_t value)
 {
-  u8g2.drawDisc(x, y, 11);
+  if (value < 10) {
-  u8g2.drawLine(x, y - 18, x, y - 14);
+    u8g2.print("0");
-  u8g2.drawLine(x, y + 14, x, y + 18);
+  }
-  u8g2.drawLine(x - 18, y, x - 14, y);
+  u8g2.print(value);
-  u8g2.drawLine(x + 14, y, x + 18, y);
-  u8g2.drawLine(x - 13, y - 13, x - 10, y - 10);
-  u8g2.drawLine(x + 10, y - 10, x + 13, y - 13);
-  u8g2.drawLine(x - 13, y + 13, x - 10, y + 10);
-  u8g2.drawLine(x + 10, y + 10, x + 13, y + 13);
 }
 
-void drawCloud(U8G2 &u8g2, uint8_t x, uint8_t y)
+const char *weatherDescription(int code)
 {
-  u8g2.drawDisc(x + 18, y + 14, 12);
+  switch (code) {
-  u8g2.drawDisc(x + 34, y + 8, 17);
+    case 0:
-  u8g2.drawDisc(x + 52, y + 15, 13);
+      return "Clear";
-  u8g2.drawBox(x + 17, y + 15, 38, 14);
+    case 1:
-  u8g2.drawRBox(x + 8, y + 18, 58, 15, 7);
+    case 2:
+      return "Partly cloudy";
+    case 3:
+      return "Cloudy";
+    case 45:
+    case 48:
+      return "Fog";
+    case 51:
+    case 53:
+    case 55:
+    case 56:
+    case 57:
+      return "Drizzle";
+    case 61:
+    case 63:
+    case 65:
+    case 66:
+    case 67:
+      return "Rain";
+    case 71:
+    case 73:
+    case 75:
+    case 77:
+      return "Snow";
+    case 80:
+    case 81:
+    case 82:
+      return "Showers";
+    case 85:
+    case 86:
+      return "Snow showers";
+    case 95:
+    case 96:
+    case 99:
+      return "Thunder";
+    default:
+      return "Forecast";
+  }
 }
 }
 
-void drawScreen1(U8G2 &u8g2)
+void setInternetTimeInfo(InternetTimeInfo timeInfo)
+{
+  internetTimeInfo = timeInfo;
+}
+
+void drawTimeScreen(U8G2 &u8g2)
+{
+  if (!internetTimeInfo.valid) {
+    u8g2.setFont(u8g2_font_6x12_tr);
+    u8g2.drawStr(0, 24, "Time has not");
+    u8g2.drawStr(0, 40, "been updated");
+    return;
+  }
+
+  u8g2.setFont(u8g2_font_6x12_tr);
+  u8g2.setCursor(0, 14);
+  printTwoDigits(u8g2, internetTimeInfo.day);
+  u8g2.print(".");
+  printTwoDigits(u8g2, internetTimeInfo.month);
+  u8g2.print(".");
+  u8g2.print(internetTimeInfo.year);
+
+  u8g2.setFont(u8g2_font_ncenB24_tr);
+  u8g2.setCursor(0, 54);
+  printTwoDigits(u8g2, internetTimeInfo.hour);
+  u8g2.print(":");
+  printTwoDigits(u8g2, internetTimeInfo.minute);
+}
+
+void drawHelloWorldScreen(U8G2 &u8g2)
 {
   u8g2.setFont(u8g2_font_ncenB14_tr);
-  u8g2.drawStr(0, 20, "Screen 1");
+  u8g2.drawStr(0, 30, "Hello");
+  u8g2.drawStr(0, 54, "world");
+}
+
+void drawInternetConnectionScreen(U8G2 &u8g2, WifiConnectionInfo wifiInfo)
+{
+  u8g2.setFont(u8g2_font_6x12_tr);
+  u8g2.drawStr(0, 12, "Internet");
+
+  if (!wifiInfo.shieldAvailable) {
+    u8g2.drawStr(0, 34, "WiFi shield missing");
+    return;
+  }
+
+  if (!wifiInfo.connected) {
+    u8g2.setFont(u8g2_font_ncenB14_tr);
+    u8g2.drawStr(0, 42, "Disconnected");
+    return;
+  }
+
+  u8g2.drawStr(0, 32, "Connected");
+  u8g2.drawStr(0, 48, "IP address:");
+  u8g2.setCursor(0, 64);
+  u8g2.print(wifiInfo.ipAddress);
 }
 
 void setEnvironmentReading(Am2302Reading reading)
@@ -58,8 +144,39 @@ void drawEnvironmentScreen(U8G2 &u8g2)
   u8g2.print(" %");
 }
 
-void drawWeatherIconScreen(U8G2 &u8g2)
+void setWeatherForecastInfo(WeatherForecastInfo forecastInfo)
 {
-  drawSun(u8g2, 78, 22);
+  weatherForecastInfo = forecastInfo;
-  drawCloud(u8g2, 29, 24);
+}
+
+void drawWeatherForecastScreen(U8G2 &u8g2)
+{
+  u8g2.setFont(u8g2_font_6x12_tr);
+  u8g2.drawStr(0, 12, "Weather next 12h");
+
+  if (!weatherForecastInfo.valid) {
+    u8g2.drawStr(0, 34, "Weather has not");
+    u8g2.drawStr(0, 50, "been updated");
+    return;
+  }
+
+  u8g2.setCursor(0, 28);
+  u8g2.print("Now ");
+  u8g2.print(weatherForecastInfo.currentTemperatureC, 1);
+  u8g2.print(" C ");
+  u8g2.print(weatherDescription(weatherForecastInfo.weatherCode));
+
+  u8g2.setCursor(0, 42);
+  u8g2.print("Temp ");
+  u8g2.print(weatherForecastInfo.minTemperatureC, 0);
+  u8g2.print("-");
+  u8g2.print(weatherForecastInfo.maxTemperatureC, 0);
+  u8g2.print(" C");
+
+  u8g2.setCursor(0, 56);
+  u8g2.print("Rain ");
+  u8g2.print(weatherForecastInfo.precipitationProbabilityPercent);
+  u8g2.print("% ");
+  u8g2.print(weatherForecastInfo.precipitationMm, 1);
+  u8g2.print(" mm");
 }

src/weather_forecast.cpp

@@ -0,0 +1,247 @@
+#include "weather_forecast.h"
+
+#include <WiFi101.h>
+
+#include "wifi_credentials.h"
+
+#ifndef WEATHER_LATITUDE
+#define WEATHER_LATITUDE 0.0
+#endif
+
+#ifndef WEATHER_LONGITUDE
+#define WEATHER_LONGITUDE 0.0
+#endif
+
+namespace
+{
+const char weatherHost[] = "api.open-meteo.com";
+const unsigned long retryInterval = 300000;
+const unsigned long refreshInterval = 3600000;
+const size_t forecastHours = 12;
+const size_t maxResponseLength = 3500;
+
+const char *weatherRequestPath()
+{
+  static String path;
+  path = "/v1/forecast?latitude=";
+  path += String(WEATHER_LATITUDE, 4);
+  path += "&longitude=";
+  path += String(WEATHER_LONGITUDE, 4);
+  path += "&hourly=temperature_2m,precipitation_probability,precipitation,weather_code";
+  path += "&forecast_hours=12&timezone=auto&forecast_days=1";
+  return path.c_str();
+}
+
+const char *arrayStartForName(const String &body, const char *name)
+{
+  const String key = String("\"") + name + "\":[";
+  const int start = body.indexOf(key);
+  if (start < 0) {
+    return nullptr;
+  }
+  return body.c_str() + start + key.length();
+}
+
+void skipWhitespace(const char *&cursor)
+{
+  while (*cursor == ' ' || *cursor == '\n' || *cursor == '\r' || *cursor == '\t') {
+    cursor++;
+  }
+}
+}
+
+WeatherForecast::WeatherForecast()
+    : current_({false, 0.0F, 0.0F, 0.0F, 0.0F, 0, 0}),
+      nextAttempt_(0),
+      dirty_(true) {}
+
+void WeatherForecast::update(unsigned long now, bool wifiConnected)
+{
+  if (!wifiConnected) {
+    return;
+  }
+
+  if (now >= nextAttempt_) {
+    fetch(now);
+  }
+}
+
+WeatherForecastInfo WeatherForecast::info() const
+{
+  return current_;
+}
+
+bool WeatherForecast::consumeDirty()
+{
+  const bool d = dirty_;
+  dirty_ = false;
+  return d;
+}
+
+void WeatherForecast::fetch(unsigned long now)
+{
+  nextAttempt_ = now + retryInterval;
+
+  String body;
+  if (!readResponse(body)) {
+    return;
+  }
+
+  WeatherForecastInfo forecast;
+  if (!parseForecast(body, forecast)) {
+    return;
+  }
+
+  current_ = forecast;
+  dirty_ = true;
+  nextAttempt_ = now + refreshInterval;
+}
+
+bool WeatherForecast::readResponse(String &body)
+{
+  WiFiClient client;
+  if (!client.connect(weatherHost, 80)) {
+    return false;
+  }
+
+  client.print("GET ");
+  client.print(weatherRequestPath());
+  client.println(" HTTP/1.0");
+  client.print("Host: ");
+  client.println(weatherHost);
+  client.println("Connection: close");
+  client.println();
+
+  const unsigned long started = millis();
+  bool inBody = false;
+  char headerTail[4] = {0, 0, 0, 0};
+  while ((client.connected() || client.available()) && millis() - started < 10000) {
+    while (client.available()) {
+      const char c = client.read();
+
+      if (!inBody) {
+        headerTail[0] = headerTail[1];
+        headerTail[1] = headerTail[2];
+        headerTail[2] = headerTail[3];
+        headerTail[3] = c;
+        inBody = headerTail[0] == '\r' &&
+                 headerTail[1] == '\n' &&
+                 headerTail[2] == '\r' &&
+                 headerTail[3] == '\n';
+        continue;
+      }
+
+      if (body.length() < maxResponseLength) {
+        body += c;
+      }
+    }
+  }
+
+  client.stop();
+  return body.indexOf("\"hourly\"") >= 0;
+}
+
+bool WeatherForecast::parseForecast(const String &body, WeatherForecastInfo &forecast) const
+{
+  float temperatures[forecastHours];
+  float precipitation[forecastHours];
+  int precipitationProbability[forecastHours];
+  int weatherCodes[forecastHours];
+  size_t temperatureCount = 0;
+  size_t precipitationCount = 0;
+  size_t probabilityCount = 0;
+  size_t weatherCodeCount = 0;
+
+  if (!parseFloatArray(body, "temperature_2m", temperatures, forecastHours, temperatureCount) ||
+      !parseFloatArray(body, "precipitation", precipitation, forecastHours, precipitationCount) ||
+      !parseIntArray(body, "precipitation_probability", precipitationProbability, forecastHours, probabilityCount) ||
+      !parseIntArray(body, "weather_code", weatherCodes, forecastHours, weatherCodeCount)) {
+    return false;
+  }
+
+  if (temperatureCount == 0 ||
+      precipitationCount == 0 ||
+      probabilityCount == 0 ||
+      weatherCodeCount == 0) {
+    return false;
+  }
+
+  float minTemperature = temperatures[0];
+  float maxTemperature = temperatures[0];
+  float totalPrecipitation = 0.0F;
+  uint8_t maxProbability = 0;
+
+  for (size_t i = 0; i < temperatureCount; i++) {
+    if (temperatures[i] < minTemperature) {
+      minTemperature = temperatures[i];
+    }
+    if (temperatures[i] > maxTemperature) {
+      maxTemperature = temperatures[i];
+    }
+  }
+
+  for (size_t i = 0; i < precipitationCount; i++) {
+    totalPrecipitation += precipitation[i];
+  }
+
+  for (size_t i = 0; i < probabilityCount; i++) {
+    if (precipitationProbability[i] > maxProbability) {
+      maxProbability = precipitationProbability[i];
+    }
+  }
+
+  forecast = {
+    true,
+    temperatures[0],
+    minTemperature,
+    maxTemperature,
+    totalPrecipitation,
+    maxProbability,
+    weatherCodes[0]
+  };
+  return true;
+}
+
+bool WeatherForecast::parseFloatArray(const String &body, const char *name, float *values, size_t maxCount, size_t &count) const
+{
+  const char *cursor = arrayStartForName(body, name);
+  if (cursor == nullptr) {
+    return false;
+  }
+
+  count = 0;
+  while (*cursor != '\0' && *cursor != ']' && count < maxCount) {
+    skipWhitespace(cursor);
+    values[count++] = atof(cursor);
+    while (*cursor != '\0' && *cursor != ',' && *cursor != ']') {
+      cursor++;
+    }
+    if (*cursor == ',') {
+      cursor++;
+    }
+  }
+
+  return count > 0;
+}
+
+bool WeatherForecast::parseIntArray(const String &body, const char *name, int *values, size_t maxCount, size_t &count) const
+{
+  const char *cursor = arrayStartForName(body, name);
+  if (cursor == nullptr) {
+    return false;
+  }
+
+  count = 0;
+  while (*cursor != '\0' && *cursor != ']' && count < maxCount) {
+    skipWhitespace(cursor);
+    values[count++] = atoi(cursor);
+    while (*cursor != '\0' && *cursor != ',' && *cursor != ']') {
+      cursor++;
+    }
+    if (*cursor == ',') {
+      cursor++;
+    }
+  }
+
+  return count > 0;
+}

src/wifi_connection.cpp

@@ -0,0 +1,84 @@
+#include "wifi_connection.h"
+
+#include <WiFi101.h>
+
+#include "wifi_credentials.h"
+
+namespace
+{
+const unsigned long reconnectInterval = 30000;
+}
+
+WifiConnection::WifiConnection()
+    : nextAttempt_(0),
+      shieldAvailable_(true),
+      connected_(false),
+      ipAddress_(0, 0, 0, 0),
+      dirty_(true) {}
+
+void WifiConnection::begin(unsigned long now)
+{
+  shieldAvailable_ = WiFi.status() != WL_NO_SHIELD;
+  connect(now);
+  recordStatus();
+}
+
+void WifiConnection::update(unsigned long now)
+{
+  if (!shieldAvailable_) {
+    return;
+  }
+
+  if (WiFi.status() == WL_CONNECTED) {
+    recordStatus();
+    return;
+  }
+
+  if (now >= nextAttempt_) {
+    connect(now);
+  }
+
+  recordStatus();
+}
+
+WifiConnectionInfo WifiConnection::info() const
+{
+  WifiConnectionInfo current = {
+    shieldAvailable_,
+    connected_,
+    ipAddress_
+  };
+  return current;
+}
+
+bool WifiConnection::consumeDirty()
+{
+  const bool d = dirty_;
+  dirty_ = false;
+  return d;
+}
+
+void WifiConnection::connect(unsigned long now)
+{
+  if (!shieldAvailable_) {
+    return;
+  }
+
+  WiFi.begin(WIFI_SSID, WIFI_PASSWORD);
+  nextAttempt_ = now + reconnectInterval;
+}
+
+void WifiConnection::recordStatus()
+{
+  const bool currentConnected = WiFi.status() == WL_CONNECTED;
+  IPAddress currentIpAddress(0, 0, 0, 0);
+  if (currentConnected) {
+    currentIpAddress = WiFi.localIP();
+  }
+
+  if (connected_ != currentConnected || ipAddress_ != currentIpAddress) {
+    connected_ = currentConnected;
+    ipAddress_ = currentIpAddress;
+    dirty_ = true;
+  }
+}