BangleApps/apps/thmswtch/app.js

const SETTINGS_FILE = "themeSwitch.json";
const storage = require("Storage");
var sunrise, sunset, date;
var SunCalc = require("suncalc"); // from modules folder
let settings = storage.readJSON('setting.json', 1);
let saved = storage.readJSON(SETTINGS_FILE, 1) || {};
if (settings.theme.fg > 0) {
  saved.darkModeActive = 1;
} else {
  saved.darkModeActive = 0;
}
let dmH, dmM, lmH, lmM;
if (require("Storage").readJSON("themeSwitch.json", 1) !== undefined) {
  dmH = parseInt(saved.darkModeAt.split(":")[0] | 0);
  dmM = parseInt(saved.darkModeAt.split(":")[1] | 0);
  lmH = parseInt(saved.lightModeAt.split(":")[0] | 0);
  lmM = parseInt(saved.lightModeAt.split(":")[1] | 0);
} else {
  dmH = 0;
  dmM = 0;
  lmH = 0;
  lmM = 0;
}
// Main menu

var mainmenu = {
  "": {
    "title": "Theme Switch"
  },
  "< Back": function () { load(); },
  "Automatic Dark Mode": {
    value: saved.darkMode | false,
    format: v => v ? "On" : "Off",
    min: 0, max: 1, step: 1,
    onchange: v => {
      saved.darkMode = v;
      storage.writeJSON(SETTINGS_FILE, saved);
    }
  },
  "Dark Mode Active": {
    value: saved.darkModeActive | false,
    format: v => v ? "On" : "Off",
    min: 0, max: 1, step: 1,
    onchange: v => {
      saved.darkModeActive = v;
      storage.writeJSON(SETTINGS_FILE, saved);
      if (v !== 0) {
        setDarkTheme();
        Bangle.drawWidgets();
      } else {
        setLightTheme();
        Bangle.drawWidgets();
      }
    }
  },
  "Dark Mode by Sun": {
    value: saved.darkModeBySun | false,
    format: v => v ? "On" : "Off",
    min: 0, max: 1, step: 1,
    onchange: v => {
      saved.darkModeBySun = v;
      if (v !== 0) {
        //print("calculating sun times");
        calculateSunTimes();
        saved.lightModeAt = sunrise;
        saved.darkModeAt = sunset;
        //print("sunrise" +sunrise);
        //print("sunset" +sunset);
      }
      storage.writeJSON(SETTINGS_FILE, saved);
    },
  },
  "light mode at": {
    value: saved.lightModeAt,
    format: v => saved.lightModeAt,
    onchange: function () {
      if (saved.darkModeBySun === 0) {
        E.showMenu(lightModeAtMenu);
      }
      else {
        E.showAlert("Deactivate dark mode first!", "Action Blocked").then(
          function () { E.showMenu(mainmenu); });
      }
    }
  },
  "dark mode at": {
    value: saved.darkModeAt,
    format: v => saved.darkModeAt,
    onchange: function () {
      if (saved.darkModeBySun === 0) {
        E.showMenu(darkModeAtMenu);
      }
      else {
        E.showAlert("Deactivate dark mode first!", "Action Blocked").then(function () { E.showMenu(mainmenu); });
      }
    }
  },
  "Exit": function () { load(); },
};

var lightModeAtMenu = {
  "": {
    "title": "light mode at"
  },
  "Hour": {
    value: lmH,
    min: 0, max: 23, step: 1,
    onchange: v => { lmH = v; }
  },
  "Minute": {
    value: lmM,
    min: 0, max: 59, step: 1,
    onchange: v => { lmM = v; }
  },
  "< Back": function () {
    saved.lightModeAt = fixTime(lmH, lmM);
    storage.writeJSON(SETTINGS_FILE, saved);
    E.showMenu(mainmenu);
  },
};

var darkModeAtMenu = {
  "": {
    "title": "dark mode at"
  },
  "Hour": {
    value: dmH,
    min: 0, max: 23, step: 1,
    onchange: v => { dmH = v; }
  },
  "Minute": {
    value: dmM,
    min: 0, max: 59, step: 1,
    onchange: v => { dmM = v; }
  },
  "< Back": function () {
    saved.darkModeAt = fixTime(dmH, dmM);
    storage.writeJSON(SETTINGS_FILE, saved);
    E.showMenu(mainmenu);
  },
};

// Actually display the menu
E.showMenu(mainmenu);

// Function to fix time format
function fixTime(h, m) {
  if (h.toString().length < 2) {
    h = "0" + h.toString();
  }
  if (m.toString().length < 2) {
    m = "0" + m.toString();
  }
  return h.toString() + ":" + m.toString();
}

function calculateSunTimes() {
  var location = require("Storage").readJSON("mylocation.json", 1) || {};
  location.lat = location.lat || 51.5072;
  location.lon = location.lon || 0.1276; // London
  date = new Date(Date.now());
  var times = SunCalc.getTimes(date, location.lat, location.lon);
  sunrise = fixTime(times.sunrise.getHours(), times.sunrise.getMinutes());
  sunset = fixTime(times.sunset.getHours(), times.sunset.getMinutes());
  /* do we want to re-calculate this every day? Or we just assume
  that 'show' will get called once a day? */
}

function cl(x) { return g.setColor(x).getColor(); }

function upd(th) {
  g.theme = th;
  settings.theme = th;
  storage.write('setting.json', settings);
  delete g.reset;
  g._reset = g.reset;
  g.reset = function (n) { return g._reset().setColor(th.fg).setBgColor(th.bg); };
  g.clear = function (n) { if (n) g.reset(); return g.clearRect(0, 0, g.getWidth(), g.getHeight()); };
  g.clear(1);
}

//flipTheme function to be used in future version 
// function flipTheme() {
//   if (!g.theme.dark) {
//     upd({
//       fg: cl("#fff"), bg: cl("#000"),
//       fg2: cl("#fff"), bg2: cl("#004"),
//       fgH: cl("#fff"), bgH: cl("#00f"),
//       dark: true
//     });
//   } else {
//     upd({
//       fg: cl("#000"), bg: cl("#fff"),
//       fg2: cl("#000"), bg2: cl("#cff"),
//       fgH: cl("#000"), bgH: cl("#0ff"),
//       dark: false
//     });
//   }
// }

function setDarkTheme() {
  if (!g.theme.dark) {
    upd({
      fg: cl("#fff"), bg: cl("#000"),
      fg2: cl("#fff"), bg2: cl("#004"),
      fgH: cl("#fff"), bgH: cl("#00f"),
      dark: true
    });
  }
}

function setLightTheme() {
  if (g.theme.dark) {
    upd({
      fg: cl("#000"), bg: cl("#fff"),
      fg2: cl("#000"), bg2: cl("#cff"),
      fgH: cl("#000"), bgH: cl("#0ff"),
      dark: false
    });
  }
}