common.js for Deluminate (Chrome extension)

/*
This is an edited version of the common.js file from
Deluminate 0.3.2_0, the Google Chrome extension. The
changes that I made are exclusively in the function:
getSiteScheme(). The purpose of these changes are to
make it so that any rules set for a domain carry over
to all subdomains, unless a rule is already set for
that specific subdomain. You can still create rules
for subdomains and they will be remembered as such
without affecting the rules for any other subdomains.
I added conditionals specifically to handle any website
regardless of whether or not the primary domain is
accessed starting with "www."

In my testing, the GUI works as expected for those
rule defining characteristics without needing to make
any other alterations to any parts of Deluminate. I
have not had anyone else test this yet, so if you see
any issues or have any questions, feel free to contact
me at soldier9599@gmail.com
*/

var DEFAULT_SCHEME = "delumine-smart";

function $(id) {
  return document.getElementById(id);
}

function getEnabled() {
  var result = localStorage['enabled'];
  if (result === 'true' || result === 'false') {
    return (result === 'true');
  }
  localStorage['enabled'] = 'true';
  return true;
}

function setEnabled(enabled) {
  localStorage['enabled'] = enabled;
}

function getKeyAction() {
  var keyAction = localStorage['keyaction'];
  if (keyAction == 'global' || keyAction == 'site') {
    return keyAction;
  }
  keyAction = 'global';
  localStorage['keyaction'] = keyAction;
  return keyAction;
}

function setKeyAction(keyAction) {
  if (keyAction != 'global' && keyAction != 'site') {
    keyAction = 'global';
  }
  localStorage['keyaction'] = keyAction;
}

function getDefaultScheme() {
  var scheme = localStorage['scheme'];
  if (scheme) {
    return scheme;
  }
  scheme = DEFAULT_SCHEME;
  localStorage['scheme'] = scheme;
  return scheme;
}

function setDefaultScheme(scheme) {
  if (!(scheme)) {
    scheme = DEFAULT_SCHEME;
  }
  localStorage['scheme'] = scheme;
}

function getSiteScheme(site) {
  var scheme = getDefaultScheme();
  try {
    var siteSchemes = JSON.parse(localStorage['siteschemes']);
    if (siteSchemes[site]) {                // If it already matches a rule, follow it.
      scheme = siteSchemes[site]
    }
    else if (site.indexOf("www") == -1) {           // If not a www and has no specific rule
      var newsite = site.substr(site.indexOf(".") + 1)  // Remove lowest level domain for new url var
      var wwwnewsite = "www.".concat(newsite)       // Add www. to newsite for another url var
      if (siteSchemes[newsite]) {               // Locate scheme if main domain doesn't use www
        scheme = siteSchemes[newsite];
      }
      else if (siteSchemes[wwwnewsite]) {           // Locate scheme if main domain uses www
        scheme = siteSchemes[wwwnewsite];
      }
    }
    if (!(scheme)) {                        // Rest of the function handles the situation where
      scheme = getDefaultScheme();              // there is no rule for the actual url or the url
    }                               // adjusted one domain up.
  } catch (e) {
    scheme = getDefaultScheme();
  }
  return scheme;
}


function setSiteScheme(site, scheme) {
  if (!(scheme)) {
    scheme = getDefaultScheme();
  }
  var siteSchemes = {};
  try {
    siteSchemes = JSON.parse(localStorage['siteschemes']);
    siteSchemes['www.example.com'] = getDefaultScheme();
  } catch (e) {
    siteSchemes = {};
  }
  siteSchemes[site] = scheme;
  localStorage['siteschemes'] = JSON.stringify(siteSchemes);
}

function resetSiteSchemes() {
  var siteSchemes = {};
  localStorage['siteschemes'] = JSON.stringify(siteSchemes);
}

function siteFromUrl(url) {
  var a = document.createElement('a');
  a.href = url;
  return a.hostname;
}

function getModifiers() {
  var modifiers = '';
  if (isLowContrast()) {
    modifiers = 'low-contrast';
  }
  return modifiers;
}

function isLowContrast() {
  var result = localStorage['low_contrast'];

  if (result === 'true' || result === 'false') {
    return (result === 'true');
  }
  localStorage['low_contrast'] = 'false';
  return false;
}

function isDisallowedUrl(url) {
  return url.indexOf('chrome') == 0 || url.indexOf('about') == 0;
}