/* global document,window,matchMedia */
var colorIndexRegExp = /((?:not )?all and )?(\(color-index: *(22|48|70)\))/i;
var prefersColorSchemeRegExp = /prefers-color-scheme:/i;

var prefersColorSchemeInit = function prefersColorSchemeInit(initialColorScheme) {
  var mediaQueryString = '(prefers-color-scheme: dark)';
  var mediaQueryList = window.matchMedia && matchMedia(mediaQueryString);
  var hasNativeSupport = mediaQueryList && mediaQueryList.media === mediaQueryString;

  var mediaQueryListener = function mediaQueryListener() {
    set(mediaQueryList.matches ? 'dark' : 'light');
  };

  var removeListener = function removeListener() {
    if (mediaQueryList) {
      mediaQueryList.removeListener(mediaQueryListener);
    }
  };

  var set = function set(colorScheme) {
    if (colorScheme !== currentColorScheme) {
      currentColorScheme = colorScheme;

      if (typeof result.onChange === 'function') {
        result.onChange();
      }
    }

    [].forEach.call(document.styleSheets || [], function (styleSheet) {
      // cssRules is a live list. Converting to an Array first.
      var rules = [];
      [].forEach.call(styleSheet.cssRules || [], function (cssRule) {
        rules.push(cssRule);
      });
      rules.forEach(function (cssRule) {
        var colorSchemeMatch = prefersColorSchemeRegExp.test(Object(cssRule.media).mediaText);

        if (colorSchemeMatch) {
          var index = [].indexOf.call(cssRule.parentStyleSheet.cssRules, cssRule);
          cssRule.parentStyleSheet.deleteRule(index);
        } else {
          var colorIndexMatch = (Object(cssRule.media).mediaText || '').match(colorIndexRegExp);

          if (colorIndexMatch) {
            // Old style which has poor browser support and can't handle complex media queries.
            cssRule.media.mediaText = ((/^dark$/i.test(colorScheme) ? colorIndexMatch[3] === '48' : /^light$/i.test(colorScheme) ? colorIndexMatch[3] === '70' : colorIndexMatch[3] === '22') ? 'not all and ' : '') + cssRule.media.mediaText.replace(colorIndexRegExp, '$2');
          } else {
            // New style which supports complex media queries.
            var colorDepthMatch = (Object(cssRule.media).mediaText || '').match(/\( *(?:color|max-color): *(48842621|70318723|22511989) *\)/i);

            if (colorDepthMatch && colorDepthMatch.length > 1) {
              if (/^dark$/i.test(colorScheme) && (colorDepthMatch[1] === '48842621' || colorDepthMatch[1] === '22511989')) {
                // No preference or preferred is dark and rule is dark.
                cssRule.media.mediaText = cssRule.media.mediaText.replace(/\( *color: *(?:48842621|70318723) *\)/i, "(max-color: " + colorDepthMatch[1] + ")");
              } else if (/^light$/i.test(colorScheme) && (colorDepthMatch[1] === '70318723' || colorDepthMatch[1] === '22511989')) {
                // No preference or preferred is light and rule is light.
                cssRule.media.mediaText = cssRule.media.mediaText.replace(/\( *color: *(?:48842621|22511989) *\)/i, "(max-color: " + colorDepthMatch[1] + ")");
              } else {
                cssRule.media.mediaText = cssRule.media.mediaText.replace(/\( *max-color: *(?:48842621|70318723|22511989) *\)/i, "(color: " + colorDepthMatch[1] + ")");
              }
            }
          }
        }
      });
    });
  };

  var result = Object.defineProperty({
    hasNativeSupport: hasNativeSupport,
    removeListener: removeListener
  }, 'scheme', {
    get: function get() {
      return currentColorScheme;
    },
    set: set
  }); // initialize the color scheme using the provided value, the system value, or light

  var currentColorScheme = initialColorScheme || (mediaQueryList && mediaQueryList.matches ? 'dark' : 'light');
  set(currentColorScheme); // listen for system changes

  if (mediaQueryList) {
    if ('addEventListener' in mediaQueryList) {
      mediaQueryList.addEventListener('change', mediaQueryListener);
    } else {
      mediaQueryList.addListener(mediaQueryListener);
    }
  }

  return result;
};

module.exports = prefersColorSchemeInit;
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