/*============================================================================*
	MIXINS
	Moved from `colours.less` to avoid flooding stylesheet with documentation.
/*============================================================================*/
@theme-colour: #ffffff;


/**
 * Brighten a colour if it would be too dim to see with a dark-coloured theme.
 *
 * @colour: CSS colour value
 * @amount: Percentile value controlling the increase
 *          to the colour's luminosity and saturation.
 *
 * HACK: Saturation will be increased slightly to account for the "washed out"
 *       look when brightening a colour will high luminosity. This will destroy
 *       achromatic values, turning shades of grey into into a pale cyan.
 *       Use `.brighten-grey-if-needed` to brighten monochromatic colours.
 */
.brighten-if-needed(@colour, @amount: 25%)
when(lightness(@theme-colour) < 50%){
  color: saturate(lighten(@colour, @amount), @amount);
}
.brighten-if-needed(@colour, @amount: 25%)
when(lightness(@theme-colour) >= 50%){
  color: @colour;
}


/**
 * Brighten a greyscale colour if it's too close to the theme's background colour.
 *
 * @colour: An acromatic CSS colour value
 * @amount: Percentile value determining how far to increase the shade's brightness.
 *
 * NOTE: This mixin is identical to `.brighten-if-needed`, except that saturation
 *       won't be modified. This should theoretically be handled by the current
 *       mixin, except Less's syntax for branching sucks and I hate this language
 *       enough already without being forced to spoonfeed it.
 */
.brighten-grey-if-needed(@colour, @amount: 25%)
when(lightness(@theme-colour) < 50%){
  color: lighten(@colour, @amount);
}


/**
 * Darken a colour if it would be too bright to see with a light-coloured theme.
 *
 * @colour: CSS colour value
 * @amount: Percentile value controlling the decrease in luminosity.
 *
 * NOTE: There's no accompanying `.darken-grey-if-needed`, because
 *       the colour's saturation is not modified when darkening.
 */
.darken-if-needed(@colour, @amount: 25%)
when(lightness(@theme-colour) >= 50%){
  color: darken(@colour, @amount);
}
.darken-if-needed(@colour, @amount: 25%)
when(lightness(@theme-colour) < 50%){
  color: @colour;
}


/**
 * Utility class to provide JavaScript with a reliable brightness indicator.
 * Not a Less mixin, but the ruleset doesn't belong in `colours.less` either.
 */
.theme-colour-check{
  background: @theme-colour;
}