@use '../utils/throw';
@use 'parse';
@use 'sass:map';
@use 'sass:math';
@use 'sass:meta';

/// # Relative Colors
/// The primary advantage of LCH color
/// is the ability to
/// generate one color from another
/// by adjust channels,
/// and expect consistent results.
///
/// @link https://www.w3.org/TR/css-color-5/ CSS Colors Level 5
/// @group adjust

/// Set individual Lab or LCH channels
/// to specific values,
/// and return the adjusted color.
/// All arguments must be given by keyword,
/// rather than positional order.
/// @example scss
///   .set {
///     chroma: blend.set(rebeccapurple, $chroma: 20);
///     shorthand: blend.set(rebeccapurple, $c: 20);
///   }
/// @param {color} $color -
///   The initial Sass color being adjusted
/// @param {percentage} $lightness [null] -
///   Set lightness to a percentage between 0 and 100%
///   (Can also use the `$l` keyword shorthand)
/// @param {number} $chroma [null] -
///   Set chroma to a positive number (generally 0-100)
///   (Can also use the `$c` keyword shorthand)
/// @param {angle} $hue [null] -
///   Set hue to an angle (0deg-360deg)
///   (Can also use the `$h` keyword shorthand)
/// @param {number} $a [null] -
///   Set the Lab `a` channel to any number ±160
/// @param {number} $b [null] -
///   Set the Lab `b` channel to any number ±160
/// @throw Cannot set both Lab & LCH channels at once
/// @group adjust
@function set(
  $color,
  $channels...
) {
  $adjust: parse.args(meta.keywords($channels), 'set');
  @return parse.do('set', $color, $adjust);
}

/// Adjust individual Lab or LCH channels
/// up or down by a given amount,
/// and return the adjusted color.
/// All arguments must be given by keyword,
/// rather than positional order.
/// @example scss
///   .set {
///     hue: blend.adjust(rebeccapurple, $hue: -60);
///     shorthand: blend.adjust(rebeccapurple, $h: -60);
///   }
/// @param {color} $color -
///   The initial Sass color being adjusted
/// @param {number} $lightness [null] -
///   Adjust lightness by given amount
///   (Can also use the `$l` keyword shorthand)
/// @param {number} $chroma [null] -
///   Adjust chroma by given amount
///   (Can also use the `$c` keyword shorthand)
/// @param {number} $hue [null] -
///   Adjust hue by given number of degrees
///   (Can also use the `$h` keyword shorthand)
/// @param {number} $a [null] -
///   Adjust Lab `a` by given amount
/// @param {number} $b [null] -
///   Adjust Lab `b` by given amount
/// @throw Cannot adjust both Lab & LCH channels at once
/// @group adjust
@function adjust(
  $color,
  $channels...
) {
  $adjust: parse.args(meta.keywords($channels), 'adjust');
  @return parse.do('adjust', $color, $adjust);
}

/// Fluidly scale Lab or LCH channels
/// up or down by a given percentage,
/// and return the adjusted color.
/// All arguments must be given by keyword,
/// rather than positional order.
/// @example scss
///   .set {
///     lightness: blend.adjust(rebeccapurple, $lightness: 50%);
///     shorthand: blend.adjust(rebeccapurple, $l: 50%);
///   }
/// @param {color} $color -
///   The initial Sass color being adjusted
/// @param {percentage} $lightness [null] -
///   Scale lightness by given percentage
///   of the distance towards 0 or 100
///   (Can also use the `$l` keyword shorthand)
/// @param {percentage} $chroma [null] -
///   Scale chroma by given percentage
///   of the distance towards 0 or 100
///   (Can also use the `$c` keyword shorthand)
/// @param {percentage} $hue [null] -
///   Adjust hue by given percentage of the hue wheel
///   (Can also use the `$h` keyword shorthand)
/// @param {percentage} $a [null] -
///   Scale Lab `a` by given percentage
///   of the distance towards 160 or -160
/// @param {percentage} $b [null] -
///   Scale Lab `b` by given percentage
///   of the distance towards 160 or -160
/// @throw Cannot scale both Lab & LCH channels at once
/// @throw Scales must be defined using `%` units
/// @group adjust
@function scale(
  $color,
  $channels...
) {
  $channels: meta.keywords($channels);

  @each $channel in map.values($channels) {
    @if (math.unit($channel) != '%') {
      @return throw.error(
        'Scales must be defined using `%` units',
        'scale()'
      );
    }
  }

  $adjust: parse.args($channels, 'scale');
  @return parse.do('scale', $color, $adjust);
}