@use '../utils/array';
@use '../convert';
@use '../cie';
@use 'parse';
@use 'sass:color';
@use 'sass:list';

/// We also provide a compact syntax for LCH adjustments,
/// based on the proposed CSS _relative color syntax_.
/// Since Sass is not able to mimic the syntax exactly,
/// we've developed a shorthand based on the CSS proposal.
///
/// For each channel:
///   - The single-letter channel name (`l | c | h`)
///     represents no change to the current value of the channel
///   - A single number will replace the current channel value
///   - A number with `l | c | h` units will multiply the channel
///   - `l | c | h` followed by a percentage will scale the channel
///     relative to available range
///   - `l | c | h` followed by an amount
///     will add or subtract that amount from the current value
///
/// @link https://www.w3.org/TR/css-color-5/#relative-colors CSS Specification
/// @colors adjust-from
/// @example scss
///   .from {
///     // set chroma to 20
///     set: blend.from(rebeccapurple, l, 20, h);
///
///     // linear adjustments to a channel
///     adjust: blend.from(rebeccapurple, l, c, h -60);
///
///     // relative scale, e.g. "half-way to white"
///     scale: blend.from(rebeccapurple, l 50%, c, h);
///
///     // multiply the channel value
///     multiply: blend.from(rebeccapurple, 2l, c, h);
///   }
/// @param {color} $color -
///   The initial Sass color being adjusted
/// @param {l | number | l number} $l [l] -
///   Adjustments to the `l` channel:
/// @param {c | number | c number} $c [c] -
///   Adjustments to the `c` channel
/// @param {h | number | h number} $h [h] -
///   Adjustments to the `h` channel
/// @return {color} - The final color after adjustments
/// @group adjust
@function from(
  $color,
  $lightness: l,
  $chroma: c,
  $hue: h,
) {
  $a: color.alpha($color);
  $lch: convert.sassToLCH($color);

  @for $i from 1 through 3 {
    $val: list.nth($lch, $i);
    $adjust: list.nth($lightness $chroma $hue, $i);
    $key: list.nth(l c h, $i);
    $lch: list.set-nth($lch, $i, parse.from($val, $adjust, $key));
  }

  @return cie.lch($lch, $a);
}