//----------------------------------------------------------------------------------------------------------------------
// RHYTHM HELPER FUNCTION
//----------------------------------------------------------------------------------------------------------------------

/// Returns a (list of) length(s) in rem that represent(s) (a) specific number(s) of lines of the vertical rhythm grid.
///   - If given a unit-less number the function will calculate the length (in rem) of that number of grid lines.
///     Given number will be rounded with the exception of .5 as the only allowed fraction. This allows the use of
///     half-lines.
///   - If given a px or rem length the function will return the length (in rem) of the first number of grid lines that
///     can contain the given length.
/// @param {Length|List} $size - Either numbers of grid lines (`.5`, `1`, `2`, `…`, `n`) or px/rem values, takes lists as well
/// @param {Length} $rhythm-unit [$rhythm-unit] - Specify a non-default rhythm base unit (optional)
/// @return {Length|List} `rem` value(s)
/// @example scss Assuming `$rhythm-unit: 16px`
///   rhythm(1)
///   // 1rem
///   rhythm(5)
///   // 5rem
///   rhythm(32px)
///   // 2rem
///   rhythm(33px)
///   // 3rem
///   rhythm(38px)
///   // 3rem
///   rhythm(48px)
///   // 3rem
///   rhythm(49px)
///   // 4rem
///   rhythm(1.5rem) // Works with rem
///   // 2rem
///   rhythm(2 1rem 16px) // Works with lists and mixed units, too
///   // 2rem 1rem 1rem
///   rhythm(32px, 12px) // Non-default rhythm base
///   // 3rem
@function rhythm($size, $rhythm-unit: $rhythm-unit) {
	@if type-of($size) == list {
		$return: ();
		@each $s in $size {
			$return: append($return, rhythm($s, $rhythm-unit), space);
		}
		@return $return;
	}
	@if unitless($size) { // If given a number of desired lines...
		@if $size != 0.5 { // Only allowed fraction is .5
			$size: round($size);
		}
		@return rem($size * $rhythm-unit); // Return height in rem
	} @else {
		@if unit($size) != "rem" {
			$size: rem($size); // Convert to rem if given length is not in rem
		}
		$i: 0.5; // Start with half line
		@while true { // Increase number of lines until $size fits
			$line-height: rhythm($i); // Return rem value
			@if $line-height >= $size {
				@return $line-height;
			}
			@if $i == 0.5 { // Special condition to increment from .5 to 1
				$i: 1;
			} @else {
				$i: $i + 1;
			}
		}
	}
}