@use 'sass:math';
@use 'sass:meta';
@use '../../functions/is-calculation' as *;
@use '../../functions/is-number' as *;

/// Apply a text shadow effect.
///
/// @param {Number} $x-offset [2px] - The x-axis offset of the shadow. Must be
/// a length or a unitless number (will be converted to a px value).
/// @param {Number} $y-offset [2px] - The x-axis offset of the shadow. Must be
/// a length or a unitless number (will be converted to a px value).
/// @param {Number} $blur [5px] - The blur-radius of the shadow. Must be
/// a length or a unitless number (will be converted to a px value).
/// @param {Color} $color [hsl(0, 0%, 0%, 0.4)] - The color of the shadow.
///
/// @group Utilities
/// @require {function} is-calculation
/// @require {function} is-number
@mixin text-shadow(
  $x-offset: 2px,
  $y-offset: 2px,
  $blur: 5px,
  $color: hsla(0, 0%, 0%, 0.4)
) {
  // Input scrubbing error check
  @if (
    not $x-offset or (not is-number($x-offset) and not is-calculation($x-offset))
  ) or (
    not $y-offset or (not is-number($y-offset) and not is-calculation($y-offset))
  ) or (
    $blur and not is-number($blur) and not is-calculation($blur)
  ) {
    @error 'Invalid input for the [ text-shadow() ] mixin. All parameters ' +
        'passed must either be a number or a calc() function, with the ' +
        'exception of the $blur parameter which is optional and may also ' +
        'be `null` or `false`.';
  }

  // If any value is unitless, convert it to a px value
  @if is-number($x-offset) and math.is-unitless($x-offset) {
    $x-offset: $x-offset * 1px;
  }

  @if is-number($y-offset) and math.is-unitless($y-offset) {
    $y-offset: $y-offset * 1px;
  }

  @if is-number($blur) and math.is-unitless($blur) {
    $blur: $blur * 1px;
  }

  // Set the blur to `null` if nothing or 0 is passed
  @if not $blur or $blur == 0px {
    $blur: null;
  }

  text-shadow: $x-offset $y-offset #{$blur} #{$color};
}