// NGN Chassis
// Golden Ratio Typography Functions -------------------------------------------

// @function get-font-size
// Select appropriate font-size for viewport-width-range.
// Compares passed viewport upper bound to Chassis typography defaults and
// returns the matching font-size
@function get-font-size($type, $upper-bound, $multiplier: $global-typography-multiplier) {
  $range-upper-bound: null;

  @if unit($upper-bound) == 'px' {
    $range-upper-bound: $upper-bound;
  } @else {
    @warn '`#{unit($upper-bound)}` cannot be used as units for breakpoint bounds. Please use `px` instead.';
  }

  $font-size: null;

  @each $font-size-def in $font-size-defs {
    $def-upper-bound: map-get($font-size-def, upper-bound);

    @if $range-upper-bound >= $def-upper-bound {
      $font-sizes: map-get($font-size-def, font-sizes);

      @each $font-size-alias, $font-size-value in $font-sizes {
        @if $type == $font-size-alias {
          @if unit($font-size-value) == 'px' {
            $font-size: $font-size-value;
          } @else {
            @warn '`#{unit($upper-bound)}` cannot be used as units for Chassis Typography plugin font size definitions. Please use `px` instead.';
          }
        }
      }
    }
  }

  @return $font-size * $multiplier;
}

// @function get-line-height
// Select appropriate line-height for viewport-width-range.
// Compares passed viewport upper bound to Chassis typography defaults and
// calculates the appropriate line-height from the returned font-size
@function get-line-height($type, $upper-bound, $multiplier: $global-typography-multiplier) {
  $font-size: get-font-size($type, $upper-bound);
  @return $font-size * calculate-line-height($font-size, $upper-bound) * $multiplier;
}

// Heading Initialization ------------------------------------------------------
// The following functions are used to establish default vertical rhythm for
// headings (h1, h2, h3, etc)

// @function get-initial-heading-font-size
// calculate initial font-size value
@function get-initial-heading-font-size($alias, $first-upper-bound) {
  @return ( ( get-font-size($alias, $first-upper-bound) / get-font-size(root, $first-upper-bound) ) * 1em );
}

// @function get-initial-heading-line-height
// calculate initial line-height value
@function get-initial-heading-line-height($alias, $first-upper-bound) {
  @return ( ( get-line-height($alias, $first-upper-bound) / get-line-height(root, $first-upper-bound) ) * 1em );
}

// @function get-initial-heading-margin-bottom
// calculate initial margin-bottom value
@function get-initial-heading-margin-bottom($alias, $first-upper-bound) {
  @return ( ( get-line-height($alias, $first-upper-bound) / get-font-size($alias, $first-upper-bound) ) / $type-scale-ratio ) * 1em;
}

// Auto line-height ------------------------------------------------------------
// Use Golden Ratio math to find ideal line-heights for different viewport widths

// @function get-optimal-line-dimensions
// Return optimized line-height and width based on font-size and type-scale-ratio
// @param {px} $font-size
// @param {int} $ratio
// Type scale ratio
@function get-optimal-line-width($font-size, $ratio) {
	$line-height: strip-units($font-size * $ratio);
  @return (exponent($line-height, 2) * 1px);
}

// @function calculate-line-height
// Returns adjusted line-height for a particular font-size and viewport-width-range
// @param {px} $font-size
// @param {px} $upper-bound
// viewport-width-range upper bound
@function calculate-line-height($font-size, $upper-bound) {
	$optimal-line-width: get-optimal-line-width($font-size, $type-scale-ratio);

  // Pearsonified Golden Ratio Typography line height equation
  // http://www.pearsonified.com
	@return ( $type-scale-ratio - ( ( 1 / ( 2 * $type-scale-ratio ) ) * ( 1 - ( $upper-bound / $optimal-line-width ) ) ) );
}