// Dirg
// ====

// Scales
$dirg-scales: (
  default: (
    font-size: 14px,
    unit: 14px * 1.5,
    factor: 1.35
  )
);

// A power calculation function. See:
// http://sassmeister.com/gist/10620fefd1ed75189f1b
@function pow($x, $y) {
  $ret: 1;

  @if $y > 0 {
    @for $i from 1 through $y {
      $ret: $ret * $x;
    }
  }

  @else {
    @for $i from $y to 0 {
      $ret: $ret / $x;
    }
  }

  @return $ret;
}

// Returns a value to be used in `font-size`.
@function font-scale($x, $size: 'default') {
  $scale: map-get($dirg-scales, $size);
  $factor: map-get($scale, 'factor');
  $font-size: map-get($scale, 'font-size');
  @return round($font-size * pow($factor, $x));
}

// Returns the diff between two values in a growth/shrink factor.
@function factor-diff($args...) {
  $arguments: keywords($args);
  @return map-get($arguments, to) / map-get($arguments, from);
}

// Returns a grid unit of space, calculated from the scale above.
@function units($x, $size: 'default') {
  $scale: map-get($dirg-scales, $size);
  @return round(map-get($scale, 'unit') * $x);
}

// Shortcut for adding multiple units and institute columns thinking.
@function columns($x, $size: 'default') {
  @return units(4, $size) * $x;
}

// A helper for setting an appropriate font size and line-height for it.
@mixin font-size($units, $size: 'default') {
  $scale: map-get($dirg-scales, $size);
  $unit: map-get($scale, 'unit');
  $lh: $unit;

  @while $lh < font-scale($units, $size) {
    $lh: $lh + $unit;
  }

  font-size: font-scale($units, $size);
  line-height: $lh;
}