_plumber-box.scss

// PLUMBER BOX - Plumber extension to align boxes to the baseline grid
// https://github.com/jamonserrano/plumber-box
// https://jamonserrano.github.io/plumber-sass
// Copyright 2017 Viktor Honti
// MIT License

@mixin plumber-box(
	$margin: 0 0,
	$border: 0px 0px,
	$padding: 0 0,
	$grid-height: null
) {
	// *** MAKE SURE THAT PLUMBER IS INCLUDED ***
	@if not function-exists(-plumber-get-default) {
		@error 'Plumber-box depends on plumber-sass. Please install and include plumber-sass first';
	}

	// *** VALIDATE PARAMETERS ***
	// if grid-height is missing try to get it from Plumber defaults
	@if not $grid-height {
		$grid-height: -plumber-get-default(grid-height);
	}
	@if not $grid-height {
		// no luck :(
		@error '$grid-height must be passed as a parameter or defined with -plumber-set-defaults';
	} @else if unitless($grid-height) or $grid-height <= 0 {
		// got it, check validity
		@error '$grid-height parameter must be a positive unit, got #{$grid-height} instead';
	}

	// if margin has one value use it for both top and bottom
	@if length($margin) == 1 {
		$top: $margin;
		$margin: ($top $top);
	}
	// check validity
	@each $value in $margin {
		@if not -plumber-is-integer($value) {
			@error '$margin values must be integers, got #{$value} instead';
		}
	}

	// if margin has one value use it for both top and bottom
	@if length($border) == 1 {
		$top: $border;
		$border: ($top $top);
	}
	// check validity
	@each $value in $border {
		@if unitless($value) and $value == 0 {
			$value: 0px;
		}
		@else if unit($value) != 'px' or $value < 0 {
			@error '$border values must be non-negative pixels, got #{$value} instead';
		}
	}

	// if padding has one value use it for both top and bottom
	@if length($padding) == 1 {
		$top: $padding;
		$padding: ($top $top);
	}
	// check validity
	@each $value in $padding {
		@if not -plumber-is-integer($value) or $value < 0 {
			@error '$padding values must be non-negative integers, got #{$value} instead';
		}
	}

	// *** CSS OUTPUT ***
	@each $position, $index in (top: 1, bottom: 2) {
		margin-#{$position}: nth($margin, $index) * $grid-height;
		
		$currentPadding: nth($padding, $index);
		$currentBorder: nth($border, $index);
		@if $currentBorder > 0 and $currentPadding == 0 {
			@error 'Cannot use borders with 0 padding';
		}

		padding-#{$position}: calc(#{$currentPadding * $grid-height} - #{$currentBorder});
		border-#{$position}-width: $currentBorder;
	}
}