// Grid Syntax
// ===========

// layout math
// - static | fluid
$layout-math          : fluid           !default;

// layout method
// - isolate | float
$layout-method        : float           !default;

// layout direction
// - ltr | rtl
$flow                 : ltr             !default;

// box-sizing
// false | border-box | content-box
$box-sizing           : false           !default;

// container justification
// - left | center | right
$container-position   : center          !default;

// gutter handling
// - before | after | split
$gutter-position      : after           !default;

// show/hide grids
// show | show-columns | show-baseline | hide
$show-grids           : show-columns    !default;

// Set Grid
// --------
// Set a new grid using a shorthand
// - $grid      : <settings>
// - [$clean]   : true | false (resets container, column-width, & box-sizing)
@mixin set-grid(
  $grid,
  $clean: false
) {

  $grid                 : get-adjusted-grid($grid, $clean);

  // get values
  $columns              : get-setting(columns, $grid);
  $gutters              : get-setting(gutters, $grid);
  $container            : get-setting(container, $grid);
  $column-width         : get-setting(column-width, $grid);
  $layout-math          : get-setting(layout-math, $grid);
  $layout-method        : get-setting(layout-method, $grid);

  $flow                 : get-setting(flow, $grid);
  $gutter-position      : get-setting(gutter-position, $grid);
  $container-position   : get-setting(container-position, $grid);
  $show-grids           : get-setting(show-grids, $grid);
  $box                  : get-setting(box-sizing, $grid);

  $container            : get-setting(container, $grid);
  $column-width         : get-setting(column-width, $grid);
  $box-sizing           : get-setting(box-sizing, $grid);
}

// Use Grid
// --------
// Use an arbitrary grid for a section of code
// - $grid      : <settings>
// - [$clean]   : true | false (resets container, column-width, & box-sizing)
@mixin use-grid(
  $grid,
  $clean: false
) {
  $old-grid: get-grid();

  @include set-grid($grid, $clean);
  @content;
  @include set-grid($old-grid, $clean);
}

// Get Grid
// --------
// Get the current grid settings as a shorthand list
@function get-grid(
) {
  $new-gutters        : $gutters;
  $new-show-grids     : false;

  // Use units for column/gutter ratio if available
  @if $column-width {
    $new-gutters: $column-width $column-width * $gutters;
  }

  // Create keyword for show-grids setting
  @if type-of($show-grids) == bool {
    @if $show-grids {
      $new-show-grids: show;
    } @else {
      $new-show-grids: hide;
    }
  } @else {
    $new-show-grids: $show-grids;
  }

  // Return grid shorthand
  @return compact($container $columns $new-gutters $layout-math $layout-method $container-position $new-show-grids $flow $gutter-position $box-sizing);
}

// Parse Grid
// ----------
// Parse a shorthand grid, and return an ordered list of settings
// - [$grid]  : <settings>
@function parse-grid(
  $grid: get-grid()
) {
  $new-columns              : false;
  $new-gutters              : false;
  $new-container            : false;
  $new-column-width         : false;
  $new-layout-math          : false;
  $new-layout-method        : false;
  $new-container-position   : false;
  $new-flow                 : false;
  $new-gutter-position      : false;
  $new-show-grids           : false;
  $new-box-sizing           : false;

  $columns-check            : false;

  @each $value in $grid {
    @if type-of($value) == string {
      // layout-math: static | fluid
      @if $value == static {
        $new-layout-math: static;
      } @else if $value == fluid {
        $new-layout-math: fluid;
      }

      // layout-method: isolate | fluid
      @if $value == isolate {
        $new-layout-method: isolate;
      } @else if $value == float {
        $new-layout-method: float;
      }

      // container-position: left | center | right
      @if $value == left {
        $new-container-position: left;
      } @else if $value == right {
        $new-container-position: right;
      } @else if $value == center {
        $new-container-position: center;
      }

      // flow: ltr | rtl
      @if $value == rtl {
        $new-flow: rtl;
      } @else if $value == ltr {
        $new-flow: ltr;
      }

      // show-grid: show | hide
      @if $value == show {
        $new-show-grids: show;
      } @else if $value == hide {
        $new-show-grids: hide;
      } @else if $value == show-columns {
        $new-show-grids: show-columns;
      } @else if $value == show-baseline {
        $new-show-grids: show-baseline;
      }

      // gutter-position: before | after | split | no-gutters
      @if $value == before {
        $new-gutter-position: before;
      } @else if $value == after {
        $new-gutter-position: after;
      } @else if $value == split {
        $new-gutter-position: split;
      } @else if $value == inside {
        $new-gutter-position: inside;
      } @else if $value == no-gutters {
        $new-gutter-position: no-gutters;
      }

      // box-sizing: border-box | content-box
      @if $value == border-box {
        $new-box-sizing: border-box;
      } @else if $value == content-box {
        $new-box-sizing: content-box;
      }

      // auto container
      @if $value == auto {
        $new-container: auto;
      }
    }

    // container, columns, or gutters
    @else if type-of($value) == number {
      @if not unitless($value) {
        $new-container: $value;
      } @else if not $columns-check {
        $new-columns: $value;
        $columns-check: true;
      } @else {
        $new-gutters: $value;
      }
    }

    // columns or gutters
    @else if type-of($value) == list {
      @if unitless(nth($value,1)) {
        $new-columns: $value;
        $columns-check: true;
      } @else {
        $new-column-width: nth($value,1);
        $new-gutters: nth($value,2) / nth($value,1);
      }
    }
  }

  @return $new-columns $new-gutters $new-container $new-column-width $new-layout-math $new-layout-method $new-container-position $new-flow $new-gutter-position $new-show-grids $new-box-sizing;
}

// Get Adjusted Grid
// -----------------
// Fill missing grid values based on global settings
// - $grid      : <settings>
// - [$clean]   : true | false (resets container, column-width, & box-sizing)
@function get-adjusted-grid(
  $grid,
  $clean: false
) {
  $grid                   : parse-grid($grid);

  $new-columns            : get-setting(columns, $grid);
  $new-gutters            : get-setting(gutters, $grid);
  $new-layout-math        : get-setting(layout-math, $grid);
  $new-layout-method      : get-setting(layout-method, $grid);
  $new-flow               : get-setting(flow, $grid);
  $new-gutter-place       : get-setting(gutter-position, $grid);
  $new-container-position : get-setting(container-position, $grid);
  $new-show-grids         : get-setting(show-grids, $grid);

  $new-container          : get-setting(container, $grid);
  $new-column-width       : get-setting(column-width, $grid);
  $new-box-sizing         : get-setting(box-sizing, $grid);

  // Set required values
  $new-columns            : if($new-columns, $new-columns, $columns);
  $new-gutters            : if($new-gutters, $new-gutters, $gutters);
  $new-layout-math        : if($new-layout-math, $new-layout-math, $layout-math);
  $new-layout-method      : if($new-layout-method, $new-layout-method, $layout-method);
  $new-flow               : if($new-flow, $new-flow, $flow);
  $new-gutter-place       : if($new-gutter-place, $new-gutter-place, $gutter-position);
  $new-container-position : if($new-container-position, $new-container-position, $container-position);
  $new-show-grids         : if($new-show-grids, $new-show-grids, $show-grids);

  // optionally fill values based on current grid
  @if $clean {
    $new-container        : if($new-container, $new-container, auto);
  } @else {
    $new-container        : if($new-container, $new-container, $container);
    $new-column-width     : if($new-column-width, $new-column-width, $column-width);
    $new-box-sizing       : if($new-box-sizing, $new-box-sizing, $box-sizing);
  }

  @return $new-columns, $new-gutters, $new-container, $new-column-width, $new-layout-math, $new-layout-method, $new-container-position, $new-flow, $new-gutter-place, $new-show-grids, $new-box-sizing;
}

// Get Setting
// -----------
// Return one setting from a shorhand grid
// - setting    : <keyword> (see $options below)
// - $grid      : <settings>
// - [$parse]   : true | false
@function get-setting(
  $setting,
  $grid   : parse-grid(),
  $parse  : false
) {
  $options  : columns gutters container column-width layout-math layout-method container-position flow gutter-position show-grids box-sizing;
  $key      : index($options, $setting);
  $value    : false;

  @if $parse {
    $grid: parse-grid($grid);
  }

  @if $key {
    $value: nth($grid, $key);
  } @else {
    @warn '"#{$setting}" is not a valid grid setting.';
  }

  @return $value;
}