// Utility mixins and functions for evalutating source code across our variables, maps, and mixins.

// Descending
// Used to evaluate Sass maps like our grid breakpoints.
@mixin _check-descending($map, $map-name) {
  $prev-key: null;
  $prev-num: null;
  @each $key, $num in $map {
    @if $prev-num == null {
      // Do nothing
    } @else if not comparable($prev-num, $num) {
      @warn "Potentially invalid value for #{$map-name}: This map must be in descending order, but key '#{$key}' has value #{$num} whose unit makes it incomparable to #{$prev-num}, the value of the previous key '#{$prev-key}' !";
    } @else if $prev-num <= $num {
      @warn "Invalid value for #{$map-name}: This map must be in descending order, but key '#{$key}' has value #{$num} which isn't greater than #{$prev-num}, the value of the previous key '#{$prev-key}' !";
    }
    $prev-key: $key;
    $prev-num: $num;
  }
}

// Ascending
// Used to evaluate Sass maps like our grid container widths.
@mixin _check-ascending($map, $map-name) {
  $prev-key: null;
  $prev-num: null;
  @each $key, $num in $map {
    @if $prev-num == null {
      // Do nothing
    } @else if not comparable($prev-num, $num) {
      @warn "Potentially invalid value for #{$map-name}: This map must be in ascending order, but key '#{$key}' has value #{$num} whose unit makes it incomparable to #{$prev-num}, the value of the previous key '#{$prev-key}' !";
    } @else if $prev-num >= $num {
      @warn "Invalid value for #{$map-name}: This map must be in ascending order, but key '#{$key}' has value #{$num} which isn't smaller than #{$prev-num}, the value of the previous key '#{$prev-key}' !";
    }
    $prev-key: $key;
    $prev-num: $num;
  }
}

// Returns a blank string if smallest breakpoint, otherwise returns the name with a dash infront.
// Useful for making responsive utilities.
@function breakpoint-infix($name, $breakpoints: $grid-breakpoints) {
  @return if(breakpoint-min($name, $breakpoints) == null, "", "-#{$name}");
}

// Check if given number is even
@mixin _check-even($number, $name) {
  @if ($number % 2) != 0 {
    @if $name == "$grid-columns-number" {
      @error "#{$name} may not be odd, was #{$number}.";
    } @else {
      @warn "#{$name} may not be odd, was #{$number}.";
    }
  }
}

// Minimum breakpoint width.
@function breakpoint-min($name, $breakpoints: $grid-breakpoints) {
  $max: map-get($breakpoints, $name);
  @return if($max != 0, $max, null);
}

@function breakpoint-max($name, $breakpoints: $grid-breakpoints) {
  $next: breakpoint-next($name, $breakpoints);
  @return if($next, breakpoint-min($next, $breakpoints) - .02px, null);
}

// REturn the name of the next breakpoint. Null for the xl breakpoint
@function breakpoint-next($name, $breakpoints: $grid-breakpoints, $breakpoint-names: map-keys($breakpoints)) {
  $n: index($breakpoint-names, $name);
  @return if($n < length($breakpoint-names), nth($breakpoint-names, $n + 1), null);
}