////
/// String to number converter
/// @author Kitty Giraudel
/// @access private
////

///
/// Casts a string into a number
///
/// @param {String | Number} $value - Value to be parsed
///
/// @return {Number}
///

@function to-number($value) {
  @if meta.type-of($value) == 'number' {
    @return $value;
  } @else if meta.type-of($value) != 'string' {
    @error 'Value for `to-number` should be a number or a string.';
  }

  $first-character: string.slice($value, 1, 1);
  $result: 0;
  $digits: 0;
  $minus: ($first-character == '-');
  $numbers: (
    '0': 0,
    '1': 1,
    '2': 2,
    '3': 3,
    '4': 4,
    '5': 5,
    '6': 6,
    '7': 7,
    '8': 8,
    '9': 9,
  );

  // Remove +/- sign if present at first character
  @if ($first-character == '+' or $first-character == '-') {
    $value: string.slice($value, 2);
  }

  @for $i from 1 through string.length($value) {
    $character: string.slice($value, $i, $i);

    @if not(list.index(map.keys($numbers), $character) or $character == '.') {
      @return to-length(if($minus, -$result, $result), string.slice($value, $i));
    }

    @if $character == '.' {
      $digits: 1;
    } @else if $digits == 0 {
      $result: $result * 10 + map.get($numbers, $character);
    } @else {
      $digits: $digits * 10;
      $result: $result + math.div(map.get($numbers, $character), $digits);
    }
  }

  @return if($minus, -$result, $result);
}

///
/// Add `$unit` to `$value`
///
/// @param {Number} $value - Value to add unit to
/// @param {String} $unit - String representation of the unit
///
/// @return {Number} - `$value` expressed in `$unit`
///
@function to-length($value, $unit) {
  $units: (
    'px': 1px,
    'cm': 1cm,
    'mm': 1mm,
    '%': 1%,
    'ch': 1ch,
    'pc': 1pc,
    'in': 1in,
    'em': 1em,
    'rem': 1rem,
    'pt': 1pt,
    'ex': 1ex,
    'vw': 1vw,
    'vh': 1vh,
    'vmin': 1vmin,
    'vmax': 1vmax,
  );

  @if not list.index(map.keys($units), $unit) {
    @error 'Invalid unit `#{$unit}`.';
  }

  @return $value * map.get($units, $unit);
}
