//
// DOCUMENTATION AND SOURCE AT
// https://github.com/tspringborg/responsively/
//

// GENERAL SETTINGS
$responsively-min-width: 375px !default;
$responsively-max-width: 1280px !default;
$responsively-rem-context: 16px !default;

// UTILITY FUNCTIONS //

@function rem($target, $context: $responsively-rem-context) {
    @return strip-unit($target / $context) * 1rem;
}
  
@function em($target, $context: 16, $unitless: false) {
    $unit: if($unitless, 1, 1em);
    @return strip-unit($target / $context) * $unit;
}


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

    $result: 0;
    $digits: 0;
    $minus: str-slice($value, 1, 1) == "-";
    $numbers: (
        "0": 0,
        "1": 1,
        "2": 2,
        "3": 3,
        "4": 4,
        "5": 5,
        "6": 6,
        "7": 7,
        "8": 8,
        "9": 9
    );

    @for $i from if($minus, 2, 1) through str-length($value) {
        $character: str-slice($value, $i, $i);

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

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

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

// Add `$unit` to `$value`
@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 index(map-keys($units), $unit) {
        $_: log("Invalid unit `#{$unit}`.");
        @return $_;
    }

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

// Removes unit from a value
@function strip-unit($value) {
    @return $value / ($value * 0 + 1);
}

// Splits a string on a separator
@function split-str($string, $separator) {
    $index: str-index($string, $separator);

    $str-1: str-slice($string, 1, $index - 1);
    $str-2: str-slice($string, $index + 1);

    @return $str-1 $str-2;
}

@mixin _r($min-vw, $max-vw, $min-value, $max-value, $properties) {
    @each $property in $properties {
        #{$property}: $min-value;
    }

    $max-minus-min-value: strip-unit($max-value - $min-value);
    @if (unit($min-value) == "rem" and unit($max-value) == "rem") {
        $max-minus-min-value: strip-unit($max-minus-min-value * $responsively-rem-context);
    }

    @media (min-width: $min-vw) {
        @each $property in $properties {
            #{$property}: calc(#{$min-value} + #{$max-minus-min-value} * (100vw - #{$min-vw}) / #{strip-unit($max-vw - $min-vw)});
        }
    }
  
    @media (min-width: $max-vw) {
        @each $property in $properties {
            #{$property}: $max-value;
        }
    }
}


@mixin responsively($properties, $values) {
    // default syntax
    $i: 1;
    @while $i <= length($values) {
        $min-vw: $responsively-min-width;
        $max-vw: $responsively-max-width;
        
        $initial: $i;
        $end: $i + 1;
        // might need to use previous end value as initial value
        @if $i + 1 > length($values) {
            $initial: $i - 1;
            $end: $i;
        }
        $initial-value: nth($values, $initial);
        $end-value: nth($values, $end);
        
        @if type-of($initial-value) == 'list' {
            // using the list syntax. like ($size: $value, $size: $value2, etc... )
            $min-vw: nth($initial-value, 1);
            $max-vw: nth($end-value, 1);
            $initial-value: nth($initial-value, 2);
            $end-value: nth($end-value, 2);
        } @else {
            // using the default shorthand syntax
            @if (type-of($initial-value) == "string") {
                // So it is a string does it have a "@" symbol to break apart
                @if (str-index($initial-value, "@")) {
                    // split string helper
                    $initial-value-list: split-str($initial-value, "@");
                    // unquote the split and cast the string to a number
                    // http://hugogiraudel.com/2014/01/15/sass-string-to-number/
                    $initial-value: to-number(unquote(nth($initial-value-list, 1)));
                    $min-vw: to-number(unquote(nth($initial-value-list, 2)));
                }
            }
            
            @if (type-of($end-value) == "string") {
                // So it is a string does it have a "@" symbol to break apart
                @if (str-index($end-value, "@")) {
                    // split string helper
                    $end-value-list: split-str($end-value, "@");
                    // unquote the split and cast the string to a number
                    // http://hugogiraudel.com/2014/01/15/sass-string-to-number/
                    $end-value: to-number(unquote(nth($end-value-list, 1)));
                    $max-vw: to-number(unquote(nth($end-value-list, 2)));
                }
            }
        }
        @include _r($min-vw, $max-vw, $initial-value, $end-value, $properties);
        
        $i: $i + 2
    }
}