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path: root/src/sass/lib/css-vars.scss
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// Downloaded from https://github.com/malyw/css-vars (and modified)

// global map to be filled via variables
$css-vars: ();

// the variable may be set to "true" anywhere in the code,
// so native CSS custom properties will be used instead of the Sass global map
$css-vars-use-native: false !default;

///
// Assigns a variable to the global map
///
@function css-var-assign($varName: null, $varValue: null) {
    @return map-merge(
        $css-vars,
        (
            $varName: $varValue,
        )
    );
}

///
// Emulates var() CSS native function behavior
//
// $args[0] {String} "--" + variable name
// [$args[1]] Optional default value if variable is not assigned yet
//
// E.G.:
// color: var(--main-color);
// background: var(--main-background, green);
///
@function var($args...) {
    // CHECK PARAMS
    @if (length($args) ==0) {
        @error 'Variable name is expected to be passed to the var() function';
    }
    @if (str-length(nth($args, 1)) < 2 or str-slice(nth($args, 1), 0, 2) != '--') {
        @error "Variable name is expected to start from '--'";
    }

    // PROCESS
    $var-name: nth($args, 1);
    $var-value: map-get($css-vars, $var-name);

    @if ($css-vars-use-native) {
        // CSS variables
        // Native CSS: don't process function in case of native
        @return unquote('var(' + $args + ')');
    } @else {
        @if ($var-value == null) {
            // variable is not provided so far
            @if (length($args) == 2) {
                $var-value: nth($args, 2);
            }
        }

        // Sass: return value from the map
        @return $var-value;
    }
}

///
// SASS mixin to provide variables
// E.G.:
// @include css-vars((
//    --color: rebeccapurple,
//    --height: 68px,
//    --margin-top: calc(2vh + 20px)
// ));
///
@mixin css-vars($var-map: null) {
    // CHECK PARAMS
    @if ($var-map == null) {
        @error 'Map of variables is expected, instead got: null';
    }
    @if (type_of($var-map) != map) {
        @error 'Map of variables is expected, instead got another type passed: #{type_of($var, ap)}';
    }

    // PROCESS
    @if ($css-vars-use-native) {
        // CSS variables
        // Native CSS: assign CSS custom properties to the global scope
        @at-root :root {
            @each $var-name, $var-value in $var-map {
                @if (type_of($var-value) == string) {
                    #{$var-name}: $var-value; // to prevent quotes interpolation
                } @else {
                    #{$var-name}: #{$var-value};
                }
            }
        }
    } @else {
        // Sass or debug
        // merge variables and values to the global map (provides no output)
        @each $var-name, $var-value in $var-map {
            $css-vars: css-var-assign($varName, $varValue) !global; // store in global variable
        }
    }
}