/** 
based on framer-motion@4.0.3,
Copyright (c) 2018 Framer B.V.
*/
import { __rest, __read } from 'tslib';
//import { invariant } from 'hey-listen';

function isCSSVariable(value) {
    return typeof value === "string" && value.startsWith("var(--");
}
/**
 * Parse Framer's special CSS variable format into a CSS token and a fallback.
 *
 * ```
 * `var(--foo, #fff)` => [`--foo`, '#fff']
 * ```
 *
 * @param current
 */
var cssVariableRegex = /var\((--[a-zA-Z0-9-_]+),? ?([a-zA-Z0-9 ()%#.,-]+)?\)/;
function parseCSSVariable(current) {
    var match = cssVariableRegex.exec(current);
    if (!match)
        return [,];
    var _a = __read(match, 3), token = _a[1], fallback = _a[2];
    return [token, fallback];
}
var maxDepth = 4;
function getVariableValue(current, element, depth) {
    if (depth === void 0) { depth = 1; }
    //invariant(depth <= maxDepth, "Max CSS variable fallback depth detected in property \"" + current + "\". This may indicate a circular fallback dependency.");
    var _a = __read(parseCSSVariable(current), 2), token = _a[0], fallback = _a[1];
    // No CSS variable detected
    if (!token)
        return;
    // Attempt to read this CSS variable off the element
    var resolved = window.getComputedStyle(element).getPropertyValue(token);
    if (resolved) {
        return resolved.trim();
    }
    else if (isCSSVariable(fallback)) {
        // The fallback might itself be a CSS variable, in which case we attempt to resolve it too.
        return getVariableValue(fallback, element, depth + 1);
    }
    else {
        return fallback;
    }
}
/**
 * Resolve CSS variables from
 *
 * @internal
 */
function resolveCSSVariables(visualElement, _a, transitionEnd) {
    var _b;
    var target = __rest(_a, []);
    var element = visualElement.getInstance();
    if (!(element instanceof HTMLElement))
        return { target: target, transitionEnd: transitionEnd };
    // If `transitionEnd` isn't `undefined`, clone it. We could clone `target` and `transitionEnd`
    // only if they change but I think this reads clearer and this isn't a performance-critical path.
    if (transitionEnd) {
        transitionEnd = Object.assign({}, transitionEnd);
    }
    // Go through existing `MotionValue`s and ensure any existing CSS variables are resolved
    visualElement.forEachValue(function (value) {
        var current = value.get();
        if (!isCSSVariable(current))
            return;
        var resolved = getVariableValue(current, element);
        if (resolved)
            value.set(resolved);
    });
    // Cycle through every target property and resolve CSS variables. Currently
    // we only read single-var properties like `var(--foo)`, not `calc(var(--foo) + 20px)`
    for (var key in target) {
        var current = target[key];
        if (!isCSSVariable(current))
            continue;
        var resolved = getVariableValue(current, element);
        if (!resolved)
            continue;
        // Clone target if it hasn't already been
        target[key] = resolved;
        // If the user hasn't already set this key on `transitionEnd`, set it to the unresolved
        // CSS variable. This will ensure that after the animation the component will reflect
        // changes in the value of the CSS variable.
        if (transitionEnd)
            (_b = transitionEnd[key]) !== null && _b !== void 0 ? _b : (transitionEnd[key] = current);
    }
    return { target: target, transitionEnd: transitionEnd };
}

export { cssVariableRegex, parseCSSVariable, resolveCSSVariables };
