source: node_modules/prismjs/plugins/match-braces/prism-match-braces.js

(function () {

        if (typeof Prism === 'undefined' || typeof document === 'undefined') {
                return;
        }

        function mapClassName(name) {
                var customClass = Prism.plugins.customClass;
                if (customClass) {
                        return customClass.apply(name, 'none');
                } else {
                        return name;
                }
        }

        var PARTNER = {
                '(': ')',
                '[': ']',
                '{': '}',
        };

        // The names for brace types.
        // These names have two purposes: 1) they can be used for styling and 2) they are used to pair braces. Only braces
        // of the same type are paired.
        var NAMES = {
                '(': 'brace-round',
                '[': 'brace-square',
                '{': 'brace-curly',
        };

        // A map for brace aliases.
        // This is useful for when some braces have a prefix/suffix as part of the punctuation token.
        var BRACE_ALIAS_MAP = {
                '${': '{', // JS template punctuation (e.g. `foo ${bar + 1}`)
        };

        var LEVEL_WARP = 12;

        var pairIdCounter = 0;

        var BRACE_ID_PATTERN = /^(pair-\d+-)(close|open)$/;

        /**
         * Returns the brace partner given one brace of a brace pair.
         *
         * @param {HTMLElement} brace
         * @returns {HTMLElement}
         */
        function getPartnerBrace(brace) {
                var match = BRACE_ID_PATTERN.exec(brace.id);
                return document.querySelector('#' + match[1] + (match[2] == 'open' ? 'close' : 'open'));
        }

        /**
         * @this {HTMLElement}
         */
        function hoverBrace() {
                if (!Prism.util.isActive(this, 'brace-hover', true)) {
                        return;
                }

                [this, getPartnerBrace(this)].forEach(function (e) {
                        e.classList.add(mapClassName('brace-hover'));
                });
        }
        /**
         * @this {HTMLElement}
         */
        function leaveBrace() {
                [this, getPartnerBrace(this)].forEach(function (e) {
                        e.classList.remove(mapClassName('brace-hover'));
                });
        }
        /**
         * @this {HTMLElement}
         */
        function clickBrace() {
                if (!Prism.util.isActive(this, 'brace-select', true)) {
                        return;
                }

                [this, getPartnerBrace(this)].forEach(function (e) {
                        e.classList.add(mapClassName('brace-selected'));
                });
        }

        Prism.hooks.add('complete', function (env) {

                /** @type {HTMLElement} */
                var code = env.element;
                var pre = code.parentElement;

                if (!pre || pre.tagName != 'PRE') {
                        return;
                }

                // find the braces to match
                /** @type {string[]} */
                var toMatch = [];
                if (Prism.util.isActive(code, 'match-braces')) {
                        toMatch.push('(', '[', '{');
                }

                if (toMatch.length == 0) {
                        // nothing to match
                        return;
                }

                if (!pre.__listenerAdded) {
                        // code blocks might be highlighted more than once
                        pre.addEventListener('mousedown', function removeBraceSelected() {
                                // the code element might have been replaced
                                var code = pre.querySelector('code');
                                var className = mapClassName('brace-selected');
                                Array.prototype.slice.call(code.querySelectorAll('.' + className)).forEach(function (e) {
                                        e.classList.remove(className);
                                });
                        });
                        Object.defineProperty(pre, '__listenerAdded', { value: true });
                }

                /** @type {HTMLSpanElement[]} */
                var punctuation = Array.prototype.slice.call(
                        code.querySelectorAll('span.' + mapClassName('token') + '.' + mapClassName('punctuation'))
                );

                /** @type {{ index: number, open: boolean, element: HTMLElement }[]} */
                var allBraces = [];

                toMatch.forEach(function (open) {
                        var close = PARTNER[open];
                        var name = mapClassName(NAMES[open]);

                        /** @type {[number, number][]} */
                        var pairs = [];
                        /** @type {number[]} */
                        var openStack = [];

                        for (var i = 0; i < punctuation.length; i++) {
                                var element = punctuation[i];
                                if (element.childElementCount == 0) {
                                        var text = element.textContent;
                                        text = BRACE_ALIAS_MAP[text] || text;
                                        if (text === open) {
                                                allBraces.push({ index: i, open: true, element: element });
                                                element.classList.add(name);
                                                element.classList.add(mapClassName('brace-open'));
                                                openStack.push(i);
                                        } else if (text === close) {
                                                allBraces.push({ index: i, open: false, element: element });
                                                element.classList.add(name);
                                                element.classList.add(mapClassName('brace-close'));
                                                if (openStack.length) {
                                                        pairs.push([i, openStack.pop()]);
                                                }
                                        }
                                }
                        }

                        pairs.forEach(function (pair) {
                                var pairId = 'pair-' + (pairIdCounter++) + '-';

                                var opening = punctuation[pair[0]];
                                var closing = punctuation[pair[1]];

                                opening.id = pairId + 'open';
                                closing.id = pairId + 'close';

                                [opening, closing].forEach(function (e) {
                                        e.addEventListener('mouseenter', hoverBrace);
                                        e.addEventListener('mouseleave', leaveBrace);
                                        e.addEventListener('click', clickBrace);
                                });
                        });
                });

                var level = 0;
                allBraces.sort(function (a, b) { return a.index - b.index; });
                allBraces.forEach(function (brace) {
                        if (brace.open) {
                                brace.element.classList.add(mapClassName('brace-level-' + (level % LEVEL_WARP + 1)));
                                level++;
                        } else {
                                level = Math.max(0, level - 1);
                                brace.element.classList.add(mapClassName('brace-level-' + (level % LEVEL_WARP + 1)));
                        }
                });
        });

}());