source: frontend/node_modules/svgo/plugins/inlineStyles.js

'use strict';

exports.type = 'full';

exports.active = true;

exports.params = {
    onlyMatchedOnce: true,
    removeMatchedSelectors: true,
    useMqs: ['', 'screen'],
    usePseudos: ['']
};

exports.description = 'inline styles (additional options)';


var csstree = require('css-tree'),
    cssTools = require('../lib/css-tools');

/**
 * Moves + merges styles from style elements to element styles
 *
 * Options
 *   onlyMatchedOnce (default: true)
 *     inline only selectors that match once
 *
 *   removeMatchedSelectors (default: true)
 *     clean up matched selectors,
 *     leave selectors that hadn't matched
 *
 *   useMqs (default: ['', 'screen'])
 *     what media queries to be used
 *     empty string element for styles outside media queries
 *
 *   usePseudos (default: [''])
 *     what pseudo-classes/-elements to be used
 *     empty string element for all non-pseudo-classes and/or -elements
 *
 * @param {Object} document document element
 * @param {Object} opts plugin params
 *
 * @author strarsis <strarsis@gmail.com>
 */
exports.fn = function(document, opts) {

    // collect <style/>s
    var styleEls = document.querySelectorAll('style');

    //no <styles/>s, nothing to do
    if (styleEls === null) {
        return document;
    }

    var styles = [],
        selectors = [];

    for (var styleEl of styleEls) {
        if (styleEl.isEmpty() || styleEl.closestElem('foreignObject')) {
            // skip empty <style/>s or <foreignObject> content.
            continue;
        }

        var cssStr = cssTools.getCssStr(styleEl);

        // collect <style/>s and their css ast
        var cssAst = {};
        try {
            cssAst = csstree.parse(cssStr, {
                parseValue: false,
                parseCustomProperty: false
            });
        } catch (parseError) {
            // console.warn('Warning: Parse error of styles of <style/> element, skipped. Error details: ' + parseError);
            continue;
        }

        styles.push({
            styleEl: styleEl,
            cssAst: cssAst
        });

        selectors = selectors.concat(cssTools.flattenToSelectors(cssAst));
    }


    // filter for mediaqueries to be used or without any mediaquery
    var selectorsMq = cssTools.filterByMqs(selectors, opts.useMqs);


    // filter for pseudo elements to be used
    var selectorsPseudo = cssTools.filterByPseudos(selectorsMq, opts.usePseudos);

    // remove PseudoClass from its SimpleSelector for proper matching
    cssTools.cleanPseudos(selectorsPseudo);


    // stable sort selectors
    var sortedSelectors = cssTools.sortSelectors(selectorsPseudo).reverse();


    var selector,
        selectedEl;

    // match selectors
    for (selector of sortedSelectors) {
        var selectorStr = csstree.generate(selector.item.data),
            selectedEls = null;

        try {
            selectedEls = document.querySelectorAll(selectorStr);
        } catch (selectError) {
            if (selectError.constructor === SyntaxError) {
                // console.warn('Warning: Syntax error when trying to select \n\n' + selectorStr + '\n\n, skipped. Error details: ' + selectError);
                continue;
            }
            throw selectError;
        }

        if (selectedEls === null) {
            // nothing selected
            continue;
        }

        selector.selectedEls = selectedEls;
    }


    // apply <style/> styles to matched elements
    for (selector of sortedSelectors) {
        if(!selector.selectedEls) {
            continue;
        }

        if (opts.onlyMatchedOnce && selector.selectedEls !== null && selector.selectedEls.length > 1) {
            // skip selectors that match more than once if option onlyMatchedOnce is enabled
            continue;
        }

        // apply <style/> to matched elements
        for (selectedEl of selector.selectedEls) {
            if (selector.rule === null) {
                continue;
            }

            // merge declarations
            csstree.walk(selector.rule, {visit: 'Declaration', enter: function(styleCsstreeDeclaration) {

                // existing inline styles have higher priority
                // no inline styles, external styles,                                    external styles used
                // inline styles,    external styles same   priority as inline styles,   inline   styles used
                // inline styles,    external styles higher priority than inline styles, external styles used
                var styleDeclaration = cssTools.csstreeToStyleDeclaration(styleCsstreeDeclaration);
                if (selectedEl.style.getPropertyValue(styleDeclaration.name) !== null &&
                    selectedEl.style.getPropertyPriority(styleDeclaration.name) >= styleDeclaration.priority) {
                    return;
                }
                selectedEl.style.setProperty(styleDeclaration.name, styleDeclaration.value, styleDeclaration.priority);
            }});
        }

        if (opts.removeMatchedSelectors && selector.selectedEls !== null && selector.selectedEls.length > 0) {
            // clean up matching simple selectors if option removeMatchedSelectors is enabled
            selector.rule.prelude.children.remove(selector.item);
        }
    }


    if (!opts.removeMatchedSelectors) {
        return document; // no further processing required
    }


    // clean up matched class + ID attribute values
    for (selector of sortedSelectors) {
        if(!selector.selectedEls) {
            continue;
        }

        if (opts.onlyMatchedOnce && selector.selectedEls !== null && selector.selectedEls.length > 1) {
            // skip selectors that match more than once if option onlyMatchedOnce is enabled
            continue;
        }

        for (selectedEl of selector.selectedEls) {
            // class
            var firstSubSelector = selector.item.data.children.first();
            if(firstSubSelector.type === 'ClassSelector') {
                selectedEl.class.remove(firstSubSelector.name);
            }
            // clean up now empty class attributes
            if(typeof selectedEl.class.item(0) === 'undefined') {
                selectedEl.removeAttr('class');
            }

            // ID
            if(firstSubSelector.type === 'IdSelector') {
                selectedEl.removeAttr('id', firstSubSelector.name);
            }
        }
    }


    // clean up now empty elements
    for (var style of styles) {
        csstree.walk(style.cssAst, {visit: 'Rule', enter: function(node, item, list) {
            // clean up <style/> atrules without any rulesets left
            if (node.type === 'Atrule' &&
                // only Atrules containing rulesets
                node.block !== null &&
                node.block.children.isEmpty()) {
                list.remove(item);
                return;
            }

            // clean up <style/> rulesets without any css selectors left
            if (node.type === 'Rule' &&
                node.prelude.children.isEmpty()) {
                list.remove(item);
            }
        }});


        if (style.cssAst.children.isEmpty()) {
            // clean up now emtpy <style/>s
            var styleParentEl = style.styleEl.parentNode;
            styleParentEl.spliceContent(styleParentEl.content.indexOf(style.styleEl), 1);

            if (styleParentEl.elem === 'defs' &&
                styleParentEl.content.length === 0) {
                // also clean up now empty <def/>s
                var defsParentEl = styleParentEl.parentNode;
                defsParentEl.spliceContent(defsParentEl.content.indexOf(styleParentEl), 1);
            }

            continue;
        }


        // update existing, left over <style>s
        cssTools.setCssStr(style.styleEl, csstree.generate(style.cssAst));
    }


    return document;
};