/
extend.js
69 lines (57 loc) · 1.54 KB
/
extend.js
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/**
* Module dependencies.
*/
var debug = require('debug')('rework:extend');
/**
* Add extension support.
*/
module.exports = function() {
debug('use extend');
return function(style, rework) {
var map = {};
var rules = style.rules.length;
for (var j = 0; j < rules; j++) {
var rule = style.rules[j];
if (!rule || !rule.selectors) return;
// map selectors
rule.selectors.forEach(function(sel, i) {
map[sel] = rule;
if ('%' == sel[0]) rule.selectors.splice(i, 1);
});
// visit extend: properties
visit(rule, map);
// clean up empty rules
if (!rule.declarations.length) {
style.rules.splice(j--, 1);
}
};
}
};
/**
* Visit declarations and extensions.
*
* @param {Object} rule
* @param {Object} map
* @api private
*/
function visit(rule, map) {
for (var i = 0; i < rule.declarations.length; ++i) {
var decl = rule.declarations[i];
var key = decl.property;
var val = decl.value;
if (!/^extends?$/.test(key)) continue;
var extend = map[val];
if (!extend) throw new Error('failed to extend "' + val + '"');
var keys = Object.keys(map);
keys.forEach(function(key) {
if (0 != key.indexOf(val)) return;
var extend = map[key];
var suffix = key.replace(val, '');
debug('extend %j with %j', rule.selectors, extend.selectors);
extend.selectors = extend.selectors.concat(rule.selectors.map(function(sel) {
return sel + suffix;
}));
});
rule.declarations.splice(i--, 1);
}
}