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'use strict';
var postcss = require('postcss');
module.exports = postcss.plugin('postcss-zindex', function (opts) {
opts = opts || {};
return function (css) {
var cache = require('./lib/layerCache')(opts);
var nodes = [];
var abort = false;
// First pass; cache all z indexes
css.walkDecls('z-index', function (decl) {
// Check that no negative values exist. Rebasing is only
// safe if all indices are positive numbers.
if (decl.value[0] === '-') {
abort = true;
// Stop PostCSS iterating through the rest of the decls
return false;
}
nodes.push(decl);
cache.addValue(decl.value);
});
// Abort if we found any negative values
// or there are no z-index declarations
if (abort || !nodes.length) {
return;
}
cache.optimizeValues();
// Second pass; optimize
nodes.forEach(function (decl) {
// Need to coerce to string so that the
// AST is updated correctly
decl.value = cache.getValue(decl.value).toString();
});
};
});