compress.js•5.15 kB
import { List, clone, walk } from 'css-tree';
import { buildIndex } from './usage.js';
import clean from './clean/index.js';
import replace from './replace/index.js';
import restructure from './restructure/index.js';
function readChunk(input, specialComments) {
const children = new List();
let nonSpaceTokenInBuffer = false;
let protectedComment;
input.nextUntil(input.head, (node, item, list) => {
if (node.type === 'Comment') {
if (!specialComments || node.value.charAt(0) !== '!') {
list.remove(item);
return;
}
if (nonSpaceTokenInBuffer || protectedComment) {
return true;
}
list.remove(item);
protectedComment = node;
return;
}
if (node.type !== 'WhiteSpace') {
nonSpaceTokenInBuffer = true;
}
children.insert(list.remove(item));
});
return {
comment: protectedComment,
stylesheet: {
type: 'StyleSheet',
loc: null,
children
}
};
}
function compressChunk(ast, firstAtrulesAllowed, num, options) {
options.logger(`Compress block #${num}`, null, true);
let seed = 1;
if (ast.type === 'StyleSheet') {
ast.firstAtrulesAllowed = firstAtrulesAllowed;
ast.id = seed++;
}
walk(ast, {
visit: 'Atrule',
enter(node) {
if (node.block !== null) {
node.block.id = seed++;
}
}
});
options.logger('init', ast);
// remove redundant
clean(ast, options);
options.logger('clean', ast);
// replace nodes for shortened forms
replace(ast, options);
options.logger('replace', ast);
// structure optimisations
if (options.restructuring) {
restructure(ast, options);
}
return ast;
}
function getCommentsOption(options) {
let comments = 'comments' in options ? options.comments : 'exclamation';
if (typeof comments === 'boolean') {
comments = comments ? 'exclamation' : false;
} else if (comments !== 'exclamation' && comments !== 'first-exclamation') {
comments = false;
}
return comments;
}
function getRestructureOption(options) {
if ('restructure' in options) {
return options.restructure;
}
return 'restructuring' in options ? options.restructuring : true;
}
function wrapBlock(block) {
return new List().appendData({
type: 'Rule',
loc: null,
prelude: {
type: 'SelectorList',
loc: null,
children: new List().appendData({
type: 'Selector',
loc: null,
children: new List().appendData({
type: 'TypeSelector',
loc: null,
name: 'x'
})
})
},
block
});
}
export default function compress(ast, options) {
ast = ast || { type: 'StyleSheet', loc: null, children: new List() };
options = options || {};
const compressOptions = {
logger: typeof options.logger === 'function' ? options.logger : function() {},
restructuring: getRestructureOption(options),
forceMediaMerge: Boolean(options.forceMediaMerge),
usage: options.usage ? buildIndex(options.usage) : false
};
const output = new List();
let specialComments = getCommentsOption(options);
let firstAtrulesAllowed = true;
let input;
let chunk;
let chunkNum = 1;
let chunkChildren;
if (options.clone) {
ast = clone(ast);
}
if (ast.type === 'StyleSheet') {
input = ast.children;
ast.children = output;
} else {
input = wrapBlock(ast);
}
do {
chunk = readChunk(input, Boolean(specialComments));
compressChunk(chunk.stylesheet, firstAtrulesAllowed, chunkNum++, compressOptions);
chunkChildren = chunk.stylesheet.children;
if (chunk.comment) {
// add \n before comment if there is another content in output
if (!output.isEmpty) {
output.insert(List.createItem({
type: 'Raw',
value: '\n'
}));
}
output.insert(List.createItem(chunk.comment));
// add \n after comment if chunk is not empty
if (!chunkChildren.isEmpty) {
output.insert(List.createItem({
type: 'Raw',
value: '\n'
}));
}
}
if (firstAtrulesAllowed && !chunkChildren.isEmpty) {
const lastRule = chunkChildren.last;
if (lastRule.type !== 'Atrule' ||
(lastRule.name !== 'import' && lastRule.name !== 'charset')) {
firstAtrulesAllowed = false;
}
}
if (specialComments !== 'exclamation') {
specialComments = false;
}
output.appendList(chunkChildren);
} while (!input.isEmpty);
return {
ast
};
};