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compress.js
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Sun, Dec 15, 07:11

compress.js
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var List = require('css-tree').List;
var clone = require('css-tree').clone;
var usageUtils = require('./usage');
var clean = require('./clean');
var replace = require('./replace');
var restructure = require('./restructure');
var walk = require('css-tree').walk;
function readChunk(children, specialComments) {
var buffer = new List();
var nonSpaceTokenInBuffer = false;
var protectedComment;
children.nextUntil(children.head, function(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;
}
buffer.insert(list.remove(item));
});
return {
comment: protectedComment,
stylesheet: {
type: 'StyleSheet',
loc: null,
children: buffer
}
};
}
function compressChunk(ast, firstAtrulesAllowed, num, options) {
options.logger('Compress block #' + num, null, true);
var seed = 1;
if (ast.type === 'StyleSheet') {
ast.firstAtrulesAllowed = firstAtrulesAllowed;
ast.id = seed++;
}
walk(ast, {
visit: 'Atrule',
enter: function markScopes(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) {
var 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: block
});
}
module.exports = function compress(ast, options) {
ast = ast || { type: 'StyleSheet', loc: null, children: new List() };
options = options || {};
var compressOptions = {
logger: typeof options.logger === 'function' ? options.logger : function() {},
restructuring: getRestructureOption(options),
forceMediaMerge: Boolean(options.forceMediaMerge),
usage: options.usage ? usageUtils.buildIndex(options.usage) : false
};
var specialComments = getCommentsOption(options);
var firstAtrulesAllowed = true;
var input;
var output = new List();
var chunk;
var chunkNum = 1;
var 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()) {
var 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: ast
};
};

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