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node_modules/csso/lib/compressor/index.js

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+var List = require('../utils/list');
+var usageUtils = require('./usage');
+var clean = require('./clean');
+var compress = require('./compress');
+var restructureBlock = require('./restructure');
+var walkRules = require('../utils/walk').rules;
+
+function readBlock(stylesheet) {
+    var buffer = new List();
+    var nonSpaceTokenInBuffer = false;
+    var protectedComment;
+
+    stylesheet.rules.nextUntil(stylesheet.rules.head, function(node, item, list) {
+        if (node.type === 'Comment' && node.value.charAt(0) === '!') {
+            if (nonSpaceTokenInBuffer || protectedComment) {
+                return true;
+            }
+
+            list.remove(item);
+            protectedComment = node;
+            return;
+        }
+
+        if (node.type !== 'Space') {
+            nonSpaceTokenInBuffer = true;
+        }
+
+        buffer.insert(list.remove(item));
+    });
+
+    return {
+        comment: protectedComment,
+        stylesheet: {
+            type: 'StyleSheet',
+            rules: buffer
+        }
+    };
+}
+
+function compressBlock(ast, usageData, num, logger) {
+    logger('Compress block #' + num, null, true);
+
+    var seed = 1;
+    ast.firstAtrulesAllowed = ast.firstAtrulesAllowed;
+    walkRules(ast, function() {
+        if (!this.stylesheet.id) {
+            this.stylesheet.id = seed++;
+        }
+    });
+    logger('init', ast);
+
+    // remove redundant
+    clean(ast, usageData);
+    logger('clean', ast);
+
+    // compress nodes
+    compress(ast, usageData);
+    logger('compress', ast);
+
+    return ast;
+}
+
+module.exports = function compress(ast, options) {
+    options = options || {};
+    ast = ast || { type: 'StyleSheet', rules: new List() };
+
+    var logger = typeof options.logger === 'function' ? options.logger : Function();
+    var restructuring =
+        'restructure' in options ? options.restructure :
+        'restructuring' in options ? options.restructuring :
+        true;
+    var result = new List();
+    var block;
+    var firstAtrulesAllowed = true;
+    var blockNum = 1;
+    var blockRules;
+    var blockMode = false;
+    var usageData = false;
+    var info = ast.info || null;
+
+    if (ast.type !== 'StyleSheet') {
+        blockMode = true;
+        ast = {
+            type: 'StyleSheet',
+            rules: new List([{
+                type: 'Ruleset',
+                selector: {
+                    type: 'Selector',
+                    selectors: new List([{
+                        type: 'SimpleSelector',
+                        sequence: new List([{
+                            type: 'Identifier',
+                            name: 'x'
+                        }])
+                    }])
+                },
+                block: ast
+            }])
+        };
+    }
+
+    if (options.usage) {
+        usageData = usageUtils.buildIndex(options.usage);
+    }
+
+    do {
+        block = readBlock(ast);
+        // console.log(JSON.stringify(block.stylesheet, null, 2));
+        block.stylesheet.firstAtrulesAllowed = firstAtrulesAllowed;
+        block.stylesheet = compressBlock(block.stylesheet, usageData, blockNum++, logger);
+
+        // structure optimisations
+        if (restructuring) {
+            restructureBlock(block.stylesheet, usageData, logger);
+        }
+
+        blockRules = block.stylesheet.rules;
+
+        if (block.comment) {
+            // add \n before comment if there is another content in result
+            if (!result.isEmpty()) {
+                result.insert(List.createItem({
+                    type: 'Raw',
+                    value: '\n'
+                }));
+            }
+
+            result.insert(List.createItem(block.comment));
+
+            // add \n after comment if block is not empty
+            if (!blockRules.isEmpty()) {
+                result.insert(List.createItem({
+                    type: 'Raw',
+                    value: '\n'
+                }));
+            }
+        }
+
+        if (firstAtrulesAllowed && !blockRules.isEmpty()) {
+            var lastRule = blockRules.last();
+
+            if (lastRule.type !== 'Atrule' ||
+               (lastRule.name !== 'import' && lastRule.name !== 'charset')) {
+                firstAtrulesAllowed = false;
+            }
+        }
+
+        result.appendList(blockRules);
+    } while (!ast.rules.isEmpty());
+
+    if (blockMode) {
+        result = !result.isEmpty() ? result.first().block : {
+            type: 'Block',
+            info: info,
+            declarations: new List()
+        };
+    } else {
+        result = {
+            type: 'StyleSheet',
+            info: info,
+            rules: result
+        };
+    }
+
+    return {
+        ast: result
+    };
+};