uglifycss-lib.js

/**
 * UglifyCSS
 * Port of YUI CSS Compressor to NodeJS
 * Author: Franck Marcia - https://github.com/fmarcia
 * MIT licenced
 */

/**
 * cssmin.js
 * Author: Stoyan Stefanov - http://phpied.com/
 * This is a JavaScript port of the CSS minification tool
 * distributed with YUICompressor, itself a port
 * of the cssmin utility by Isaac Schlueter - http://foohack.com/
 * Permission is hereby granted to use the JavaScript version under the same
 * conditions as the YUICompressor (original YUICompressor note below).
 */

/**
 * YUI Compressor
 * http://developer.yahoo.com/yui/compressor/
 * Author: Julien Lecomte - http://www.julienlecomte.net/
 * Copyright (c) 2011 Yahoo! Inc. All rights reserved.
 * The copyrights embodied in the content of this file are licensed
 * by Yahoo! Inc. under the BSD (revised) open source license.
 */


const { readFileSync } = require('fs')
const { sep, resolve } = require('path')

/**
 * @type {string} - Output path separator
 */

const SEP = '/'

/**
 * @type {string} - System path separator
 */

const PATH_SEP = sep

/**
 * @type {string} - placeholder prefix
 */

const ___PRESERVED_TOKEN_ = '___PRESERVED_TOKEN_'

/**
 * @typedef {object} options - UglifyCSS options
 * @property {number} [maxLineLen=0] - Maximum line length of uglified CSS
 * @property {boolean} [expandVars=false] - Expand variables
 * @property {boolean} [uglyComments=false] - Removes newlines within preserved comments
 * @property {boolean} [cuteComments=false] - Preserves newlines within and around preserved comments
 * @property {string} [convertUrls=''] - Converts relative urls using the given directory as location target
 * @property {boolean} [debug=false] - Prints full error stack on error
 * @property {string} [output=''] - Output file name
 */

/**
 * @type {options} - UglifyCSS options
 */

const defaultOptions = {
    maxLineLen: 0,
    expandVars: false,
    uglyComments: false,
    cuteComments: false,
    convertUrls: '',
    debug: false,
    output: ''
}

/**
 * convertRelativeUrls converts relative urls and replaces them with tokens
 * before we start compressing. It must be called *after* extractDataUrls
 *
 * @param {string} css - CSS content
 * @param {options} options - UglifyCSS Options
 * @param {string[]} preservedTokens - Global array of tokens to preserve
 *
 * @return {string} Processed css
 */

function convertRelativeUrls(css, options, preservedTokens) {

    const pattern = /(url\s*\()\s*(["']?)/g
    const maxIndex = css.length - 1
    const sb = []

    let appendIndex = 0
    let match

    // Since we need to account for non-base64 data urls, we need to handle
    // ' and ) being part of the data string. Hence switching to indexOf,
    // to determine whether or not we have matching string terminators and
    // handling sb appends directly, instead of using matcher.append* methods.

    while ((match = pattern.exec(css)) !== null) {

        let startIndex = match.index + match[1].length  // 'url('.length()
        let terminator = match[2]         // ', " or empty (not quoted)

        if (terminator.length === 0) {
            terminator = ')'
        }

        let foundTerminator = false

        let endIndex = pattern.lastIndex - 1

        while (foundTerminator === false && endIndex + 1 <= maxIndex) {
            endIndex = css.indexOf(terminator, endIndex + 1)

            // endIndex == 0 doesn't really apply here
            if ((endIndex > 0) && (css.charAt(endIndex - 1) !== '\\')) {
                foundTerminator = true
                if (')' != terminator) {
                    endIndex = css.indexOf(')', endIndex)
                }
            }
        }

        // Enough searching, start moving stuff over to the buffer
        sb.push(css.substring(appendIndex, match.index))

        if (foundTerminator) {

            let token = css.substring(startIndex, endIndex).replace(/(^\s*|\s*$)/g, '')
            if (token.slice(0, 19) !== ___PRESERVED_TOKEN_) {

                if (terminator === "'" || terminator === '"') {
                    token = token.slice(1, -1)
                } else if (terminator === ')') {
                    terminator = ''
                }

                let url

                if (options.convertUrls && token.charAt(0) !== SEP && token.slice(0, 7) !== 'http://' && token.slice(0, 8) !== 'https://') {

                    // build path of detected urls
                    let target = options.target.slice()

                    token = token.split(SEP).join(PATH_SEP) // assuming urls in css use '/'
                    url = resolve(options.source.join(PATH_SEP), token).split(PATH_SEP)

                    let file = url.pop()

                    // remove common part of both paths
                    while (target[0] === url[0]) {
                        target.shift()
                        url.shift()
                    }

                    for (let i = 0, l = target.length; i < l; ++i) {
                        target[i] = '..'
                    }
                    url = terminator + [ ...target, ...url, file].join(SEP) + terminator

                } else {
                    url = terminator + token + terminator
                }

                preservedTokens.push(url)

                let preserver = 'url(' + ___PRESERVED_TOKEN_ + (preservedTokens.length - 1) + '___)'
                sb.push(preserver)

            } else {
                sb.push(`url(${token})`)
            }

            appendIndex = endIndex + 1

        } else {
            // No end terminator found, re-add the whole match. Should we throw/warn here?
            sb.push(css.substring(match.index, pattern.lastIndex))
            appendIndex = pattern.lastIndex
        }
    }

    sb.push(css.substring(appendIndex))

    return sb.join('')
}

/**
 * extractDataUrls replaces all data urls with tokens before we start
 * compressing, to avoid performance issues running some of the subsequent
 * regexes against large strings chunks.
 *
 * @param {string} css - CSS content
 * @param {string[]} preservedTokens - Global array of tokens to preserve
 *
 * @return {string} Processed CSS
 */

function extractDataUrls(css, preservedTokens) {

    // Leave data urls alone to increase parse performance.
    const pattern = /url\(\s*(["']?)data\:/g
    const maxIndex = css.length - 1
    const sb = []

    let appendIndex = 0
    let match

    // Since we need to account for non-base64 data urls, we need to handle
    // ' and ) being part of the data string. Hence switching to indexOf,
    // to determine whether or not we have matching string terminators and
    // handling sb appends directly, instead of using matcher.append* methods.

    while ((match = pattern.exec(css)) !== null) {

        let startIndex = match.index + 4  // 'url('.length()
        let terminator = match[1]         // ', " or empty (not quoted)

        if (terminator.length === 0) {
            terminator = ')'
        }

        let foundTerminator = false
        let endIndex = pattern.lastIndex - 1

        while (foundTerminator === false && endIndex + 1 <= maxIndex) {
            endIndex = css.indexOf(terminator, endIndex + 1)

            // endIndex == 0 doesn't really apply here
            if ((endIndex > 0) && (css.charAt(endIndex - 1) !== '\\')) {
                foundTerminator = true
                if (')' != terminator) {
                    endIndex = css.indexOf(')', endIndex)
                }
            }
        }

        // Enough searching, start moving stuff over to the buffer
        sb.push(css.substring(appendIndex, match.index))

        if (foundTerminator) {

            let token = css.substring(startIndex, endIndex)
            let parts = token.split(',')
            if (parts.length > 1 && parts[0].slice(-7) == ';base64') {
                token = token.replace(/\s+/g, '')
            } else {
                token = token.replace(/\n/g, ' ')
                token = token.replace(/\s+/g, ' ')
                token = token.replace(/(^\s+|\s+$)/g, '')
            }

            preservedTokens.push(token)

            let preserver = 'url(' + ___PRESERVED_TOKEN_ + (preservedTokens.length - 1) + '___)'
            sb.push(preserver)

            appendIndex = endIndex + 1
        } else {
            // No end terminator found, re-add the whole match. Should we throw/warn here?
            sb.push(css.substring(match.index, pattern.lastIndex))
            appendIndex = pattern.lastIndex
        }
    }

    sb.push(css.substring(appendIndex))

    return sb.join('')
}

/**
 * compressHexColors compresses hex color values of the form #AABBCC to #ABC.
 *
 * DOES NOT compress CSS ID selectors which match the above pattern (which would
 * break things), like #AddressForm { ... }
 *
 * DOES NOT compress IE filters, which have hex color values (which would break
 * things), like chroma(color='#FFFFFF');
 *
 * DOES NOT compress invalid hex values, like background-color: #aabbccdd
 *
 * @param {string} css - CSS content
 *
 * @return {string} Processed CSS
 */

function compressHexColors(css) {

    // Look for hex colors inside { ... } (to avoid IDs) and which don't have a =, or a " in front of them (to avoid filters)

    const pattern = /(\=\s*?["']?)?#([0-9a-f])([0-9a-f])([0-9a-f])([0-9a-f])([0-9a-f])([0-9a-f])(\}|[^0-9a-f{][^{]*?\})/gi
    const sb = []

    let index = 0
    let match

    while ((match = pattern.exec(css)) !== null) {

        sb.push(css.substring(index, match.index))

        let isFilter = match[1]

        if (isFilter) {
            // Restore, maintain case, otherwise filter will break
            sb.push(match[1] + '#' + (match[2] + match[3] + match[4] + match[5] + match[6] + match[7]))
        } else {
            if (match[2].toLowerCase() == match[3].toLowerCase() &&
                match[4].toLowerCase() == match[5].toLowerCase() &&
                match[6].toLowerCase() == match[7].toLowerCase()) {

                // Compress.
                sb.push('#' + (match[3] + match[5] + match[7]).toLowerCase())
            } else {
                // Non compressible color, restore but lower case.
                sb.push('#' + (match[2] + match[3] + match[4] + match[5] + match[6] + match[7]).toLowerCase())
            }
        }

        index = pattern.lastIndex = pattern.lastIndex - match[8].length
    }

    sb.push(css.substring(index))

    return sb.join('')
}

/** keyframes preserves 0 followed by unit in keyframes steps
 *
 * @param {string} content - CSS content
 * @param {string[]} preservedTokens - Global array of tokens to preserve
 *
 * @return {string} Processed CSS
 */

function keyframes(content, preservedTokens) {

    const pattern = /@[a-z0-9-_]*keyframes\s+[a-z0-9-_]+\s*{/gi

    let index = 0
    let buffer

    const preserve = (part, i) => {
        part = part.replace(/(^\s|\s$)/g, '')
        if (part.charAt(0) === '0') {
            preservedTokens.push(part)
            buffer[i] = ___PRESERVED_TOKEN_ + (preservedTokens.length - 1) + '___'
        }
    }

    while (true) {

        let level = 0
        buffer = ''

        let startIndex = content.slice(index).search(pattern)
        if (startIndex < 0) {
            break
        }

        index += startIndex
        startIndex = index

        let len = content.length
        let buffers = []

        for (; index < len; ++index) {

            let ch = content.charAt(index)

            if (ch === '{') {

                if (level === 0) {
                    buffers.push(buffer.replace(/(^\s|\s$)/g, ''))

                } else if (level === 1) {

                    buffer = buffer.split(',')

                    buffer.forEach(preserve)

                    buffers.push(buffer.join(',').replace(/(^\s|\s$)/g, ''))
                }

                buffer = ''
                level += 1

            } else if (ch === '}') {

                if (level === 2) {
                    buffers.push('{' + buffer.replace(/(^\s|\s$)/g, '') + '}')
                    buffer = ''

                } else if (level === 1) {
                    content = content.slice(0, startIndex) +
                        buffers.shift() + '{' +
                        buffers.join('') +
                        content.slice(index)
                    break
                }

                level -= 1
            }

            if (level < 0) {
                break

            } else if (ch !== '{' && ch !== '}') {
                buffer += ch
            }
        }
    }

    return content
}

/**
 * collectComments collects all comment blocks and return new content with comment placeholders
 *
 * @param {string} content - CSS content
 * @param {string[]} comments - Global array of extracted comments
 *
 * @return {string} Processed CSS
 */

function collectComments(content, comments) {

    const table = []

    let from = 0
    let end

    while (true) {

        let start = content.indexOf('/*', from)

        if (start > -1) {

            end = content.indexOf('*/', start + 2)

            if (end > -1) {
                comments.push(content.slice(start + 2, end))
                table.push(content.slice(from, start))
                table.push('/*___PRESERVE_CANDIDATE_COMMENT_' + (comments.length - 1) + '___*/')
                from = end + 2

            } else {
                // unterminated comment
                end = -2
                break
            }

        } else {
            break
        }
    }

    table.push(content.slice(end + 2))

    return table.join('')
}

/**
 * processString uglifies a CSS string
 *
 * @param {string} content - CSS string
 * @param {options} options - UglifyCSS options
 *
 * @return {string} Uglified result
 */

function processString(content = '', options = defaultOptions) {

    const comments = []
    const preservedTokens = []

    let pattern

    content = extractDataUrls(content, preservedTokens)
    content = convertRelativeUrls(content, options, preservedTokens)
    content = collectComments(content, comments)

    // preserve strings so their content doesn't get accidentally minified
    pattern = /("([^\\"]|\\.|\\)*")|('([^\\']|\\.|\\)*')/g
    content = content.replace(pattern, token => {
        const quote = token.substring(0, 1)
        token = token.slice(1, -1)
        // maybe the string contains a comment-like substring or more? put'em back then
        if (token.indexOf('___PRESERVE_CANDIDATE_COMMENT_') >= 0) {
            for (let i = 0, len = comments.length; i < len; i += 1) {
                token = token.replace('___PRESERVE_CANDIDATE_COMMENT_' + i + '___', comments[i])
            }
        }
        // minify alpha opacity in filter strings
        token = token.replace(/progid:DXImageTransform.Microsoft.Alpha\(Opacity=/gi, 'alpha(opacity=')
        preservedTokens.push(token)
        return quote + ___PRESERVED_TOKEN_ + (preservedTokens.length - 1) + '___' + quote
    })

    // strings are safe, now wrestle the comments
    for (let i = 0, len = comments.length; i < len; i += 1) {

        let token = comments[i]
        let placeholder = '___PRESERVE_CANDIDATE_COMMENT_' + i + '___'

        // ! in the first position of the comment means preserve
        // so push to the preserved tokens keeping the !
        if (token.charAt(0) === '!') {
            if (options.cuteComments) {
                preservedTokens.push(token.substring(1).replace(/\r\n/g, '\n'))
            } else if (options.uglyComments) {
                preservedTokens.push(token.substring(1).replace(/[\r\n]/g, ''))
            } else {
                preservedTokens.push(token)
            }
            content = content.replace(placeholder, ___PRESERVED_TOKEN_ + (preservedTokens.length - 1) + '___')
            continue
        }

        // \ in the last position looks like hack for Mac/IE5
        // shorten that to /*\*/ and the next one to /**/
        if (token.charAt(token.length - 1) === '\\') {
            preservedTokens.push('\\')
            content = content.replace(placeholder, ___PRESERVED_TOKEN_ + (preservedTokens.length - 1) + '___')
            i = i + 1 // attn: advancing the loop
            preservedTokens.push('')
            content = content.replace(
                '___PRESERVE_CANDIDATE_COMMENT_' + i + '___',
                ___PRESERVED_TOKEN_ + (preservedTokens.length - 1) + '___'
            )
            continue
        }

        // keep empty comments after child selectors (IE7 hack)
        // e.g. html >/**/ body
        if (token.length === 0) {
            let startIndex = content.indexOf(placeholder)
            if (startIndex > 2) {
                if (content.charAt(startIndex - 3) === '>') {
                    preservedTokens.push('')
                    content = content.replace(placeholder, ___PRESERVED_TOKEN_ + (preservedTokens.length - 1) + '___')
                }
            }
        }

        // in all other cases kill the comment
        content = content.replace(`/*${placeholder}*/`, '')
    }

    // parse simple @variables blocks and remove them
    if (options.expandVars) {
        const vars = {}
        pattern = /@variables\s*\{\s*([^\}]+)\s*\}/g
        content = content.replace(pattern, (_, f1) => {
            pattern = /\s*([a-z0-9\-]+)\s*:\s*([^;\}]+)\s*/gi
            f1.replace(pattern, (_, f1, f2) => {
                if (f1 && f2) {
                    vars[f1] = f2
                }
                return ''
            })
            return ''
        })

        // replace var(x) with the value of x
        pattern = /var\s*\(\s*([^\)]+)\s*\)/g
        content = content.replace(pattern, (_, f1) => {
            return vars[f1] || 'none'
        })
    }

    // normalize all whitespace strings to single spaces. Easier to work with that way.
    content = content.replace(/\s+/g, ' ')

    // preserve formulas in calc() before removing spaces
    pattern = /calc\(([^;}]*)\)/g
    content = content.replace(pattern, (_, f1) => {
        preservedTokens.push(
            'calc(' +
            f1.replace(/(^\s*|\s*$)/g, '')
                .replace(/\( /g, '(')
                .replace(/ \)/g, ')') +
            ')'
        )
        return ___PRESERVED_TOKEN_ + (preservedTokens.length - 1) + '___'
    })

    // preserve matrix
    pattern = /\s*filter:\s*progid:DXImageTransform.Microsoft.Matrix\(([^\)]+)\);/g
    content = content.replace(pattern, (_, f1) => {
        preservedTokens.push(f1)
        return 'filter:progid:DXImageTransform.Microsoft.Matrix(' + ___PRESERVED_TOKEN_ + (preservedTokens.length - 1) + '___);'
    })

    // remove the spaces before the things that should not have spaces before them.
    // but, be careful not to turn 'p :link {...}' into 'p:link{...}'
    // swap out any pseudo-class colons with the token, and then swap back.
    pattern = /(^|\})(([^\{:])+:)+([^\{]*\{)/g
    content = content.replace(pattern, token => token.replace(/:/g, '___PSEUDOCLASSCOLON___'))

    // remove spaces before the things that should not have spaces before them.
    content = content.replace(/\s+([!{};:>+\(\)\],])/g, '$1')

    // restore spaces for !important
    content = content.replace(/!important/g, ' !important')

    // bring back the colon
    content = content.replace(/___PSEUDOCLASSCOLON___/g, ':')

    // preserve 0 followed by a time unit for properties using time units
    pattern = /\s*(animation|animation-delay|animation-duration|transition|transition-delay|transition-duration):\s*([^;}]+)/gi
    content = content.replace(pattern, (_, f1, f2) => {

        f2 = f2.replace(/(^|\D)0?\.?0(m?s)/gi, (_, g1, g2) => {
            preservedTokens.push('0' + g2)
            return g1 + ___PRESERVED_TOKEN_ + (preservedTokens.length - 1) + '___'
        })

        return f1 + ':' + f2
    })

    // preserve unit for flex-basis within flex and flex-basis (ie10 bug)
    pattern = /\s*(flex|flex-basis):\s*([^;}]+)/gi
    content = content.replace(pattern, (_, f1, f2) => {
        let f2b = f2.split(/\s+/)
        preservedTokens.push(f2b.pop())
        f2b.push(___PRESERVED_TOKEN_ + (preservedTokens.length - 1) + '___')
        f2b = f2b.join(' ')
        return `${f1}:${f2b}`
    })

    // preserve 0% in hsl and hsla color definitions
    content = content.replace(/(hsla?)\(([^)]+)\)/g, (_, f1, f2) => {
        var f0 = []
        f2.split(',').forEach(part => {
            part = part.replace(/(^\s+|\s+$)/g, '')
            if (part === '0%') {
                preservedTokens.push('0%')
                f0.push(___PRESERVED_TOKEN_ + (preservedTokens.length - 1) + '___')
            } else {
                f0.push(part)
            }
        })
        return f1 + '(' + f0.join(',') + ')'
    })

    // preserve 0 followed by unit in keyframes steps (WIP)
    content = keyframes(content, preservedTokens)

    // retain space for special IE6 cases
    content = content.replace(/:first-(line|letter)(\{|,)/gi, (_, f1, f2) => ':first-' + f1.toLowerCase() + ' ' + f2)

    // newlines before and after the end of a preserved comment
    if (options.cuteComments) {
        content = content.replace(/\s*\/\*/g, '___PRESERVED_NEWLINE___/*')
        content = content.replace(/\*\/\s*/g, '*/___PRESERVED_NEWLINE___')
        // no space after the end of a preserved comment
    } else {
        content = content.replace(/\*\/\s*/g, '*/')
    }

    // If there are multiple @charset directives, push them to the top of the file.
    pattern = /^(.*)(@charset)( "[^"]*";)/gi
    content = content.replace(pattern, (_, f1, f2, f3) => f2.toLowerCase() + f3 + f1)

    // When all @charset are at the top, remove the second and after (as they are completely ignored).
    pattern = /^((\s*)(@charset)( [^;]+;\s*))+/gi
    content = content.replace(pattern, (_, __, f2, f3, f4) => f2 + f3.toLowerCase() + f4)

    // lowercase some popular @directives (@charset is done right above)
    pattern = /@(font-face|import|(?:-(?:atsc|khtml|moz|ms|o|wap|webkit)-)?keyframe|media|page|namespace)/gi
    content = content.replace(pattern, (_, f1) => '@' + f1.toLowerCase())

    // lowercase some more common pseudo-elements
    pattern = /:(active|after|before|checked|disabled|empty|enabled|first-(?:child|of-type)|focus|hover|last-(?:child|of-type)|link|only-(?:child|of-type)|root|:selection|target|visited)/gi
    content = content.replace(pattern, (_, f1) => ':' + f1.toLowerCase())

    // if there is a @charset, then only allow one, and push to the top of the file.
    content = content.replace(/^(.*)(@charset \"[^\"]*\";)/g, '$2$1')
    content = content.replace(/^(\s*@charset [^;]+;\s*)+/g, '$1')

    // lowercase some more common functions
    pattern = /:(lang|not|nth-child|nth-last-child|nth-last-of-type|nth-of-type|(?:-(?:atsc|khtml|moz|ms|o|wap|webkit)-)?any)\(/gi
    content = content.replace(pattern, (_, f1) => ':' + f1.toLowerCase() + '(')

    // lower case some common function that can be values
    // NOTE: rgb() isn't useful as we replace with #hex later, as well as and() is already done for us right after this
    pattern = /([:,\( ]\s*)(attr|color-stop|from|rgba|to|url|(?:-(?:atsc|khtml|moz|ms|o|wap|webkit)-)?(?:calc|max|min|(?:repeating-)?(?:linear|radial)-gradient)|-webkit-gradient)/gi
    content = content.replace(pattern, (_, f1, f2) => f1 + f2.toLowerCase())

    // put the space back in some cases, to support stuff like
    // @media screen and (-webkit-min-device-pixel-ratio:0){
    content = content.replace(/\band\(/gi, 'and (')

    // remove the spaces after the things that should not have spaces after them.
    content = content.replace(/([!{}:;>+\(\[,])\s+/g, '$1')

    // remove unnecessary semicolons
    content = content.replace(/;+\}/g, '}')

    // replace 0(px,em,%) with 0.
    content = content.replace(/(^|[^.0-9\\])(?:0?\.)?0(?:ex|ch|r?em|vw|vh|vmin|vmax|cm|mm|in|pt|pc|px|deg|g?rad|turn|m?s|k?Hz|dpi|dpcm|dppx|%)/gi, '$10')

    // Replace x.0(px,em,%) with x(px,em,%).
    content = content.replace(/([0-9])\.0(ex|ch|r?em|vw|vh|vmin|vmax|cm|mm|in|pt|pc|px|deg|g?rad|turn|m?s|k?Hz|dpi|dpcm|dppx|%| |;)/gi, '$1$2')

    // replace 0 0 0 0; with 0.
    content = content.replace(/:0 0 0 0(;|\})/g, ':0$1')
    content = content.replace(/:0 0 0(;|\})/g, ':0$1')
    content = content.replace(/:0 0(;|\})/g, ':0$1')

    // replace background-position:0; with background-position:0 0;
    // same for transform-origin and box-shadow
    pattern = /(background-position|transform-origin|webkit-transform-origin|moz-transform-origin|o-transform-origin|ms-transform-origin|box-shadow):0(;|\})/gi
    content = content.replace(pattern, (_, f1, f2) => f1.toLowerCase() + ':0 0' + f2)

    // replace 0.6 to .6, but only when preceded by : or a white-space
    content = content.replace(/(:|\s)0+\.(\d+)/g, '$1.$2')

    // shorten colors from rgb(51,102,153) to #336699
    // this makes it more likely that it'll get further compressed in the next step.
    pattern = /rgb\s*\(\s*([0-9,\s]+)\s*\)/gi
    content = content.replace(pattern, (_, f1) => {
        const rgbcolors = f1.split(',')
        let hexcolor = '#'
        for (let i = 0; i < rgbcolors.length; i += 1) {
            let val = parseInt(rgbcolors[i], 10)
            if (val < 16) {
                hexcolor += '0'
            }
            if (val > 255) {
                val = 255
            }
            hexcolor += val.toString(16)
        }
        return hexcolor
    })

    // Shorten colors from #AABBCC to #ABC.
    content = compressHexColors(content)

    // Replace #f00 -> red
    content = content.replace(/(:|\s)(#f00)(;|})/g, '$1red$3')

    // Replace other short color keywords
    content = content.replace(/(:|\s)(#000080)(;|})/g, '$1navy$3')
    content = content.replace(/(:|\s)(#808080)(;|})/g, '$1gray$3')
    content = content.replace(/(:|\s)(#808000)(;|})/g, '$1olive$3')
    content = content.replace(/(:|\s)(#800080)(;|})/g, '$1purple$3')
    content = content.replace(/(:|\s)(#c0c0c0)(;|})/g, '$1silver$3')
    content = content.replace(/(:|\s)(#008080)(;|})/g, '$1teal$3')
    content = content.replace(/(:|\s)(#ffa500)(;|})/g, '$1orange$3')
    content = content.replace(/(:|\s)(#800000)(;|})/g, '$1maroon$3')

    // border: none -> border:0
    pattern = /(border|border-top|border-right|border-bottom|border-left|outline|background):none(;|\})/gi
    content = content.replace(pattern, (_, f1, f2) => f1.toLowerCase() + ':0' + f2)

    // shorter opacity IE filter
    content = content.replace(/progid:DXImageTransform\.Microsoft\.Alpha\(Opacity=/gi, 'alpha(opacity=')

    // Find a fraction that is used for Opera's -o-device-pixel-ratio query
    // Add token to add the '\' back in later
    content = content.replace(/\(([\-A-Za-z]+):([0-9]+)\/([0-9]+)\)/g, '($1:$2___QUERY_FRACTION___$3)')

    // remove empty rules.
    content = content.replace(/[^\};\{\/]+\{\}/g, '')

    // Add '\' back to fix Opera -o-device-pixel-ratio query
    content = content.replace(/___QUERY_FRACTION___/g, '/')

    // some source control tools don't like it when files containing lines longer
    // than, say 8000 characters, are checked in. The linebreak option is used in
    // that case to split long lines after a specific column.
    if (options.maxLineLen > 0) {
        const lines = []
        let line = []
        for (let i = 0, len = content.length; i < len; i += 1) {
            let ch = content.charAt(i)
            line.push(ch)
            if (ch === '}' && line.length > options.maxLineLen) {
                lines.push(line.join(''))
                line = []
            }
        }
        if (line.length) {
            lines.push(line.join(''))
        }

        content = lines.join('\n')
    }

    // replace multiple semi-colons in a row by a single one
    // see SF bug #1980989
    content = content.replace(/;;+/g, ';')

    // trim the final string (for any leading or trailing white spaces)
    content = content.replace(/(^\s*|\s*$)/g, '')

    // restore preserved tokens
    for (let i = preservedTokens.length - 1; i >= 0; i--) {
        content = content.replace(___PRESERVED_TOKEN_ + i + '___', preservedTokens[i], 'g')
    }

    // restore preserved newlines
    content = content.replace(/___PRESERVED_NEWLINE___/g, '\n')

    // return
    return content
}

/**
 * processFiles uglifies a set of CSS files
 *
 * @param {string[]} filenames - List of filenames
 * @param {options} options - UglifyCSS options
 *
 * @return {string} Uglified result
 */

function processFiles(filenames = [], options = defaultOptions) {

    if (options.convertUrls) {
        options.target = resolve(process.cwd(), options.convertUrls).split(PATH_SEP)
    }

    const uglies = []

    // process files
    filenames.forEach(filename => {
        try {
            const content = readFileSync(filename, 'utf8')
            if (content.length) {
                if (options.convertUrls) {
                    options.source = resolve(process.cwd(), filename).split(PATH_SEP)
                    options.source.pop()
                }
                uglies.push(processString(content, options))
            }
        } catch (e) {
            if (options.debug) {
                console.error(`uglifycss: unable to process "${filename}"\n${e.stack}`)
            } else {
                console.error(`uglifycss: unable to process "${filename}"\n\t${e}`)
            }
            process.exit(1)
        }
    })

    // return concat'd results
    return uglies.join('')
}

module.exports = {
    defaultOptions,
    processString,
    processFiles
}