/*
 * YUI Compressor
 * http://developer.yahoo.com/yui/compressor/
 * Author: Julien Lecomte -  http://www.julienlecomte.net/
 * Author: Isaac Schlueter - http://foohack.com/
 * Author: Stoyan Stefanov - http://phpied.com/
 * Contributor: Dan Beam - http://danbeam.org/
 * Copyright (c) 2013 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.
 */
package org.apache.tapestry5.internal.webresources;

import java.io.IOException;
import java.io.Reader;
import java.io.Writer;
import java.util.regex.Pattern;
import java.util.regex.Matcher;
import java.util.ArrayList;

public class CssCompressor {

    private StringBuffer srcsb = new StringBuffer();

    public CssCompressor(Reader in) throws IOException {
        // Read the stream...
        int c;
        while ((c = in.read()) != -1) {
            srcsb.append((char) c);
        }
    }

    /**
     * @param css - full css string
     * @param preservedToken - token to preserve
     * @param tokenRegex - regex to find token
     * @param removeWhiteSpace - remove any white space in the token
     * @param preservedTokens - array of token values
     * @return
     */
    protected String preserveToken(String css, String preservedToken,
            String tokenRegex, boolean removeWhiteSpace, ArrayList preservedTokens) {

        int maxIndex = css.length() - 1;
        int appendIndex = 0;

        StringBuffer sb = new StringBuffer();

        Pattern p = Pattern.compile(tokenRegex);
        Matcher m = p.matcher(css);

        while (m.find()) {
            int startIndex = m.start() + (preservedToken.length() + 1);
            String terminator = m.group(1);

            // skip this, if CSS was already copied to "sb" upto this position
            if (m.start() < appendIndex) {
                continue;
            }

            if (terminator.length() == 0) {
                terminator = ")";
            }

            boolean foundTerminator = false;

            int endIndex = m.end() - 1;
            while(foundTerminator == false && endIndex+1 <= maxIndex) {
                endIndex = css.indexOf(terminator, endIndex+1);

                if (endIndex <= 0) {
                    break;
                } else if ((endIndex > 0) && (css.charAt(endIndex-1) != '\\')) {
                    foundTerminator = true;
                    if (!")".equals(terminator)) {
                        endIndex = css.indexOf(")", endIndex);
                    }
                }
            }

            // Enough searching, start moving stuff over to the buffer
            sb.append(css.substring(appendIndex, m.start()));

            if (foundTerminator) {
                String token = css.substring(startIndex, endIndex);
                if(removeWhiteSpace)
                    token = token.replaceAll("\\s+", "");
                preservedTokens.add(token);

                String preserver = preservedToken + "(___YUICSSMIN_PRESERVED_TOKEN_" + (preservedTokens.size() - 1) + "___)";
                sb.append(preserver);

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

        sb.append(css.substring(appendIndex));

        return sb.toString();
    }

    public void compress(Writer out, int linebreakpos)
            throws IOException {

        Pattern p;
        Matcher m;
        String css = srcsb.toString();

        int startIndex = 0;
        int endIndex = 0;
        int i = 0;
        int max = 0;
        ArrayList preservedTokens = new ArrayList(0);
        ArrayList comments = new ArrayList(0);
        String token;
        int totallen = css.length();
        String placeholder;


        StringBuffer sb = new StringBuffer(css);

        // collect all comment blocks...
        while ((startIndex = sb.indexOf("/*", startIndex)) >= 0) {
            endIndex = sb.indexOf("*/", startIndex + 2);
            if (endIndex < 0) {
                endIndex = totallen;
            }

            token = sb.substring(startIndex + 2, endIndex);
            comments.add(token);
            sb.replace(startIndex + 2, endIndex, "___YUICSSMIN_PRESERVE_CANDIDATE_COMMENT_" + (comments.size() - 1) + "___");
            startIndex += 2;
        }
        css = sb.toString();


        css = this.preserveToken(css, "url", "(?i)url\\(\\s*([\"']?)data\\:\\s*image/svg\\+xml", false, preservedTokens);
        css = this.preserveToken(css, "url", "(?i)url\\(\\s*([\"']?)data\\:\\s*(?!(image/svg\\+xml))", true, preservedTokens);
        css = this.preserveToken(css, "calc",  "(?i)calc\\(\\s*([\"']?)", false, preservedTokens);
        css = this.preserveToken(css, "progid:DXImageTransform.Microsoft.Matrix",  "(?i)progid:DXImageTransform.Microsoft.Matrix\\s*([\"']?)", false, preservedTokens);


        // preserve strings so their content doesn't get accidentally minified
        sb = new StringBuffer();
        p = Pattern.compile("(\"([^\\\\\"]|\\\\.|\\\\)*\")|(\'([^\\\\\']|\\\\.|\\\\)*\')");
        m = p.matcher(css);
        while (m.find()) {
            token = m.group();
            char quote = token.charAt(0);
            token = token.substring(1, token.length() - 1);

            // maybe the string contains a comment-like substring?
            // one, maybe more? put'em back then
            if (token.indexOf("___YUICSSMIN_PRESERVE_CANDIDATE_COMMENT_") >= 0) {
                for (i = 0, max = comments.size(); i < max; i += 1) {
                    token = token.replace("___YUICSSMIN_PRESERVE_CANDIDATE_COMMENT_" + i + "___", comments.get(i).toString());
                }
            }

            // minify alpha opacity in filter strings
            token = token.replaceAll("(?i)progid:DXImageTransform.Microsoft.Alpha\\(Opacity=", "alpha(opacity=");

            preservedTokens.add(token);
            String preserver = quote + "___YUICSSMIN_PRESERVED_TOKEN_" + (preservedTokens.size() - 1) + "___" + quote;
            m.appendReplacement(sb, preserver);
        }
        m.appendTail(sb);
        css = sb.toString();


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

            token = comments.get(i).toString();
            placeholder = "___YUICSSMIN_PRESERVE_CANDIDATE_COMMENT_" + i + "___";

            // ! in the first position of the comment means preserve
            // so push to the preserved tokens while stripping the !
            if (token.startsWith("!")) {
                preservedTokens.add(token);
                css = css.replace(placeholder,  "___YUICSSMIN_PRESERVED_TOKEN_" + (preservedTokens.size() - 1) + "___");
                continue;
            }

            // \ in the last position looks like hack for Mac/IE5
            // shorten that to /*\*/ and the next one to /**/
            if (token.endsWith("\\")) {
                preservedTokens.add("\\");
                css = css.replace(placeholder,  "___YUICSSMIN_PRESERVED_TOKEN_" + (preservedTokens.size() - 1) + "___");
                i = i + 1; // attn: advancing the loop
                preservedTokens.add("");
                css = css.replace("___YUICSSMIN_PRESERVE_CANDIDATE_COMMENT_" + i + "___",  "___YUICSSMIN_PRESERVED_TOKEN_" + (preservedTokens.size() - 1) + "___");
                continue;
            }

            // keep empty comments after child selectors (IE7 hack)
            // e.g. html >/**/ body
            if (token.length() == 0) {
                startIndex = css.indexOf(placeholder);
                if (startIndex > 2) {
                    if (css.charAt(startIndex - 3) == '>') {
                        preservedTokens.add("");
                        css = css.replace(placeholder,  "___YUICSSMIN_PRESERVED_TOKEN_" + (preservedTokens.size() - 1) + "___");
                    }
                }
            }

            // in all other cases kill the comment
            css = css.replace("/*" + placeholder + "*/", "");
        }

        // preserve \9 IE hack
        final String backslash9 = "\\9"; 
        while (css.indexOf(backslash9) > -1) {
            preservedTokens.add(backslash9);
            css = css.replace(backslash9,  "___YUICSSMIN_PRESERVED_TOKEN_" + (preservedTokens.size() - 1) + "___");
     	}
        
        // Normalize all whitespace strings to single spaces. Easier to work with that way.
        css = css.replaceAll("\\s+", " ");

        // 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.
        sb = new StringBuffer();
        p = Pattern.compile("(^|\\})((^|([^\\{:])+):)+([^\\{]*\\{)");
        m = p.matcher(css);
        while (m.find()) {
            String s = m.group();
            s = s.replaceAll(":", "___YUICSSMIN_PSEUDOCLASSCOLON___");
            s = s.replaceAll( "\\\\", "\\\\\\\\" ).replaceAll( "\\$", "\\\\\\$" );
            m.appendReplacement(sb, s);
        }
        m.appendTail(sb);
        css = sb.toString();
        // Remove spaces before the things that should not have spaces before them.
        css = css.replaceAll("\\s+([!{};:>+\\(\\)\\],])", "$1");
        // Restore spaces for !important
        css = css.replaceAll("!important", " !important");
        // bring back the colon
        css = css.replaceAll("___YUICSSMIN_PSEUDOCLASSCOLON___", ":");

        // retain space for special IE6 cases
        sb = new StringBuffer();
        p = Pattern.compile("(?i):first\\-(line|letter)(\\{|,)");
        m = p.matcher(css);
        while (m.find()) {
            m.appendReplacement(sb, ":first-" + m.group(1).toLowerCase() + " " + m.group(2));
        }
        m.appendTail(sb);
        css = sb.toString();

        // no space after the end of a preserved comment
        css = css.replaceAll("\\*/ ", "*/");

        // If there are multiple @charset directives, push them to the top of the file.
        sb = new StringBuffer();
        p = Pattern.compile("(?i)^(.*)(@charset)( \"[^\"]*\";)");
        m = p.matcher(css);
        while (m.find()) {
            String s = m.group(1).replaceAll("\\\\", "\\\\\\\\").replaceAll("\\$", "\\\\\\$");
            m.appendReplacement(sb, m.group(2).toLowerCase() + m.group(3) + s);
        }
        m.appendTail(sb);
        css = sb.toString();

        // When all @charset are at the top, remove the second and after (as they are completely ignored).
        sb = new StringBuffer();
        p = Pattern.compile("(?i)^((\\s*)(@charset)( [^;]+;\\s*))+");
        m = p.matcher(css);
        while (m.find()) {
            m.appendReplacement(sb, m.group(2) + m.group(3).toLowerCase() + m.group(4));
        }
        m.appendTail(sb);
        css = sb.toString();

        // lowercase some popular @directives (@charset is done right above)
        sb = new StringBuffer();
        p = Pattern.compile("(?i)@(font-face|import|(?:-(?:atsc|khtml|moz|ms|o|wap|webkit)-)?keyframe|media|page|namespace)");
        m = p.matcher(css);
        while (m.find()) {
            m.appendReplacement(sb, '@' + m.group(1).toLowerCase());
        }
        m.appendTail(sb);
        css = sb.toString();

        // lowercase some more common pseudo-elements
        sb = new StringBuffer();
        p = Pattern.compile("(?i):(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)");
        m = p.matcher(css);
        while (m.find()) {
            m.appendReplacement(sb, ':' + m.group(1).toLowerCase());
        }
        m.appendTail(sb);
        css = sb.toString();

        // lowercase some more common functions
        sb = new StringBuffer();
        p = Pattern.compile("(?i):(lang|not|nth-child|nth-last-child|nth-last-of-type|nth-of-type|(?:-(?:moz|webkit)-)?any)\\(");
        m = p.matcher(css);
        while (m.find()) {
            m.appendReplacement(sb, ':' + m.group(1).toLowerCase() + '(');
        }
        m.appendTail(sb);
        css = sb.toString();

        // 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
        sb = new StringBuffer();
        p = Pattern.compile("(?i)([:,\\( ]\\s*)(attr|color-stop|from|rgba|to|url|(?:-(?:atsc|khtml|moz|ms|o|wap|webkit)-)?(?:calc|max|min|(?:repeating-)?(?:linear|radial)-gradient)|-webkit-gradient)");
        m = p.matcher(css);
        while (m.find()) {
            m.appendReplacement(sb, m.group(1) + m.group(2).toLowerCase());
        }
        m.appendTail(sb);
        css = sb.toString();

        // Put the space back in some cases, to support stuff like
        // @media screen and (-webkit-min-device-pixel-ratio:0){
        css = css.replaceAll("(?i)\\band\\(", "and (");

        // Remove the spaces after the things that should not have spaces after them.
        css = css.replaceAll("([!{}:;>+\\(\\[,])\\s+", "$1");

        // remove unnecessary semicolons
        css = css.replaceAll(";+}", "}");

        // Replace 0(px,em,%) with 0.
        String oldCss;
        p = Pattern.compile("(?i)(^|: ?)((?:[0-9a-z-.]+ )*?)?(?:0?\\.)?0(?:px|em|%|in|cm|mm|pc|pt|ex|deg|g?rad|m?s|k?hz)");
        do {
          oldCss = css;
          m = p.matcher(css);
          css = m.replaceAll("$1$20");
        } while (!(css.equals(oldCss)));

        // Replace 0(px,em,%) with 0 inside groups (e.g. -MOZ-RADIAL-GRADIENT(CENTER 45DEG, CIRCLE CLOSEST-SIDE, ORANGE 0%, RED 100%))
        p = Pattern.compile("(?i)\\( ?((?:[0-9a-z-.]+[ ,])*)?(?:0?\\.)?0(?:px|em|%|in|cm|mm|pc|pt|ex|deg|g?rad|m?s|k?hz)");
        do {
          oldCss = css;
          m = p.matcher(css);
          css = m.replaceAll("($10");
        } while (!(css.equals(oldCss)));

        // Replace x.0(px,em,%) with x(px,em,%).
        css = css.replaceAll("([0-9])\\.0(px|em|%|in|cm|mm|pc|pt|ex|deg|g?rad|m?s|k?hz| |;)", "$1$2");

        // Replace 0 0 0 0; with 0.
        css = css.replaceAll(":0 0 0 0(;|})", ":0$1");
        css = css.replaceAll(":0 0 0(;|})", ":0$1");
        css = css.replaceAll("(?<!flex):0 0(;|})", ":0$1");


        // Replace background-position:0; with background-position:0 0;
        // same for transform-origin
        sb = new StringBuffer();
        p = Pattern.compile("(?i)(background-position|webkit-mask-position|transform-origin|webkit-transform-origin|moz-transform-origin|o-transform-origin|ms-transform-origin):0(;|})");
        m = p.matcher(css);
        while (m.find()) {
            m.appendReplacement(sb, m.group(1).toLowerCase() + ":0 0" + m.group(2));
        }
        m.appendTail(sb);
        css = sb.toString();

        // Replace 0.6 to .6, but only when preceded by : or a white-space
        css = css.replaceAll("(:|\\s)0+\\.(\\d+)", "$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.
        p = Pattern.compile("rgb\\s*\\(\\s*([0-9,\\s]+)\\s*\\)");
        m = p.matcher(css);
        sb = new StringBuffer();
        while (m.find()) {
            String[] rgbcolors = m.group(1).split(",");
            StringBuffer hexcolor = new StringBuffer("#");
            for (i = 0; i < rgbcolors.length; i++) {
                int val = Integer.parseInt(rgbcolors[i]);
                if (val < 16) {
                    hexcolor.append('0');
                }

                // If someone passes an RGB value that's too big to express in two characters, round down.
                // Probably should throw out a warning here, but generating valid CSS is a bigger concern.
                if (val > 255) {
                    val = 255;
                }
                hexcolor.append(Integer.toHexString(val));
            }
            m.appendReplacement(sb, hexcolor.toString());
        }
        m.appendTail(sb);
        css = sb.toString();

        // Shorten colors from #AABBCC to #ABC. Note that we want to make sure
        // the color is not preceded by either ", " or =. Indeed, the property
        //     filter: chroma(color="#FFFFFF");
        // would become
        //     filter: chroma(color="#FFF");
        // which makes the filter break in IE.
        // We also want to make sure we're only compressing #AABBCC patterns inside { }, not id selectors ( #FAABAC {} )
        // We also want to avoid compressing invalid values (e.g. #AABBCCD to #ABCD)
        p = Pattern.compile("(\\=\\s*?[\"']?)?" + "#([0-9a-fA-F])([0-9a-fA-F])([0-9a-fA-F])([0-9a-fA-F])([0-9a-fA-F])([0-9a-fA-F])" + "(:?\\}|[^0-9a-fA-F{][^{]*?\\})");

        m = p.matcher(css);
        sb = new StringBuffer();
        int index = 0;

        while (m.find(index)) {

            sb.append(css.substring(index, m.start()));

            boolean isFilter = (m.group(1) != null && !"".equals(m.group(1)));

            if (isFilter) {
                // Restore, as is. Compression will break filters
                sb.append(m.group(1) + "#" + m.group(2) + m.group(3) + m.group(4) + m.group(5) + m.group(6) + m.group(7));
            } else {
                if( m.group(2).equalsIgnoreCase(m.group(3)) &&
                    m.group(4).equalsIgnoreCase(m.group(5)) &&
                    m.group(6).equalsIgnoreCase(m.group(7))) {

                    // #AABBCC pattern
                    sb.append("#" + (m.group(3) + m.group(5) + m.group(7)).toLowerCase());

                } else {

                    // Non-compressible color, restore, but lower case.
                    sb.append("#" + (m.group(2) + m.group(3) + m.group(4) + m.group(5) + m.group(6) + m.group(7)).toLowerCase());
                }
            }

            index = m.end(7);
        }

        sb.append(css.substring(index));
        css = sb.toString();

        // Replace #f00 -> red
        css = css.replaceAll("(:|\\s)(#f00)(;|})", "$1red$3");
        // Replace other short color keywords
        css = css.replaceAll("(:|\\s)(#000080)(;|})", "$1navy$3");
        css = css.replaceAll("(:|\\s)(#808080)(;|})", "$1gray$3");
        css = css.replaceAll("(:|\\s)(#808000)(;|})", "$1olive$3");
        css = css.replaceAll("(:|\\s)(#800080)(;|})", "$1purple$3");
        css = css.replaceAll("(:|\\s)(#c0c0c0)(;|})", "$1silver$3");
        css = css.replaceAll("(:|\\s)(#008080)(;|})", "$1teal$3");
        css = css.replaceAll("(:|\\s)(#ffa500)(;|})", "$1orange$3");
        css = css.replaceAll("(:|\\s)(#800000)(;|})", "$1maroon$3");

        // border: none -> border:0
        sb = new StringBuffer();
        p = Pattern.compile("(?i)(border|border-top|border-right|border-bottom|border-left|outline|background):none(;|})");
        m = p.matcher(css);
        while (m.find()) {
            m.appendReplacement(sb, m.group(1).toLowerCase() + ":0" + m.group(2));
        }
        m.appendTail(sb);
        css = sb.toString();

        // shorter opacity IE filter
        css = css.replaceAll("(?i)progid:DXImageTransform.Microsoft.Alpha\\(Opacity=", "alpha(opacity=");

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

        // Remove empty rules.
        css = css.replaceAll("[^\\}\\{/;]+\\{\\}", "");

        // Add "\" back to fix Opera -o-device-pixel-ratio query
        css = css.replaceAll("___YUI_QUERY_FRACTION___", "/");

        // TODO: Should this be after we re-insert tokens. These could alter the break points. However then
        // we'd need to make sure we don't break in the middle of a string etc.
        if (linebreakpos >= 0) {
            // 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.
            i = 0;
            int linestartpos = 0;
            sb = new StringBuffer(css);
            while (i < sb.length()) {
                char c = sb.charAt(i++);
                if (c == '}' && i - linestartpos > linebreakpos) {
                    sb.insert(i, '\n');
                    linestartpos = i;
                }
            }

            css = sb.toString();
        }

        // Replace multiple semi-colons in a row by a single one
        // See SF bug #1980989
        css = css.replaceAll(";;+", ";");

        // restore preserved comments and strings
        for(i = 0, max = preservedTokens.size(); i < max; i++) {
            css = css.replace("___YUICSSMIN_PRESERVED_TOKEN_" + i + "___", preservedTokens.get(i).toString());
        }
        
        // Add spaces back in between operators for css calc function
        // https://developer.mozilla.org/en-US/docs/Web/CSS/calc
        // Added by Eric Arnol-Martin (earnolmartin@gmail.com)
        sb = new StringBuffer();
        p = Pattern.compile("calc\\([^\\)]*\\)");
        m = p.matcher(css);
        while (m.find()) {
            String s = m.group();
            
            s = s.replaceAll("(?<=[-|%|px|em|rem|vw|\\d]+)\\+", " + ");
            s = s.replaceAll("(?<=[-|%|px|em|rem|vw|\\d]+)\\-", " - ");
            s = s.replaceAll("(?<=[-|%|px|em|rem|vw|\\d]+)\\*", " * ");
            s = s.replaceAll("(?<=[-|%|px|em|rem|vw|\\d]+)\\/", " / ");
            
            m.appendReplacement(sb, s);
        }
        m.appendTail(sb);
        css = sb.toString(); 

        // Trim the final string (for any leading or trailing white spaces)
        css = css.trim();

        // Write the output...
        out.write(css);
    }
}
