user/src/com/google/gwt/resources/converter/GssGenerationVisitor.java - gwt - Git at Google

 /*
  * Copyright 2014 Google Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License"); you may not
  * use this file except in compliance with the License. You may obtain a copy of
  * the License at
  *
  * http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
  * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
  * License for the specific language governing permissions and limitations under
  * the License.
  */
 package com.google.gwt.resources.converter;

 import com.google.gwt.core.ext.TreeLogger;
 import com.google.gwt.core.ext.TreeLogger.Type;
 import com.google.gwt.dev.util.TextOutput;
 import com.google.gwt.resources.css.ast.Context;
 import com.google.gwt.resources.css.ast.CssCharset;
 import com.google.gwt.resources.css.ast.CssDef;
 import com.google.gwt.resources.css.ast.CssEval;
 import com.google.gwt.resources.css.ast.CssExternalSelectors;
 import com.google.gwt.resources.css.ast.CssFontFace;
 import com.google.gwt.resources.css.ast.CssIf;
 import com.google.gwt.resources.css.ast.CssMediaRule;
 import com.google.gwt.resources.css.ast.CssNoFlip;
 import com.google.gwt.resources.css.ast.CssPageRule;
 import com.google.gwt.resources.css.ast.CssProperty;
 import com.google.gwt.resources.css.ast.CssProperty.DotPathValue;
 import com.google.gwt.resources.css.ast.CssProperty.FunctionValue;
 import com.google.gwt.resources.css.ast.CssProperty.Value;
 import com.google.gwt.resources.css.ast.CssRule;
 import com.google.gwt.resources.css.ast.CssSelector;
 import com.google.gwt.resources.css.ast.CssSprite;
 import com.google.gwt.resources.css.ast.CssUnknownAtRule;
 import com.google.gwt.resources.css.ast.CssUrl;
 import com.google.gwt.thirdparty.common.css.SourceCode;
 import com.google.gwt.thirdparty.common.css.compiler.ast.GssParser;
 import com.google.gwt.thirdparty.common.css.compiler.ast.GssParserException;
 import com.google.gwt.thirdparty.guava.common.base.Predicate;
 import com.google.gwt.thirdparty.guava.common.base.Splitter;
 import com.google.gwt.thirdparty.guava.common.base.Strings;

 import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;

 /**
  * The GssGenerationVisitor turns a css tree into a gss string.
  */
 public class GssGenerationVisitor extends ExtendedCssVisitor {
   /* templates and tokens list */
   private static final String AND = " && ";
   private static final String CHARSET = "@charset \"%s\";";
   private static final String DEF = "@def ";
   private static final String ELSE = "@else ";
   private static final String ELSE_IF = "@elseif (%s)";
   private static final String EVAL = "eval('%s')";
   private static final String EXTERNAL = "@external";
   private static final String GWT_SPRITE = "gwt-sprite: \"%s\"";
   private static final String IF = "@if (%s)";
   private static final String IMPORTANT = " !important";
   private static final String IS = "is(\"%s\", \"%s\")";
   private static final String NO_FLIP = "/* @noflip */";
   private static final String NOT = "!";
   private static final String OR = " || ";
   private static final Pattern UNESCAPE = Pattern.compile("\\\\");
   private static final Pattern UNESCAPE_EXTERNAL = Pattern.compile("\\\\|@external|,|\\n|\\r");
   private static final String URL = "resourceUrl(\"%s\")";
   private static final String VALUE = "value('%s')";
   private static final String VALUE_WITH_SUFFIX = "value('%s', '%s')";

   // Used to quote font family name that contains white space(s) and aren't quoted yet.
   private static Pattern NOT_QUOTED_WITH_WITHESPACE = Pattern.compile("^[^'\"].*\\s.*[^'\"]$");

   // Used to sanitize the boolean conditions
   private static Pattern BANG_OPERATOR = Pattern.compile("^(!+)(.*)");

   // GSS impose constant names to be in uppercase. This Map will contains the mapping between
   // the name of constants defined in the CSS and the corresponding name that will be used in GSS.
   private final Map<String, String> cssToGssConstantMapping;
   private final TextOutput out;
   private final boolean lenient;
   private final TreeLogger treeLogger;
   private final Predicate<String> simpleBooleanConditionPredicate;
   // list of external at-rules defined inside a media at-rule.
   // In lenient mode, these nodes will be extracted and print outside the media at-rule.
   private final List<CssExternalSelectors> wrongExternalNodes = new
       ArrayList<CssExternalSelectors>();

   // list of constant definition nodes defined inside a media at-rule.
   // In lenient mode, these nodes will be extracted and print outside the media at-rule.
   private final List<CssDef> wrongDefNodes = new ArrayList<CssDef>();

   private boolean insideNoFlipNode;
   private boolean needsNewLine;
   private boolean needsOpenBrace;
   private boolean needsComma;
   private boolean insideMediaAtRule;
   // used to group a sequence of @def in one block
   private boolean previousNodeIsDef;
   // used to group asequence of @external in one block
   private boolean previousNodeIsExternal;

   public GssGenerationVisitor(TextOutput out, Map<String, String> cssToGssConstantMapping,
       boolean lenient, TreeLogger treeLogger, Predicate<String> simpleBooleanConditionPredicate) {
     this.cssToGssConstantMapping = cssToGssConstantMapping;
     this.out = out;
     this.lenient = lenient;
     this.treeLogger = treeLogger;
     this.simpleBooleanConditionPredicate = simpleBooleanConditionPredicate;
   }

   public String getContent() {
     return out.toString();
   }

   @Override
   public void endVisit(CssFontFace x, Context ctx) {
     closeBrace();
   }

   @Override
   public void endVisit(CssMediaRule x, Context ctx) {
     closeBrace();

     insideMediaAtRule = false;

     maybePrintWrongExternalNodes();
     maybePrintWrongDefNodes(ctx);
   }

   @Override
   public void endVisit(CssPageRule x, Context ctx) {
     closeBrace();
   }

   @Override
   public void endVisit(CssUnknownAtRule x, Context ctx) {
     // The old CSS resource has no support for many at-rules, like animations. There is no way
     // for us to parse them using the old CSS parser, so we will just output them as a string to
     // the GSS stylesheet and hope that the GSS parser is okay with the rule
     out.print(x.getRule());
   }

   @Override
   public boolean visit(CssSprite x, Context ctx) {
     return false;
   }

   @Override
   public void endVisit(CssSprite x, Context ctx) {
     needsComma = false;

     accept(x.getSelectors());
     openBrace();

     out.print(String.format(GWT_SPRITE, x.getResourceFunction().getPath()));
     semiColon();

     accept(x.getProperties());

     closeBrace();
   }

   @Override
   public boolean visit(CssDef x, Context ctx) {
     printDef(x, null, "def", false);

     previousNodeIsDef = true;
     previousNodeIsExternal = false;

     return false;
   }

   @Override
   public boolean visit(CssEval x, Context ctx) {
     printDef(x, EVAL, "eval", false);

     return false;
   }

   @Override
   public boolean visit(CssUrl x, Context ctx) {
     printDef(x, URL, "url", true);

     return false;
   }

   @Override
   public boolean visit(CssRule x, Context ctx) {
     maybePrintNewLine();

     needsOpenBrace = true;
     needsComma = false;
     needsNewLine = false;
     previousNodeIsDef = false;
     previousNodeIsExternal = false;

     return true;
   }

   @Override
   public void endVisit(CssRule x, Context ctx) {
     // empty rule block case.
     maybePrintOpenBrace();

     closeBrace();

     needsNewLine = true;
   }

   @Override
   public boolean visit(CssNoFlip x, Context ctx) {
     insideNoFlipNode = true;
     previousNodeIsDef = false;
     previousNodeIsExternal = false;
     return true;
   }

   @Override
   public boolean visit(CssExternalSelectors x, Context ctx) {
     if (insideMediaAtRule) {
       if (lenient) {
         treeLogger.log(Type.WARN, "An external at-rule is not allowed inside a @media at-rule. " +
             "The following external at-rule [" + x + "] will be moved in the upper scope");
         wrongExternalNodes.add(x);
       } else {
         treeLogger.log(Type.ERROR, "An external at-rule is not allowed inside a @media at-rule. " +
             "[" + x + "].");
         throw new Css2GssConversionException("An external at-rule is not allowed inside a @media" +
             " at-rule.");
       }
     } else {
       printExternal(x);
     }

     return false;
   }

   @Override
   public boolean visit(CssCharset x, Context ctx) {
     out.print(String.format(CHARSET, x.getCharset()));
     out.newlineOpt();

     needsNewLine = true;
     previousNodeIsDef = false;
     previousNodeIsExternal = false;

     return true;
   }

   private void maybePrintWrongExternalNodes() {
     if (!lenient) {
       return;
     }

     for (CssExternalSelectors external : wrongExternalNodes) {
       printExternal(external);
     }
     wrongExternalNodes.clear();
   }

   private void maybePrintWrongDefNodes(Context ctx) {
     if (!lenient) {
       return;
     }

     for (CssDef def : wrongDefNodes) {
       if (def instanceof CssUrl) {
         visit((CssUrl) def, ctx);
       } else if (def instanceof CssEval) {
         visit((CssEval) def, ctx);
       } else {
         visit(def, ctx);
       }
     }
     wrongDefNodes.clear();
   }

   private void printExternal(CssExternalSelectors x) {
     boolean first = true;
     for (String selector : x.getClasses()) {
       String unescaped = unescapeExternalClass(selector);
       if (validateExternalClass(selector) && !Strings.isNullOrEmpty(unescaped)) {
         if (first) {
           if (!previousNodeIsExternal) {
             maybePrintNewLine();
           }

           out.print(EXTERNAL);
           first = false;
         }

         out.print(" ");

         boolean needQuote = selector.endsWith("*");

         if (needQuote) {
           out.print("'");
         }

         out.printOpt(unescaped);

         if (needQuote) {
           out.print("'");
         }
       }
     }

     if (!first) {
       semiColon();
     }

     previousNodeIsDef = false;
     previousNodeIsExternal = true;
   }

   private boolean validateExternalClass(String selector) {
     if (selector.contains(":")) {
       if (lenient) {
         treeLogger.log(Type.WARN, "This invalid external selector will be skipped: " + selector);
         return false;
       } else {
         throw new Css2GssConversionException(
             "One of your external statements contains a pseudo class: " + selector);
       }
     }
     return true;
   }

   @Override
   public void endVisit(CssNoFlip x, Context ctx) {
     insideNoFlipNode = false;
   }

   @Override
   public boolean visit(CssProperty x, Context ctx) {
     maybePrintOpenBrace();

     StringBuilder propertyBuilder = new StringBuilder();

     if (insideNoFlipNode) {
       propertyBuilder.append(NO_FLIP);
       propertyBuilder.append(' ');
     }

     propertyBuilder.append(x.getName());
     propertyBuilder.append(": ");

     String valueListCss = printValuesList(x.getValues().getValues(), false);

     if ("font-family".equals(x.getName())) {
       // Font family names containing whitespace should be quoted.
       valueListCss = quoteFontFamilyWithWhiteSpace(valueListCss);
     }

     propertyBuilder.append(valueListCss);

     if (x.isImportant()) {
       propertyBuilder.append(IMPORTANT);
     }

     String cssProperty = propertyBuilder.toString();

     // See if we can parse the rule using the GSS parser and thus verify that the
     // rule is indeed correct CSS.
     try {
       new GssParser(new SourceCode(null, "body{" + cssProperty + "}")).parse();
     } catch (GssParserException e) {
       if (lenient) {
         // print a warning message and don't print the rule.
         treeLogger.log(Type.WARN, "The following rule is not valid and will be skipped: " +
             cssProperty);
         return false;
       } else {
         treeLogger.log(Type.ERROR, "The following rule is not valid. " +
             cssProperty);
         throw new Css2GssConversionException("Invalid css rule", e);
       }
     }

     out.print(cssProperty);

     semiColon();

     return true;
   }

   /**
    * Quotes the font family names that contains white space but aren't quoted yet. thus allowing
    * usage of fonts that might be mistaken for constants. RTis is also recommended by the CSS
    * specification: http://www.w3.org/TR/CSS2/fonts.html#propdef-font-family
    * <p>It's important to notice that the converter doesn't manage the case where a constant is
    * used inside a font family name with whitespace. The font family name will be quoted and
    * won't be replaced.
    * {@code
    *   @def myFontFamily Comic;
    *
    *   .div {
    *     font-family: Arial, myFontFamily sans MS;
    *   }
    * }
    *
    * will be converted to:
    *
    * {@code
    *   @def MY_FONT_FAMILY Comic;
    *
    *   .div {
    *    font-family: Arial, "MY_FONT_FAMILY sans MS";
    *   }
    * }
    * @param cssProperty
    */
   private String quoteFontFamilyWithWhiteSpace(String cssProperty) {
     StringBuilder valueBuilder = new StringBuilder();

     boolean first = true;

     for (String subProperty : Splitter.on(",").trimResults().omitEmptyStrings().split(cssProperty)) {
       if (first) {
         first = false;
       } else {
         valueBuilder.append(",");
       }

       if (NOT_QUOTED_WITH_WITHESPACE.matcher(subProperty).matches()) {
         valueBuilder.append("'" + subProperty + "'");
       } else {
         valueBuilder.append(subProperty);
       }
     }

     return valueBuilder.toString();
   }

   @Override
   public boolean visit(CssElse x, Context ctx) {
     closeBrace();

     out.print(ELSE);

     openBrace();

     needsNewLine = false;
     previousNodeIsDef = false;
     previousNodeIsExternal = false;

     return true;
   }

   @Override
   public boolean visit(CssElIf x, Context ctx) {
     closeBrace();

     openConditional(ELSE_IF, x);

     return true;
   }

   @Override
   public void endVisit(CssIf x, Context ctx) {
     closeBrace();
     needsNewLine = true;
   }

   @Override
   public boolean visit(CssIf x, Context ctx) {
     maybePrintNewLine();

     openConditional(IF, x);

     return true;
   }

   private void openConditional(String template, CssIf ifOrElif) {
     String condition;

     String runtimeCondition = extractExpression(ifOrElif);

     if (runtimeCondition != null) {
       if (simpleBooleanConditionPredicate.apply(runtimeCondition)) {
         condition = runtimeCondition;
       } else {
         condition = String.format(EVAL, runtimeCondition);
       }
     } else {
       condition = printConditionnalExpression(ifOrElif);
     }

     out.print(String.format(template, condition));

     openBrace();

     needsNewLine = false;
     previousNodeIsDef = false;
     previousNodeIsExternal = false;
   }

   private String extractExpression(CssIf ifOrElif) {
     String condition = ifOrElif.getExpression();

     if (condition == null) {
       return null;
     }

     if (condition.trim().startsWith("(")) {
       condition = condition.substring(1, condition.length() - 1);
     }

     // sanitize the expression. GSS doesn't accept more than one ! operator
     Matcher m = BANG_OPERATOR.matcher(condition);
     if (m.matches()) {
       String bangs = m.group(1);
       String replacement;
       if (bangs.length() % 2 == 0) {
         replacement = "";
       } else {
         replacement = "!";
       }

       condition = m.replaceFirst(replacement + "$2");
     }

     return condition;
   }

   @Override
   public boolean visit(CssFontFace x, Context ctx) {
     out.print("@font-face");

     openBrace();

     previousNodeIsDef = false;
     previousNodeIsExternal = false;

     return true;
   }

   @Override
   public boolean visit(CssMediaRule x, Context ctx) {
     maybePrintNewLine();

     insideMediaAtRule = true;

     out.print("@media");
     boolean isFirst = true;
     for (String m : x.getMedias()) {
       if (isFirst) {
         out.print(" ");
         isFirst = false;
       } else {
         comma();
       }
       out.print(m);
     }
     spaceOpt();
     out.print("{");
     out.newlineOpt();
     out.indentIn();

     needsNewLine = false;
     previousNodeIsDef = false;
     previousNodeIsExternal = false;

     return true;
   }

   @Override
   public boolean visit(CssPageRule x, Context ctx) {
     out.print("@page");
     if (x.getPseudoPage() != null) {
       out.print(" :");
       out.print(x.getPseudoPage());
     }
     spaceOpt();
     out.print("{");
     out.newlineOpt();
     out.indentIn();

     previousNodeIsDef = false;
     previousNodeIsExternal = false;

     return true;
   }

   @Override
   public boolean visit(CssSelector x, Context ctx) {
     if (needsComma) {
       comma(false);
     }

     maybePrintNewLine();

     needsComma = true;

     needsNewLine = true;

     out.print(unescape(x.getSelector()));

     return true;
   }

   private void printDef(CssDef def, String valueTemplate, String atRule, boolean insideUrlNode) {
     if (validateDefNode(def, atRule)) {
       if (!previousNodeIsDef) {
         maybePrintNewLine();
       }

       out.print(DEF);

       String name = cssToGssConstantMapping.get(def.getKey());

       if (name == null) {
         throw new Css2GssConversionException("unknown @" + atRule + " rule [" + def.getKey() + "]");
       }

       out.print(name);
       out.print(' ');

       String values = printValuesList(def.getValues(), insideUrlNode);

       if (valueTemplate != null) {
         out.print(String.format(valueTemplate, values));
       } else {
         out.print(values);
       }

       semiColon();

       previousNodeIsDef = true;
       needsNewLine = true;
     }
   }

   private boolean validateDefNode(CssDef def, String atRule) {
     if (insideMediaAtRule) {
       if (lenient) {
         treeLogger.log(Type.WARN, "A " + atRule + " is not allowed inside a @media at-rule." +
             "The following " + atRule + " [" + def + "] will be moved in the upper scope");
         wrongDefNodes.add(def);
         return false;
       } else {
         treeLogger.log(Type.ERROR, "A " + atRule + " is not allowed inside a @media at-rule. ["
             + def + "]");
         throw new Css2GssConversionException("A " + atRule + " is not allowed inside a @media " +
             "at-rule.");
       }
     }
     return true;
   }

   private void closeBrace() {
     out.indentOut();
     out.print('}');
     out.newlineOpt();
   }

   private void comma() {
     comma(true);
   }

   private void comma(boolean addSpace) {
     out.print(',');

     if (addSpace) {
       spaceOpt();
     }
   }

   private void openBrace() {
     spaceOpt();
     out.print('{');
     out.newlineOpt();
     out.indentIn();
   }

   private void semiColon() {
     out.print(';');
     out.newlineOpt();
   }

   private void spaceOpt() {
     out.printOpt(' ');
   }

   private void maybePrintOpenBrace() {
     if (needsOpenBrace) {
       openBrace();
       needsOpenBrace = false;
     }
   }

   private void maybePrintNewLine() {
     if (needsNewLine) {
       out.newlineOpt();
     }
   }

   private String printConditionnalExpression(CssIf x) {
     if (x == null || x.getExpression() != null) {
       throw new IllegalStateException();
     }

     StringBuilder builder = new StringBuilder();

     String propertyName = x.getPropertyName();

     for (String propertyValue : x.getPropertyValues()) {
       if (builder.length() != 0) {
         if (x.isNegated()) {
           builder.append(AND);
         } else {
           builder.append(OR);
         }
       }

       if (x.isNegated()) {
         builder.append(NOT);
       }

       builder.append(String.format(IS, propertyName, propertyValue));
     }

     return builder.toString();
   }

   private String printValuesList(List<Value> values, boolean insideUrlNode) {
     StringBuilder builder = new StringBuilder();

     for (Value value : values) {
       if (value.isSpaceRequired() && builder.length() != 0) {
         builder.append(' ');
       }

       String expression = value.toCss();

       if (value.isIdentValue() != null && cssToGssConstantMapping.containsKey(expression)) {
         expression = cssToGssConstantMapping.get(expression);
       } else if (value.isExpressionValue() != null) {
         expression = value.getExpression();
       } else if (value.isDotPathValue() != null) {
         DotPathValue dotPathValue = value.isDotPathValue();
         if (insideUrlNode) {
           expression = dotPathValue.getPath();
         } else {
           if (Strings.isNullOrEmpty(dotPathValue.getSuffix())) {
             expression = String.format(VALUE, dotPathValue.getPath());
           } else {
             expression =
                 String.format(VALUE_WITH_SUFFIX, dotPathValue.getPath(), dotPathValue.getSuffix());
           }
         }
       } else if (value.isFunctionValue() != null) {
         FunctionValue functionValue = value.isFunctionValue();

         // process the argument list values
         String arguments = printValuesList(functionValue.getValues().getValues(), insideUrlNode);

         expression = unescape(functionValue.getName()) + "(" + arguments + ")";
       }

       // don't escape content of quoted string and don't escape isFunctionValue because the
       // arguments and the name of the functions are already unescaped if needed.
       if (value.isStringValue() != null || value.isFunctionValue() != null) {
         builder.append(expression);
       } else {
         builder.append(unescape(expression));
       }
     }

     return builder.toString();
   }

   private String unescape(String toEscape) {
     return UNESCAPE.matcher(toEscape).replaceAll("");
   }

   private String unescapeExternalClass(String external) {
     return UNESCAPE_EXTERNAL.matcher(external).replaceAll("");
   }
 }
	/*
	* Copyright 2014 Google Inc.
	*
	* Licensed under the Apache License, Version 2.0 (the "License"); you may not
	* use this file except in compliance with the License. You may obtain a copy of
	* the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
	* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
	* License for the specific language governing permissions and limitations under
	* the License.
	*/
	package com.google.gwt.resources.converter;

	import com.google.gwt.core.ext.TreeLogger;
	import com.google.gwt.core.ext.TreeLogger.Type;
	import com.google.gwt.dev.util.TextOutput;
	import com.google.gwt.resources.css.ast.Context;
	import com.google.gwt.resources.css.ast.CssCharset;
	import com.google.gwt.resources.css.ast.CssDef;
	import com.google.gwt.resources.css.ast.CssEval;
	import com.google.gwt.resources.css.ast.CssExternalSelectors;
	import com.google.gwt.resources.css.ast.CssFontFace;
	import com.google.gwt.resources.css.ast.CssIf;
	import com.google.gwt.resources.css.ast.CssMediaRule;
	import com.google.gwt.resources.css.ast.CssNoFlip;
	import com.google.gwt.resources.css.ast.CssPageRule;
	import com.google.gwt.resources.css.ast.CssProperty;
	import com.google.gwt.resources.css.ast.CssProperty.DotPathValue;
	import com.google.gwt.resources.css.ast.CssProperty.FunctionValue;
	import com.google.gwt.resources.css.ast.CssProperty.Value;
	import com.google.gwt.resources.css.ast.CssRule;
	import com.google.gwt.resources.css.ast.CssSelector;
	import com.google.gwt.resources.css.ast.CssSprite;
	import com.google.gwt.resources.css.ast.CssUnknownAtRule;
	import com.google.gwt.resources.css.ast.CssUrl;
	import com.google.gwt.thirdparty.common.css.SourceCode;
	import com.google.gwt.thirdparty.common.css.compiler.ast.GssParser;
	import com.google.gwt.thirdparty.common.css.compiler.ast.GssParserException;
	import com.google.gwt.thirdparty.guava.common.base.Predicate;
	import com.google.gwt.thirdparty.guava.common.base.Splitter;
	import com.google.gwt.thirdparty.guava.common.base.Strings;

	import java.util.ArrayList;
	import java.util.List;
	import java.util.Map;
	import java.util.regex.Matcher;
	import java.util.regex.Pattern;

	/**
	* The GssGenerationVisitor turns a css tree into a gss string.
	*/
	public class GssGenerationVisitor extends ExtendedCssVisitor {
	/* templates and tokens list */
	private static final String AND = " && ";
	private static final String CHARSET = "@charset \"%s\";";
	private static final String DEF = "@def ";
	private static final String ELSE = "@else ";
	private static final String ELSE_IF = "@elseif (%s)";
	private static final String EVAL = "eval('%s')";
	private static final String EXTERNAL = "@external";
	private static final String GWT_SPRITE = "gwt-sprite: \"%s\"";
	private static final String IF = "@if (%s)";
	private static final String IMPORTANT = " !important";
	private static final String IS = "is(\"%s\", \"%s\")";
	private static final String NO_FLIP = "/* @noflip */";
	private static final String NOT = "!";
	private static final String OR = " \|\| ";
	private static final Pattern UNESCAPE = Pattern.compile("\\\\");
	private static final Pattern UNESCAPE_EXTERNAL = Pattern.compile("\\\\\|@external\|,\|\\n\|\\r");
	private static final String URL = "resourceUrl(\"%s\")";
	private static final String VALUE = "value('%s')";
	private static final String VALUE_WITH_SUFFIX = "value('%s', '%s')";

	// Used to quote font family name that contains white space(s) and aren't quoted yet.
	private static Pattern NOT_QUOTED_WITH_WITHESPACE = Pattern.compile("^[^'\"].\\s.[^'\"]$");

	// Used to sanitize the boolean conditions
	private static Pattern BANG_OPERATOR = Pattern.compile("^(!+)(.*)");

	// GSS impose constant names to be in uppercase. This Map will contains the mapping between
	// the name of constants defined in the CSS and the corresponding name that will be used in GSS.
	private final Map<String, String> cssToGssConstantMapping;
	private final TextOutput out;
	private final boolean lenient;
	private final TreeLogger treeLogger;
	private final Predicate<String> simpleBooleanConditionPredicate;
	// list of external at-rules defined inside a media at-rule.
	// In lenient mode, these nodes will be extracted and print outside the media at-rule.
	private final List<CssExternalSelectors> wrongExternalNodes = new
	ArrayList<CssExternalSelectors>();

	// list of constant definition nodes defined inside a media at-rule.
	// In lenient mode, these nodes will be extracted and print outside the media at-rule.
	private final List<CssDef> wrongDefNodes = new ArrayList<CssDef>();

	private boolean insideNoFlipNode;
	private boolean needsNewLine;
	private boolean needsOpenBrace;
	private boolean needsComma;
	private boolean insideMediaAtRule;
	// used to group a sequence of @def in one block
	private boolean previousNodeIsDef;
	// used to group asequence of @external in one block
	private boolean previousNodeIsExternal;

	public GssGenerationVisitor(TextOutput out, Map<String, String> cssToGssConstantMapping,
	boolean lenient, TreeLogger treeLogger, Predicate<String> simpleBooleanConditionPredicate) {
	this.cssToGssConstantMapping = cssToGssConstantMapping;
	this.out = out;
	this.lenient = lenient;
	this.treeLogger = treeLogger;
	this.simpleBooleanConditionPredicate = simpleBooleanConditionPredicate;
	}

	public String getContent() {
	return out.toString();
	}

	@Override
	public void endVisit(CssFontFace x, Context ctx) {
	closeBrace();
	}

	@Override
	public void endVisit(CssMediaRule x, Context ctx) {
	closeBrace();

	insideMediaAtRule = false;

	maybePrintWrongExternalNodes();
	maybePrintWrongDefNodes(ctx);
	}

	@Override
	public void endVisit(CssPageRule x, Context ctx) {
	closeBrace();
	}

	@Override
	public void endVisit(CssUnknownAtRule x, Context ctx) {
	// The old CSS resource has no support for many at-rules, like animations. There is no way
	// for us to parse them using the old CSS parser, so we will just output them as a string to
	// the GSS stylesheet and hope that the GSS parser is okay with the rule
	out.print(x.getRule());
	}

	@Override
	public boolean visit(CssSprite x, Context ctx) {
	return false;
	}

	@Override
	public void endVisit(CssSprite x, Context ctx) {
	needsComma = false;

	accept(x.getSelectors());
	openBrace();

	out.print(String.format(GWT_SPRITE, x.getResourceFunction().getPath()));
	semiColon();

	accept(x.getProperties());

	closeBrace();
	}

	@Override
	public boolean visit(CssDef x, Context ctx) {
	printDef(x, null, "def", false);

	previousNodeIsDef = true;
	previousNodeIsExternal = false;

	return false;
	}

	@Override
	public boolean visit(CssEval x, Context ctx) {
	printDef(x, EVAL, "eval", false);

	return false;
	}

	@Override
	public boolean visit(CssUrl x, Context ctx) {
	printDef(x, URL, "url", true);

	return false;
	}

	@Override
	public boolean visit(CssRule x, Context ctx) {
	maybePrintNewLine();

	needsOpenBrace = true;
	needsComma = false;
	needsNewLine = false;
	previousNodeIsDef = false;
	previousNodeIsExternal = false;

	return true;
	}

	@Override
	public void endVisit(CssRule x, Context ctx) {
	// empty rule block case.
	maybePrintOpenBrace();

	closeBrace();

	needsNewLine = true;
	}

	@Override
	public boolean visit(CssNoFlip x, Context ctx) {
	insideNoFlipNode = true;
	previousNodeIsDef = false;
	previousNodeIsExternal = false;
	return true;
	}

	@Override
	public boolean visit(CssExternalSelectors x, Context ctx) {
	if (insideMediaAtRule) {
	if (lenient) {
	treeLogger.log(Type.WARN, "An external at-rule is not allowed inside a @media at-rule. " +
	"The following external at-rule [" + x + "] will be moved in the upper scope");
	wrongExternalNodes.add(x);
	} else {
	treeLogger.log(Type.ERROR, "An external at-rule is not allowed inside a @media at-rule. " +
	"[" + x + "].");
	throw new Css2GssConversionException("An external at-rule is not allowed inside a @media" +
	" at-rule.");
	}
	} else {
	printExternal(x);
	}

	return false;
	}

	@Override
	public boolean visit(CssCharset x, Context ctx) {
	out.print(String.format(CHARSET, x.getCharset()));
	out.newlineOpt();

	needsNewLine = true;
	previousNodeIsDef = false;
	previousNodeIsExternal = false;

	return true;
	}

	private void maybePrintWrongExternalNodes() {
	if (!lenient) {
	return;
	}

	for (CssExternalSelectors external : wrongExternalNodes) {
	printExternal(external);
	}
	wrongExternalNodes.clear();
	}

	private void maybePrintWrongDefNodes(Context ctx) {
	if (!lenient) {
	return;
	}

	for (CssDef def : wrongDefNodes) {
	if (def instanceof CssUrl) {
	visit((CssUrl) def, ctx);
	} else if (def instanceof CssEval) {
	visit((CssEval) def, ctx);
	} else {
	visit(def, ctx);
	}
	}
	wrongDefNodes.clear();
	}

	private void printExternal(CssExternalSelectors x) {
	boolean first = true;
	for (String selector : x.getClasses()) {
	String unescaped = unescapeExternalClass(selector);
	if (validateExternalClass(selector) && !Strings.isNullOrEmpty(unescaped)) {
	if (first) {
	if (!previousNodeIsExternal) {
	maybePrintNewLine();
	}

	out.print(EXTERNAL);
	first = false;
	}

	out.print(" ");

	boolean needQuote = selector.endsWith("*");

	if (needQuote) {
	out.print("'");
	}

	out.printOpt(unescaped);

	if (needQuote) {
	out.print("'");
	}
	}
	}

	if (!first) {
	semiColon();
	}

	previousNodeIsDef = false;
	previousNodeIsExternal = true;
	}

	private boolean validateExternalClass(String selector) {
	if (selector.contains(":")) {
	if (lenient) {
	treeLogger.log(Type.WARN, "This invalid external selector will be skipped: " + selector);
	return false;
	} else {
	throw new Css2GssConversionException(
	"One of your external statements contains a pseudo class: " + selector);
	}
	}
	return true;
	}

	@Override
	public void endVisit(CssNoFlip x, Context ctx) {
	insideNoFlipNode = false;
	}

	@Override
	public boolean visit(CssProperty x, Context ctx) {
	maybePrintOpenBrace();

	StringBuilder propertyBuilder = new StringBuilder();

	if (insideNoFlipNode) {
	propertyBuilder.append(NO_FLIP);
	propertyBuilder.append(' ');
	}

	propertyBuilder.append(x.getName());
	propertyBuilder.append(": ");

	String valueListCss = printValuesList(x.getValues().getValues(), false);

	if ("font-family".equals(x.getName())) {
	// Font family names containing whitespace should be quoted.
	valueListCss = quoteFontFamilyWithWhiteSpace(valueListCss);
	}

	propertyBuilder.append(valueListCss);

	if (x.isImportant()) {
	propertyBuilder.append(IMPORTANT);
	}

	String cssProperty = propertyBuilder.toString();

	// See if we can parse the rule using the GSS parser and thus verify that the
	// rule is indeed correct CSS.
	try {
	new GssParser(new SourceCode(null, "body{" + cssProperty + "}")).parse();
	} catch (GssParserException e) {
	if (lenient) {
	// print a warning message and don't print the rule.
	treeLogger.log(Type.WARN, "The following rule is not valid and will be skipped: " +
	cssProperty);
	return false;
	} else {
	treeLogger.log(Type.ERROR, "The following rule is not valid. " +
	cssProperty);
	throw new Css2GssConversionException("Invalid css rule", e);
	}
	}

	out.print(cssProperty);

	semiColon();

	return true;
	}

	/**
	* Quotes the font family names that contains white space but aren't quoted yet. thus allowing
	* usage of fonts that might be mistaken for constants. RTis is also recommended by the CSS
	* specification: http://www.w3.org/TR/CSS2/fonts.html#propdef-font-family
	* <p>It's important to notice that the converter doesn't manage the case where a constant is
	* used inside a font family name with whitespace. The font family name will be quoted and
	* won't be replaced.
	* {@code
	* @def myFontFamily Comic;
	*
	* .div {
	* font-family: Arial, myFontFamily sans MS;
	* }
	* }
	*
	* will be converted to:
	*
	* {@code
	* @def MY_FONT_FAMILY Comic;
	*
	* .div {
	* font-family: Arial, "MY_FONT_FAMILY sans MS";
	* }
	* }
	* @param cssProperty
	*/
	private String quoteFontFamilyWithWhiteSpace(String cssProperty) {
	StringBuilder valueBuilder = new StringBuilder();

	boolean first = true;

	for (String subProperty : Splitter.on(",").trimResults().omitEmptyStrings().split(cssProperty)) {
	if (first) {
	first = false;
	} else {
	valueBuilder.append(",");
	}

	if (NOT_QUOTED_WITH_WITHESPACE.matcher(subProperty).matches()) {
	valueBuilder.append("'" + subProperty + "'");
	} else {
	valueBuilder.append(subProperty);
	}
	}

	return valueBuilder.toString();
	}

	@Override
	public boolean visit(CssElse x, Context ctx) {
	closeBrace();

	out.print(ELSE);

	openBrace();

	needsNewLine = false;
	previousNodeIsDef = false;
	previousNodeIsExternal = false;

	return true;
	}

	@Override
	public boolean visit(CssElIf x, Context ctx) {
	closeBrace();

	openConditional(ELSE_IF, x);

	return true;
	}

	@Override
	public void endVisit(CssIf x, Context ctx) {
	closeBrace();
	needsNewLine = true;
	}

	@Override
	public boolean visit(CssIf x, Context ctx) {
	maybePrintNewLine();

	openConditional(IF, x);

	return true;
	}

	private void openConditional(String template, CssIf ifOrElif) {
	String condition;

	String runtimeCondition = extractExpression(ifOrElif);

	if (runtimeCondition != null) {
	if (simpleBooleanConditionPredicate.apply(runtimeCondition)) {
	condition = runtimeCondition;
	} else {
	condition = String.format(EVAL, runtimeCondition);
	}
	} else {
	condition = printConditionnalExpression(ifOrElif);
	}

	out.print(String.format(template, condition));

	openBrace();

	needsNewLine = false;
	previousNodeIsDef = false;
	previousNodeIsExternal = false;
	}

	private String extractExpression(CssIf ifOrElif) {
	String condition = ifOrElif.getExpression();

	if (condition == null) {
	return null;
	}

	if (condition.trim().startsWith("(")) {
	condition = condition.substring(1, condition.length() - 1);
	}

	// sanitize the expression. GSS doesn't accept more than one ! operator
	Matcher m = BANG_OPERATOR.matcher(condition);
	if (m.matches()) {
	String bangs = m.group(1);
	String replacement;
	if (bangs.length() % 2 == 0) {
	replacement = "";
	} else {
	replacement = "!";
	}

	condition = m.replaceFirst(replacement + "$2");
	}

	return condition;
	}

	@Override
	public boolean visit(CssFontFace x, Context ctx) {
	out.print("@font-face");

	openBrace();

	previousNodeIsDef = false;
	previousNodeIsExternal = false;

	return true;
	}

	@Override
	public boolean visit(CssMediaRule x, Context ctx) {
	maybePrintNewLine();

	insideMediaAtRule = true;

	out.print("@media");
	boolean isFirst = true;
	for (String m : x.getMedias()) {
	if (isFirst) {
	out.print(" ");
	isFirst = false;
	} else {
	comma();
	}
	out.print(m);
	}
	spaceOpt();
	out.print("{");
	out.newlineOpt();
	out.indentIn();

	needsNewLine = false;
	previousNodeIsDef = false;
	previousNodeIsExternal = false;

	return true;
	}

	@Override
	public boolean visit(CssPageRule x, Context ctx) {
	out.print("@page");
	if (x.getPseudoPage() != null) {
	out.print(" :");
	out.print(x.getPseudoPage());
	}
	spaceOpt();
	out.print("{");
	out.newlineOpt();
	out.indentIn();

	previousNodeIsDef = false;
	previousNodeIsExternal = false;

	return true;
	}

	@Override
	public boolean visit(CssSelector x, Context ctx) {
	if (needsComma) {
	comma(false);
	}

	maybePrintNewLine();

	needsComma = true;

	needsNewLine = true;

	out.print(unescape(x.getSelector()));

	return true;
	}

	private void printDef(CssDef def, String valueTemplate, String atRule, boolean insideUrlNode) {
	if (validateDefNode(def, atRule)) {
	if (!previousNodeIsDef) {
	maybePrintNewLine();
	}

	out.print(DEF);

	String name = cssToGssConstantMapping.get(def.getKey());

	if (name == null) {
	throw new Css2GssConversionException("unknown @" + atRule + " rule [" + def.getKey() + "]");
	}

	out.print(name);
	out.print(' ');

	String values = printValuesList(def.getValues(), insideUrlNode);

	if (valueTemplate != null) {
	out.print(String.format(valueTemplate, values));
	} else {
	out.print(values);
	}

	semiColon();

	previousNodeIsDef = true;
	needsNewLine = true;
	}
	}

	private boolean validateDefNode(CssDef def, String atRule) {
	if (insideMediaAtRule) {
	if (lenient) {
	treeLogger.log(Type.WARN, "A " + atRule + " is not allowed inside a @media at-rule." +
	"The following " + atRule + " [" + def + "] will be moved in the upper scope");
	wrongDefNodes.add(def);
	return false;
	} else {
	treeLogger.log(Type.ERROR, "A " + atRule + " is not allowed inside a @media at-rule. ["
	+ def + "]");
	throw new Css2GssConversionException("A " + atRule + " is not allowed inside a @media " +
	"at-rule.");
	}
	}
	return true;
	}

	private void closeBrace() {
	out.indentOut();
	out.print('}');
	out.newlineOpt();
	}

	private void comma() {
	comma(true);
	}

	private void comma(boolean addSpace) {
	out.print(',');

	if (addSpace) {
	spaceOpt();
	}
	}

	private void openBrace() {
	spaceOpt();
	out.print('{');
	out.newlineOpt();
	out.indentIn();
	}

	private void semiColon() {
	out.print(';');
	out.newlineOpt();
	}

	private void spaceOpt() {
	out.printOpt(' ');
	}

	private void maybePrintOpenBrace() {
	if (needsOpenBrace) {
	openBrace();
	needsOpenBrace = false;
	}
	}

	private void maybePrintNewLine() {
	if (needsNewLine) {
	out.newlineOpt();
	}
	}

	private String printConditionnalExpression(CssIf x) {
	if (x == null \|\| x.getExpression() != null) {
	throw new IllegalStateException();
	}

	StringBuilder builder = new StringBuilder();

	String propertyName = x.getPropertyName();

	for (String propertyValue : x.getPropertyValues()) {
	if (builder.length() != 0) {
	if (x.isNegated()) {
	builder.append(AND);
	} else {
	builder.append(OR);
	}
	}

	if (x.isNegated()) {
	builder.append(NOT);
	}

	builder.append(String.format(IS, propertyName, propertyValue));
	}

	return builder.toString();
	}

	private String printValuesList(List<Value> values, boolean insideUrlNode) {
	StringBuilder builder = new StringBuilder();

	for (Value value : values) {
	if (value.isSpaceRequired() && builder.length() != 0) {
	builder.append(' ');
	}

	String expression = value.toCss();

	if (value.isIdentValue() != null && cssToGssConstantMapping.containsKey(expression)) {
	expression = cssToGssConstantMapping.get(expression);
	} else if (value.isExpressionValue() != null) {
	expression = value.getExpression();
	} else if (value.isDotPathValue() != null) {
	DotPathValue dotPathValue = value.isDotPathValue();
	if (insideUrlNode) {
	expression = dotPathValue.getPath();
	} else {
	if (Strings.isNullOrEmpty(dotPathValue.getSuffix())) {
	expression = String.format(VALUE, dotPathValue.getPath());
	} else {
	expression =
	String.format(VALUE_WITH_SUFFIX, dotPathValue.getPath(), dotPathValue.getSuffix());
	}
	}
	} else if (value.isFunctionValue() != null) {
	FunctionValue functionValue = value.isFunctionValue();

	// process the argument list values
	String arguments = printValuesList(functionValue.getValues().getValues(), insideUrlNode);

	expression = unescape(functionValue.getName()) + "(" + arguments + ")";
	}

	// don't escape content of quoted string and don't escape isFunctionValue because the
	// arguments and the name of the functions are already unescaped if needed.
	if (value.isStringValue() != null \|\| value.isFunctionValue() != null) {
	builder.append(expression);
	} else {
	builder.append(unescape(expression));
	}
	}

	return builder.toString();
	}

	private String unescape(String toEscape) {
	return UNESCAPE.matcher(toEscape).replaceAll("");
	}

	private String unescapeExternalClass(String external) {
	return UNESCAPE_EXTERNAL.matcher(external).replaceAll("");
	}
	}