/*
* 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.gss;
import com.google.gwt.core.ext.Generator;
import com.google.gwt.resources.gss.ast.CssDotPathNode;
import com.google.gwt.resources.gss.ast.CssJavaExpressionNode;
import com.google.gwt.resources.gss.ast.CssRuntimeConditionalRuleNode;
import com.google.gwt.thirdparty.common.css.compiler.ast.CssAtRuleNode.Type;
import com.google.gwt.thirdparty.common.css.compiler.ast.CssConditionalBlockNode;
import com.google.gwt.thirdparty.common.css.compiler.ast.CssConditionalRuleNode;
import com.google.gwt.thirdparty.common.css.compiler.ast.CssNode;
import com.google.gwt.thirdparty.common.css.compiler.ast.CssRootNode;
import com.google.gwt.thirdparty.common.css.compiler.ast.CssTree;
import com.google.gwt.thirdparty.common.css.compiler.ast.CssValueNode;
import com.google.gwt.thirdparty.common.css.compiler.passes.CompactPrinter;
import java.util.Stack;
/**
* Visitor that converts the AST to a {@code String} that can be evaluated as a Java expression.
*
* <p>For example, the following GSS code
* <pre>
* @if(eval("com.foo.bar()")) {
* .foo {
* padding: 5px;
* }
* }
* {@literal @}else {
* .foo {
* padding: 15px;
* }
* }
* .bar {
* width:10px;
* }
* }
* </pre>
* will be translated to
* {@code "(com.foo.bar() ? (\".foo{padding:5px}\") : (\".foo{padding:15px}\")) + (\".bar{width:10px}\")"}
*/
public class CssPrinter extends CompactPrinter {
/**
* This value is used by {@link #concat} to help create a more balanced AST
* tree by producing parenthetical expressions.
*/
private static final int CONCAT_EXPRESSION_LIMIT = 20;
private static final String CONTATENATION = " + ";
private static final String COLON = " : ";
private static final String LEFT_PARENTHESIS = "(";
private static final String RIGHT_PARENTHESIS = ")";
private static final String DOUBLE_QUOTE = "\"";
private static final String CONTATENATION_BLOCK = ") + (";
private static final String CONDITIONAL_OPERATOR = ") ? (";
private final Stack<Boolean> elseNodeFound = new Stack<Boolean>();
private StringBuilder masterStringBuilder;
private String css;
private int concatenationNumber;
public CssPrinter(CssTree tree) {
super(tree);
}
public CssPrinter(CssNode node) {
super(node);
}
@Override
public boolean enterTree(CssRootNode root) {
masterStringBuilder.append(LEFT_PARENTHESIS);
return super.enterTree(root);
}
@Override
public String getCompactPrintedString() {
return css;
}
@Override
public void leaveTree(CssRootNode root) {
masterStringBuilder.append(flushInternalStringBuilder()).append(RIGHT_PARENTHESIS);
super.leaveTree(root);
}
@Override
public void runPass() {
masterStringBuilder = new StringBuilder();
concatenationNumber = 0;
super.runPass();
css = masterStringBuilder
.toString()
// remove empty string concatenation : '+ ("")'
.replaceAll(" \\+ \\(\"\"\\)", "")
// remove possible empty string concatenation '("") + ' at the beginning
.replaceAll("^\\(\"\"\\) \\+ ", "");
}
@Override
public boolean enterConditionalBlock(CssConditionalBlockNode node) {
masterStringBuilder.append(flushInternalStringBuilder());
masterStringBuilder.append(CONTATENATION_BLOCK);
elseNodeFound.push(false);
return true;
}
@Override
public void leaveConditionalBlock(CssConditionalBlockNode block) {
if (!elseNodeFound.pop()) {
masterStringBuilder.append(DOUBLE_QUOTE).append(DOUBLE_QUOTE);
}
masterStringBuilder.append(CONTATENATION_BLOCK);
// Reset concatenation counter
concatenationNumber = 0;
}
@Override
public boolean enterConditionalRule(CssConditionalRuleNode node) {
if (node.getType() == Type.ELSE) {
elseNodeFound.pop();
elseNodeFound.push(true);
masterStringBuilder.append(LEFT_PARENTHESIS);
} else {
CssRuntimeConditionalRuleNode conditionalRuleNode = (CssRuntimeConditionalRuleNode) node;
masterStringBuilder.append(LEFT_PARENTHESIS);
masterStringBuilder.append(conditionalRuleNode.getRuntimeCondition().getValue());
masterStringBuilder.append(CONDITIONAL_OPERATOR);
// Reset concatenation counter
concatenationNumber = 0;
}
return true;
}
@Override
public void leaveConditionalRule(CssConditionalRuleNode node) {
masterStringBuilder.append(flushInternalStringBuilder()).append(RIGHT_PARENTHESIS);
if (node.getType() != Type.ELSE) {
masterStringBuilder.append(COLON);
}
}
@Override
protected void appendValueNode(CssValueNode node) {
if (node instanceof CssJavaExpressionNode || node instanceof CssDotPathNode) {
concat(LEFT_PARENTHESIS + node.getValue() + RIGHT_PARENTHESIS);
} else {
super.appendValueNode(node);
}
}
private void concat(String stringToAppend) {
masterStringBuilder.append(flushInternalStringBuilder());
appendConcatOperation();
masterStringBuilder.append(stringToAppend);
appendConcatOperation();
}
private void appendConcatOperation() {
// Avoid long string concatenation chain
if (concatenationNumber >= CONCAT_EXPRESSION_LIMIT) {
masterStringBuilder.append(CONTATENATION_BLOCK);
concatenationNumber = 0;
} else {
masterStringBuilder.append(CONTATENATION);
concatenationNumber++;
}
}
/**
* Read what the internal StringBuilder used by the CompactPrinter has already built. Escape it.
* and reset the internal StringBuilder
*
* @return
*/
private String flushInternalStringBuilder() {
// NOTE(flan): Note that you have to be careful where you do this. Internally,
// the compact printer sometimes deletes characters from the end of the stringBuilder to save
// space. I believe that you'll be safe because, if there's nothing in the buffer, there is
// nothing to delete, but you may have some unnecessary characters in the output. you may
// want to call that out explicitly in the code.
String content = DOUBLE_QUOTE + Generator.escape(sb.toString()) + DOUBLE_QUOTE;
sb = new StringBuilder();
return content;
}
}