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Google XML Pages (GXP) is a templating system used to generate XML/SGML markup (most often HTML).
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/*
* Copyright (C) 2008 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.gxp.compiler.collapse;
import com.google.common.base.Function;
import com.google.common.base.Preconditions;
import com.google.common.collect.Lists;
import com.google.gxp.compiler.alerts.SourcePosition;
import com.google.gxp.compiler.base.AttrBundleParam;
import com.google.gxp.compiler.base.Call;
import com.google.gxp.compiler.base.CollapseExpression;
import com.google.gxp.compiler.base.Concatenation;
import com.google.gxp.compiler.base.DefaultingExpressionVisitor;
import com.google.gxp.compiler.base.ExhaustiveExpressionVisitor;
import com.google.gxp.compiler.base.Expression;
import com.google.gxp.compiler.base.ExtractedMessage;
import com.google.gxp.compiler.base.NoMessage;
import com.google.gxp.compiler.base.OutputElement;
import com.google.gxp.compiler.base.Root;
import com.google.gxp.compiler.base.SpaceOperator;
import com.google.gxp.compiler.base.SpaceOperatorSet;
import com.google.gxp.compiler.base.StringConstant;
import com.google.gxp.compiler.base.UnexpectedNodeException;
import com.google.gxp.compiler.base.UnextractedMessage;
import com.google.gxp.compiler.base.Util;
import com.google.gxp.compiler.bind.BoundTree;
import com.google.gxp.compiler.reparent.Attribute;
import com.google.gxp.compiler.schema.ElementValidator;
import com.google.gxp.compiler.schema.Schema;
import java.util.*;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
/**
* Performs new-style
* space collapsing.
*/
public class SpaceCollapser implements Function {
public SpaceCollapsedTree apply(BoundTree tree) {
Root root = tree.getRoot().acceptVisitor(new SearchingVisitor());
return new SpaceCollapsedTree(tree.getSourcePosition(), tree.getAlerts(), root);
}
private static final Pattern LEADING_SPACES =
Pattern.compile("^(\\s+)(.*?)$", Pattern.DOTALL);
private static final Pattern TRAILING_SPACES =
Pattern.compile("^(.*?)(\\s+)$", Pattern.DOTALL);
private static final Pattern ONLY_SPACES =
Pattern.compile("^\\s*$", Pattern.DOTALL);
private static final Pattern SPACES =
Pattern.compile("\\s+", Pattern.DOTALL);
// TODO(laurence): add concept of a default SpaceOperatorSet for each
// Schema, and use that instead of these constants.
private static final SpaceOperatorSet DEFAULT_SPACE_OPERATORS =
new SpaceOperatorSet(SpaceOperator.COLLAPSE, SpaceOperator.REMOVE);
private static final SpaceOperatorSet PRESERVING_SPACE_OPERATORS =
new SpaceOperatorSet(SpaceOperator.PRESERVE, SpaceOperator.PRESERVE);
private static final SpaceOperatorSet ATTR_SPACE_OPERATORS =
new SpaceOperatorSet(SpaceOperator.NORMALIZE, SpaceOperator.REMOVE);
private static final SpaceOperatorSet MESSAGE_SPACE_OPERATORS =
new SpaceOperatorSet(SpaceOperator.NORMALIZE, SpaceOperator.REMOVE);
/**
* Visitor which does not collapse the current value, but recursively
* searches for nested values that need collapsing and collapses them.
*/
private static class SearchingVisitor extends ExhaustiveExpressionVisitor {
private final SpaceOperatorSet spaceOperators;
private boolean useSpecialAttrCollapsing = true;
SearchingVisitor() {
this(DEFAULT_SPACE_OPERATORS);
}
private SearchingVisitor(SpaceOperatorSet spaceOperators) {
this.spaceOperators = Preconditions.checkNotNull(spaceOperators);
}
public SearchingVisitor with(SpaceOperatorSet newSpaceOperators) {
return spaceOperators.equals(newSpaceOperators)
? this
: new SearchingVisitor(newSpaceOperators);
}
@Override
public Expression visitCollapseExpression(CollapseExpression value) {
SpaceOperatorSet newSpaceOperators =
value.getSpaceOperators().inheritFrom(spaceOperators);
SearchingVisitor subVisitor = this.with(newSpaceOperators);
Expression subExpression =
value.getSubexpression().acceptVisitor(subVisitor);
CollapsingVisitor collapsingVisitor =
new CollapsingVisitor(newSpaceOperators);
return subExpression.acceptVisitor(collapsingVisitor);
}
public Expression visitExtractedMessage(ExtractedMessage msg) {
throw new UnexpectedNodeException(msg);
}
public Expression visitUnextractedMessage(UnextractedMessage msg) {
SearchingVisitor contentVisitor = this.with(MESSAGE_SPACE_OPERATORS);
return msg.withContent(
msg.getContent().acceptVisitor(contentVisitor));
}
public Expression visitNoMessage(NoMessage nomsg) {
SearchingVisitor contentVisitor = this.with(MESSAGE_SPACE_OPERATORS);
return nomsg.withSubexpression(
nomsg.getSubexpression().acceptVisitor(contentVisitor));
}
@Override
public Attribute visitAttribute(Attribute attr) {
// useSpecialAttrCollapsing is used here to decide if ispace should
// (by default) be normalized. We do this for Attributes of OutputElements
// and Attribute Bundles (which are essentially for OutputElements) because
// we generally don't want \ns in these cases. We do NOT use alternate
// collapsing rules for Attributes that belong to calls.
Expression newValue = useSpecialAttrCollapsing
? this.with(ATTR_SPACE_OPERATORS).apply(attr.getValue())
: apply(attr.getValue());
Expression newCondition = attr.getCondition();
if (newCondition != null) {
newCondition = apply(newCondition);
}
return attr.withValue(newValue).withCondition(newCondition);
}
@Override
public Expression visitOutputElement(OutputElement element) {
boolean oldUseSpecialAttrCollapsing = useSpecialAttrCollapsing;
useSpecialAttrCollapsing = true;
ElementValidator validator = element.getValidator();
SearchingVisitor contentVisitor =
validator.isFlagSet(ElementValidator.Flag.PRESERVESPACES)
? this.with(PRESERVING_SPACE_OPERATORS)
: this;
Expression result = element.withAttributesAndContent(
Util.map(element.getAttributes(), getAttributeFunction()),
element.getContent().acceptVisitor(contentVisitor));
useSpecialAttrCollapsing = oldUseSpecialAttrCollapsing;
return result;
}
@Override
public Expression visitAttrBundleParam(AttrBundleParam bundle) {
boolean oldUseSpecialAttrCollapsing = useSpecialAttrCollapsing;
useSpecialAttrCollapsing = true;
Expression result = super.visitAttrBundleParam(bundle);
useSpecialAttrCollapsing = oldUseSpecialAttrCollapsing;
return result;
}
@Override
public Expression visitCall(Call call) {
boolean oldUseSpecialAttrCollapsing = useSpecialAttrCollapsing;
useSpecialAttrCollapsing = false;
Expression result = super.visitCall(call);
useSpecialAttrCollapsing = oldUseSpecialAttrCollapsing;
return result;
}
}
/**
* Visitor which space-collapses an Expression. Should only be invoked on
* the subexpression of a CollapseExpression, and only collapses the
* top-level.
*/
private static class CollapsingVisitor
extends DefaultingExpressionVisitor {
private final SpaceOperatorSet spaceOperators;
CollapsingVisitor(SpaceOperatorSet spaceOperators) {
this.spaceOperators = Preconditions.checkNotNull(spaceOperators);
}
@Override
public Expression defaultVisitExpression(Expression value) {
return value;
}
@Override
public Expression visitCollapseExpression(CollapseExpression value) {
throw new UnexpectedNodeException(value);
}
@Override
public Expression visitStringConstant(StringConstant value) {
return Concatenation.create(value.getSourcePosition(),
null,
processConcatenation(
value.getSchema(),
Collections.singletonList(value)));
}
@Override
public Expression visitConcatenation(Concatenation value) {
return value.withValues(processConcatenation(value.getSchema(),
value.getValues()));
}
private List processConcatenation(
Schema schema, List values) {
StringBuilder sb = new StringBuilder();
// Create a pair of lists that describe the alternating text and
// non-text regions. Text segments go at even-numbered positions (0, 2,
// 4, etc.) while non-text values go at odd numbered positions. There
// will always be one more text segment than non-text value.
List textSegments = Lists.newArrayList();
List textPositions = Lists.newArrayList();
List nonTextValues = Lists.newArrayList();
{
SourcePosition sbPos = null;
for (Expression value : values) {
if (value instanceof StringConstant) {
StringConstant stringConstant = (StringConstant) value;
sb.append(stringConstant.evaluate());
if (sbPos == null) {
sbPos = stringConstant.getSourcePosition();
}
} else {
textSegments.add(sb.toString());
sb.setLength(0);
textPositions.add(sbPos);
sbPos = null;
nonTextValues.add(value);
}
}
textSegments.add(sb.toString());
textPositions.add(sbPos);
}
List result = Lists.newArrayList();
SpaceOperator interiorSpaceOperator =
spaceOperators.getInteriorSpaceOperator();
SpaceOperator exteriorSpaceOperator =
spaceOperators.getExteriorSpaceOperator();
int textSegmentCount = textSegments.size();
if (textSegmentCount > 0) {
// pull off leading spaces
Matcher m = LEADING_SPACES.matcher(textSegments.get(0));
String leadingSpaces = "";
if (m.matches()) {
leadingSpaces = exteriorSpaceOperator.apply(m.group(1));
textSegments.set(0, m.group(2));
}
// pull off trailing spaces
m = TRAILING_SPACES.matcher(textSegments.get(textSegmentCount - 1));
String trailingSpaces = "";
if (m.matches()) {
trailingSpaces = exteriorSpaceOperator.apply(m.group(2));
textSegments.set(textSegmentCount - 1, m.group(1));
}
// process interior spaces
for (int i = 0; i < textSegmentCount; i++) {
String text = textSegments.get(i);
if (text.length() > 0) {
sb.setLength(0);
m = SPACES.matcher(text);
int start = 0;
while (true) {
if (m.find(start)) {
sb.append(text, start, m.start());
start = m.end();
sb.append(interiorSpaceOperator.apply(m.group()));
} else {
sb.append(text, start, text.length());
break;
}
}
textSegments.set(i, sb.toString());
}
}
// re-attach leading and trailing spaces
textSegments.set(0, leadingSpaces + textSegments.get(0));
textSegments.set(textSegmentCount - 1,
textSegments.get(textSegmentCount - 1)
+ trailingSpaces);
for (int i = 0; i < textSegmentCount; i++) {
String text = textSegments.get(i);
if (text.length() > 0) {
result.add(new StringConstant(textPositions.get(i), schema, text));
}
if (i < (textSegmentCount - 1)) {
result.add(nonTextValues.get(i));
}
}
}
return result;
}
}
}