/*
* 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.io;
import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableList;
import java.io.IOException;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
/**
* Utility class for generating nicely indented code in C-like languages. It's
* almost an Appendable "decorator" in that it wraps around an existing
* Appendable. It has a different interface from Appendable though, so it
* doesn't implement Appendable.
*
* <p>It performs the following transformations on the input before passing it
* through to the underlying Appendable:
* <ul>
* <li>adds newlines. CIndenter is line based.
* <li>adds indentation. The indentation level is automatically adjusted based
* on the presence of curly braces.
* <li>(optionally) adds trailing comments.
* </ul>
*/
public final class CIndenter {
private static final String INDENT = " ";
private static final String HALF_INDENT = " ";
private static final Pattern NEWLINE_PATTERN = Pattern.compile("\n");
private final Appendable out;
private final List<String> halfIndentMarkers;
private int indentationLevel = 0;
public CIndenter(Appendable out, String... halfIndentMarkers) {
this.out = Preconditions.checkNotNull(out);
this.halfIndentMarkers = ImmutableList.copyOf(halfIndentMarkers);
}
private void appendIndent(boolean oneLessSpace) throws IOException {
for (int i = 0; i < indentationLevel; i++) {
out.append((oneLessSpace && (i == indentationLevel - 1)) ? HALF_INDENT : INDENT);
}
}
/**
* Appends the tail comment to the line (if there is one). Inserts an
* appropriate amount of spaces so that the tail comment will begin at
* column 80, unless the line is already too long in which case 3 spaces
* are inserted.
*/
private void appendTailComment(int lineLength, String tailComment)
throws IOException {
if (tailComment.length() > 0) {
int indentLength = indentationLevel * INDENT.length();
int spacerLength = Math.max(80 - (lineLength + indentLength), 3);
for (int i = 0; i < spacerLength; i++) {
out.append(" ");
}
out.append(tailComment);
}
}
public void addIndent() {
indentationLevel++;
}
/**
* Appends the specified line with indentation and a trailing newline.
* The presence of leading or trailing curly braces will adjust the
* indentation. A leading "}" will cause this line and subsequent lines to be
* outdented, while a trailing "{" will cause subsequent lines to be
* indented.
* @param line the line to be appended
* @throws RuntimeIOException if underlying Appendable throws IOException.
*/
public void appendLine(CharSequence line) {
appendLine(line, "");
}
/**
* Like {@link #appendLine(CharSequence)}, but also accepts a trailing
* comment.
* @param line the line to be appended
* @param tailComment a "line comment" to add to the end of the line. This is
* appended after the braces are inspected, making it possible to have a
* "trailing" open brace which causes an indent which is actually followed by
* this comment. Note that the caller is responsible for ensuring that this
* is actually a comment by using a "//" prefix, or whatever else is
* necessary for the language being generated.
* @throws RuntimeIOException if underlying Appendable throws IOException.
*/
public void appendLine(CharSequence line, String tailComment) {
try {
if (line.length() == 0) {
if (tailComment.length() > 0) {
appendIndent(false);
appendTailComment(0, tailComment);
}
out.append("\n");
} else {
if (line.charAt(0) == '}') {
indentationLevel--;
}
appendIndent(halfIndentMarkers.contains(line));
Matcher m = NEWLINE_PATTERN.matcher(line);
int sliceStart = 0;
while (m.find()) {
CharSequence cs = line.subSequence(sliceStart, m.start());
out.append(cs);
appendTailComment(cs.length(), tailComment);
out.append("\n");
appendIndent(halfIndentMarkers.contains(line));
sliceStart = m.end();
}
CharSequence cs = line.subSequence(sliceStart, line.length());
out.append(cs);
appendTailComment(cs.length(), tailComment);
out.append("\n");
if (line.charAt(line.length() - 1) == '{') {
indentationLevel++;
}
}
} catch (IOException iox) {
throw new RuntimeIOException(iox);
}
}
}