Merge pull request #3639 from k9mail/html_to_text
Use Jsoup to convert HTML to plain text
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cketti
GitHub
commit
7b105d7c78
2 changed files with 128 additions and 85 deletions
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@ -1,19 +1,14 @@
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package com.fsck.k9.message.html;
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import java.util.Collections;
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import java.util.HashSet;
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import java.util.Locale;
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import java.util.Set;
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import android.text.Annotation;
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import android.text.Editable;
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import android.text.Html;
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import android.text.Html.TagHandler;
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import android.text.Spannable;
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import android.text.Spanned;
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import com.fsck.k9.K9;
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import org.jsoup.Jsoup;
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import org.jsoup.nodes.Document;
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import org.xml.sax.XMLReader;
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/**
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@ -42,88 +37,12 @@ public class HtmlConverter {
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* @return Plain text result.
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*/
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public static String htmlToText(final String html) {
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return Html.fromHtml(html, null, new HtmlToTextTagHandler()).toString()
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Document document = Jsoup.parse(html);
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return HtmlToPlainText.toPlainText(document.body())
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.replace(PREVIEW_OBJECT_CHARACTER, PREVIEW_OBJECT_REPLACEMENT)
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.replace(NBSP_CHARACTER, NBSP_REPLACEMENT);
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}
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/**
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* Custom tag handler to use when converting HTML messages to text. It currently handles text
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* representations of HTML tags that Android's built-in parser doesn't understand and hides code
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* contained in STYLE and SCRIPT blocks.
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*/
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private static class HtmlToTextTagHandler implements Html.TagHandler {
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// List of tags whose content should be ignored.
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private static final Set<String> TAGS_WITH_IGNORED_CONTENT;
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static {
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Set<String> set = new HashSet<>();
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set.add("style");
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set.add("script");
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set.add("title");
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set.add("!"); // comments
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TAGS_WITH_IGNORED_CONTENT = Collections.unmodifiableSet(set);
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}
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@Override
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public void handleTag(boolean opening, String tag, Editable output, XMLReader xmlReader) {
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tag = tag.toLowerCase(Locale.US);
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if (tag.equals("hr") && opening) {
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// In the case of an <hr>, replace it with a bunch of underscores. This is roughly
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// the behaviour of Outlook in Rich Text mode.
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output.append("_____________________________________________\r\n");
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} else if (TAGS_WITH_IGNORED_CONTENT.contains(tag)) {
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handleIgnoredTag(opening, output);
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}
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}
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private static final String IGNORED_ANNOTATION_KEY = "K9_ANNOTATION";
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private static final String IGNORED_ANNOTATION_VALUE = "hiddenSpan";
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/**
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* When we come upon an ignored tag, we mark it with an Annotation object with a specific key
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* and value as above. We don't really need to be checking these values since Html.fromHtml()
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* doesn't use Annotation spans, but we should do it now to be safe in case they do start using
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* it in the future.
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* @param opening If this is an opening tag or not.
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* @param output Spannable string that we're working with.
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*/
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private void handleIgnoredTag(boolean opening, Editable output) {
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int len = output.length();
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if (opening) {
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output.setSpan(new Annotation(IGNORED_ANNOTATION_KEY, IGNORED_ANNOTATION_VALUE), len,
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len, Spannable.SPAN_MARK_MARK);
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} else {
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Object start = getOpeningAnnotation(output);
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if (start != null) {
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int where = output.getSpanStart(start);
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// Remove the temporary Annotation span.
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output.removeSpan(start);
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// Delete everything between the start of the Annotation and the end of the string
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// (what we've generated so far).
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output.delete(where, len);
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}
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}
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}
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/**
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* Fetch the matching opening Annotation object and verify that it's the one added by K9.
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* @param output Spannable string we're working with.
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* @return Starting Annotation object.
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*/
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private Object getOpeningAnnotation(Editable output) {
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Object[] objs = output.getSpans(0, output.length(), Annotation.class);
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for (int i = objs.length - 1; i >= 0; i--) {
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Annotation span = (Annotation) objs[i];
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if (output.getSpanFlags(objs[i]) == Spannable.SPAN_MARK_MARK
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&& span.getKey().equals(IGNORED_ANNOTATION_KEY)
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&& span.getValue().equals(IGNORED_ANNOTATION_VALUE)) {
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return objs[i];
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}
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}
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return null;
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}
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}
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/**
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* Convert a text string into an HTML document.
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*
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@ -0,0 +1,124 @@
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package com.fsck.k9.message.html
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import org.jsoup.nodes.Element
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import org.jsoup.nodes.Node
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import org.jsoup.nodes.TextNode
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import org.jsoup.select.NodeTraversor
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import org.jsoup.select.NodeVisitor
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/**
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* Convert an HTML element to plain text.
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*
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* Based on Jsoup's HtmlToPlainText example.
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*/
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object HtmlToPlainText {
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@JvmStatic
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fun toPlainText(element: Element): String {
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val formatter = FormattingVisitor()
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NodeTraversor.traverse(formatter, element)
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return formatter.toString()
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}
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}
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private class FormattingVisitor : NodeVisitor {
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private var width = 0
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private val output = StringBuilder()
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override fun head(node: Node, depth: Int) {
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val name = node.nodeName()
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when {
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node is TextNode -> append(node.text())
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name == "li" -> {
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startNewLine()
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append("* ")
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}
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node is Element && node.isBlock -> startNewLine()
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}
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}
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override fun tail(node: Node, depth: Int) {
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val name = node.nodeName()
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when {
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name == "li" -> append("\n")
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node is Element && node.isBlock -> {
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if (node.hasText()) {
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addEmptyLine()
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}
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}
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name == "a" -> {
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if (node.absUrl("href").isNotEmpty()) {
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append(" <${node.attr("href")}>")
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}
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}
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}
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}
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private fun append(text: String) {
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if (text.startsWith("\n")) {
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width = 0
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}
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if (text == " " && (output.isEmpty() || output.last() in listOf(' ', '\n'))) {
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return
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}
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if (text.length + width > MAX_WIDTH) {
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val words = text.split(Regex("\\s+"))
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for (i in words.indices) {
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var word = words[i]
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val last = i == words.size - 1
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if (!last) {
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word = "$word "
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}
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if (word.length + width > MAX_WIDTH) {
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output.append("\n").append(word)
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width = word.length
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} else {
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output.append(word)
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width += word.length
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}
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}
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} else {
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output.append(text)
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width += text.length
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}
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}
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private fun startNewLine() {
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if (output.isEmpty() || output.last() == '\n') {
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return
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}
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append("\n")
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}
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private fun addEmptyLine() {
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if (output.isEmpty() || output.endsWith("\n\n")) {
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return
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}
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startNewLine()
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append("\n")
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}
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override fun toString(): String {
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if (output.isEmpty()) {
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return ""
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}
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var lastIndex = output.lastIndex
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while (lastIndex >= 0 && output[lastIndex] == '\n') {
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lastIndex--
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}
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return output.substring(0, lastIndex + 1)
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}
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companion object {
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private const val MAX_WIDTH = 76
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}
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}
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