// Copyright 2024 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
package org.chromium.chrome.browser.readaloud;
import org.chromium.chrome.modules.readaloud.Playback;
import org.chromium.chrome.modules.readaloud.Playback.PlaybackTextPart;
import org.chromium.chrome.modules.readaloud.Playback.PlaybackTextType;
import java.util.Arrays;
import java.util.Comparator;
/**
* Handles the tap to seek feature for Read Aloud.
*
* <p>Uses the following heuristics to search for the selected page content in the playback's
* distilled text:
*
* <ul>
* <li>selected word and +-15 characters on either side, without parenthesized text
* <li>selected word and 15 characters before it, without parenthesized text
* <li>selected word and 15 characters after it, without parenthesized text
* </ul>
*
* The full text and content has had all whitespaces replaced with a single space to remove new
* lines and duplicate white spaces.
*/
public class TapToSeekHandler {
/**
* Finds the first substring match of content in the playback's full text and seeks playback to
* the selected word. If no match is found, this doesn't seek. Different substrings of content
* are used to search since there can be discrepancies between the tab's content and the
* playback's distilled text.
*
* @param content Selected word and surrounding content
* @param beginOffset index of where the selected word starts within the content
* @param endOffset index of where the selected word ends within the content
* @param playback the playback that will be seeked
* @param playing whether the playback is in the play state when the tap to seek request was
* started
*/
public static void tapToSeek(
String content, int beginOffset, int endOffset, Playback playback, boolean playing) {
if (content == null || content.isEmpty()) {
return;
}
char[] fullText = playback.getMetadata().fullText().toCharArray();
// Set the needle to the word +- 15 characters on either side.
int substringStartIndex = Math.max(0, beginOffset - 15);
int substringEndIndex = Math.min(content.length() - 1, endOffset + 15);
if (substringEndIndex <= 0) {
return;
}
String needle =
content.substring(substringStartIndex, substringEndIndex)
.replaceAll(
"[\\[\\(][\\s\\S]*?[\\]\\)]",
"") // removes any () and [] and inner content
.replaceAll("\\s+", " "); // replaces any white-spaces with a space.
int found = BoyerMoore.indexOf(fullText, needle.toCharArray());
if (found > 0) {
maybeTapToSeek(found + beginOffset - substringStartIndex, content, playback, playing);
} else {
// Last needle not matched, try with the word and -15 characters.
substringStartIndex = Math.max(0, beginOffset - 15);
substringEndIndex = endOffset;
needle =
content.substring(substringStartIndex, substringEndIndex)
.trim()
.replaceAll(
"[\\[\\(][\\s\\S]*?[\\]\\)]",
"") // removes any () and [] and inner content
.replaceAll("\\s+", " "); // replaces any white-spaces with a space.
found = BoyerMoore.indexOf(fullText, needle.toCharArray());
if (found > 0) {
maybeTapToSeek(
found + beginOffset - substringStartIndex, content, playback, playing);
} else {
// Last needle not matched, try with the word and +15 characters.
substringStartIndex = beginOffset;
substringEndIndex = Math.min(content.length() - 1, endOffset + 15);
needle =
content.substring(substringStartIndex, substringEndIndex)
.trim()
.replaceAll(
"[\\[\\(][\\s\\S]*?[\\]\\)]",
"") // removes any () and [] and inner content
.replaceAll("\\s+", " "); // replaces any white-space with a space.
found = BoyerMoore.indexOf(fullText, needle.toCharArray());
if (found > 0) {
maybeTapToSeek(found, content, playback, playing);
} else {
// TODO: b/325654229 Improve heuristics with more substrings to match with.
ReadAloudMetrics.recordHasTapToSeekFoundMatch(false);
}
}
}
}
private static Comparator<PlaybackTextPart> sComparator =
new Comparator<>() {
@Override
public int compare(PlaybackTextPart a, PlaybackTextPart b) {
return Integer.compare(a.getOffset(), b.getOffset());
}
};
/**
* If the insertion point is found in the playbacks paragraphs, seek the playback to the word
* and play.
*
* @param index index of the selected word found in the full text using Boyer moore
* @param content selected word and surrounding content
* @param playback playback that will be seeked
*/
private static void maybeTapToSeek(
int index, String content, Playback playback, boolean playing) {
int paragraphIndex = findParagraph(playback.getMetadata().paragraphs(), index);
int wordIndex = findWord(playback.getMetadata().paragraphs()[paragraphIndex], index);
if (wordIndex < 0) {
ReadAloudMetrics.recordHasTapToSeekFoundMatch(false);
} else {
playback.seekToWord(paragraphIndex, wordIndex);
if (playing) {
playback.play();
} else {
playback.pause();
}
ReadAloudMetrics.recordHasTapToSeekFoundMatch(true);
}
}
private static int findParagraph(PlaybackTextPart[] paragraphs, int offset) {
if (offset > paragraphs[paragraphs.length - 1].getOffset()) {
return paragraphs.length - 1;
}
PlaybackTextPart p =
new PlaybackTextPart() {
@Override
public int getOffset() {
return offset;
}
@Override
public int getType() {
return PlaybackTextType.TEXT_TYPE_UNSPECIFIED;
}
@Override
public int getParagraphIndex() {
return -1;
}
@Override
public int getLength() {
return -1;
}
};
int i = Arrays.binarySearch(paragraphs, p, sComparator);
if (i >= 0) {
return i;
}
int insertionPoint = -i - 1;
return insertionPoint - 1;
}
private static int findWord(PlaybackTextPart paragraph, int offset) {
if (offset < paragraph.getOffset()) {
return -1;
} else {
return offset - paragraph.getOffset();
}
}
}
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