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MrbWebLibre/app/lib/utils/text_highlight.dart
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Dart

/*
* Copyright (c) 2024-2025 Fabian Freund.
*
* This file is part of WebLibre
* (see https://weblibre.eu).
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as
* published by the Free Software Foundation, either version 3 of the
* License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
import 'package:flutter/material.dart';
/// Builds a [TextSpan] with highlighted sections based on prefix/suffix markers.
///
/// This function parses text that contains highlight markers (e.g., from FTS5
/// search results) and creates a [TextSpan] with different styles for regular
/// and highlighted text.
///
/// Example:
/// ```dart
/// final span = buildHighlightedText(
/// 'Hello ***world***!',
/// baseStyle,
/// highlightStyle,
/// '***',
/// '***',
/// );
/// // Results in: "Hello " (base) + "world" (highlighted) + "!" (base)
/// ```
///
/// [text] The text to parse for highlights
/// [baseStyle] Style for non-highlighted text
/// [highlightStyle] Style for highlighted text
/// [matchPrefix] Marker that indicates the start of a highlight
/// [matchSuffix] Marker that indicates the end of a highlight
TextSpan buildHighlightedText(
String text,
TextStyle? baseStyle,
TextStyle? highlightStyle,
String matchPrefix,
String matchSuffix, {
bool normalizeWhitespaces = false,
}) {
final spans = <TextSpan>[];
var currentIndex = 0;
if (normalizeWhitespaces) {
// ignore: parameter_assignments
text = text.replaceAll(RegExp(r'\s+'), ' ');
}
while (currentIndex < text.length) {
final prefixIndex = text.indexOf(matchPrefix, currentIndex);
if (prefixIndex == -1) {
spans.add(TextSpan(text: text.substring(currentIndex), style: baseStyle));
break;
}
if (prefixIndex > currentIndex) {
spans.add(
TextSpan(
text: text.substring(currentIndex, prefixIndex),
style: baseStyle,
),
);
}
final suffixIndex = text.indexOf(
matchSuffix,
prefixIndex + matchPrefix.length,
);
if (suffixIndex == -1) {
// No closing marker - highlight everything from prefix to end
final highlightedText = text.substring(prefixIndex + matchPrefix.length);
spans.add(TextSpan(text: highlightedText, style: highlightStyle));
break;
}
final highlightedText = text.substring(
prefixIndex + matchPrefix.length,
suffixIndex,
);
spans.add(TextSpan(text: highlightedText, style: highlightStyle));
currentIndex = suffixIndex + matchSuffix.length;
}
return TextSpan(children: spans);
}