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-rw-r--r--ext/js/general/regex-util.js93
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diff --git a/ext/js/general/regex-util.js b/ext/js/general/regex-util.js
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+/*
+ * Copyright (C) 2021 Yomichan Authors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <https://www.gnu.org/licenses/>.
+ */
+
+/**
+ * This class provides some general utility functions for regular expressions.
+ */
+class RegexUtil {
+ /**
+ * Applies string.replace using a regular expression and replacement string as arguments.
+ * A source map of the changes is also maintained.
+ * @param text A string of the text to replace.
+ * @param sourceMap An instance of `TextSourceMap` which corresponds to `text`.
+ * @param pattern A regular expression to use as the replacement.
+ * @param replacement A replacement string that follows the format of the standard
+ * JavaScript regular expression replacement string.
+ * @return A new string with the pattern replacements applied and the source map updated.
+ */
+ static applyTextReplacement(text, sourceMap, pattern, replacement) {
+ const isGlobal = pattern.global;
+ if (isGlobal) { pattern.lastIndex = 0; }
+ for (let loop = true; loop; loop = isGlobal) {
+ const match = pattern.exec(text);
+ if (match === null) { break; }
+
+ const matchText = match[0];
+ const index = match.index;
+ const actualReplacement = this.applyMatchReplacement(replacement, match);
+ const actualReplacementLength = actualReplacement.length;
+ const delta = actualReplacementLength - (matchText.length > 0 ? matchText.length : -1);
+
+ text = `${text.substring(0, index)}${actualReplacement}${text.substring(index + matchText.length)}`;
+ pattern.lastIndex += delta;
+
+ if (actualReplacementLength > 0) {
+ sourceMap.insert(index, ...(new Array(actualReplacementLength).fill(0)));
+ sourceMap.combine(index - 1 + actualReplacementLength, matchText.length);
+ } else {
+ sourceMap.combine(index, matchText.length);
+ }
+ }
+ return text;
+ }
+
+ /**
+ * Applies the replacement string for a given regular expression match.
+ * @param replacement The replacement string that follows the format of the standard
+ * JavaScript regular expression replacement string.
+ * @param match A match object returned from RegExp.match.
+ * @return A new string with the pattern replacement applied.
+ */
+ static applyMatchReplacement(replacement, match) {
+ const pattern = this._matchReplacementPattern;
+ pattern.lastIndex = 0;
+ return replacement.replace(pattern, (g0, g1, g2) => {
+ if (typeof g1 !== 'undefined') {
+ const matchIndex = Number.parseInt(g1, 10);
+ if (matchIndex >= 1 && matchIndex <= match.length) {
+ return match[matchIndex];
+ }
+ } else if (typeof g2 !== 'undefined') {
+ const {groups} = match;
+ if (typeof groups === 'object' && groups !== null && Object.prototype.hasOwnProperty.call(groups, g2)) {
+ return groups[g2];
+ }
+ } else {
+ switch (g0) {
+ case '$': return '$';
+ case '&': return match[0];
+ case '`': return replacement.substring(0, match.index);
+ case '\'': return replacement.substring(match.index + g0.length);
+ }
+ }
+ return g0;
+ });
+ }
+}
+
+// eslint-disable-next-line no-underscore-dangle
+RegexUtil._matchReplacementPattern = /\$(?:\$|&|`|'|(\d\d?)|<([^>]*)>)/g;