1 files changed, 118 insertions, 0 deletions
diff --git a/ext/js/general/text-source-map.js b/ext/js/general/text-source-map.js
new file mode 100644
index 00000000..49b6d99f
--- /dev/null
+++ b/ext/js/general/text-source-map.js
@@ -0,0 +1,118 @@
+/*
+ * Copyright (C) 2020-2021  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/>.
+ */
+
+class TextSourceMap {
+    constructor(source, mapping=null) {
+        this._source = source;
+        this._mapping = (mapping !== null ? TextSourceMap.normalizeMapping(mapping) : null);
+    }
+
+    get source() {
+        return this._source;
+    }
+
+    equals(other) {
+        if (this === other) {
+            return true;
+        }
+
+        const source = this._source;
+        if (!(other instanceof TextSourceMap && source === other.source)) {
+            return false;
+        }
+
+        let mapping = this._mapping;
+        let otherMapping = other.getMappingCopy();
+        if (mapping === null) {
+            if (otherMapping === null) {
+                return true;
+            }
+            mapping = TextSourceMap.createMapping(source);
+        } else if (otherMapping === null) {
+            otherMapping = TextSourceMap.createMapping(source);
+        }
+
+        const mappingLength = mapping.length;
+        if (mappingLength !== otherMapping.length) {
+            return false;
+        }
+
+        for (let i = 0; i < mappingLength; ++i) {
+            if (mapping[i] !== otherMapping[i]) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+
+    getSourceLength(finalLength) {
+        const mapping = this._mapping;
+        if (mapping === null) {
+            return finalLength;
+        }
+
+        let sourceLength = 0;
+        for (let i = 0; i < finalLength; ++i) {
+            sourceLength += mapping[i];
+        }
+        return sourceLength;
+    }
+
+    combine(index, count) {
+        if (count <= 0) { return; }
+
+        if (this._mapping === null) {
+            this._mapping = TextSourceMap.createMapping(this._source);
+        }
+
+        let sum = this._mapping[index];
+        const parts = this._mapping.splice(index + 1, count);
+        for (const part of parts) {
+            sum += part;
+        }
+        this._mapping[index] = sum;
+    }
+
+    insert(index, ...items) {
+        if (this._mapping === null) {
+            this._mapping = TextSourceMap.createMapping(this._source);
+        }
+
+        this._mapping.splice(index, 0, ...items);
+    }
+
+    getMappingCopy() {
+        return this._mapping !== null ? [...this._mapping] : null;
+    }
+
+    static createMapping(text) {
+        return new Array(text.length).fill(1);
+    }
+
+    static normalizeMapping(mapping) {
+        const result = [];
+        for (const value of mapping) {
+            result.push(
+                (typeof value === 'number' && Number.isFinite(value)) ?
+                Math.floor(value) :
+                0
+            );
+        }
+        return result;
+    }
+}