Move more logic into sync-client

frontend/sync-client/src/utils/line-and-column-to-position.ts

@@ -0,0 +1,34 @@
+/**
+ * Converts line and column coordinates to an absolute character position in a text string.
+ *
+ * @param line - The zero-based line number
+ * @param column - The zero-based column number
+ * @param text - The text string to calculate position in
+ * @returns The absolute character position (zero-based index) in the text string
+ * @throws Error if line number is out of range
+ * @throws Error if column number is out of range
+ */
+export function lineAndColumnToPosition(
+	text: string,
+	line: number,
+	column: number
+): number {
+	const lines = text.replace("\r", "").split("\n");
+
+	if (line >= lines.length) {
+		throw new Error(`Line number ${line} is out of range.`);
+	}
+
+	if (column > lines[line].length) {
+		throw new Error(`Column number ${column} is out of range.`);
+	}
+
+	let position = 0;
+	for (let i = 0; i < line; i++) {
+		position += lines[i].length + 1;
+	}
+
+	position += column;
+
+	return position;
+}