feat: basic auto encoding detection (Acode-Foundation#787)

Author: bajrangCoder

src/lib/openFile.js

@@ -4,7 +4,7 @@ import alert from "dialogs/alert";
 import confirm from "dialogs/confirm";
 import loader from "dialogs/loader";
 import { reopenWithNewEncoding } from "palettes/changeEncoding";
-import { decode } from "utils/encodings";
+import { decode, detectEncoding } from "utils/encodings";
 import helpers from "utils/helpers";
 import EditorFile from "./editorFile";
 import fileTypeHandler from "./fileTypeHandler";
@@ -84,7 +84,7 @@ export default async function openFile(file, options = {}) {
 		const fileInfo = await fs.stat();
 		const name = fileInfo.name || file.filename || uri;
 		const readOnly = fileInfo.canWrite ? false : true;
-		const createEditor = (isUnsaved, text) => {
+		const createEditor = (isUnsaved, text, detectedEncoding) => {
 			new EditorFile(name, {
 				uri,
 				text,
@@ -93,7 +93,7 @@ export default async function openFile(file, options = {}) {
 				render,
 				onsave,
 				readOnly,
-				encoding,
+				encoding: detectedEncoding || encoding,
 				SAFMode: mode,
 			});
 		};
@@ -385,12 +385,21 @@ export default async function openFile(file, options = {}) {
 		}
 
 		const binData = await fs.readFile();
-		const fileContent = await decode(
-			binData,
-			file.encoding || appSettings.value.defaultFileEncoding,
-		);
 
-		createEditor(false, fileContent);
+		// Detect encoding if not explicitly provided
+		let detectedEncoding = file.encoding || encoding;
+		if (!detectedEncoding) {
+			try {
+				detectedEncoding = await detectEncoding(binData);
+			} catch (error) {
+				console.warn("Encoding detection failed, using default:", error);
+				detectedEncoding = appSettings.value.defaultFileEncoding;
+			}
+		}
+
+		const fileContent = await decode(binData, detectedEncoding);
+
+		createEditor(false, fileContent, detectedEncoding);
 		if (mode !== "single") recents.addFile(uri);
 		return;
 	} catch (error) {

src/utils/encodings.js

@@ -40,6 +40,78 @@ export function getEncoding(charset) {
 	return encodings["UTF-8"];
 }
 
+function detectBOM(bytes) {
+	if (
+		bytes.length >= 3 &&
+		bytes[0] === 0xef &&
+		bytes[1] === 0xbb &&
+		bytes[2] === 0xbf
+	)
+		return "UTF-8";
+	if (bytes.length >= 2 && bytes[0] === 0xff && bytes[1] === 0xfe)
+		return "UTF-16LE";
+	if (bytes.length >= 2 && bytes[0] === 0xfe && bytes[1] === 0xff)
+		return "UTF-16BE";
+	return null;
+}
+
+export async function detectEncoding(buffer) {
+	if (!buffer || buffer.byteLength === 0) {
+		return settings.value.defaultFileEncoding || "UTF-8";
+	}
+
+	const bytes = new Uint8Array(buffer);
+
+	const bomEncoding = detectBOM(bytes);
+	if (bomEncoding) return bomEncoding;
+
+	const sample = bytes.subarray(0, Math.min(2048, bytes.length));
+	let nulls = 0,
+		ascii = 0;
+
+	for (const byte of sample) {
+		if (byte === 0) nulls++;
+		else if (byte < 0x80) ascii++;
+	}
+
+	if (ascii / sample.length > 0.95) return "UTF-8";
+	if (nulls > sample.length * 0.3) return "UTF-16LE";
+
+	const encodings = [
+		...new Set([
+			"UTF-8",
+			settings.value.defaultFileEncoding || "UTF-8",
+			"windows-1252",
+			"ISO-8859-1",
+		]),
+	];
+
+	const testSample = sample.subarray(0, 512);
+	const testBuffer = testSample.buffer.slice(
+		testSample.byteOffset,
+		testSample.byteOffset + testSample.byteLength,
+	);
+
+	for (const encoding of encodings) {
+		try {
+			const encodingObj = getEncoding(encoding);
+			if (!encodingObj) continue;
+
+			const text = await execDecode(testBuffer, encodingObj.name);
+			if (
+				!text.includes("\uFFFD") &&
+				!/[\x00-\x08\x0B\x0C\x0E-\x1F\x7F]/.test(text)
+			) {
+				return encoding;
+			}
+		} catch (error) {
+			continue;
+		}
+	}
+
+	return settings.value.defaultFileEncoding || "UTF-8";
+}
+
 /**
  * Decodes arrayBuffer to String according given encoding type
  * @param {ArrayBuffer} buffer