diff --git a/source/app.d b/source/app.d
index 7b3a7ed..30e9f34 100644
--- a/source/app.d
+++ b/source/app.d
@@ -1,322 +1,25 @@
-import std.stdio : writeln, stderr, File;
-import std.getopt;
-import std.file : read, exists;
-import std.exception : enforce, collectException;
-import core.stdc.stdlib : malloc, free, realloc;
-import core.stdc.string : memcpy;
-import core.sys.posix.unistd : posix_write = write;
+import std.stdio : writeln, stderr;
+import std.exception : collectException;
 
-import xdiff;
-
-// ------------------------------
-// RAII для mmfile_t
-// ------------------------------
-struct MmFile
-{
-	mmfile_t mf;
-
-	// фабрика вместо конструктора по умолчанию
-	static MmFile create(long bsize = 8 * 1024, ulong flags = XDL_MMF_ATOMIC)
-	{
-		MmFile m;
-		enforce(xdl_init_mmfile(&m.mf, bsize, flags) == 0, "xdl_init_mmfile failed");
-		return m;
-	}
-
-	void deinit()
-	{
-		xdl_free_mmfile(&mf);
-	}
-}
-
-// ------------------------------
-// Коллбэки вывода
-// ------------------------------
-extern (C) int mmfileOut(void* priv, mmbuffer_t* mb, int nbuf)
-{
-	auto mmfOut = cast(mmfile_t*) priv;
-	return xdl_writem_mmfile(mmfOut, mb, nbuf) < 0 ? -1 : 0;
-}
-
-extern (C) int fdOut(void* priv, mmbuffer_t* mb, int nbuf)
-{
-	const fd = cast(int) cast(size_t) priv; // 1=stdout, 2=stderr
-	foreach (i; 0 .. nbuf)
-	{
-		auto ptr = mb[i].ptr;
-		auto left = cast(size_t) mb[i].size;
-		while (left)
-		{
-			auto n = posix_write(fd, ptr, left);
-			if (n < 0)
-				return -1;
-			ptr += n;
-			left -= cast(size_t) n;
-		}
-	}
-	return 0;
-}
-
-// ------------------------------
-// Загрузка/выгрузка
-// ------------------------------
-void loadMmFile(ref MmFile m, string path)
-{
-	try
-	{
-		enforce(exists(path), "no such file: " ~ path);
-		auto data = cast(const(char)[]) read(path); // читает весь файл
-		auto dst = cast(char*) xdl_mmfile_writeallocate(&m.mf, data.length);
-		enforce(dst !is null, "xdl_mmfile_writeallocate failed (null)");
-		if (data.length)
-			memcpy(dst, data.ptr, data.length);
-	}
-	catch (Exception e)
-	{
-		// пробрасываем с контекстом пути
-		throw new Exception("loadMmFile(" ~ path ~ "): " ~ e.msg);
-	}
-}
-
-void dumpMmFile(const ref MmFile m, string path)
-{
-	File f = File(path, "wb");
-	scope (exit)
-		f.close();
-	long sz = 0;
-	auto blk = cast(char*) xdl_mmfile_first(cast(mmfile_t*)&m.mf, &sz);
-	while (blk !is null)
-	{
-		f.rawWrite(blk[0 .. cast(size_t) sz]);
-		blk = cast(char*) xdl_mmfile_next(cast(mmfile_t*)&m.mf, &sz);
-	}
-}
-
-// ------------------------------
-// Аллокатор
-// ------------------------------
-extern (C) void* wrap_malloc(void*, uint size)
-{
-	return malloc(size);
-}
-
-extern (C) void wrap_free(void*, void* ptr)
-{
-	free(ptr);
-}
-
-extern (C) void* wrap_realloc(void*, void* ptr, uint size)
-{
-	return realloc(ptr, size);
-}
-
-void installAllocator()
-{
-	memallocator_t malt;
-	malt.priv = null;
-	malt.malloc = &wrap_malloc;
-	malt.free = &wrap_free;
-	malt.realloc = &wrap_realloc;
-	enforce(xdl_set_allocator(&malt) == 0, "xdl_set_allocator failed");
-}
-
-// ------------------------------
-// Команды
-// ------------------------------
-int doDiff(ref MmFile a, ref MmFile b, long ctxlen)
-{
-	xpparam_t xpp;
-	xpp.flags = 0;
-	xdemitconf_t xecfg;
-	xecfg.ctxlen = ctxlen;
-	xdemitcb_t ecb;
-	ecb.priv = cast(void*) cast(size_t) 1;
-	ecb.outf = &fdOut;
-	return xdl_diff(&a.mf, &b.mf, &xpp, &xecfg, &ecb);
-}
-
-int doPatch(ref MmFile orig, ref MmFile patch, int mode)
-{
-	xdemitcb_t outcb;
-	outcb.priv = cast(void*) cast(size_t) 1;
-	outcb.outf = &fdOut;
-	xdemitcb_t rejcb;
-	rejcb.priv = cast(void*) cast(size_t) 2;
-	rejcb.outf = &fdOut;
-	return xdl_patch(&orig.mf, &patch.mf, mode, &outcb, &rejcb);
-}
-
-int doBDiff(ref MmFile a, ref MmFile b, long bsize)
-{
-	bdiffparam_t bdp;
-	bdp.bsize = bsize;
-	xdemitcb_t ecb;
-	ecb.priv = cast(void*) cast(size_t) 1;
-	ecb.outf = &fdOut;
-	return xdl_bdiff(&a.mf, &b.mf, &bdp, &ecb);
-}
-
-int doRaBDiff(ref MmFile a, ref MmFile b)
-{
-	xdemitcb_t ecb;
-	ecb.priv = cast(void*) cast(size_t) 1;
-	ecb.outf = &fdOut;
-	return xdl_rabdiff(&a.mf, &b.mf, &ecb);
-}
-
-int doBPatch(ref MmFile base, ref MmFile binPatch)
-{
-	xdemitcb_t ecb;
-	ecb.priv = cast(void*) cast(size_t) 1;
-	ecb.outf = &fdOut;
-	return xdl_bpatch(&base.mf, &binPatch.mf, &ecb);
-}
-
-// ------------------------------
-// CLI
-// ------------------------------
-enum Cmd
-{
-	diff,
-	patch,
-	bdiff,
-	rabdiff,
-	bpatch
-}
-
-private Cmd parseCmd(string s)
-{
-	final switch (s)
-	{
-	case "diff":
-		return Cmd.diff;
-	case "patch":
-		return Cmd.patch;
-	case "bdiff":
-		return Cmd.bdiff;
-	case "rabdiff":
-		return Cmd.rabdiff;
-	case "bpatch":
-		return Cmd.bpatch;
-	}
-}
-
-/// Короткая справка
-void printUsage(string prg)
-{
-	stderr.writefln(
-		"use: %1$s diff   [-C N]  FROM TO\n" ~
-			"     %1$s patch           ORIG PATCH\n" ~
-			"     %1$s bdiff  [-B N]   FROM TO\n" ~
-			"     %1$s rabdiff         FROM TO\n" ~
-			"     %1$s bpatch          ORIG PATCH\n",
-			prg);
-}
-
-/// Парсинг подкоманды + её опций. Возвращаем уже «очищенный» список позиционных.
-struct Parsed
-{
-	Cmd cmd;
-	long ctxlen = 3; // для diff
-	long bsize = 16; // для bdiff
-	string[] positional; // оставшиеся позиционные (пути)
-}
-
-Parsed parseArgs(string[] args)
-{
-	enforce(args.length >= 2, "no subcommand");
-	auto sub = args[1];
-	auto cmd = parseCmd(sub);
-
-	long ctxlen = 3;
-	long bsize = 16;
-	bool helpWanted = false;
-
-	// Опции и позиционные ТОЛЬКО после подкоманды
-	string[] optArgs = args.length > 2 ? args[2 .. $].dup : [];
-
-	// getopt выкинет опции из optArgs и оставит только позиционные
-	auto r = getopt(optArgs,
-		"h|help", &helpWanted,
-		"C", &ctxlen, // актуально для `diff`
-		"B", &bsize // актуально для `bdiff`
-
-		
-
-	);
-	enforce(!helpWanted, "help");
-
-	Parsed p;
-	p.cmd = cmd;
-	p.ctxlen = ctxlen;
-	p.bsize = bsize;
-	p.positional = optArgs; // здесь уже только пути
-	return p;
-}
+import diff;
 
 int main(string[] args)
 {
-	// 1) Парсим
-	Parsed p;
-	try
+	if (args.length != 3)
 	{
-		p = parseArgs(args);
-	}
-	catch (Exception)
-	{
-		printUsage(args[0]);
-		return 1;
-	}
-	if (p.positional.length != 2)
-	{
-		// каждая подкоманда требует ровно 2 пути
-		printUsage(args[0]);
-		return 1;
-	}
-	auto p1 = p.positional[0];
-	auto p2 = p.positional[1];
-
-	// 2) Аллокатор libxdiff
-	installAllocator();
-
-	// 3) Готовим входы
-	auto mf1 = MmFile.create();
-	scope (exit)
-		mf1.deinit();
-	auto mf2 = MmFile.create();
-	scope (exit)
-		mf2.deinit();
-
-	try
-	{
-		loadMmFile(mf1, p1);
-		loadMmFile(mf2, p2);
-	}
-	catch (Exception e)
-	{
-		stderr.writeln(e.msg);
+		stderr.writeln("use: ", args[0], " OLD NEW");
 		return 1;
 	}
 
-	// 4) Запускаем действие
-	int rc = 0;
-	final switch (p.cmd)
+	auto eng = new DiffEngine(3);
+
+	string result; // сюда положим результат
+	auto ex = collectException(result = eng.diffFiles(args[1], args[2]));
+	if (ex !is null)
 	{
-	case Cmd.diff:
-		rc = doDiff(mf1, mf2, p.ctxlen);
-		break;
-	case Cmd.patch:
-		rc = doPatch(mf1, mf2, XDL_PATCH_NORMAL);
-		break;
-	case Cmd.bdiff:
-		rc = doBDiff(mf1, mf2, p.bsize);
-		break;
-	case Cmd.rabdiff:
-		rc = doRaBDiff(mf1, mf2);
-		break;
-	case Cmd.bpatch:
-		rc = doBPatch(mf1, mf2);
-		break;
+		stderr.writeln(ex.msg);
+		return 2;
 	}
-	return rc < 0 ? 2 : 0;
+	writeln(result);
+	return 0;
 }
diff --git a/source/diff.d b/source/diff.d
new file mode 100644
index 0000000..d3b1310
--- /dev/null
+++ b/source/diff.d
@@ -0,0 +1,197 @@
+module diff;
+
+import std.exception : enforce;
+import std.file : read, exists; // бинарное чтение
+import std.array : Appender, appender;
+import std.string : representation, format;
+import std.datetime : Clock, UTC;
+
+import core.stdc.string : memcpy;
+import core.stdc.stdlib : malloc, free, realloc;
+
+import xdiff;
+
+//-----------------------------
+// Аллокатор для libxdiff (обязателен на ряде сборок)
+//-----------------------------
+private extern (C) void* _wrap_malloc(void*, uint size)
+{
+	return malloc(size);
+}
+
+private extern (C) void _wrap_free(void*, void* ptr)
+{
+	free(ptr);
+}
+
+private extern (C) void* _wrap_realloc(void*, void* ptr, uint size)
+{
+	return realloc(ptr, size);
+}
+
+private __gshared bool _allocatorReady = false;
+
+private void ensureAllocator()
+{
+	if (_allocatorReady)
+		return;
+	memallocator_t malt;
+	malt.priv = null;
+	malt.malloc = &_wrap_malloc;
+	malt.free = &_wrap_free;
+	malt.realloc = &_wrap_realloc;
+	enforce(xdl_set_allocator(&malt) == 0, "xdl_set_allocator failed");
+	_allocatorReady = true;
+}
+
+//-----------------------------
+// RAII для mmfile_t
+//-----------------------------
+private struct MmFile
+{
+	mmfile_t mf;
+
+	static MmFile fromBytes(const(ubyte)[] data,
+		long bsize = 8 * 1024,
+		ulong flags = XDL_MMF_ATOMIC)
+	{
+		ensureAllocator(); // критично: до init/writeallocate
+		MmFile m;
+		enforce(xdl_init_mmfile(&m.mf, bsize, flags) == 0, "xdl_init_mmfile failed");
+
+		if (data.length)
+		{
+			auto dst = cast(char*) xdl_mmfile_writeallocate(&m.mf, data.length);
+			enforce(dst !is null, "xdl_mmfile_writeallocate failed");
+			memcpy(dst, data.ptr, data.length);
+		}
+		return m;
+	}
+
+	~this()
+	{
+		xdl_free_mmfile(&mf);
+	}
+}
+
+//-----------------------------
+// Синк-коллектор вывода libxdiff
+//-----------------------------
+private class BufferSink
+{
+	Appender!(ubyte[]) outbuf;
+
+	this()
+	{
+		outbuf = appender!(ubyte[])();
+	}
+
+	extern (C) static int writeCB(void* priv, mmbuffer_t* mb, int nbuf)
+	{
+		auto self = cast(BufferSink) priv;
+		foreach (i; 0 .. nbuf)
+		{
+			size_t sz = cast(size_t) mb[i].size;
+			if (sz == 0)
+				continue;
+			self.outbuf.put((cast(ubyte*) mb[i].ptr)[0 .. sz]);
+		}
+		return 0;
+	}
+
+	string toStringOwned() @trusted
+	{
+		return cast(string) outbuf.data.idup;
+	}
+}
+
+//-----------------------------
+// Публичный движок unified-diff
+//-----------------------------
+final class DiffEngine
+{
+	private long _ctxlen;
+	private bool _stripTrailingNewline;
+
+	this(long ctxlen = 3, bool stripTrailingNewline = false)
+	{
+		_ctxlen = ctxlen;
+		_stripTrailingNewline = stripTrailingNewline;
+	}
+
+	/// Diff двух текстов (UTF-8 строки)
+	string diffText(string oldText, string newText,
+		string oldLabel = "old", string newLabel = "new")
+	{
+		const(ubyte)[] a = _prep(oldText);
+		const(ubyte)[] b = _prep(newText);
+		return diffBytes(a, b, oldLabel, newLabel);
+	}
+
+	/// Diff по путям (файлы читаются целиком, бинарно)
+	string diffFiles(string oldPath, string newPath,
+		string oldLabel = "", string newLabel = "")
+	{
+		enforce(exists(oldPath), "no such file: " ~ oldPath);
+		enforce(exists(newPath), "no such file: " ~ newPath);
+
+		auto a = cast(const(ubyte)[]) read(oldPath); // бинарное чтение
+		auto b = cast(const(ubyte)[]) read(newPath);
+
+		if (oldLabel.length == 0)
+			oldLabel = oldPath;
+		if (newLabel.length == 0)
+			newLabel = newPath;
+
+		return diffBytes(a, b, oldLabel, newLabel);
+	}
+
+	/// Базовый метод: diff двух буферов
+	string diffBytes(const(ubyte)[] oldBytes, const(ubyte)[] newBytes,
+		string oldLabel = "old", string newLabel = "new")
+	{
+		auto a = MmFile.fromBytes(oldBytes);
+		auto b = MmFile.fromBytes(newBytes);
+
+		auto sink = new BufferSink;
+		xdemitcb_t ecb;
+		ecb.priv = cast(void*) sink;
+		ecb.outf = &BufferSink.writeCB;
+
+		xpparam_t xpp;
+		xpp.flags = 0;
+
+		xdemitconf_t xecfg;
+		xecfg.ctxlen = _ctxlen;
+
+		auto pre = formatHeaders(oldLabel, newLabel);
+
+		auto rc = xdl_diff(&a.mf, &b.mf, &xpp, &xecfg, &ecb);
+		enforce(rc >= 0, format("xdl_diff failed (rc=%s)", rc));
+
+		return pre ~ sink.toStringOwned();
+	}
+
+	static string formatHeaders(string oldLabel, string newLabel)
+	{
+		auto ts = Clock.currTime(UTC()).toISOExtString(); // YYYY-MM-DDTHH:MM:SS
+		return "--- " ~ oldLabel ~ "\t" ~ ts ~ "\n"
+			~ "+++ " ~ newLabel ~ "\t" ~ ts ~ "\n";
+	}
+
+private:
+	const(ubyte)[] _prep(string s) @trusted
+	{
+		auto bytes = cast(const(ubyte)[]) s.representation;
+		if (_stripTrailingNewline && (bytes.length && bytes[$ - 1] != '\n'))
+		{
+			ubyte[] tmp;
+			tmp.length = bytes.length + 1;
+			if (bytes.length)
+				memcpy(tmp.ptr, bytes.ptr, bytes.length);
+			tmp[$ - 1] = cast(ubyte) '\n';
+			return cast(const(ubyte)[]) tmp;
+		}
+		return bytes;
+	}
+}