Support generating mtcute sessions

islands/SessionStringGenerator.tsx

@@ -1,4 +1,4 @@
-import { Client, DEVICE_MODEL, StorageMemory } from "mtkruto/mod.ts";
+import { Client, StorageMemory } from "mtkruto/mod.ts";
 import { signal } from "@preact/signals";
 import { Button } from "../components/Button.tsx";
 import { Caption } from "../components/Caption.tsx";
@@ -9,6 +9,7 @@ import { Error, error } from "./Error.tsx";
 import { getDcIps } from "mtkruto/transport/2_transport_provider.ts";
 import {
   serializeGramJS,
+  serializeMtcute,
   serializePyrogram,
   serializeTelethon,
 } from "../lib/session_string.tsx";
@@ -30,7 +31,7 @@ const library = signal<
   | "GramJS"
   | "mtcute"
   | "MTKruto"
->("Telethon");
+>("Telethon"); // TODO: url-based
 
 export function SessionStringGenerator() {
   if (loading.value) {
@@ -193,6 +194,7 @@ async function generateSessionString() {
 
   const ip = getDcIps(dc, "ipv4")[0]; // TODO
   const dcId = Number(dc.split("-")[0]);
+  const testMode = environment.value == "Test" ? true : false;
 
   switch (library.value) {
     case "Telethon":
@@ -203,7 +205,7 @@ async function generateSessionString() {
       sessionString.value = serializePyrogram(
         dcId,
         apiId_,
-        environment.value == "Test" ? true : false,
+        testMode,
         authKey,
         me.id,
         me.isBot,
@@ -213,6 +215,19 @@ async function generateSessionString() {
     case "GramJS":
       sessionString.value = serializeGramJS(dcId, ip, 80, authKey);
       break;
+    case "mtcute": {
+      const me = await client.getMe();
+      sessionString.value = serializeMtcute(
+        testMode,
+        dcId,
+        ip,
+        80,
+        me.id,
+        me.isBot,
+        authKey,
+      ); // TODO: tests
+      return;
+    }
     case "MTKruto":
       sessionString.value = await client.exportAuthString();
       break;

lib/session_string.tsx

@@ -116,3 +116,54 @@ export function serializePyrogram(
   writer.write(new Uint8Array([isBot ? 1 : 0]));
   return base64EncodeUrlSafe(writer.buffer).replace(/(=+)$/, "");
 }
+
+/**
+ * Serialize an mtcute session string.
+ *
+ * +--------+------------+------------+
+ * |  Size  |    Type    |  Content   |
+ * +--------+------------+------------+
+ * | 1      | 0x03 const | version    |
+ * | 4      | int32 LE   | flags      |
+ * | 1      | 0x01 const | dc_version |
+ * | 1      | uint8      | dc_id      |
+ * | 1      | uint8      | dc_flags   |
+ * | varies | TL string  | dc_ip      |
+ * | 4      | int32 LE   | dc_port    |
+ * | 8      | int64 LE   | user_id    |
+ * | 1      | boolean    | is_bot     |
+ * | 256    | bytes      | auth_key   |
+ * +--------+------------+------------+
+ *
+ * Encoded in URL-safe Base64, with the "=" at its end trimmed.
+ */
+export function serializeMtcute(
+  testMode: boolean,
+  dcId: number,
+  ip: string,
+  port: number,
+  userId: number,
+  isBot: boolean,
+  authKey: Uint8Array,
+) {
+  const writer = new TLRawWriter();
+  writer.write(new Uint8Array([0x03])); // version
+  writer.writeInt32(
+    MTCUTE_HAS_SELF_FLAG | (testMode ? MTCUTE_TEST_MODE_FLAG : 0),
+  ); // flags
+
+  writer.write(new Uint8Array([0x01])); // dc_version
+  writer.write(new Uint8Array([dcId])); // dc_id
+  writer.writeInt32(ip.includes(":") ? MTCUTE_IPV6_FLAG : 0); // dc_flags
+  writer.writeString(ip); // dc_ip
+  writer.writeInt32(port); // dc_port
+
+  writer.writeInt64(BigInt(userId)); // user_id
+  writer.write(new Uint8Array([isBot ? 1 : 0])); // is_bot
+  writer.write(authKey); // authKey
+
+  return base64EncodeUrlSafe(writer.buffer);
+}
+const MTCUTE_HAS_SELF_FLAG = 1;
+const MTCUTE_TEST_MODE_FLAG = 2; // TODO: flag 4?
+const MTCUTE_IPV6_FLAG = 1;