feat: enhance Telegram adapter to support parsing legacy session_string and fetching thumbnails

domain/adapters/providers/telegram.py

@@ -1,9 +1,13 @@
 from typing import List, Dict, Tuple, AsyncIterator
+import base64
 import io
 import os
+import struct
 from models import StorageAdapter
 from telethon import TelegramClient
+from telethon.crypto import AuthKey
 from telethon.sessions import StringSession
+from telethon.tl import types
 import socks
 
 # 适配器类型标识
@@ -54,9 +58,93 @@ class TelegramAdapter:
         if not all([self.api_id, self.api_hash, self.session_string, self.chat_id]):
             raise ValueError("Telegram 适配器需要 api_id, api_hash, session_string 和 chat_id")
 
+    @staticmethod
+    def _parse_legacy_session_string(value: str) -> StringSession:
+        """
+        兼容旧版 session_string 格式:
+        - version(1B char) + base64(data)
+        - data: dc_id(1B) + ip_len(2B) + ip(ASCII, ip_len bytes) + port(2B) + auth_key(256B)
+        """
+        s = (value or "").strip()
+        if not s:
+            raise ValueError("session_string 为空")
+
+        body = s[1:] if s.startswith("1") else s
+        raw = base64.urlsafe_b64decode(body)
+        if len(raw) < 1 + 2 + 2 + 256:
+            raise ValueError("legacy session 数据长度不足")
+
+        dc_id = raw[0]
+        ip_len = struct.unpack(">H", raw[1:3])[0]
+        expected_len = 1 + 2 + ip_len + 2 + 256
+        if len(raw) != expected_len:
+            raise ValueError("legacy session 数据长度不匹配")
+
+        ip_start = 3
+        ip_end = ip_start + ip_len
+        ip = raw[ip_start:ip_end].decode("utf-8")
+        port = struct.unpack(">H", raw[ip_end : ip_end + 2])[0]
+        key = raw[ip_end + 2 : ip_end + 2 + 256]
+
+        sess = StringSession()
+        sess.set_dc(dc_id, ip, port)
+        sess.auth_key = AuthKey(key)
+        return sess
+
+    @staticmethod
+    def _pick_photo_thumb(thumbs: list | None):
+        if not thumbs:
+            return None
+
+        cached = []
+        others = []
+        for t in thumbs:
+            if isinstance(t, (types.PhotoCachedSize, types.PhotoStrippedSize)):
+                cached.append(t)
+            elif isinstance(t, (types.PhotoSize, types.PhotoSizeProgressive)):
+                if not isinstance(t, types.PhotoSizeEmpty):
+                    others.append(t)
+
+        if cached:
+            cached.sort(key=lambda x: len(getattr(x, "bytes", b"") or b""))
+            return cached[-1]
+
+        if others:
+            def _sz(x):
+                if isinstance(x, types.PhotoSizeProgressive):
+                    return max(x.sizes or [0])
+                return int(getattr(x, "size", 0) or 0)
+
+            others.sort(key=_sz)
+            return others[-1]
+
+        return None
+
+    def _build_session(self) -> StringSession:
+        s = (self.session_string or "").strip()
+        if not s:
+            raise ValueError("Telegram 适配器 session_string 为空")
+
+        try:
+            return StringSession(s)
+        except Exception:
+            pass
+
+        # 少数工具可能去掉了 version 前缀，这里做一次兼容
+        if not s.startswith("1"):
+            try:
+                return StringSession("1" + s)
+            except Exception:
+                pass
+
+        try:
+            return self._parse_legacy_session_string(s)
+        except Exception as exc:
+            raise ValueError("Telegram session_string 无效，请使用 Telethon StringSession 重新生成") from exc
+
     def _get_client(self) -> TelegramClient:
         """创建一个新的 TelegramClient 实例"""
-        return TelegramClient(StringSession(self.session_string), self.api_id, self.api_hash, proxy=self.proxy)
+        return TelegramClient(self._build_session(), self.api_id, self.api_hash, proxy=self.proxy)
 
     def get_effective_root(self, sub_path: str | None) -> str:
         return ""
@@ -198,6 +286,41 @@ class TelegramAdapter:
     async def mkdir(self, root: str, rel: str):
         raise NotImplementedError("Telegram 适配器不支持创建目录。")
 
+    async def get_thumbnail(self, root: str, rel: str, size: str = "medium"):
+        try:
+            message_id_str, _ = rel.split('_', 1)
+            message_id = int(message_id_str)
+        except (ValueError, IndexError):
+            return None
+
+        client = self._get_client()
+        try:
+            await client.connect()
+            message = await client.get_messages(self.chat_id, ids=message_id)
+            if not message:
+                return None
+
+            doc = message.document or message.video
+            thumbs = None
+            if doc and getattr(doc, "thumbs", None):
+                thumbs = list(doc.thumbs or [])
+            elif message.photo and getattr(message.photo, "sizes", None):
+                thumbs = list(message.photo.sizes or [])
+
+            thumb = self._pick_photo_thumb(thumbs)
+            if not thumb:
+                return None
+
+            result = await client.download_media(message, bytes, thumb=thumb)
+            if isinstance(result, (bytes, bytearray)):
+                return bytes(result)
+            return None
+        except Exception:
+            return None
+        finally:
+            if client.is_connected():
+                await client.disconnect()
+
     async def delete(self, root: str, rel: str):
         """删除一个文件 (即一条消息)"""
         try: