fix MiniMax api error (#1567)

### What problem does this PR solve?

#1353 

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

---------

Co-authored-by: Zhedong Cen <cenzhedong2@126.com>

rag/llm/chat_model.py

@@ -24,7 +24,8 @@ from volcengine.maas.v2 import MaasService
 from rag.nlp import is_english
 from rag.utils import num_tokens_from_string
 from groq import Groq
-
+import json
+import requests
 
 class Base(ABC):
     def __init__(self, key, model_name, base_url):
@@ -475,11 +476,83 @@ class VolcEngineChat(Base):
 
 
 class MiniMaxChat(Base):
-    def __init__(self, key, model_name="abab6.5s-chat",
-                 base_url="https://api.minimax.chat/v1/text/chatcompletion_v2"):
+    def __init__(
+        self,
+        key,
+        model_name,
+        base_url="https://api.minimax.chat/v1/text/chatcompletion_v2",
+    ):
         if not base_url:
-            base_url="https://api.minimax.chat/v1/text/chatcompletion_v2"
-        super().__init__(key, model_name, base_url)
+            base_url = "https://api.minimax.chat/v1/text/chatcompletion_v2"
+        self.base_url = base_url
+        self.model_name = model_name
+        self.api_key = key
+
+    def chat(self, system, history, gen_conf):
+        if system:
+            history.insert(0, {"role": "system", "content": system})
+        for k in list(gen_conf.keys()):
+            if k not in ["temperature", "top_p", "max_tokens"]:
+                del gen_conf[k]
+        headers = {
+            "Authorization": f"Bearer {self.api_key}",
+            "Content-Type": "application/json",
+        }
+        payload = json.dumps(
+            {"model": self.model_name, "messages": history, **gen_conf}
+        )
+        try:
+            response = requests.request(
+                "POST", url=self.base_url, headers=headers, data=payload
+            )
+            print(response, flush=True)
+            response = response.json()
+            ans = response["choices"][0]["message"]["content"].strip()
+            if response["choices"][0]["finish_reason"] == "length":
+                ans += "...\nFor the content length reason, it stopped, continue?" if is_english(
+                    [ans]) else "······\n由于长度的原因，回答被截断了，要继续吗？"
+            return ans, response["usage"]["total_tokens"]
+        except Exception as e:
+            return "**ERROR**: " + str(e), 0
+
+    def chat_streamly(self, system, history, gen_conf):
+        if system:
+            history.insert(0, {"role": "system", "content": system})
+        ans = ""
+        total_tokens = 0
+        try:
+            headers = {
+                "Authorization": f"Bearer {self.api_key}",
+                "Content-Type": "application/json",
+            }
+            payload = json.dumps(
+                {
+                    "model": self.model_name,
+                    "messages": history,
+                    "stream": True,
+                    **gen_conf,
+                }
+            )
+            response = requests.request(
+                "POST",
+                url=self.base_url,
+                headers=headers,
+                data=payload,
+            )
+            for resp in response.text.split("\n\n")[:-1]:
+                resp = json.loads(resp[6:])
+                if "delta" in resp["choices"][0]:
+                    text = resp["choices"][0]["delta"]["content"]
+                else:
+                    continue
+                ans += text
+                total_tokens += num_tokens_from_string(text)
+                yield ans
+
+        except Exception as e:
+            yield ans + "\n**ERROR**: " + str(e)
+
+        yield total_tokens
 
 
 class MistralChat(Base):
@@ -748,4 +821,3 @@ class OpenRouterChat(Base):
         self.base_url = "https://openrouter.ai/api/v1"
         self.client = OpenAI(base_url=self.base_url, api_key=key)
         self.model_name = model_name
-