✨ feat: add DEFAULT_MODEL environment variable (#280)

* ✨ feat: add DEFAULT_MODEL environment variable

* set the model maxLength setting in the models definition

* set the model tokenLimit setting in the models definition

pages/api/chat.ts

@@ -1,5 +1,4 @@
 import { ChatBody, Message } from '@/types/chat';
-import { OpenAIModelID } from '@/types/openai';
 import { DEFAULT_SYSTEM_PROMPT } from '@/utils/app/const';
 import { OpenAIStream } from '@/utils/server';
 import tiktokenModel from '@dqbd/tiktoken/encoders/cl100k_base.json';
@@ -22,8 +21,6 @@ const handler = async (req: Request): Promise<Response> => {
       tiktokenModel.pat_str,
     );
 
-    const tokenLimit = model.id === OpenAIModelID.GPT_4 ? 6000 : 3000;
-
     let promptToSend = prompt;
     if (!promptToSend) {
       promptToSend = DEFAULT_SYSTEM_PROMPT;
@@ -38,7 +35,7 @@ const handler = async (req: Request): Promise<Response> => {
       const message = messages[i];
       const tokens = encoding.encode(message.content);
 
-      if (tokenCount + tokens.length > tokenLimit) {
+      if (tokenCount + tokens.length > model.tokenLimit) {
         break;
       }
       tokenCount += tokens.length;