feat: add ability to override global "fetch"

src/chatgpt-api.ts

@@ -5,7 +5,7 @@ import QuickLRU from 'quick-lru'
 import { v4 as uuidv4 } from 'uuid'
 
 import * as types from './types'
-import { fetch } from './fetch'
+import { fetch as globalFetch } from './fetch'
 import { fetchSSE } from './fetch-sse'
 
 // Official model (costs money and is not fine-tuned for chat)
@@ -27,6 +27,7 @@ export class ChatGPTAPI {
   protected _assistantLabel: string
   protected _endToken: string
   protected _sepToken: string
+  protected _fetch: types.FetchFn
 
   protected _getMessageById: types.GetMessageByIdFunction
   protected _upsertMessage: types.UpsertMessageFunction
@@ -47,6 +48,7 @@ export class ChatGPTAPI {
    * @param messageStore - Optional [Keyv](https://github.com/jaredwray/keyv) store to persist chat messages to. If not provided, messages will be lost when the process exits.
    * @param getMessageById - Optional function to retrieve a message by its ID. If not provided, the default implementation will be used (using an in-memory `messageStore`).
    * @param upsertMessage - Optional function to insert or update a message. If not provided, the default implementation will be used (using an in-memory `messageStore`).
+   * @param fetch - Optional override for the `fetch` implementation to use. Defaults to the global `fetch` function.
    */
   constructor(opts: {
     apiKey: string
@@ -77,6 +79,8 @@ export class ChatGPTAPI {
     messageStore?: Keyv
     getMessageById?: types.GetMessageByIdFunction
     upsertMessage?: types.UpsertMessageFunction
+
+    fetch?: types.FetchFn
   }) {
     const {
       apiKey,
@@ -90,13 +94,15 @@ export class ChatGPTAPI {
       userLabel = USER_LABEL_DEFAULT,
       assistantLabel = ASSISTANT_LABEL_DEFAULT,
       getMessageById = this._defaultGetMessageById,
-      upsertMessage = this._defaultUpsertMessage
+      upsertMessage = this._defaultUpsertMessage,
+      fetch = globalFetch
     } = opts
 
     this._apiKey = apiKey
     this._apiBaseUrl = apiBaseUrl
     this._apiReverseProxyUrl = apiReverseProxyUrl
     this._debug = !!debug
+    this._fetch = fetch
 
     this._completionParams = {
       model: CHATGPT_MODEL,
@@ -141,6 +147,14 @@ export class ChatGPTAPI {
     if (!this._apiKey) {
       throw new Error('ChatGPT invalid apiKey')
     }
+
+    if (!this._fetch) {
+      throw new Error('Invalid environment; fetch is not defined')
+    }
+
+    if (typeof this._fetch !== 'function') {
+      throw new Error('Invalid "fetch" is not a function')
+    }
   }
 
   /**
@@ -229,7 +243,9 @@ export class ChatGPTAPI {
         }
 
         if (stream) {
-          fetchSSE(url, {
+          fetchSSE(
+            url,
+            {
               method: 'POST',
               headers,
               body: JSON.stringify(body),
@@ -259,10 +275,12 @@ export class ChatGPTAPI {
                   return reject(err)
                 }
               }
-          }).catch(reject)
+            },
+            this._fetch
+          ).catch(reject)
         } else {
           try {
-            const res = await fetch(url, {
+            const res = await this._fetch(url, {
               method: 'POST',
               headers,
               body: JSON.stringify(body),

src/fetch-sse.ts

@@ -1,12 +1,13 @@
 import { createParser } from 'eventsource-parser'
 
 import * as types from './types'
-import { fetch } from './fetch'
+import { fetch as globalFetch } from './fetch'
 import { streamAsyncIterable } from './stream-async-iterable'
 
 export async function fetchSSE(
   url: string,
-  options: Parameters<typeof fetch>[1] & { onMessage: (data: string) => void }
+  options: Parameters<typeof fetch>[1] & { onMessage: (data: string) => void },
+  fetch: types.FetchFn = globalFetch
 ) {
   const { onMessage, ...fetchOptions } = options
   const res = await fetch(url, fetchOptions)

src/fetch.ts

@@ -2,8 +2,4 @@
 
 const fetch = globalThis.fetch
 
-if (typeof fetch !== 'function') {
-  throw new Error('Invalid environment: global fetch not defined')
-}
-
 export { fetch }

src/types.ts

@@ -1,5 +1,7 @@
 export type Role = 'user' | 'assistant'
 
+export type FetchFn = typeof fetch
+
 export type SendMessageOptions = {
   conversationId?: string
   parentMessageId?: string