feat: allow changing the API base URL

[djmuted]

This allows you to specify a different base URL for the API. This can be helpful when using Microsoft Azure OpenAI Services for example.

[lino-levan]

Maybe I'm not understanding something, but why are we using posix.join? Is there a situation where the base URL could be a file?

[djmuted]

Maybe I'm not understanding something, but why are we using posix.join? Is there a situation where the base URL could be a file?

It's just a way to safely concatenate paths in case of unsanitized user input for the baseUrl, normalizing the path and avoiding double slashes.

[lino-levan]

That feels really icky to me. Double slashes have no effect on URL resolution (at least according to spec), so I don't really see an argument there. Does OpenAI handle double slashes incorrectly?

[djmuted]

No, but the baseUrl can also be used with other services that implement the openai API, like gpt-llama.cpp. There might be a case of a server handling double slashes incorrectly, so I thought it's best to normalize them just to be on the safe side. I think there is no downside of this approach.

[lino-levan]

I am not in favor of this change, as it makes the code much harder to parse and maintain. This

await fetch(`${baseUrl}/files/${fileId}/content`)

is a lot more clear than

await fetch(new URL(
        join(this.#baseUrl.pathname, `/files/${fileId}/content`),
        this.#baseUrl.origin,
      ).href)

If we really want to prevent the client from shooting themselves in the foot, we should normalize the URL in the constructor, and not at every individual fetch request.

[lino-levan]

Could this be split out into a separate example (I think the current one is a lot more applicable to average users)?

[lino-levan]

Could we change this to a "bag of options". I find it likely that we may want to add more options in the future and would hate to make a breaking change to the API.

Suggested change

	constructor(privateKey: string, baseUrl?: string) {
	constructor(privateKey: string, options?: { baseUrl?: string }) {

[lino-levan]

I think if you fix the normalization issue and my two small comments, this LGTM. Thanks for the PR! We love to see community improvements!

[djmuted]

Whoops, I did not mean to commit the changes in the chatCompletion.ts example. I'll fix that and include suggested changes.

[lino-levan]

LGTM