Add a way to configure destination directory

[froger]

I have a use case where I need to cache permanently the images.
The application we are on will be used most of the time offline, and should not ever destroy image caches.

I just added in this pull request the ability to edit the BASE_URL configuration outside the lib.

[wcandillon]

@froger Can you put these methods part of the CacheManager instead? If you think that makes sense? 🤔

[froger]

@wcandillon yes sure, when I started I though "it could have more options". But when finished writing, my thoughts were "all this code just to rewrite BASE_URL". I will find something more straight forward and write some unit-tests as well.

But I don't know if this feature is somewhat useful in the scope of the lib. The no-brainer&no-config of the lib is quiet pleasant, so at this end maybe this feature have no places in your lib.

[froger]

@wcandillon I've updated my pull request, and did some tests on a project of mine.
It hasn't any unit tests for now, but still, a review of this code would be welcome.

What I've done

setBaseDir(baseDir: string): string
Setup the cache directory used by the library. Can be outside the FileSystem.cacheDirectory .

removeCacheEntry(url: string): Promise
Remove a file from cache from it's url.

What's next

Basically, introducing a setBaseDir add various edge-cases that should be considered before merging to the lib:

• setBaseDir(baseDir: string): string Should validade that the new baseDir is an url. Currently, if the url is invalid, nothing will be cached and no warning, no error will be raised.
• If you define a baseDir which is not in the cache directory, then the files won't be garbage-collected. It's why I added a removeCacheEntry(url: string): Promise function. But this function provoques more edges-cases (File locking ? File does not exsits?). I am not that much in RN-Expo, so I hope the Filesystem API is robust.

These updates worked good for my project, but again, maybe this lib doesn't need them.

[wcandillon]

Looks good. Made two minor comments. I will integrate your branch in my own projects in order to do a bit more testing.

[wcandillon]

For simplicity, would it be possible to add this method to CacheManager for simplicity?

[wcandillon]

should return be await and Promise be Promise<void>?

[wcandillon]

@froger Could you rebase against the latest version?