I work on exactly this kind of app, and it’s open source: https://github.com/mickael-kerjean/filestash.

It’s a Dropbox-like file manager that instead of owning your data integrates with your existing storage, authentication, and authorization systems. Under the hood, there’s a lot going on, very recently I added plugins to handle various kind of file types that are not typically handled by browser, we're talking > 100 kind of file types handled entirely in the browser for niches like astronomy, data engineering, GIS, 3D models, dev and even embroidery patterns

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skydhash 4 days ago | parent [-]

Where do these files come from? And the viewer?

	▲	mickael-kerjean 4 days ago \| parent [-]
		The file comes from wherever you have it stored in the first place (FTP, S3, SFTP, virtually anything) and viewer are plugins implementing various interfaces which are packaged up onto a zip file. With this approach, to add support for psd, I just implemented the image viewer interface (https://github.com/mickael-kerjean/filestash/blob/a605988d5c...), to add support for parquet files I implemented the table viewer interface (https://github.com/mickael-kerjean/filestash/blob/a605988d5c...) and still have the freedom for custom stuff like this docx editor based of libre office wasm: https://github.com/mickael-kerjean/filestash/tree/master/ser... Most of the actual implementations of the base interfaces are done in C, compiled to wasm and running via a web worker