RetroArch asset server

This is an implementation of the Online Updater Content Downloader that is built into RetroArch.
You can use it to serve up your ROMs, and their required BIOS files, from a full rom set to your devices running RetroArch.
My use case is I have a PC with the MAME 0.78 ROM set that I want to be able to easily get select games onto my switchrooted Nintendo Switch without faffing around with memory cards.

Features

• Browse ROMs by Description, Manufacturer, ROM Name and Year
• Download your ROM plus any required BIOS to your device

Start your server where your ROMs are

Download your ROMs to your device

First Run the server

Download the server executable for your platform from https://github.com/NickHeap2/retroarch-asset-server/releases

Usage: retroarch-asset-server [options]

Options:
  -V, --version                 output the version number
  -d, --dat-file <datfile>      MAME dat file to serve
  -r, --rom-folder <romfolder>  ROM folder for roms defined in dat file
  -p, --port <port>             Port for server to listen on (default: 5050)
  -v, --verbose                 Verbose logging (default: false)
  -h, --help                    display help for command

Run server on default port 5050 with required options

retroarch-asset-server --dat-file "./MAME 078.dat" --rom-folder ./roms

Run server on port 6000 with verbose request logging

retroarch-asset-server --dat-file "./MAME 078.dat" --rom-folder ./roms --port 6000 --verbose

Then Configure your RetroArch install

In your retroarch.cfg change the line below:

core_updater_buildbot_assets_url = "http://buildbot.libretro.com/assets/"

to

core_updater_buildbot_assets_url = "http://localhost:5050/assets/"

You can also use ngrok to allow the content downloader to work over the internet.

The pattern that the Online Updater Content Downloader uses

The calls below are what we implement in our content downloader.

GET /assets/cores/.index-dirs

This should return a \n delimited list of directories.
For my case atm I just return Arcade.

GET /assets/cores/Arcade

This has to return a 301 permanent redirect to the location /assets/cores/Arcade/.

GET /assets/cores/Arcade/.index

This should return a \n delimited list of zip files.
In our case though we return a file name with the ROM description, manufacturer and year included.
e.g. 1943 - The Battle of Midway (US) [Capcom 1987]--1943.zip
Luckily the selected file name in RetroArch has a scrolling preview if it doesn't fit on screen.

GET /assets/cores/Arcade/.index-dirs

This should return a list of sub-directories. As there currently aren't any sub-directories this returns a 404.

GET /assets/cores/Arcade/1943%20-%20The%20Battle%20of%20Midway%20%28US%29%20%20%20%20%20%20%20%20%5BCapcom%201987%5D--1943.zip

This should return the zip file that is selected.
In our case we create an in memory zip file with that name, add a directory of Arcade and add the actual 1943.zip into that directory.
This then gets extracted into the downloads directory in RetroArch as Arcade/1943.zip.
We also now attach any needed bios file that the rom needs.