roulette/README.md

## About

Sometimes, you just need a way to randomly display images from your filesystem.

Simply point this tool at one or more directories, and then open the specified port (default `8080`) in your browser.

A new file will be selected if you open `/` directly, or if you click on any displayed images.

Browser history is preserved, so you can always go back to any previously displayed images.

Supported file types and extensions are `bmp`, `gif`, `jp[e]g`, `png`, and `webp`.

Feature requests, code criticism, bug reports, general chit-chat, and unrelated angst accepted at `roulette@seedno.de`.

Static binary builds available [here](https://cdn.seedno.de/builds/roulette).

I only test the linux/amd64, linux/arm64, and windows/amd64 builds, the rest are all best-effort™.

x86_64 and ARM Docker images of latest version: `oci.seedno.de/seednode/roulette:latest`.

Dockerfile available [here](https://git.seedno.de/seednode/roulette/raw/branch/master/docker/Dockerfile).

## Filtering

You can provide a comma-delimited string of alphanumeric patterns to match via the `include=` query parameter, assuming the `-f|--filter` flag is enabled.

Only filenames matching one or more of the patterns will be served.

You can also provide a comma-delimited string of alphanumeric patterns to exclude, via the `exclude=` query parameter.

Filenames matching any of these patterns will not be served.

You can also combine these two parameters, with exclusions taking priority over inclusions.

Both filtering parameters ignore the file extension and full path; they only compare against the bare filename.

## Sorting

You can specify a sorting pattern via the `sort=` query parameter, assuming the `-s|--sort` flag is enabled.

A value of `sort=asc` means files will be served in ascending order (lowest-numbered to highest).

If a file exists with a numbered suffix one higher than the currently displayed file, it will be served next.

A value of `sort=desc` means files will be served in descending order (highest-numbered to lowest).

If a file exists with a numbered suffix one lower than the currently displayed file, it will be served next.

In either case, if no sequential file is found, a new random one will be chosen.

For `sort=asc`, the lowest-numbered file matching a given name will be served first.

For `sort=desc`, the highest-numbered file will be served instead.

If any other (or no) value is provided, the selected file will be random.

Note: These patterns require sequentially-numbered files matching the following pattern: `filename###.extension`.

## Refresh

If a positive-value `refresh=<integer><unit>` query parameter is provided, the page will reload after that interval.

This can be used to generate a sort of slideshow of files.

Minimum accepted value is 500ms, as anything lower seems to cause inconsistent behavior. This might be changed in a future release.

Supported units are `ns`, `us`/`µs`, `ms`, `s`, `m`, and `h`.

## Caching

If the `-c|--cache` flag is passed, the indices of all specified paths will be cached on start.

This will slightly increase the delay before the application begins responding to requests, but should significantly speed up subsequent requests.

If any `include=`/`exclude=` filters are specified in a given request, the cache will be bypassed for that specific request.

The cache can be regenerated at any time by accessing the `/clear_cache` endpoint.

If `--cache-file` is set, the cache will be loaded from the specified file on start, and written to the file whenever it is re-generated.

## Statistics

If the `--stats` flag is passed, an additional endpoint, `/stats`, is registered.

When accessed, this endpoint returns a JSON document listing every file served, along with the number of times it has been served, its filesize, and timestamps of when it was served.

## Debug
If the `-d|--debug` flag is passed, two additional endpoints—`/html` and `/json`—are registered.

When accessed, these endpoints return the contents of the index, in HTML and JSON formats respectively. This can prove useful when confirming whether the index is generated successfully, or whether a given file is in the index.

## Usage output
```
Serves random images from the specified directories.

Usage:
  roulette <path> [path]... [flags]

Flags:
  -b, --bind string               address to bind to (default "0.0.0.0")
  -c, --cache                     generate directory cache at startup
      --cache-file string         path to optional persistent cache file
  -d, --debug                     expose debug endpoint
  -f, --filter                    enable filtering
  -h, --help                      help for roulette
      --maximum-files uint32      skip directories with file counts over this value (default 4294967295)
      --minimum-files uint32      skip directories with file counts under this value
      --page-length uint16        pagination length for stats page
  -p, --port uint16               port to listen on (default 8080)
      --profile                   register net/http/pprof handlers
  -r, --recursive                 recurse into subdirectories
      --refresh-interval string   force refresh interval equal to this duration (minimum 500ms)
  -s, --sort                      enable sorting
      --stats                     expose stats endpoint
      --stats-file string         path to optional persistent stats file
  -v, --verbose                   log accessed files to stdout
  -V, --version                   display version and exit
```

## Building the Docker container
From inside the `docker/` subdirectory, build the image using the following command:

`REGISTRY=<registry url> LATEST=yes TAG=alpine ./build.sh`