# [WIP] minna-pima

> Picture manager intended for usage with Minna.

**`minna-pima`** integrates with [`minna-caos`](https://git.moritzruth.de/minna/minna-caos) to provide picture management features.

Similarly to the latter, it is intended as a companion to a single application (“the app”) that has full authority.


## Features

- automatic conversion of unwanted file formats

- [ThumbHash](https://evanw.github.io/thumbhash/) generation

- on-demand resizing and format conversion (without caching, see below)

- similarity search for finding duplicates

- CLI for administrative tasks


## Notes

### Pictures are not cached

`minna-pima` does not cache the pictures it generates on-demand.
This is by design: Caching is hard and better left to tools designated for this purpose.
It is therefore recommended to use a caching reverse-proxy in front of **minna-pima**.

<!-- TODO: example configuration for Caddy with https://github.com/darkweak/souin#caddy-module -->


### Example picture upload flow

1. The _client_ uploads a PNG file to _`minna-caos`_ in cooperation with the _app_.
2. Because _`minna-caos`_ detected that the file is a PNG image, the _app_ decides to use `minna-pima`.
3. The _app_ sends a `GET /objects/ORIGINAL_UPLOAD_HASH/similar` request to _`minna-pima`_:
    1. _`minna-pima`_ fetches the object’s content and media type from _`minna-caos`_.
    2. _`minna-pima`_ computes a perceptual hash of the picture and uses it to search its database for similar pictures.
    3. It finds two matching pictures and returns the following result:
    ```json
    {
      "similar_picture_ids": ["abc123", "def456"]
    }
    ```

4. The _app_ notifies the _client_ that there are similar pictures.
5. The _user_ decides that…
   1. the first picture is unrelated, and
   2. the second picture is a lower-quality version of the uploaded picture and should be replaced by the higher-quality version.
6. The _client_ notifies the _app_ of the user’s decision.
7. The _app_ creates a new upload through _`minna-caos`_. It’s ID is `CONVERTED_UPLOAD_ID`.
8. The _app_ sends a `POST /pictures/` request to _`minna_pima`_ with the following payload:
   ```json
   {
     "hash": "ORIGINAL_UPLOAD_HASH",
     "upload_id": "CONVERTED_UPLOAD_ID",
     "replaces": ["def456"]
   }
   ```
   1. _`minna-pima`_ fetches the content and the media type of the object from _`minna-caos`_.
   2. _`minna-pima`_ generates a ThumbHash and converts the picture to AVIF because PNG is not in the list of allowed source formats.
   3. _`minna-pima`_ uploads the picture to _`minna-caos`_ using `PATCH /uploads/CONVERTED_UPLOAD_ID`.

9. The _app_ waits for the `CONVERTED_UPLOAD_ID` upload to finish. The new picture’s ID is also `CONVERTED_UPLOAD_ID`.
   
   A 100×100 WebP version can be fetched from `/pictures/CONVERTED_UPLOAD_ID/100x100.webp`.