# imm

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*imm* is a program that executes arbitrary callbacks (e.g. sending a mail, or writing a file) for each element of RSS/Atom feeds.

*imm* is written in [Haskell][2], configured in [Dhall][3]. The project includes:

- a main executable `imm` that users run directly
- secondary executables (`imm-writefile`, `imm-sendmail`, `imm-monolith`) meant to be used as callbacks triggered by `imm`
- a [Haskell][2] library, that exports functions useful to both the main executable and callbacks; the API is documented [in Hackage][1].

## Installation

[![Packaging status](https://repology.org/badge/vertical-allrepos/haskell:imm.svg)](https://repology.org/project/haskell:imm/versions)

### Using nix

This repository is notably a [Nix flake][flakes] that can be installed by running the following command at the root folder:
```bash
nix develop --command cabal build
```

### Without nix

*imm*'s executables can be installed using *cabal-install* tool:
```bash
cabal install imm
```

Then, the following runtime dependencies must be installed separately and provided in `PATH`:
- [monolith](https://github.com/Y2Z/monolith) (if using `imm-monolith`)
- [pup](https://github.com/ericchiang/pup)

## Configuration

### Callbacks

Callbacks are configured through the `$XDG_CONFIG_HOME/imm/callbacks.dhall` file. A commented template file is bundled with the project.

*imm* will call each callback once per feed item, and will fill its standard input (`stdin`) with a JSON structure, which schema is described in file [`schema/imm.json`](schema/imm.json).

Callback process is expected to return `0` in case of success, or any other exit code in case of failure, in which case the standard error output (`stderr`) will be displayed.


## Example use cases

### Online feed reader

For the sake of *I-want-the-mutt-of-feed-readers* zealots, it is possible to turn any mail reader into a feed reader, by having *imm* send an e-mail with unread elements to an arbitrary address.
You can then browse your feeds through your favourite mail reader, and leverage any mail-related tool on your feeds.
Bonus points if your mail reader is online as you can now access your feeds from any computer connected to the Internet.

Here is an example configuration:
```dhall
let Callback : Type =
  { _executable : Text
  , _arguments : List Text
  }

let sendMail =
  { _executable = "imm-sendmail"
  , _arguments = []
  }

let config : List Callback = [ sendMail ]
in config
```

`imm-sendmail` does not have a built-in SMTP client, instead it must rely on an external SMTP client program, which is configured in `$XDG_CONFIG_HOME/imm/sendmail.dhall` (cf example bundled with the project.) `imm-sendmail` writes the mail bytestring to the standard input of the configured external program.

### Offline read-it-later

*imm* is able to store a local copy of unread elements, to read them later while offline for example. There are 3 alternate ways of achieving this.

#### `imm-writefile`
`imm-writefile` will produce a light HTML file with no stylesheets, no scripts and with links to online resources (images, fonts, ...) that won't be available offline:
  ```dhall
  let Callback : Type =
    { _executable : Text
    , _arguments : List Text
    }

  let writeFile =
    { _executable = "imm-writefile"
    , _arguments = [ "-d", "/path/to/folder" ]
    }

  let config : List Callback = [ writeFile ]
  in config
  ```

#### `imm-monolith`
`imm-monolith` will produce a heavy, self-contained HTML file, with embedded stylesheets, scripts, images and fonts; links to external web pages will still require an internet connection:
  ```dhall
  let Callback : Type =
    { _executable : Text
    , _arguments : List Text
    }

  let downloadPage =
    { _executable = "imm-monolith"
    , _arguments = [ "-d", "/path/to/folder" ]
    }

  let config : List Callback = [ downloadPage ]
  in config
  ```
#### `imm-wallabag`
`imm-wallabag` will save webpages into a [Wallabag][wallabag] server through its REST API:
  ```dhall
  let Callback : Type =
    { _executable : Text
    , _arguments : List Text
    }

  let wallabag =
    { _executable = "imm-wallabag"
    , _arguments =
        [ "--host"
        , "INSERT_HOST"
        , "--port"
        , "INSERT_PORT"
        , "--client-id"
        , "INSERT_CLIENT_ID"
        , "--client-secret"
        , "INSERT_CLIENT_SECRET"
        , "--username"
        , "INSERT_WALLABAG_USERNAME"
        , "--password"
        , "INSERT_WALLABAG_PASSWORD"
        ]
    }

  let config : List Callback = [ wallabag ]
  in config
  ```

## Example usage

- Subscribe to a feed through direct URL:
  ```bash
  imm subscribe http://your.feed.org
  ```

- Subscribe to a feed through an alternate link:
  ```bash
  imm subscribe http://your.website.org
  ```

- List subscribed feeds:
  ```bash
  imm list
  ```

- Show details about a feed:
  ```bash
  imm show 10  # 10 is the index of a subscribed feed, as shown with `imm list`
  ```

- Unsubscribe from a feed:
  ```bash
  imm unsubscribe 10  # 10 is the index of a subscribed feed, as shown with `imm list`
  ```

- Check for new elements without executing any action:
  ```bash
  imm --read-only run --no-callbacks
  ```

- Execute configured callbacks for each new element from all subscribed feeds:
  ```bash
  imm run --all
  ```

[1]: http://hackage.haskell.org/package/imm
[2]: https://www.haskell.org
[3]: https://dhall-lang.org/
[flakes]: https://nixos.wiki/wiki/Flakes
[wallabag]: https://www.wallabag.it/