intake/README.md

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# intake
Intake is an arbitrary feed aggregator that generalizes the concept of a feed. Rather than being restricted to parsing items out of an RSS feed, Intake provides a middle layer of executing arbitrary programs that conform to a JSON-based specification. An Intake source can parse an RSS feed, but it can also scrape a website without a feed, provide additional logic to filter or annotate feed items, or integrate with an API.
A basic demonstration in a VM can be run with `nixos-shell` using the `#demo` flake attribute.
## Feed source definitions
The base Intake directory is `$XDG_DATA_HOME/intake`. Each feed source's data is contained within a subdirectory of the base directory. The name of the feed source is the name of the subdirectory.
Feed source directories have the following structure:
```
intake
|- <source name>
| |- intake.json
| |- state
| |- <item id>.item
| |- <item id>.item
| |- ...
|- <source name>
| | ...
| ...
```
`intake.json` must be present; the other files are optional. Each `.item` file contains the data for one feed item. `state` provides a file for the feed source to write arbitrary data, e.g. JSON or binary data.
`intake.json` has the following structure:
```json
{
"action": {
"fetch": {
"exe": "<absolute path to program or name on intake's PATH>",
"args": ["list", "of", "program", "arguments"]
},
"<action name>": {
"exe": "...",
"args": "..."
}
},
"env": {
"...": "..."
}
}
```
Each key under `action` defines an action that can be taken for the source. `action` must be present with a `fetch` action. `env` is optional.
## Interface for source programs
Intake interacts with sources by executing the actions defined in the source's `intake.json`. The `fetch` action is required and used to check for new feed items.
When any action is executed, intake executes the `exe` program for the action with the corresponding `args` as arguments. The process's working directory is set to the source's folder, i.e. the folder containing `intake.json`. The process's environment is as follows:
* intake's environment is inherited.
* `STATE_PATH` is set to the absolute path of `state`.
* Each key in `env` in `config.json` is passed with its value.
Anything written to `stderr` by the process will be captured and logged by Intake.
The `fetch` action is used to fetch the current state of the feed source. It receives no input and should write feed items to `stdout` as JSON objects, each on one line. All other actions are taken in the context of a single item. These actions receive the item as a JSON object on the first line of `stdin`. The process should write the item back to `stdout` with any changes as a result of the action.
An item must have a key under `action` with that action's name to support executing that action for that item. The value under that key may be any JSON structure used to manage the item-specific state.
All encoding is done with UTF-8. If an item cannot be parsed or the exit code of the process is nonzero, Intake will consider the action to be a failure. No items or other feed changes will happen as a result of a failed action, except for changes to `state` done by the action process.
## Top-level item fields
| Field name | Specification | Description |
| ---------- | ------------- | ----------- |
| `id` | **Required** | A unique identifier within the scope of the feed source. |
| `created` | **Automatic** | The Unix timestamp at which intake first processed the item. |
| `active` | **Automatic** | Whether the item is active. Inactive items are not displayed in channels. |
| `title` | Optional | The title of the item. If an item has no title, `id` is used as a fallback title.
| `author` | Optional | An author name associated with the item. Displayed in the item footer.
| `body` | Optional | Body text of the item as raw HTML. This will be displayed in the item without further processing! Consider your sources' threat models against injection attacks.
| `link` | Optional | A hyperlink associated with the item.
| `time` | Optional | A time associated with the item, not necessarily when the item was created. Feeds sort by `time` when it is defined and fall back to `created`. Displayed in the item footer.
| `tags` | Optional | A list of tags that describe the item. Tags help filter feeds that contain different kinds of content.
| `tts` | Optional | The time-to-show of the item. An item with `tts` defined is hidden from channel feeds until the current time is after `created + tts`.
| `ttl` | Optional | The time-to-live of the item. An item with `ttl` defined is not deleted by feed updates as long as `created + ttl` is in the future, even if it is inactive.
| `ttd` | Optional | The time-to-die of the item. An item with `ttd` defined is deleted by feed updates if `created + ttd` is in the past, even if it is active.
| `action` | Optional | An object with keys for all supported actions. The schema of the values depends on the source.