activitystreams/README.md

# ActivityStreams
__A set of Traits and Types that make up the ActivityStreams and ActivityPub specifications__

- [Read the documentation on docs.rs](https://docs.rs/activitystreams)
- [Find the crate on crates.io](https://crates.io/crates/activitystreams)
- [hit me up on Mastodon](https://asonix.dog/@asonix)

## Usage

First, add ActivityStreams to your dependencies
```toml
activitystreams = "0.4.0"
```

### Types

The project is laid out by Kind => vocabulary => Type

So to use an ActivityStreams Video, you'd write
```rust
use activitystreams::object::streams::Video;
```

And to use an ActivityPub profile, you'd write
```rust
use activitystreams::object::apub::Profile;
```

Link is a little different, since there's only one defined link type, called Mention.
```rust
use activitystreams::link::Mention;
```

### Properties

Each concrete type implements `AsRef<>` for each of their properties fields. A basic
ActivityStreams object will implement `AsRef<ObjectProperties>`, while an ActivityPub Actor
might implement `AsRef<ObjectProperties>`, `AsRef<ApObjectProperties>`, and
`AsRef<ApActorProperties>`.

The Properties types can be found near the kind they're associated with. `ObjectProperties` and
`ApObjectProperties` are located in `activitystreams::object::properties`.

The Properties types are generated by the `properties` macro, which attempts to create fields
that represent exactly the bounds of the ActivityStreams and ActivityPub specifications.

For example, the Object type in ActivityStreams has a `summary` field, which can either be
represented as an `xsd:string` or an `rdf:langString`. It also states that the `summary` field
is not `functional`, meaning that any number of `xsd:string` or `rdf:langString`, or a
combination thereof, can be present. To represent this, the `properties` macro generates a
couple `enum` types.

First, it generates `ObjectPropertiesSummaryTermEnum`, which is a "terminating" enum.
"terminating" in this context means it is the smallest unit of the type. This enum has two
variants, named after the types they contain, `XsdString(...)` and `RdfLangString(...)`.

Next, it generates `ObjectPropertiesSummaryEnum`, which contains two variants, `Term(...)` and
`Array(...)`. The `Term` variant contains an `ObjectPropertiesSummaryTermEnum`, and the `Array`
variant contains a `Vec<ObjectPropertiesSummaryTermEnum>`.

Finally, when declaring the field, it generates `summary: Option<ObjectPropertiesSummaryEnum>`,
since `summary` is not a required field.

This resulting type is exactly specific enough to match the following valid ActivityStreams
json, without matching any invalid json.

With no summary:
```json
{}
```

With a sring summary:
```json
{
    "summary": "A string"
}
```

With an rdf langstring
```json
{
    "summary": {
        "@value": "A string",
        "@language": "en"
    }
}
```

With multiple values
```json
{
    "summary": [
        {
            "@value": "A string",
            "@language": "en"
        },
        "An xsd:string this time"
    ]
}
```

It may seem like interacting with these types might get unweildy, so the `properties` macro
also generates methods for interacting with each field.

```ignore
fn set_summary_xsd_string<T>(&mut self, T) -> Result<...>;
fn set_summary_rdf_lang_string<T>(&mut self, T) -> Result<...>;
fn set_many_summary_xsd_strings<T>(&mut self, Vec<T>) -> Result<...>;
fn set_many_summary_rdf_lang_strings<T>(&mut self, Vec<T>) -> Result<...>;

fn delete_summary(&mut self) -> &mut Self;

fn get_summary_xsd_string(&self) -> Option<XsdString>;
fn get_summary_rdf_lang_string(&self) -> Option<RdfLangString>;
fn get_many_summary_xsd_strings(&self) -> Option<Vec<&XsdString>>;
fn get_many_summary_rdf_lang_strings(&self) -> Option<Vec<&RdfLangString>>;
```
These methods provide access to setting and fetching uniformly typed data, as well as deleting
the data. In the setter methods, the type parameter T is bound by
`TryInto<XsdString>` or `TryInto<RdfLangString>`. This allows passing values to the method that
can be converted into the types, rather than requiring the caller to perform the conversion.

Types like `XsdString` and `RdfLangString` can be found in the `primitives` module. Unless
you're building your own custom types, you shouldn't need to import them yourself. They each
implement `FromStr` for parsing and `Display` to convert back to strings, as well as `From` and
`Into` or `TryFrom` and `TryInto` for types you might expect them to (e.g.
`XsdNonNegativeInteger` implements `From<u64>` and `Into<u64>`).

For some fields, like `id`, there is only one valid type. methods generated for fields like
these will leave out the type name from the function name.

```ignore
fn set_id<T>(&mut self, T) -> Result<...>;
fn delete_id(&mut self) -> &mut Self;
fn get_id(&self) -> Option<XsdAnyUri>;
```

### Traits

This library provides a number of traits, such as `Object`, `Link`, `Actor`, `Activity`,
`Collection`, and `CollectionPage`. The majority of these traits exist solely to "mark" types,
meaning they don't provide value, at runtime, but exist to add constraints to generics at
compiletime.

If you want to make a function that manipulates an Activity, but not a normal object, you could
bound the function like so:
```ignore
fn my_manipulator<T>(some_activity: T) -> Result<&mut ObjectProperties, SomeErrorType>
where
    T: Activity + AsMut<ObjectProperties>,
{
    some_activity.as_mut().set_whatever_tbh()
}
```

### Kinds

This library has a set of unit structs that serialize and deserialize to strings. This is to
enable different ActivityPub Object types to be deserialized into different Named structs.
These can be found in `activitystreams::objects::kind`, and similar paths.

To build your own Person struct, for example, you could write
```ignore
use activitystreams::actor::kind::PersonType;

#[derive(serde::Deserialize, serde::Serialize)]
pub struct MyPerson {
    // Do a rename since `type` is not a valid rust field name
    #[serde(rename = "type")]
    kind: PersonType,
}
```
And this type would only deserialize for JSON where `"type":"Person"`

### Features
There are a number of features that can be disabled in this crate. By default, everything is
enabled.

```toml
activitystreams = { version = "0.4.0", default-features = "false", features = ["derive"] }
```

| feature    | what you get                                              |
| ---------- | --------------------------------------------------------- |
| none       | Just the Marker Traits                                    |
| derive     | Marker Traits + derive macros from activitystreams-derive |
| kinds      | Marker Traits + derive macros + Kind UnitStructs          |
| primitives | Marker Traits + Primitive values                          |
| types      | Everything, this is the default                           |

## Examples

### Basic

```rust
use activitystreams::object::{streams::Video, properties::ObjectProperties};
use anyhow::Error;

// We perform configuration in a dedicated function to specify which Properties type we want to
// perform the operations on.
fn configure_video(mut v: impl AsMut<ObjectProperties>) -> Result<(), Error> {
    v.as_mut()
        .set_context_xsd_any_uri("https://www.w3.org/ns/activitystreams")?
        .set_id("https://example.com/@example/lions")?
        .set_url_xsd_any_uri("https://example.com/@example/lions/video.webm")?
        .set_name_xsd_string("My Cool Video")?
        .set_summary_xsd_string("A video about some cool lions")?
        .set_media_type("video/webm")?
        .set_duration("PT4M20S")?;

    Ok(())
}

fn main() -> Result<(), Error> {
    let mut v = Video::default();

    configure_video(&mut v)?;

    println!("Video, {:#?}", v);

    let s = serde_json::to_string(&v)?;

    println!("json, {}", s);

    let v: Video = serde_json::from_str(&s)?;

    println!("Video again, {:#?}", v);

    Ok(())
}
```

### Intermediate

```rust
use activitystreams::{
    context,
    object::{
        properties::{
            ObjectProperties,
            ProfileProperties
        },
        apub::Profile,
    },
    primitives::XsdAnyUri,
    Actor,
    Object,
};
use serde::{Deserialize, Serialize};
use std::any::Any;

#[derive(Clone, Debug, Default, Deserialize, Serialize)]
#[serde(rename_all = "camelCase")]
pub struct Persona {
    #[serde(rename = "@context")]
    context: XsdAnyUri,

    #[serde(rename = "type")]
    kind: String,
}

#[typetag::serde]
impl Object for Persona {
    fn as_any(&self) -> &(dyn Any + 'static) {
        self
    }

    fn as_any_mut(&mut self) -> &mut (dyn Any + 'static) {
        self
    }

    fn duplicate(&self) -> Box<dyn Object + 'static> {
        Box::new(self.clone())
    }
}
impl Actor for Persona {}

fn main() -> Result<(), anyhow::Error> {
    let mut profile = Profile::default();

    let pprops: &mut ProfileProperties = profile.as_mut();

    pprops.set_describes_object_box(Persona {
        context: context(),
        kind: "Persona".to_owned(),
    })?;

    let oprops: &mut ObjectProperties = profile.as_mut();
    oprops.set_context_xsd_any_uri(context())?;

    let profile_string = serde_json::to_string(&profile)?;

    let profile: Profile = serde_json::from_str(&profile_string)?;

    Ok(())
}
```

### Advanced

```rust
use activitystreams::{
    properties,
    link::{
        properties::LinkProperties,
        Mention,
    },
    Link,
    PropRefs,
    UnitString,
};
use serde::{Deserialize, Serialize};

/// Using the UnitString derive macro
///
/// This macro implements Serialize and Deserialize for the given type, making this type
/// represent the string "MyLink" in JSON.
#[derive(Clone, Debug, Default, UnitString)]
#[activitystreams(MyLink)]
pub struct MyKind;

properties! {
    My {
        docs [ "Defining our own properties struct called MyProperties" ],

        required_key {
            docs [
                "Our own required key field",
                "",
                "'types' defines the range of values that can be stored in required_key",
                "",
                "'functional' means there is at most one value for required_key",
                "'required' means there is at least one value for required_key",
            ],
            types [ String ],
            functional,
            required,
        },
    }
}

/// Using the Properties derive macro
///
/// This macro generates getters and setters for the associated fields.
#[derive(Clone, Debug, Default, Deserialize, Serialize, PropRefs)]
#[serde(rename_all = "camelCase")]
pub struct My {
    /// Use the UnitString MyKind to enforce the type of the object by "MyLink"
    pub kind: MyKind,

    /// Derive AsRef/AsMut for My -> MyProperties
    #[activitystreams(None)]
    pub my_properties: MyProperties,

    /// Derive AsRef/AsMut/Link for My -> LinkProperties
    #[activitystreams(Link)]
    pub link_properties: LinkProperties,
}

fn main() -> Result<(), anyhow::Error> {
    let mut my_link = My::default();

    let lprops: &mut MyProperties = my_link.as_mut();
    lprops.set_required_key("Hey")?;

    let my_link_string = serde_json::to_string(&my_link)?;

    let my_link: My = serde_json::from_str(&my_link_string)?;

    Ok(())
}
```

## Contributing
Feel free to open issues for anything you find an issue with. Please note that any contributed code will be licensed under the GPLv3.

## License

Copyright © 2018 Riley Trautman

ActivityStreams is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

ActivityStreams is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. This file is part of ActivityStreams.

You should have received a copy of the GNU General Public License along with ActivityStreams. If not, see [http://www.gnu.org/licenses/](http://www.gnu.org/licenses/).