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/* * This file is part of ActivityStreams. * * Copyright © 2020 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. * * You should have received a copy of the GNU General Public License * along with ActivityStreams. If not, see <http://www.gnu.org/licenses/>. */ //! Defining extensibility in the ActivityStreams spec //! //! In ActivityStreams, there are many times you may want to use an extension. For example, to //! interact with Mastodon, you need to at least understand the `publicKey` field on their actor //! type. If not, you won't be able to use HTTP Signatures, and will have your messages rejected. //! //! But this library doesn't provide any of the security extensions to ActivityStreams. In order to //! support it, you could implment your own extensions to this library. Let's cover a basic //! example. //! //! ```rust //! // For this example, we'll use the Extensible trait, the Extension trait, the Actor trait, and //! // the Person type //! use activitystreams::{ //! actor::{Actor, Person}, //! ext::{Extensible, Extension}, //! }; //! //! /// Let's define the PublicKey type. The three fields in this PublicKey struct are how Mastodon //! /// represents Public Keys on actors. We'll need to derive Serialize and Deserialize for these //! /// in order for them to be useful. //! #[derive(Clone, Debug, Default, serde::Deserialize, serde::Serialize)] //! #[serde(rename_all = "camelCase")] //! pub struct PublicKey { //! /// The ID of the key. //! /// //! /// In mastodon, this is the same as the actor's URL with a #main-key on //! /// the end. //! pub id: String, //! //! /// The ID of the actor who owns this key. //! pub owner: String, //! //! /// This is a PEM file with PKCS#8 encoded data. //! pub public_key_pem: String, //! } //! //! /// Now, we'll need more than just a PublicKey struct to make this work. We'll need to define a //! /// second struct that declares the correct key to house this information inside of //! /// //! /// The information is represented as the following json: //! /// ```json //! /// { //! /// "publicKey": { //! /// "id": "key id", //! /// "owner": "actor id", //! /// "publicKeyPem": "pem string" //! /// } //! /// } //! /// ``` //! /// //! /// This means we'll need to define the 'publicKey' key //! #[derive(Clone, Debug, Default, serde::Deserialize, serde::Serialize)] //! #[serde(rename_all = "camelCase")] //! pub struct PublicKeyExtension { //! /// The public key's information //! pub public_key: PublicKey //! } //! //! impl PublicKey { //! /// Let's add a convenience method to turn a PublicKey into a PublicKeyExtension //! pub fn to_ext(self) -> PublicKeyExtension { //! PublicKeyExtension { public_key: self } //! } //! } //! //! // And finally, we'll implement the Extension trait for PublicKeyExtension //! // //! // We'll bound this extension by the Actor trait, since we don't care about non-actors having //! // keys. This means that you can put a key on a `Person`, but not on a `Video`. //! impl<T> Extension<T> for PublicKeyExtension where T: Actor {} //! //! // Now that these types are defined, we can put them to use! //! fn main() { //! let person = Person::new(); //! //! // let's just create a dummy key for this example //! let public_key = PublicKey { //! id: "My ID".to_owned(), //! owner: "Owner ID".to_owned(), //! public_key_pem: "My Public Key".to_owned(), //! }; //! //! // We're doing it! The person is being extended with a public key //! // //! // Note that calling `extend` on person here is possible because the Extensible trait is in //! // scope //! let person_with_key = person.extend(public_key.to_ext()); //! } //! ``` use crate::{ activity::{Activity, ActivityBox, IntransitiveActivity, IntransitiveActivityBox}, actor::{Actor, ActorBox}, collection::{Collection, CollectionBox, CollectionPage, CollectionPageBox}, link::{Link, LinkBox}, object::{Object, ObjectBox}, Base, BaseBox, }; use std::{convert::TryFrom, fmt::Debug}; /// Defines an extension to an activitystreams object or link /// /// This type provides two fields, the first field, `base`, should always the be base /// ActivityStreams type. As long as `base` implements an ActivityStreams trait, Ext will also. /// /// For example, the type `Ext<Video, HashMap<String, String>>` will implement the `Object` trait, /// because `Video` implements that trait. /// /// Additionally, AsRef and AsMut have been implemented for Ext. If type type /// `Ext<Ext<Follow, SomeTime>, AnotherType>` exists, that will implement /// `AsRef<ActivityProperties>` just like the innermost `Follow`. /// /// Usage: /// ```rust /// use activitystreams::object::Video; /// /// fn main() -> Result<(), Box<dyn std::error::Error>> { /// let mut video = Video::full(); /// /// // AsMut works even though this is an Ext<Video, ApObjectProperties> /// video /// .as_mut() /// .set_id("https://example.com")?; /// /// // set information on the extension /// video /// .extension /// .set_source_xsd_any_uri("https://example.com")?; /// /// Ok(()) /// } /// ``` #[derive(Clone, Debug, Default)] #[cfg_attr(feature = "derive", derive(serde::Deserialize, serde::Serialize))] pub struct Ext<T, U> { /// The ActivityStreams base type, or another extension containing one #[cfg_attr(feature = "derive", serde(flatten))] pub base: T, /// The extension being applied to the type #[cfg_attr(feature = "derive", serde(flatten))] pub extension: U, } /// A trait implemented by extensions to the ActivityStreams specification /// /// This is implemented for a couple types by default, such as /// ApObjectProperties, and ApActorProperties. /// /// Extensions are not intended to be used as trait objects pub trait Extension<T> where T: Base, { /// A default implementation that simply returns the Ext type with Self and the base type /// inside of it. fn extends(self, base: T) -> Ext<T, Self> where Self: Sized, { Ext { base, extension: self, } } } /// A trait implemented (automatically) by objects and links in the ActivityStreams specification /// /// This is used to easily extend objects. /// /// ```rust /// # use activitystreams::object::{Video, properties::ApObjectProperties}; /// use activitystreams::ext::Extensible; /// let vid = Video::new(); /// let ap_props = ApObjectProperties::default(); /// /// let extended_vid = vid.extend(ap_props); /// ``` pub trait Extensible<U> { fn extend(self, extension: U) -> Ext<Self, U> where Self: Sized; } impl<T, U, V> AsRef<V> for Ext<T, U> where T: Base + AsRef<V>, U: Extension<T> + Debug, { fn as_ref(&self) -> &V { self.base.as_ref() } } impl<T, U, V> AsMut<V> for Ext<T, U> where T: Base + AsMut<V>, U: Extension<T> + Debug, { fn as_mut(&mut self) -> &mut V { self.base.as_mut() } } impl<T, U> TryFrom<Ext<T, U>> for BaseBox where T: Base + serde::ser::Serialize, U: Extension<T> + serde::ser::Serialize + Debug, { type Error = std::io::Error; fn try_from(e: Ext<T, U>) -> Result<Self, Self::Error> { BaseBox::from_concrete(e) } } impl<T, U> TryFrom<Ext<T, U>> for ObjectBox where T: Object + serde::ser::Serialize, U: Extension<T> + serde::ser::Serialize + Debug, { type Error = std::io::Error; fn try_from(e: Ext<T, U>) -> Result<Self, Self::Error> { ObjectBox::from_concrete(e) } } impl<T, U> TryFrom<Ext<T, U>> for LinkBox where T: Link + serde::ser::Serialize, U: Extension<T> + serde::ser::Serialize + Debug, { type Error = std::io::Error; fn try_from(e: Ext<T, U>) -> Result<Self, Self::Error> { LinkBox::from_concrete(e) } } impl<T, U> TryFrom<Ext<T, U>> for CollectionBox where T: Collection + serde::ser::Serialize, U: Extension<T> + serde::ser::Serialize + Debug, { type Error = std::io::Error; fn try_from(e: Ext<T, U>) -> Result<Self, Self::Error> { CollectionBox::from_concrete(e) } } impl<T, U> TryFrom<Ext<T, U>> for CollectionPageBox where T: CollectionPage + serde::ser::Serialize, U: Extension<T> + serde::ser::Serialize + Debug, { type Error = std::io::Error; fn try_from(e: Ext<T, U>) -> Result<Self, Self::Error> { CollectionPageBox::from_concrete(e) } } impl<T, U> TryFrom<Ext<T, U>> for ActivityBox where T: Activity + serde::ser::Serialize, U: Extension<T> + serde::ser::Serialize + Debug, { type Error = std::io::Error; fn try_from(e: Ext<T, U>) -> Result<Self, Self::Error> { ActivityBox::from_concrete(e) } } impl<T, U> TryFrom<Ext<T, U>> for IntransitiveActivityBox where T: IntransitiveActivity + serde::ser::Serialize, U: Extension<T> + serde::ser::Serialize + Debug, { type Error = std::io::Error; fn try_from(e: Ext<T, U>) -> Result<Self, Self::Error> { IntransitiveActivityBox::from_concrete(e) } } impl<T, U> TryFrom<Ext<T, U>> for ActorBox where T: Actor + serde::ser::Serialize, U: Extension<T> + serde::ser::Serialize + Debug, { type Error = std::io::Error; fn try_from(e: Ext<T, U>) -> Result<Self, Self::Error> { ActorBox::from_concrete(e) } } impl<T, U> Extensible<U> for T where T: crate::Base, U: Extension<T>, { fn extend(self, item: U) -> Ext<Self, U> { item.extends(self) } } impl<T, U> Base for Ext<T, U> where T: Base, U: Debug, { } impl<T, U> Object for Ext<T, U> where T: Object, U: Debug, { } impl<T, U> Link for Ext<T, U> where T: Link, U: Debug, { } impl<T, U> Actor for Ext<T, U> where T: Actor, U: Debug, { } impl<T, U> Collection for Ext<T, U> where T: Collection, U: Debug, { } impl<T, U> CollectionPage for Ext<T, U> where T: CollectionPage, U: Debug, { } impl<T, U> Activity for Ext<T, U> where T: Activity, U: Debug, { } impl<T, U> IntransitiveActivity for Ext<T, U> where T: IntransitiveActivity, U: Debug, { }