From 70053021a5c4c9d258817aa70aa257dc7432efa5 Mon Sep 17 00:00:00 2001
From: Stefano Pigozzi <me@steffo.eu>
Date: Mon, 30 Dec 2024 02:50:04 +0100
Subject: [PATCH] `astreams`: Implement entity processing and Entity.preview

---
 acrate_astreams/src/activitystreams/jsonld.rs | 31 ++++++++++++++++---
 acrate_astreams/src/activitystreams/mod.rs    | 14 +++++++--
 acrate_astreams/tests/test_activitystreams.rs | 25 ++++++++++++++-
 3 files changed, 63 insertions(+), 7 deletions(-)

diff --git a/acrate_astreams/src/activitystreams/jsonld.rs b/acrate_astreams/src/activitystreams/jsonld.rs
index a930496..39b0a45 100644
--- a/acrate_astreams/src/activitystreams/jsonld.rs
+++ b/acrate_astreams/src/activitystreams/jsonld.rs
@@ -6,11 +6,11 @@ use json_ld::Direction;
 use json_ld::object::Any;
 use json_ld::syntax::LangTagBuf;
 use mediatype::MediaType;
-use crate::activitystreams::StreamsLink;
+use crate::activitystreams::{StreamsEntity, StreamsLink};
 
 pub type LangTriple = (String, Option<LangTagBuf>, Option<Direction>);
 
-pub trait StreamsJsonLD {
+pub trait StreamsJsonLD<Entity> {
 	fn jsonld_any_value_string(&self, id: &Iri) -> Option<AResult<String>>;
 	fn jsonld_iter_value_string(&self, id: &Iri) -> impl Iterator<Item = AResult<String>>;
 	fn jsonld_iter_value_langstring(&self, id: &Iri) -> impl Iterator<Item = AResult<LangTriple>>;
@@ -19,9 +19,10 @@ pub trait StreamsJsonLD {
 	fn jsonld_any_value_langtag(&self, id: &Iri) -> Option<AResult<LangTagBuf>>;
 	fn jsonld_any_value_u32(&self, id: &Iri) -> Option<AResult<u32>>;
 	fn jsonld_any_value_u64(&self, id: &Iri) -> Option<AResult<u64>>;
+	fn jsonld_iter_node_entity(&self, id: &Iri) -> impl Iterator<Item = AResult<Entity>>;
 }
 
-impl StreamsJsonLD for &json_ld::Node {
+impl StreamsJsonLD<json_ld::Node> for json_ld::Node {
 	fn jsonld_any_value_string(&self, id: &Iri) -> Option<AResult<String>> {
 		let property = match self.properties.get_any(&id) {
 			None => return None,
@@ -222,9 +223,31 @@ impl StreamsJsonLD for &json_ld::Node {
 		
 		Some(Ok(r#u64))
 	}
+	
+	fn jsonld_iter_node_entity(&self, id: &Iri) -> impl Iterator<Item = AResult<json_ld::Node>> {
+		let properties = self.properties.get(&id);
+		
+		let nodes = properties.map(|v| v
+			.as_node()
+			.ok_or(anyhow!("Couldn't process property as JSON-LD node"))
+			.map(|v| v
+				.clone()
+			)
+		);
+		
+		nodes
+	}
 }
 
-impl StreamsLink for &json_ld::Node {
+impl StreamsEntity<json_ld::Node> for json_ld::Node {
+	fn activitystreams_previews(&self) -> impl Iterator<Item = AResult<json_ld::Node>> {
+		self.jsonld_iter_node_entity(
+			iri!("https://www.w3.org/ns/activitystreams#preview")
+		)
+	}
+}
+
+impl StreamsLink<json_ld::Node> for json_ld::Node {
 	fn activitystreams_href(&self) -> Option<AResult<String>> {
 		self.jsonld_any_node_string(
 			iri!("https://www.w3.org/ns/activitystreams#href")
diff --git a/acrate_astreams/src/activitystreams/mod.rs b/acrate_astreams/src/activitystreams/mod.rs
index dff8614..b5b657f 100644
--- a/acrate_astreams/src/activitystreams/mod.rs
+++ b/acrate_astreams/src/activitystreams/mod.rs
@@ -18,13 +18,23 @@ use mediatype::MediaType;
 
 pub mod jsonld;
 
+/// Something that is either a [`StreamsObject`] or a [`StreamsLink`].
+pub trait StreamsEntity<Preview> {
+	fn activitystreams_previews(&self) -> impl Iterator<Item = AResult<Preview>>;
+}
+
 /// Something that can be considered a `https://www.w3.org/ns/activitystreams#Object`.
-pub trait StreamsObject {
+pub trait StreamsObject<Preview> where
+	Self: StreamsEntity<Preview>,
+{
 
 }
 
 /// Something that can be considered a `https://www.w3.org/ns/activitystreams#Link`.
-pub trait StreamsLink {
+pub trait StreamsLink<Preview> where
+	Self: StreamsEntity<Preview>,
+	Preview: StreamsEntity<Preview>,
+{
 	fn activitystreams_href(&self) -> Option<AResult<String>>;
 	
 	// FIXME: This accepts any kind of string, and does not filter to HTML link relations
diff --git a/acrate_astreams/tests/test_activitystreams.rs b/acrate_astreams/tests/test_activitystreams.rs
index 83bae47..cc6aaf2 100644
--- a/acrate_astreams/tests/test_activitystreams.rs
+++ b/acrate_astreams/tests/test_activitystreams.rs
@@ -1,6 +1,5 @@
 use json_ld::syntax::LangTagBuf;
 use acrate_astreams::activitystreams::jsonld::LangTriple;
-use acrate_astreams::activitystreams::StreamsLink;
 
 macro_rules! test_example {
 	($modname:ident, $filename:literal) => {
@@ -383,3 +382,27 @@ async fn test_link_width() {
 	
 	assert_eq!(width, 100u64)
 }
+
+#[tokio::test]
+async fn test_link_preview() {
+	let doc = e102::expand().await;
+	
+	let node = doc.main_node()
+		.expect("Main node was not found");
+	
+	let previews: Vec<json_ld::Node> = {
+		use acrate_astreams::activitystreams::StreamsEntity;
+		
+		node.activitystreams_previews()
+			.map(|v| v
+				.expect("Property `preview` failed to process")
+			)
+			.collect()
+	};
+	
+	let mut previews = previews.into_iter();
+	
+	let _preview = previews.next().expect("Expected `preview` [0] to be present");
+	
+	// TODO: More tests when StreamsObject is implemented
+}