Implement category playlist browsing in library

Fixes #187

src/model/category.rs

@@ -0,0 +1,66 @@
+use std::sync::Arc;
+
+use crate::{
+    traits::{IntoBoxedViewExt, ListItem},
+    ui::listview::ListView,
+};
+
+#[derive(Clone, Deserialize, Serialize)]
+pub struct Category {
+    pub id: String,
+    pub name: String,
+}
+
+impl From<&rspotify::model::Category> for Category {
+    fn from(c: &rspotify::model::Category) -> Self {
+        Category {
+            id: c.id.clone(),
+            name: c.name.clone(),
+        }
+    }
+}
+
+impl ListItem for Category {
+    fn is_playing(&self, _queue: Arc<crate::queue::Queue>) -> bool {
+        false
+    }
+
+    fn display_left(&self, _library: Arc<crate::library::Library>) -> String {
+        self.name.clone()
+    }
+
+    fn display_right(&self, _library: Arc<crate::library::Library>) -> String {
+        "".to_string()
+    }
+
+    fn play(&mut self, _queue: Arc<crate::queue::Queue>) {}
+
+    fn play_next(&mut self, _queue: Arc<crate::queue::Queue>) {}
+
+    fn queue(&mut self, _queue: Arc<crate::queue::Queue>) {}
+
+    fn toggle_saved(&mut self, _library: Arc<crate::library::Library>) {}
+
+    fn save(&mut self, _library: Arc<crate::library::Library>) {}
+
+    fn unsave(&mut self, _library: Arc<crate::library::Library>) {}
+
+    fn open(
+        &self,
+        queue: Arc<crate::queue::Queue>,
+        library: Arc<crate::library::Library>,
+    ) -> Option<Box<dyn crate::traits::ViewExt>> {
+        let playlists = queue.get_spotify().api.category_playlists(&self.id);
+        let view = ListView::new(playlists.items.clone(), queue, library).with_title(&self.name);
+        playlists.apply_pagination(view.get_pagination());
+        Some(view.into_boxed_view_ext())
+    }
+
+    fn share_url(&self) -> Option<String> {
+        Some(format!("https://open.spotify.com/genre/{}", self.id))
+    }
+
+    fn as_listitem(&self) -> Box<dyn ListItem> {
+        Box::new(self.clone())
+    }
+}

src/model/mod.rs

@@ -1,5 +1,6 @@
 pub mod album;
 pub mod artist;
+pub mod category;
 pub mod episode;
 pub mod playable;
 pub mod playlist;