1 files changed, 62 insertions, 0 deletions
diff --git a/web/src/element.rs b/web/src/element.rs
new file mode 100644
index 00000000..8270d8db
--- /dev/null
+++ b/web/src/element.rs
@@ -0,0 +1,62 @@
+use crate::{Bus, Color, Widget};
+
+use dodrio::bumpalo;
+use std::rc::Rc;
+
+pub struct Element<'a, Message> {
+    pub(crate) widget: Box<dyn Widget<Message> + 'a>,
+}
+
+impl<'a, Message> Element<'a, Message> {
+    pub fn new(widget: impl Widget<Message> + 'a) -> Self {
+        Self {
+            widget: Box::new(widget),
+        }
+    }
+
+    pub fn explain(self, _color: Color) -> Element<'a, Message> {
+        self
+    }
+
+    pub fn map<F, B>(self, f: F) -> Element<'a, B>
+    where
+        Message: 'static,
+        B: 'static,
+        F: 'static + Fn(Message) -> B,
+    {
+        Element {
+            widget: Box::new(Map::new(self.widget, f)),
+        }
+    }
+}
+
+struct Map<'a, A, B> {
+    widget: Box<dyn Widget<A> + 'a>,
+    mapper: Rc<Box<dyn Fn(A) -> B>>,
+}
+
+impl<'a, A, B> Map<'a, A, B> {
+    pub fn new<F>(widget: Box<dyn Widget<A> + 'a>, mapper: F) -> Map<'a, A, B>
+    where
+        F: 'static + Fn(A) -> B,
+    {
+        Map {
+            widget,
+            mapper: Rc::new(Box::new(mapper)),
+        }
+    }
+}
+
+impl<'a, A, B> Widget<B> for Map<'a, A, B>
+where
+    A: 'static,
+    B: 'static,
+{
+    fn node<'b>(
+        &self,
+        bump: &'b bumpalo::Bump,
+        bus: &Bus<B>,
+    ) -> dodrio::Node<'b> {
+        self.widget.node(bump, &bus.map(self.mapper.clone()))
+    }
+}