assistant2: Factor out ContextStrip (#22096)

This PR factors a `ContextStrip` view out of the `MessageEditor` so that
we can use it in other places.

Release Notes:

- N/A

crates/assistant2/src/context_strip.rs

@@ -0,0 +1,101 @@
+use std::rc::Rc;
+
+use gpui::{View, WeakModel, WeakView};
+use ui::{prelude::*, IconButtonShape, PopoverMenu, PopoverMenuHandle, Tooltip};
+use workspace::Workspace;
+
+use crate::context::{Context, ContextId, ContextKind};
+use crate::context_picker::ContextPicker;
+use crate::thread_store::ThreadStore;
+use crate::ui::ContextPill;
+
+pub struct ContextStrip {
+    context: Vec<Context>,
+    next_context_id: ContextId,
+    context_picker: View<ContextPicker>,
+    pub(crate) context_picker_handle: PopoverMenuHandle<ContextPicker>,
+}
+
+impl ContextStrip {
+    pub fn new(
+        workspace: WeakView<Workspace>,
+        thread_store: WeakModel<ThreadStore>,
+        cx: &mut ViewContext<Self>,
+    ) -> Self {
+        let weak_self = cx.view().downgrade();
+
+        Self {
+            context: Vec::new(),
+            next_context_id: ContextId(0),
+            context_picker: cx.new_view(|cx| {
+                ContextPicker::new(workspace.clone(), thread_store.clone(), weak_self, cx)
+            }),
+            context_picker_handle: PopoverMenuHandle::default(),
+        }
+    }
+
+    pub fn drain(&mut self) -> Vec<Context> {
+        self.context.drain(..).collect()
+    }
+
+    pub fn insert_context(
+        &mut self,
+        kind: ContextKind,
+        name: impl Into<SharedString>,
+        text: impl Into<SharedString>,
+    ) {
+        self.context.push(Context {
+            id: self.next_context_id.post_inc(),
+            name: name.into(),
+            kind,
+            text: text.into(),
+        });
+    }
+}
+
+impl Render for ContextStrip {
+    fn render(&mut self, cx: &mut ViewContext<Self>) -> impl IntoElement {
+        let context_picker = self.context_picker.clone();
+
+        h_flex()
+            .flex_wrap()
+            .gap_2()
+            .child(
+                PopoverMenu::new("context-picker")
+                    .menu(move |_cx| Some(context_picker.clone()))
+                    .trigger(
+                        IconButton::new("add-context", IconName::Plus)
+                            .shape(IconButtonShape::Square)
+                            .icon_size(IconSize::Small),
+                    )
+                    .attach(gpui::AnchorCorner::TopLeft)
+                    .anchor(gpui::AnchorCorner::BottomLeft)
+                    .offset(gpui::Point {
+                        x: px(0.0),
+                        y: px(-16.0),
+                    })
+                    .with_handle(self.context_picker_handle.clone()),
+            )
+            .children(self.context.iter().map(|context| {
+                ContextPill::new(context.clone()).on_remove({
+                    let context = context.clone();
+                    Rc::new(cx.listener(move |this, _event, cx| {
+                        this.context.retain(|other| other.id != context.id);
+                        cx.notify();
+                    }))
+                })
+            }))
+            .when(!self.context.is_empty(), |parent| {
+                parent.child(
+                    IconButton::new("remove-all-context", IconName::Eraser)
+                        .shape(IconButtonShape::Square)
+                        .icon_size(IconSize::Small)
+                        .tooltip(move |cx| Tooltip::text("Remove All Context", cx))
+                        .on_click(cx.listener(|this, _event, cx| {
+                            this.context.clear();
+                            cx.notify();
+                        })),
+                )
+            })
+    }
+}