assistant2: Sketch in context picker (#21560)

This PR sketches in a context picker into the message editor in
Assistant 2. Not functional yet.

<img width="1138" alt="Screenshot 2024-12-04 at 5 45 19 PM"
src="https://github.com/user-attachments/assets/053d6224-de76-4fde-914b-41fe835761eb">

Release Notes:

- N/A

crates/assistant2/src/context_picker.rs

@@ -0,0 +1,197 @@
+use std::sync::Arc;
+
+use gpui::{DismissEvent, SharedString, Task, WeakView};
+use picker::{Picker, PickerDelegate, PickerEditorPosition};
+use ui::{prelude::*, ListItem, ListItemSpacing, PopoverMenu, PopoverTrigger, Tooltip};
+
+use crate::message_editor::MessageEditor;
+
+#[derive(IntoElement)]
+pub(super) struct ContextPicker<T: PopoverTrigger> {
+    message_editor: WeakView<MessageEditor>,
+    trigger: T,
+}
+
+#[derive(Clone)]
+struct ContextPickerEntry {
+    name: SharedString,
+    description: SharedString,
+    icon: IconName,
+}
+
+pub(crate) struct ContextPickerDelegate {
+    all_entries: Vec<ContextPickerEntry>,
+    filtered_entries: Vec<ContextPickerEntry>,
+    message_editor: WeakView<MessageEditor>,
+    selected_ix: usize,
+}
+
+impl<T: PopoverTrigger> ContextPicker<T> {
+    pub(crate) fn new(message_editor: WeakView<MessageEditor>, trigger: T) -> Self {
+        ContextPicker {
+            message_editor,
+            trigger,
+        }
+    }
+}
+
+impl PickerDelegate for ContextPickerDelegate {
+    type ListItem = ListItem;
+
+    fn match_count(&self) -> usize {
+        self.filtered_entries.len()
+    }
+
+    fn selected_index(&self) -> usize {
+        self.selected_ix
+    }
+
+    fn set_selected_index(&mut self, ix: usize, cx: &mut ViewContext<Picker<Self>>) {
+        self.selected_ix = ix.min(self.filtered_entries.len().saturating_sub(1));
+        cx.notify();
+    }
+
+    fn placeholder_text(&self, _cx: &mut WindowContext) -> Arc<str> {
+        "Select a context source…".into()
+    }
+
+    fn update_matches(&mut self, query: String, cx: &mut ViewContext<Picker<Self>>) -> Task<()> {
+        let all_commands = self.all_entries.clone();
+        cx.spawn(|this, mut cx| async move {
+            let filtered_commands = cx
+                .background_executor()
+                .spawn(async move {
+                    if query.is_empty() {
+                        all_commands
+                    } else {
+                        all_commands
+                            .into_iter()
+                            .filter(|model_info| {
+                                model_info
+                                    .name
+                                    .to_lowercase()
+                                    .contains(&query.to_lowercase())
+                            })
+                            .collect()
+                    }
+                })
+                .await;
+
+            this.update(&mut cx, |this, cx| {
+                this.delegate.filtered_entries = filtered_commands;
+                this.delegate.set_selected_index(0, cx);
+                cx.notify();
+            })
+            .ok();
+        })
+    }
+
+    fn confirm(&mut self, _secondary: bool, cx: &mut ViewContext<Picker<Self>>) {
+        if let Some(entry) = self.filtered_entries.get(self.selected_ix) {
+            self.message_editor
+                .update(cx, |_message_editor, _cx| {
+                    println!("Insert context from {}", entry.name);
+                })
+                .ok();
+            cx.emit(DismissEvent);
+        }
+    }
+
+    fn dismissed(&mut self, _cx: &mut ViewContext<Picker<Self>>) {}
+
+    fn editor_position(&self) -> PickerEditorPosition {
+        PickerEditorPosition::End
+    }
+
+    fn render_match(
+        &self,
+        ix: usize,
+        selected: bool,
+        _cx: &mut ViewContext<Picker<Self>>,
+    ) -> Option<Self::ListItem> {
+        let entry = self.filtered_entries.get(ix)?;
+
+        Some(
+            ListItem::new(ix)
+                .inset(true)
+                .spacing(ListItemSpacing::Dense)
+                .selected(selected)
+                .tooltip({
+                    let description = entry.description.clone();
+                    move |cx| cx.new_view(|_cx| Tooltip::new(description.clone())).into()
+                })
+                .child(
+                    v_flex()
+                        .group(format!("context-entry-label-{ix}"))
+                        .w_full()
+                        .py_0p5()
+                        .min_w(px(250.))
+                        .max_w(px(400.))
+                        .child(
+                            h_flex()
+                                .gap_1p5()
+                                .child(Icon::new(entry.icon).size(IconSize::XSmall))
+                                .child(
+                                    Label::new(entry.name.clone())
+                                        .single_line()
+                                        .size(LabelSize::Small),
+                                ),
+                        )
+                        .child(
+                            div().overflow_hidden().text_ellipsis().child(
+                                Label::new(entry.description.clone())
+                                    .size(LabelSize::Small)
+                                    .color(Color::Muted),
+                            ),
+                        ),
+                ),
+        )
+    }
+}
+
+impl<T: PopoverTrigger> RenderOnce for ContextPicker<T> {
+    fn render(self, cx: &mut WindowContext) -> impl IntoElement {
+        let entries = vec![
+            ContextPickerEntry {
+                name: "directory".into(),
+                description: "Insert any directory".into(),
+                icon: IconName::Folder,
+            },
+            ContextPickerEntry {
+                name: "file".into(),
+                description: "Insert any file".into(),
+                icon: IconName::File,
+            },
+            ContextPickerEntry {
+                name: "web".into(),
+                description: "Fetch content from URL".into(),
+                icon: IconName::Globe,
+            },
+        ];
+
+        let delegate = ContextPickerDelegate {
+            all_entries: entries.clone(),
+            message_editor: self.message_editor.clone(),
+            filtered_entries: entries,
+            selected_ix: 0,
+        };
+
+        let picker =
+            cx.new_view(|cx| Picker::uniform_list(delegate, cx).max_height(Some(rems(20.).into())));
+
+        let handle = self
+            .message_editor
+            .update(cx, |this, _| this.context_picker_handle.clone())
+            .ok();
+        PopoverMenu::new("context-picker")
+            .menu(move |_cx| Some(picker.clone()))
+            .trigger(self.trigger)
+            .attach(gpui::AnchorCorner::TopLeft)
+            .anchor(gpui::AnchorCorner::BottomLeft)
+            .offset(gpui::Point {
+                x: px(0.0),
+                y: px(-16.0),
+            })
+            .when_some(handle, |this, handle| this.with_handle(handle))
+    }
+}