assistant2: Add configuration (#23481)

This PR wires up the ability to configure Assistant2.

<img width="1309" alt="Screenshot 2025-01-22 at 1 52 56 PM"
src="https://github.com/user-attachments/assets/3de47797-7959-47af-bd93-51f105e87c28"
/>

Release Notes:

- N/A

crates/assistant2/src/assistant_configuration.rs

@@ -0,0 +1,159 @@
+use std::sync::Arc;
+
+use collections::HashMap;
+use gpui::{AnyView, AppContext, EventEmitter, FocusHandle, FocusableView, Subscription};
+use language_model::{LanguageModelProvider, LanguageModelProviderId, LanguageModelRegistry};
+use ui::{prelude::*, ElevationIndex};
+
+pub struct AssistantConfiguration {
+    focus_handle: FocusHandle,
+    configuration_views_by_provider: HashMap<LanguageModelProviderId, AnyView>,
+    _registry_subscription: Subscription,
+}
+
+impl AssistantConfiguration {
+    pub fn new(cx: &mut ViewContext<Self>) -> Self {
+        let focus_handle = cx.focus_handle();
+
+        let registry_subscription = cx.subscribe(
+            &LanguageModelRegistry::global(cx),
+            |this, _, event: &language_model::Event, cx| match event {
+                language_model::Event::AddedProvider(provider_id) => {
+                    let provider = LanguageModelRegistry::read_global(cx).provider(provider_id);
+                    if let Some(provider) = provider {
+                        this.add_provider_configuration_view(&provider, cx);
+                    }
+                }
+                language_model::Event::RemovedProvider(provider_id) => {
+                    this.remove_provider_configuration_view(provider_id);
+                }
+                _ => {}
+            },
+        );
+
+        let mut this = Self {
+            focus_handle,
+            configuration_views_by_provider: HashMap::default(),
+            _registry_subscription: registry_subscription,
+        };
+        this.build_provider_configuration_views(cx);
+        this
+    }
+
+    fn build_provider_configuration_views(&mut self, cx: &mut ViewContext<Self>) {
+        let providers = LanguageModelRegistry::read_global(cx).providers();
+        for provider in providers {
+            self.add_provider_configuration_view(&provider, cx);
+        }
+    }
+
+    fn remove_provider_configuration_view(&mut self, provider_id: &LanguageModelProviderId) {
+        self.configuration_views_by_provider.remove(provider_id);
+    }
+
+    fn add_provider_configuration_view(
+        &mut self,
+        provider: &Arc<dyn LanguageModelProvider>,
+        cx: &mut ViewContext<Self>,
+    ) {
+        let configuration_view = provider.configuration_view(cx);
+        self.configuration_views_by_provider
+            .insert(provider.id(), configuration_view);
+    }
+}
+
+impl FocusableView for AssistantConfiguration {
+    fn focus_handle(&self, _: &AppContext) -> FocusHandle {
+        self.focus_handle.clone()
+    }
+}
+
+pub enum AssistantConfigurationEvent {
+    NewThread(Arc<dyn LanguageModelProvider>),
+}
+
+impl EventEmitter<AssistantConfigurationEvent> for AssistantConfiguration {}
+
+impl AssistantConfiguration {
+    fn render_provider_configuration(
+        &mut self,
+        provider: &Arc<dyn LanguageModelProvider>,
+        cx: &mut ViewContext<Self>,
+    ) -> impl IntoElement {
+        let provider_id = provider.id().0.clone();
+        let provider_name = provider.name().0.clone();
+        let configuration_view = self
+            .configuration_views_by_provider
+            .get(&provider.id())
+            .cloned();
+
+        v_flex()
+            .gap_2()
+            .child(
+                h_flex()
+                    .justify_between()
+                    .child(Headline::new(provider_name.clone()).size(HeadlineSize::Small))
+                    .when(provider.is_authenticated(cx), |parent| {
+                        parent.child(
+                            h_flex().justify_end().child(
+                                Button::new(
+                                    SharedString::from(format!("new-thread-{provider_id}")),
+                                    "Open New Thread",
+                                )
+                                .icon_position(IconPosition::Start)
+                                .icon(IconName::Plus)
+                                .style(ButtonStyle::Filled)
+                                .layer(ElevationIndex::ModalSurface)
+                                .on_click(cx.listener({
+                                    let provider = provider.clone();
+                                    move |_this, _event, cx| {
+                                        cx.emit(AssistantConfigurationEvent::NewThread(
+                                            provider.clone(),
+                                        ))
+                                    }
+                                })),
+                            ),
+                        )
+                    }),
+            )
+            .child(
+                div()
+                    .p(DynamicSpacing::Base08.rems(cx))
+                    .bg(cx.theme().colors().surface_background)
+                    .border_1()
+                    .border_color(cx.theme().colors().border_variant)
+                    .rounded_md()
+                    .map(|parent| match configuration_view {
+                        Some(configuration_view) => parent.child(configuration_view),
+                        None => parent.child(div().child(Label::new(format!(
+                            "No configuration view for {provider_name}",
+                        )))),
+                    }),
+            )
+    }
+}
+
+impl Render for AssistantConfiguration {
+    fn render(&mut self, cx: &mut ViewContext<Self>) -> impl IntoElement {
+        let providers = LanguageModelRegistry::read_global(cx).providers();
+
+        v_flex()
+            .id("assistant-configuration")
+            .track_focus(&self.focus_handle(cx))
+            .bg(cx.theme().colors().editor_background)
+            .size_full()
+            .overflow_y_scroll()
+            .child(
+                v_flex()
+                    .p(DynamicSpacing::Base16.rems(cx))
+                    .mt_1()
+                    .gap_6()
+                    .flex_1()
+                    .children(
+                        providers
+                            .into_iter()
+                            .map(|provider| self.render_provider_configuration(&provider, cx)),
+                    ),
+            )
+    }
+}