assistant2: Add create buffer tool (#11219)

This PR adds a new tool to the `assistant2` crate that allows the
assistant to create a new buffer with some content.

Release Notes:

- N/A

---------

Co-authored-by: Nathan <nathan@zed.dev>

crates/assistant2/src/tools/create_buffer.rs

@@ -0,0 +1,111 @@
+use anyhow::Result;
+use assistant_tooling::LanguageModelTool;
+use editor::Editor;
+use gpui::{prelude::*, Model, Task, View, WeakView};
+use project::Project;
+use schemars::JsonSchema;
+use serde::Deserialize;
+use ui::prelude::*;
+use util::ResultExt;
+use workspace::Workspace;
+
+pub struct CreateBufferTool {
+    workspace: WeakView<Workspace>,
+    project: Model<Project>,
+}
+
+impl CreateBufferTool {
+    pub fn new(workspace: WeakView<Workspace>, project: Model<Project>) -> Self {
+        Self { workspace, project }
+    }
+}
+
+#[derive(Debug, Deserialize, JsonSchema)]
+pub struct CreateBufferInput {
+    /// The contents of the buffer.
+    text: String,
+
+    /// The name of the language to use for the buffer.
+    ///
+    /// This should be a human-readable name, like "Rust", "JavaScript", or "Python".
+    language: String,
+}
+
+pub struct CreateBufferOutput {}
+
+impl LanguageModelTool for CreateBufferTool {
+    type Input = CreateBufferInput;
+    type Output = CreateBufferOutput;
+    type View = CreateBufferView;
+
+    fn name(&self) -> String {
+        "create_buffer".to_string()
+    }
+
+    fn description(&self) -> String {
+        "Create a new buffer in the current codebase".to_string()
+    }
+
+    fn execute(&self, input: &Self::Input, cx: &mut WindowContext) -> Task<Result<Self::Output>> {
+        cx.spawn({
+            let workspace = self.workspace.clone();
+            let project = self.project.clone();
+            let text = input.text.clone();
+            let language_name = input.language.clone();
+            |mut cx| async move {
+                let language = cx
+                    .update(|cx| {
+                        project
+                            .read(cx)
+                            .languages()
+                            .language_for_name(&language_name)
+                    })?
+                    .await?;
+
+                let buffer = cx.update(|cx| {
+                    project.update(cx, |project, cx| {
+                        project.create_buffer(&text, Some(language), cx)
+                    })
+                })??;
+
+                workspace
+                    .update(&mut cx, |workspace, cx| {
+                        workspace.add_item_to_active_pane(
+                            Box::new(
+                                cx.new_view(|cx| Editor::for_buffer(buffer, Some(project), cx)),
+                            ),
+                            None,
+                            cx,
+                        );
+                    })
+                    .log_err();
+
+                Ok(CreateBufferOutput {})
+            }
+        })
+    }
+
+    fn format(input: &Self::Input, output: &Result<Self::Output>) -> String {
+        match output {
+            Ok(_) => format!("Created a new {} buffer", input.language),
+            Err(err) => format!("Failed to create buffer: {err:?}"),
+        }
+    }
+
+    fn output_view(
+        _tool_call_id: String,
+        _input: Self::Input,
+        _output: Result<Self::Output>,
+        cx: &mut WindowContext,
+    ) -> View<Self::View> {
+        cx.new_view(|_cx| CreateBufferView {})
+    }
+}
+
+pub struct CreateBufferView {}
+
+impl Render for CreateBufferView {
+    fn render(&mut self, _cx: &mut ViewContext<Self>) -> impl IntoElement {
+        div().child("Opening a buffer")
+    }
+}