assistant2: Factor out tool use into its own module (#25819)

This PR factors out the concerns related to tool use out of `Thread` and
into their own module.

Release Notes:

- N/A

crates/assistant2/src/tool_use.rs

@@ -0,0 +1,221 @@
+use std::sync::Arc;
+
+use anyhow::Result;
+use collections::HashMap;
+use futures::future::Shared;
+use futures::FutureExt as _;
+use gpui::{SharedString, Task};
+use language_model::{
+    LanguageModelRequestMessage, LanguageModelToolResult, LanguageModelToolUse,
+    LanguageModelToolUseId, MessageContent,
+};
+
+use crate::thread::MessageId;
+
+#[derive(Debug)]
+pub struct ToolUse {
+    pub id: LanguageModelToolUseId,
+    pub name: SharedString,
+    pub status: ToolUseStatus,
+    pub input: serde_json::Value,
+}
+
+#[derive(Debug, Clone)]
+pub enum ToolUseStatus {
+    Pending,
+    Running,
+    Finished(SharedString),
+    Error(SharedString),
+}
+
+#[derive(Default)]
+pub struct ToolUseState {
+    tool_uses_by_assistant_message: HashMap<MessageId, Vec<LanguageModelToolUse>>,
+    tool_uses_by_user_message: HashMap<MessageId, Vec<LanguageModelToolUseId>>,
+    tool_results: HashMap<LanguageModelToolUseId, LanguageModelToolResult>,
+    pending_tool_uses_by_id: HashMap<LanguageModelToolUseId, PendingToolUse>,
+}
+
+impl ToolUseState {
+    pub fn pending_tool_uses(&self) -> Vec<&PendingToolUse> {
+        self.pending_tool_uses_by_id.values().collect()
+    }
+
+    pub fn tool_uses_for_message(&self, id: MessageId) -> Vec<ToolUse> {
+        let Some(tool_uses_for_message) = &self.tool_uses_by_assistant_message.get(&id) else {
+            return Vec::new();
+        };
+
+        let mut tool_uses = Vec::new();
+
+        for tool_use in tool_uses_for_message.iter() {
+            let tool_result = self.tool_results.get(&tool_use.id);
+
+            let status = (|| {
+                if let Some(tool_result) = tool_result {
+                    return if tool_result.is_error {
+                        ToolUseStatus::Error(tool_result.content.clone().into())
+                    } else {
+                        ToolUseStatus::Finished(tool_result.content.clone().into())
+                    };
+                }
+
+                if let Some(pending_tool_use) = self.pending_tool_uses_by_id.get(&tool_use.id) {
+                    return match pending_tool_use.status {
+                        PendingToolUseStatus::Idle => ToolUseStatus::Pending,
+                        PendingToolUseStatus::Running { .. } => ToolUseStatus::Running,
+                        PendingToolUseStatus::Error(ref err) => {
+                            ToolUseStatus::Error(err.clone().into())
+                        }
+                    };
+                }
+
+                ToolUseStatus::Pending
+            })();
+
+            tool_uses.push(ToolUse {
+                id: tool_use.id.clone(),
+                name: tool_use.name.clone().into(),
+                input: tool_use.input.clone(),
+                status,
+            })
+        }
+
+        tool_uses
+    }
+
+    pub fn message_has_tool_results(&self, message_id: MessageId) -> bool {
+        self.tool_uses_by_user_message
+            .get(&message_id)
+            .map_or(false, |results| !results.is_empty())
+    }
+
+    pub fn request_tool_use(
+        &mut self,
+        assistant_message_id: MessageId,
+        tool_use: LanguageModelToolUse,
+    ) {
+        self.tool_uses_by_assistant_message
+            .entry(assistant_message_id)
+            .or_default()
+            .push(tool_use.clone());
+
+        // The tool use is being requested by the Assistant, so we want to
+        // attach the tool results to the next user message.
+        let next_user_message_id = MessageId(assistant_message_id.0 + 1);
+        self.tool_uses_by_user_message
+            .entry(next_user_message_id)
+            .or_default()
+            .push(tool_use.id.clone());
+
+        self.pending_tool_uses_by_id.insert(
+            tool_use.id.clone(),
+            PendingToolUse {
+                assistant_message_id,
+                id: tool_use.id,
+                name: tool_use.name,
+                input: tool_use.input,
+                status: PendingToolUseStatus::Idle,
+            },
+        );
+    }
+
+    pub fn run_pending_tool(&mut self, tool_use_id: LanguageModelToolUseId, task: Task<()>) {
+        if let Some(tool_use) = self.pending_tool_uses_by_id.get_mut(&tool_use_id) {
+            tool_use.status = PendingToolUseStatus::Running {
+                _task: task.shared(),
+            };
+        }
+    }
+
+    pub fn insert_tool_output(
+        &mut self,
+        tool_use_id: LanguageModelToolUseId,
+        output: Result<String>,
+    ) {
+        match output {
+            Ok(output) => {
+                self.tool_results.insert(
+                    tool_use_id.clone(),
+                    LanguageModelToolResult {
+                        tool_use_id: tool_use_id.clone(),
+                        content: output.into(),
+                        is_error: false,
+                    },
+                );
+                self.pending_tool_uses_by_id.remove(&tool_use_id);
+            }
+            Err(err) => {
+                self.tool_results.insert(
+                    tool_use_id.clone(),
+                    LanguageModelToolResult {
+                        tool_use_id: tool_use_id.clone(),
+                        content: err.to_string().into(),
+                        is_error: true,
+                    },
+                );
+
+                if let Some(tool_use) = self.pending_tool_uses_by_id.get_mut(&tool_use_id) {
+                    tool_use.status = PendingToolUseStatus::Error(err.to_string().into());
+                }
+            }
+        }
+    }
+
+    pub fn attach_tool_uses(
+        &self,
+        message_id: MessageId,
+        request_message: &mut LanguageModelRequestMessage,
+    ) {
+        if let Some(tool_uses) = self.tool_uses_by_assistant_message.get(&message_id) {
+            for tool_use in tool_uses {
+                request_message
+                    .content
+                    .push(MessageContent::ToolUse(tool_use.clone()));
+            }
+        }
+    }
+
+    pub fn attach_tool_results(
+        &self,
+        message_id: MessageId,
+        request_message: &mut LanguageModelRequestMessage,
+    ) {
+        if let Some(tool_uses) = self.tool_uses_by_user_message.get(&message_id) {
+            for tool_use_id in tool_uses {
+                if let Some(tool_result) = self.tool_results.get(tool_use_id) {
+                    request_message
+                        .content
+                        .push(MessageContent::ToolResult(tool_result.clone()));
+                }
+            }
+        }
+    }
+}
+
+#[derive(Debug, Clone)]
+pub struct PendingToolUse {
+    pub id: LanguageModelToolUseId,
+    /// The ID of the Assistant message in which the tool use was requested.
+    pub assistant_message_id: MessageId,
+    pub name: Arc<str>,
+    pub input: serde_json::Value,
+    pub status: PendingToolUseStatus,
+}
+
+#[derive(Debug, Clone)]
+pub enum PendingToolUseStatus {
+    Idle,
+    Running { _task: Shared<Task<()>> },
+    Error(#[allow(unused)] Arc<str>),
+}
+
+impl PendingToolUseStatus {
+    pub fn is_idle(&self) -> bool {
+        matches!(self, PendingToolUseStatus::Idle)
+    }
+
+    pub fn is_error(&self) -> bool {
+        matches!(self, PendingToolUseStatus::Error(_))
+    }
+}