claude_code_acp/session/

permission_manager.rs

//! Permission Manager - Async permission handling for MCP tools
//!
//! Based on Zed's permission system pattern:
//! - Hook sends permission request and returns immediately
//! - Background task handles the request
//! - Uses unbounded channels (never block)
//! - Uses one-shot channels for request/response

use std::sync::Arc;

use sacp::JrConnectionCx;
use sacp::link::AgentToClient;
use sacp::schema::{
    PermissionOption, PermissionOptionId, PermissionOptionKind, RequestPermissionOutcome,
    RequestPermissionRequest, SessionId, ToolCallUpdate, ToolCallUpdateFields,
};

use crate::types::AgentError;

/// Permission decision result
#[derive(Debug, Clone, PartialEq)]
pub enum PermissionManagerDecision {
    /// User allowed this tool call (one-time)
    AllowOnce,
    /// User allowed this tool call and wants to always allow this pattern
    AllowAlways,
    /// User rejected this tool call
    Rejected,
    /// Permission request was cancelled
    Cancelled,
}

/// Pending permission request from hook
pub struct PendingPermissionRequest {
    pub tool_name: String,
    pub tool_input: serde_json::Value,
    pub tool_call_id: String,
    pub session_id: String,
    pub response_tx: tokio::sync::oneshot::Sender<PermissionManagerDecision>,
}

/// Permission Manager - handles permission requests in background tasks
///
/// # Architecture
///
/// Based on Zed's async permission pattern:
/// 1. Hook sends request via unbounded channel (never blocks)
/// 2. Background task processes request
/// 3. One-shot channel returns result to caller
///
/// # Example
///
/// ```rust,ignore
/// let manager = PermissionManager::new(connection_cx);
/// let rx = manager.request_permission("Edit", input, "call_123", "session_456");
/// let decision = rx.await?;
/// ```
pub struct PermissionManager {
    /// Pending permission requests (unbounded, never blocks on send)
    pending_requests: tokio::sync::mpsc::UnboundedSender<PendingPermissionRequest>,

    /// Connection to client for sending permission requests
    /// Note: Currently used by `send_permission_request_to_client` which is prepared
    /// for future interactive permission dialog implementation.
    #[allow(dead_code)]
    connection_cx: Arc<JrConnectionCx<AgentToClient>>,
}

impl PermissionManager {
    /// Create a new PermissionManager
    pub fn new(connection_cx: Arc<JrConnectionCx<AgentToClient>>) -> Self {
        let (tx, rx) = tokio::sync::mpsc::unbounded_channel();

        // Spawn background task to handle permission requests
        tokio::spawn(async move {
            Self::handle_permission_requests(rx).await;
        });

        Self {
            pending_requests: tx,
            connection_cx,
        }
    }

    /// Request permission (non-blocking)
    ///
    /// Returns a receiver that will resolve when user responds.
    ///
    /// This never blocks - it immediately sends to the background task
    /// and returns a receiver for the result.
    pub fn request_permission(
        &self,
        tool_name: String,
        tool_input: serde_json::Value,
        tool_call_id: String,
        session_id: String,
    ) -> tokio::sync::oneshot::Receiver<PermissionManagerDecision> {
        let (tx, rx) = tokio::sync::oneshot::channel();

        let request = PendingPermissionRequest {
            tool_name,
            tool_input,
            tool_call_id,
            session_id,
            response_tx: tx,
        };

        // Send to background task (unbounded channel never blocks)
        drop(self.pending_requests.send(request));

        rx
    }

    /// Background task: handle permission requests
    async fn handle_permission_requests(
        mut receiver: tokio::sync::mpsc::UnboundedReceiver<PendingPermissionRequest>,
    ) {
        while let Some(request) = receiver.recv().await {
            tracing::info!(
                tool_name = %request.tool_name,
                tool_call_id = %request.tool_call_id,
                "Processing permission request in background task"
            );

            // TODO: Send permission request to client via SACP
            // For now, we'll simulate the request and response

            // This is where we would:
            // 1. Build the RequestPermissionRequest
            // 2. Send it via SACP to the client
            // 3. Wait for the client's response
            // 4. Send the result to response_tx

            // For now, deny with a message explaining the limitation
            let _ = request
                .response_tx
                .send(PermissionManagerDecision::Cancelled);

            tracing::warn!(
                tool_name = %request.tool_name,
                "Permission request sent but interactive dialog not yet implemented"
            );
        }
    }

    /// Send permission request to client via SACP
    ///
    /// Note: This method is prepared for future interactive permission dialog implementation.
    /// Currently, permission requests are handled by the SDK's `can_use_tool` callback.
    #[allow(dead_code)]
    async fn send_permission_request_to_client(
        &self,
        tool_name: &str,
        tool_input: &serde_json::Value,
        tool_call_id: &str,
        session_id: &str,
    ) -> Result<PermissionManagerDecision, AgentError> {
        // Build the permission options
        let options = vec![
            PermissionOption::new(
                PermissionOptionId::new("allow_always"),
                "Always Allow",
                PermissionOptionKind::AllowAlways,
            ),
            PermissionOption::new(
                PermissionOptionId::new("allow_once"),
                "Allow",
                PermissionOptionKind::AllowOnce,
            ),
            PermissionOption::new(
                PermissionOptionId::new("reject_once"),
                "Reject",
                PermissionOptionKind::RejectOnce,
            ),
        ];

        // Build the tool call update with title
        let tool_call_update = ToolCallUpdate::new(
            tool_call_id.to_string(),
            ToolCallUpdateFields::new()
                .title(&format_tool_title(tool_name, tool_input))
                .raw_input(tool_input.clone()),
        );

        // Build the request
        let request =
            RequestPermissionRequest::new(SessionId::new(session_id), tool_call_update, options);

        // Send request and wait for response
        let response = self
            .connection_cx
            .send_request(request)
            .block_task()
            .await
            .map_err(|e| AgentError::Internal(format!("Permission request failed: {}", e)))?;

        // Parse the response
        Ok(parse_permission_response(response.outcome))
    }
}

/// Parse a permission response outcome into our decision type
///
/// Note: Prepared for future interactive permission dialog implementation.
#[allow(dead_code)]
fn parse_permission_response(outcome: RequestPermissionOutcome) -> PermissionManagerDecision {
    match outcome {
        RequestPermissionOutcome::Selected(selected) => {
            match selected.option_id.0.as_ref() {
                "allow_always" => PermissionManagerDecision::AllowAlways,
                "allow_once" => PermissionManagerDecision::AllowOnce,
                "reject_once" => PermissionManagerDecision::Rejected,
                _ => PermissionManagerDecision::Rejected, // Unknown option, treat as reject
            }
        }
        RequestPermissionOutcome::Cancelled => PermissionManagerDecision::Cancelled,
        // Handle any future variants (non_exhaustive enum)
        _ => PermissionManagerDecision::Cancelled,
    }
}

/// Format a title for the permission dialog based on tool name and input
///
/// Note: Prepared for future interactive permission dialog implementation.
#[allow(dead_code)]
fn format_tool_title(tool_name: &str, input: &serde_json::Value) -> String {
    // Strip mcp__acp__ prefix for display
    let display_name = tool_name.strip_prefix("mcp__acp__").unwrap_or(tool_name);

    match display_name {
        "Read" => {
            let path = input
                .get("file_path")
                .and_then(|v| v.as_str())
                .unwrap_or("file");
            format!("Read {}", path)
        }
        "Write" => {
            let path = input
                .get("file_path")
                .and_then(|v| v.as_str())
                .unwrap_or("file");
            format!("Write to {}", path)
        }
        "Edit" => {
            let path = input
                .get("file_path")
                .and_then(|v| v.as_str())
                .unwrap_or("file");
            format!("Edit {}", path)
        }
        "Bash" => {
            let cmd = input.get("command").and_then(|v| v.as_str()).unwrap_or("");
            let desc = input.get("description").and_then(|v| v.as_str());
            desc.map(String::from)
                .unwrap_or_else(|| format!("Run: {}", truncate_string(cmd, 50)))
        }
        _ => display_name.to_string(),
    }
}

/// Truncate a string to max length, adding "..." if truncated
///
/// Note: Prepared for future interactive permission dialog implementation.
#[allow(dead_code)]
fn truncate_string(s: &str, max_len: usize) -> String {
    if s.len() <= max_len {
        s.to_string()
    } else {
        format!("{}...", &s[..max_len.saturating_sub(3)])
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_format_tool_title_read() {
        let title = format_tool_title("Read", &serde_json::json!({"file_path": "/tmp/test.txt"}));
        assert_eq!(title, "Read /tmp/test.txt");
    }

    #[test]
    fn test_format_tool_title_edit() {
        let title = format_tool_title("Edit", &serde_json::json!({"file_path": "/tmp/file.txt"}));
        assert_eq!(title, "Edit /tmp/file.txt");
    }

    #[test]
    fn test_format_tool_title_mcp_prefix() {
        let title = format_tool_title(
            "mcp__acp__Read",
            &serde_json::json!({"file_path": "/tmp/test.txt"}),
        );
        assert_eq!(title, "Read /tmp/test.txt");
    }

    #[test]
    fn test_truncate_string() {
        assert_eq!(truncate_string("hello", 10), "hello");
        assert_eq!(truncate_string("hello world", 8), "hello...");
        assert_eq!(truncate_string("hi", 2), "hi");
    }

    #[test]
    fn test_parse_permission_response_selected() {
        // This would require constructing RequestPermissionOutcome
        // For now, just verify the function compiles
        let _ = parse_permission_response;
    }
}