use std::sync::Arc;

use tokio::sync::RwLock;
use tokio_util::either::Either;
use tokio_util::sync::CancellationToken;
use tokio_util::task::AbortOnDropHandle;

use crate::codex::Session;
use crate::codex::TurnContext;
use crate::error::CodexErr;
use crate::function_tool::FunctionCallError;
use crate::tools::context::SharedTurnDiffTracker;
use crate::tools::context::ToolPayload;
use crate::tools::router::ToolCall;
use crate::tools::router::ToolRouter;
use codex_protocol::models::FunctionCallOutputPayload;
use codex_protocol::models::ResponseInputItem;
use codex_utils_readiness::Readiness;

pub(crate) struct ToolCallRuntime {
    router: Arc<ToolRouter>,
    session: Arc<Session>,
    turn_context: Arc<TurnContext>,
    tracker: SharedTurnDiffTracker,
    parallel_execution: Arc<RwLock<()>>,
}

impl ToolCallRuntime {
    pub(crate) fn new(
        router: Arc<ToolRouter>,
        session: Arc<Session>,
        turn_context: Arc<TurnContext>,
        tracker: SharedTurnDiffTracker,
    ) -> Self {
        Self {
            router,
            session,
            turn_context,
            tracker,
            parallel_execution: Arc::new(RwLock::new(())),
        }
    }

    pub(crate) fn handle_tool_call(
        &self,
        call: ToolCall,
        cancellation_token: CancellationToken,
    ) -> impl std::future::Future<Output = Result<ResponseInputItem, CodexErr>> {
        let supports_parallel = self.router.tool_supports_parallel(&call.tool_name);

        let router = Arc::clone(&self.router);
        let session = Arc::clone(&self.session);
        let turn = Arc::clone(&self.turn_context);
        let tracker = Arc::clone(&self.tracker);
        let lock = Arc::clone(&self.parallel_execution);
        let aborted_response = Self::aborted_response(&call);
        let readiness = self.turn_context.tool_call_gate.clone();

        let handle: AbortOnDropHandle<Result<ResponseInputItem, FunctionCallError>> =
            AbortOnDropHandle::new(tokio::spawn(async move {
                tokio::select! {
                    _ = cancellation_token.cancelled() => Ok(aborted_response),
                    res = async {
                        tracing::info!("waiting for tool gate");
                        readiness.wait_ready().await;
                        tracing::info!("tool gate released");
                        let _guard = if supports_parallel {
                            Either::Left(lock.read().await)
                        } else {
                            Either::Right(lock.write().await)
                        };

                        router
                            .dispatch_tool_call(session, turn, tracker, call)
                            .await
                    } => res,
                }
            }));

        async move {
            match handle.await {
                Ok(Ok(response)) => Ok(response),
                Ok(Err(FunctionCallError::Fatal(message))) => Err(CodexErr::Fatal(message)),
                Ok(Err(other)) => Err(CodexErr::Fatal(other.to_string())),
                Err(err) => Err(CodexErr::Fatal(format!(
                    "tool task failed to receive: {err:?}"
                ))),
            }
        }
    }
}

impl ToolCallRuntime {
    fn aborted_response(call: &ToolCall) -> ResponseInputItem {
        match &call.payload {
            ToolPayload::Custom { .. } => ResponseInputItem::CustomToolCallOutput {
                call_id: call.call_id.clone(),
                output: "aborted".to_string(),
            },
            ToolPayload::Mcp { .. } => ResponseInputItem::McpToolCallOutput {
                call_id: call.call_id.clone(),
                result: Err("aborted".to_string()),
            },
            _ => ResponseInputItem::FunctionCallOutput {
                call_id: call.call_id.clone(),
                output: FunctionCallOutputPayload {
                    content: "aborted".to_string(),
                    success: None,
                },
            },
        }
    }
}