use chrono::Utc;
use dashmap::DashSet;
use db::database::AppDatabase;
use models::rooms::room;
use queue::{AgentTaskEvent, MessageProducer};
use sea_orm::EntityTrait;
use std::sync::Arc;
use std::sync::OnceLock;
use uuid::Uuid;

use crate::connection::{make_persist_fn, RoomConnectionManager};

/// Tracks rooms for which NATS subscriptions have already been spawned.
static SPAWNED_ROOMS: OnceLock<DashSet<Uuid>> = OnceLock::new();

/// Remove a room from the spawned set (called on room shutdown).
pub fn unmark_room_spawned(room_id: Uuid) {
    if let Some(set) = SPAWNED_ROOMS.get() {
        set.remove(&room_id);
    }
}

pub async fn spawn_agent_task<F, Fut>(
    project_id: Uuid,
    agent_type: models::agent_task::AgentType,
    input: String,
    task_service: Arc<agent::TaskService>,
    queue: MessageProducer,
    room_manager: Arc<RoomConnectionManager>,
    worker_semaphore: Arc<tokio::sync::Semaphore>,
    execute: F,
) -> anyhow::Result<i64>
where
    F: FnOnce(i64, Arc<agent::TaskService>) -> Fut + Send + 'static,
    Fut: std::future::Future<Output = Result<String, String>> + Send,
{
    let task = task_service
        .create(project_id, input, agent_type)
        .await
        .map_err(|e| anyhow::anyhow!("create task failed: {}", e))?;
    let task_id = task.id;

    let started_event = AgentTaskEvent {
        task_id,
        project_id,
        parent_id: task.parent_id,
        event: "started".to_string(),
        message: None,
        output: None,
        error: None,
        status: models::agent_task::TaskStatus::Running.to_string(),
        timestamp: Utc::now(),
    };
    queue
        .publish_agent_task_event(project_id, started_event)
        .await;

    if let Err(e) = task_service.start(task_id).await {
        tracing::warn!(error = %e, task_id = %task_id, "AI task start failed");
    }

    let queue_clone = queue.clone();
    let room_manager_clone = room_manager.clone();
    let semaphore = worker_semaphore.clone();

    tokio::spawn(async move {
        let Ok(_permit) = semaphore.acquire().await else {
            tracing::warn!(task_id = %task_id, "semaphore closed, skipping task");
            return;
        };

        let result = execute(task_id, task_service.clone()).await;

        let event = match result {
            Ok(output) => {
                if let Err(e) = task_service.complete(task_id, &output).await {
                    tracing::warn!(error = %e, task_id = %task_id, "AI task complete failed");
                }
                AgentTaskEvent {
                    task_id,
                    project_id,
                    parent_id: None,
                    event: "done".to_string(),
                    message: None,
                    output: Some(output),
                    error: None,
                    status: models::agent_task::TaskStatus::Done.to_string(),
                    timestamp: chrono::Utc::now(),
                }
            }
            Err(err) => {
                if let Err(e) = task_service.fail(task_id, &err).await {
                    tracing::warn!(error = %e, task_id = %task_id, "AI task fail failed");
                }
                AgentTaskEvent {
                    task_id,
                    project_id,
                    parent_id: None,
                    event: "failed".to_string(),
                    message: None,
                    output: None,
                    error: Some(err),
                    status: models::agent_task::TaskStatus::Failed.to_string(),
                    timestamp: chrono::Utc::now(),
                }
            }
        };

        queue_clone
            .publish_agent_task_event(project_id, event.clone())
            .await;
        room_manager_clone
            .broadcast_agent_task(project_id, event)
            .await;
        tracing::info!(task_id = task_id, project_id = %project_id, "agent task finished");
    });

    Ok(task_id)
}

/// Spawns per-room workers: NATS subscribe tasks + optional JetStream consumer.
/// Replaces the old Redis Streams + Redis Pub/Sub workers.
pub fn spawn_room_workers(
    room_id: uuid::Uuid,
    db: AppDatabase,
    room_manager: Arc<RoomConnectionManager>,
    _queue: MessageProducer,
    nats: Option<Arc<queue::NatsClient>>,
    worker_semaphore: Arc<tokio::sync::Semaphore>,
    embed_service: Option<Arc<agent::embed::EmbedService>>,
) {
    if !SPAWNED_ROOMS.get_or_init(DashSet::new).insert(room_id) {
        return;
    }
    let dedup_cache = Arc::new(dashmap::DashMap::with_capacity_and_hasher(
        10000,
        Default::default(),
    ));
    let persist_fn = make_persist_fn(
        db.clone(),
        room_manager.metrics.clone(),
        dedup_cache,
        embed_service.clone(),
    );
    let db1 = db.clone();
    let db2 = db.clone();
    let manager1 = room_manager.clone();
    let manager2 = room_manager.clone();
    let manager3 = room_manager.clone();
    let manager4 = room_manager.clone();
    let manager5 = room_manager.clone();
    let semaphore = worker_semaphore.clone();

    // JetStream consumer for message persistence (only if NATS available)
    if let Some(nats) = nats.clone() {
        let nats_consumer = nats.clone();
        let persist_fn = persist_fn.clone();
        tokio::spawn(async move {
            let Ok(_permit) = semaphore.acquire_owned().await else {
                return;
            };
            let shutdown_rx = manager1.register_room(room_id).await;
            queue::room_worker_task(room_id, nats_consumer, persist_fn, shutdown_rx).await;
        });
    }

    // Room message broadcast subscriber
    if let Some(nats) = nats.clone() {
        tokio::spawn(async move {
            let shutdown_rx = manager2.register_room(room_id).await;
            crate::connection::subscribe_room_events(nats, manager2, room_id, shutdown_rx).await;
        });
    }

    // Project-level event subscriber
    if let Some(nats) = nats.clone() {
        tokio::spawn(async move {
            let project_id = match room::Entity::find_by_id(room_id)
                .one(&db1)
                .await
                .ok()
                .flatten()
            {
                Some(r) => r.project,
                None => return,
            };
            let shutdown_rx = manager3.register_project(project_id).await;
            crate::connection::subscribe_project_room_events(
                nats,
                manager3,
                project_id,
                shutdown_rx,
            )
            .await;
        });
    }

    // Agent task event subscriber
    if let Some(nats) = nats.clone() {
        tokio::spawn(async move {
            let project_id = match room::Entity::find_by_id(room_id)
                .one(&db2)
                .await
                .ok()
                .flatten()
            {
                Some(r) => r.project,
                None => return,
            };
            let shutdown_rx = manager5.register_project(project_id).await;
            crate::connection::subscribe_task_events_fn(nats, manager5, project_id, shutdown_rx)
                .await;
        });
    }

    // Stream chunk subscriber
    if let Some(nats) = nats {
        tokio::spawn(async move {
            let shutdown_rx = manager4.register_room(room_id).await;
            crate::connection::subscribe_room_stream_chunk_events(
                nats,
                manager4,
                room_id,
                shutdown_rx,
            )
            .await;
        });
    }
}