//! BroadcastPoller background task.
//!
//! Polls each channel that has a webhook_url configured. On each tick (every 1s)
//! it checks which channels are due for a poll (elapsed >= webhook_poll_interval_secs)
//! and emits BroadcastTransition or NoSignal events when the current slot changes.

use std::collections::HashMap;
use std::sync::Arc;
use std::time::{Duration, Instant};

use chrono::Utc;
use tokio::sync::broadcast;
use tracing::error;
use uuid::Uuid;

use domain::{ChannelRepository, DomainError, DomainEvent, ScheduleEngineService};

/// Per-channel poller state.
#[derive(Debug)]
struct ChannelPollState {
    /// ID of the last slot we saw as current (None = no signal).
    last_slot_id: Option<Uuid>,
    /// Wall-clock instant of the last poll for this channel.
    last_checked: Instant,
}

/// Polls channels with webhook URLs and emits broadcast transition events.
pub async fn run_broadcast_poller(
    schedule_engine: Arc<ScheduleEngineService>,
    channel_repo: Arc<dyn ChannelRepository>,
    event_tx: broadcast::Sender<DomainEvent>,
) {
    let mut state: HashMap<Uuid, ChannelPollState> = HashMap::new();

    loop {
        tokio::time::sleep(Duration::from_secs(1)).await;
        poll_tick(&schedule_engine, &channel_repo, &event_tx, &mut state).await;
    }
}

pub(crate) async fn poll_tick(
    schedule_engine: &Arc<ScheduleEngineService>,
    channel_repo: &Arc<dyn ChannelRepository>,
    event_tx: &broadcast::Sender<DomainEvent>,
    state: &mut HashMap<Uuid, ChannelPollState>,
) {
    let channels = match channel_repo.find_all().await {
        Ok(c) => c,
        Err(e) => {
            error!("broadcast poller: failed to load channels: {}", e);
            return;
        }
    };

    // Remove deleted channels from state
    let live_ids: std::collections::HashSet<Uuid> = channels.iter().map(|c| c.id).collect();
    state.retain(|id, _| live_ids.contains(id));

    let now = Utc::now();

    for channel in channels {
        // Only poll channels with a configured webhook URL
        if channel.webhook_url.is_none() {
            state.remove(&channel.id);
            continue;
        }

        let poll_interval = Duration::from_secs(channel.webhook_poll_interval_secs as u64);

        let entry = state.entry(channel.id).or_insert_with(|| ChannelPollState {
            last_slot_id: None,
            last_checked: Instant::now() - poll_interval, // trigger immediately on first encounter
        });

        if entry.last_checked.elapsed() < poll_interval {
            continue; // Not yet due for a poll
        }

        entry.last_checked = Instant::now();

        // Find the current slot
        let current_slot_id = match schedule_engine.get_active_schedule(channel.id, now).await {
            Ok(Some(schedule)) => {
                schedule
                    .slots
                    .iter()
                    .find(|s| s.start_at <= now && now < s.end_at)
                    .map(|s| s.id)
            }
            Ok(None) => None,
            Err(DomainError::NoActiveSchedule(_)) => None,
            Err(DomainError::ChannelNotFound(_)) => {
                state.remove(&channel.id);
                continue;
            }
            Err(e) => {
                error!(
                    "broadcast poller: error checking schedule for channel {}: {}",
                    channel.id, e
                );
                continue;
            }
        };

        if current_slot_id == entry.last_slot_id {
            continue;
        }

        // State changed — emit appropriate event
        match &current_slot_id {
            Some(slot_id) => {
                if let Ok(Some(schedule)) = schedule_engine.get_active_schedule(channel.id, now).await {
                    if let Some(slot) = schedule.slots.iter().find(|s| s.id == *slot_id).cloned() {
                        let _ = event_tx.send(DomainEvent::BroadcastTransition {
                            channel_id: channel.id,
                            slot,
                        });
                    }
                }
            }
            None => {
                let _ = event_tx.send(DomainEvent::NoSignal {
                    channel_id: channel.id,
                });
            }
        }

        entry.last_slot_id = current_slot_id;
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::collections::HashMap;
    use std::sync::{Arc, Mutex};

    use async_trait::async_trait;
    use chrono::{DateTime, Duration, Utc};
    use domain::{
        Channel, ChannelRepository, Collection, DomainResult, GeneratedSchedule, IProviderRegistry,
        MediaFilter, MediaItem, MediaItemId, PlaybackRecord, ProviderCapabilities,
        ScheduleEngineService, ScheduleRepository, SeriesSummary, StreamQuality, StreamingProtocol,
    };
    use domain::value_objects::{ChannelId, ContentType, UserId};
    use tokio::sync::broadcast;
    use uuid::Uuid;

    // ── Mocks ─────────────────────────────────────────────────────────────────

    struct MockChannelRepo {
        channels: Vec<Channel>,
    }

    #[async_trait]
    impl ChannelRepository for MockChannelRepo {
        async fn find_by_id(&self, id: ChannelId) -> DomainResult<Option<Channel>> {
            Ok(self.channels.iter().find(|c| c.id == id).cloned())
        }
        async fn find_by_owner(&self, _owner_id: UserId) -> DomainResult<Vec<Channel>> {
            unimplemented!()
        }
        async fn find_all(&self) -> DomainResult<Vec<Channel>> {
            Ok(self.channels.clone())
        }
        async fn find_auto_schedule_enabled(&self) -> DomainResult<Vec<Channel>> {
            unimplemented!()
        }
        async fn save(&self, _channel: &Channel) -> DomainResult<()> {
            unimplemented!()
        }
        async fn delete(&self, _id: ChannelId) -> DomainResult<()> {
            unimplemented!()
        }
    }

    struct MockScheduleRepo {
        active: Option<GeneratedSchedule>,
        saved: Arc<Mutex<Vec<GeneratedSchedule>>>,
    }

    #[async_trait]
    impl ScheduleRepository for MockScheduleRepo {
        async fn find_active(
            &self,
            _channel_id: ChannelId,
            _at: DateTime<Utc>,
        ) -> DomainResult<Option<GeneratedSchedule>> {
            Ok(self.active.clone())
        }
        async fn find_latest(&self, _channel_id: ChannelId) -> DomainResult<Option<GeneratedSchedule>> {
            Ok(self.active.clone())
        }
        async fn save(&self, schedule: &GeneratedSchedule) -> DomainResult<()> {
            self.saved.lock().unwrap().push(schedule.clone());
            Ok(())
        }
        async fn find_playback_history(&self, _channel_id: ChannelId) -> DomainResult<Vec<PlaybackRecord>> {
            Ok(vec![])
        }
        async fn save_playback_record(&self, _record: &PlaybackRecord) -> DomainResult<()> {
            Ok(())
        }
    }

    struct MockRegistry;

    #[async_trait]
    impl IProviderRegistry for MockRegistry {
        async fn fetch_items(&self, _provider_id: &str, _filter: &MediaFilter) -> DomainResult<Vec<MediaItem>> {
            Ok(vec![])
        }
        async fn fetch_by_id(&self, _item_id: &MediaItemId) -> DomainResult<Option<MediaItem>> {
            Ok(None)
        }
        async fn get_stream_url(&self, _item_id: &MediaItemId, _quality: &StreamQuality) -> DomainResult<String> {
            unimplemented!()
        }
        fn provider_ids(&self) -> Vec<String> {
            vec![]
        }
        fn primary_id(&self) -> &str {
            ""
        }
        fn capabilities(&self, _provider_id: &str) -> Option<ProviderCapabilities> {
            None
        }
        async fn list_collections(&self, _provider_id: &str) -> DomainResult<Vec<Collection>> {
            unimplemented!()
        }
        async fn list_series(&self, _provider_id: &str, _collection_id: Option<&str>) -> DomainResult<Vec<SeriesSummary>> {
            unimplemented!()
        }
        async fn list_genres(&self, _provider_id: &str, _content_type: Option<&ContentType>) -> DomainResult<Vec<String>> {
            unimplemented!()
        }
    }

    // ── Helpers ───────────────────────────────────────────────────────────────

    fn make_channel_with_webhook(channel_id: Uuid) -> Channel {
        let mut ch = Channel::new(Uuid::new_v4(), "Test", "UTC");
        ch.id = channel_id;
        ch.webhook_url = Some("http://example.com/hook".to_string());
        ch.webhook_poll_interval_secs = 0; // always due
        ch
    }

    fn make_slot(channel_id: Uuid, slot_id: Uuid) -> domain::ScheduledSlot {
        use domain::entities::MediaItem;
        let now = Utc::now();
        domain::ScheduledSlot {
            id: slot_id,
            start_at: now - Duration::minutes(1),
            end_at: now + Duration::minutes(29),
            item: MediaItem {
                id: MediaItemId::new("test-item"),
                title: "Test Movie".to_string(),
                content_type: ContentType::Movie,
                duration_secs: 1800,
                description: None,
                genres: vec![],
                year: None,
                tags: vec![],
                series_name: None,
                season_number: None,
                episode_number: None,
            },
            source_block_id: Uuid::new_v4(),
        }
    }

    fn make_schedule(channel_id: Uuid, slots: Vec<domain::ScheduledSlot>) -> GeneratedSchedule {
        let now = Utc::now();
        GeneratedSchedule {
            id: Uuid::new_v4(),
            channel_id,
            valid_from: now - Duration::hours(1),
            valid_until: now + Duration::hours(47),
            generation: 1,
            slots,
        }
    }

    fn make_engine(
        channel_repo: Arc<dyn ChannelRepository>,
        schedule_repo: Arc<dyn ScheduleRepository>,
    ) -> Arc<ScheduleEngineService> {
        Arc::new(ScheduleEngineService::new(
            Arc::new(MockRegistry),
            channel_repo,
            schedule_repo,
        ))
    }

    // ── Tests ─────────────────────────────────────────────────────────────────

    #[tokio::test]
    async fn test_broadcast_transition_emitted_on_slot_change() {
        let channel_id = Uuid::new_v4();
        let slot_id = Uuid::new_v4();
        let ch = make_channel_with_webhook(channel_id);
        let slot = make_slot(channel_id, slot_id);
        let schedule = make_schedule(channel_id, vec![slot]);

        let channel_repo: Arc<dyn ChannelRepository> =
            Arc::new(MockChannelRepo { channels: vec![ch] });
        let schedule_repo: Arc<dyn ScheduleRepository> = Arc::new(MockScheduleRepo {
            active: Some(schedule),
            saved: Arc::new(Mutex::new(vec![])),
        });
        let engine = make_engine(channel_repo.clone(), schedule_repo);

        let (event_tx, mut event_rx) = broadcast::channel(8);
        let mut state: HashMap<Uuid, ChannelPollState> = HashMap::new();

        poll_tick(&engine, &channel_repo, &event_tx, &mut state).await;

        let event = event_rx.try_recv().expect("expected an event");
        match event {
            DomainEvent::BroadcastTransition { channel_id: cid, slot: s } => {
                assert_eq!(cid, channel_id);
                assert_eq!(s.id, slot_id);
            }
            other => panic!("expected BroadcastTransition, got something else"),
        }
    }

    #[tokio::test]
    async fn test_no_event_when_slot_unchanged() {
        let channel_id = Uuid::new_v4();
        let slot_id = Uuid::new_v4();
        let ch = make_channel_with_webhook(channel_id);
        let slot = make_slot(channel_id, slot_id);
        let schedule = make_schedule(channel_id, vec![slot]);

        let channel_repo: Arc<dyn ChannelRepository> =
            Arc::new(MockChannelRepo { channels: vec![ch] });
        let schedule_repo: Arc<dyn ScheduleRepository> = Arc::new(MockScheduleRepo {
            active: Some(schedule),
            saved: Arc::new(Mutex::new(vec![])),
        });
        let engine = make_engine(channel_repo.clone(), schedule_repo);

        let (event_tx, mut event_rx) = broadcast::channel(8);
        let mut state: HashMap<Uuid, ChannelPollState> = HashMap::new();

        // First tick — emits BroadcastTransition
        poll_tick(&engine, &channel_repo, &event_tx, &mut state).await;
        let _ = event_rx.try_recv();

        // Second tick — same slot, no event
        poll_tick(&engine, &channel_repo, &event_tx, &mut state).await;
        assert!(
            event_rx.try_recv().is_err(),
            "no event expected when slot unchanged"
        );
    }

    #[tokio::test]
    async fn test_no_signal_emitted_when_slot_goes_to_none() {
        let channel_id = Uuid::new_v4();
        let slot_id = Uuid::new_v4();
        let ch = make_channel_with_webhook(channel_id);
        let slot = make_slot(channel_id, slot_id);
        let schedule_with_slot = make_schedule(channel_id, vec![slot]);

        // Repo that starts with a slot then returns empty schedule
        use std::sync::atomic::{AtomicBool, Ordering};
        struct SwitchingScheduleRepo {
            first: GeneratedSchedule,
            second: GeneratedSchedule,
            called: AtomicBool,
        }
        #[async_trait]
        impl ScheduleRepository for SwitchingScheduleRepo {
            async fn find_active(
                &self,
                _channel_id: ChannelId,
                _at: DateTime<Utc>,
            ) -> DomainResult<Option<GeneratedSchedule>> {
                if self.called.swap(true, Ordering::SeqCst) {
                    Ok(Some(self.second.clone()))
                } else {
                    Ok(Some(self.first.clone()))
                }
            }
            async fn find_latest(&self, _: ChannelId) -> DomainResult<Option<GeneratedSchedule>> {
                Ok(None)
            }
            async fn save(&self, _: &GeneratedSchedule) -> DomainResult<()> { Ok(()) }
            async fn find_playback_history(&self, _: ChannelId) -> DomainResult<Vec<PlaybackRecord>> {
                Ok(vec![])
            }
            async fn save_playback_record(&self, _: &PlaybackRecord) -> DomainResult<()> { Ok(()) }
        }

        let now = Utc::now();
        let empty_schedule = GeneratedSchedule {
            id: Uuid::new_v4(),
            channel_id,
            valid_from: now - Duration::hours(1),
            valid_until: now + Duration::hours(47),
            generation: 2,
            slots: vec![], // no current slot
        };

        let channel_repo: Arc<dyn ChannelRepository> =
            Arc::new(MockChannelRepo { channels: vec![ch] });
        let schedule_repo: Arc<dyn ScheduleRepository> = Arc::new(SwitchingScheduleRepo {
            first: schedule_with_slot,
            second: empty_schedule,
            called: AtomicBool::new(false),
        });
        let engine = make_engine(channel_repo.clone(), schedule_repo);

        let (event_tx, mut event_rx) = broadcast::channel(8);
        let mut state: HashMap<Uuid, ChannelPollState> = HashMap::new();

        // First tick — emits BroadcastTransition (slot present)
        poll_tick(&engine, &channel_repo, &event_tx, &mut state).await;
        let _ = event_rx.try_recv();

        // Second tick — schedule has no current slot, emits NoSignal
        poll_tick(&engine, &channel_repo, &event_tx, &mut state).await;
        let event = event_rx.try_recv().expect("expected NoSignal event");
        match event {
            DomainEvent::NoSignal { channel_id: cid } => assert_eq!(cid, channel_id),
            _ => panic!("expected NoSignal"),
        }
    }
}