//! PlaylistManager : gestionnaire singleton central de toutes les playlists

use crate::handle::{ReadHandle, WriteHandle};
use crate::persistence::PersistenceManager;
use crate::playlist::core::PlaylistConfig;
use crate::playlist::Playlist;
use crate::Result;
use pmocache::{CacheBroadcastEvent, CacheSubscription};
use once_cell::sync::OnceCell;
use std::collections::HashMap;
use std::path::PathBuf;
use std::sync::{Arc, atomic::{AtomicU64, Ordering}};
use std::time::Duration;
use tokio::sync::RwLock;
use tokio::sync::broadcast;
use std::sync::RwLock as StdRwLock;

/// Singleton PlaylistManager
static PLAYLIST_MANAGER: OnceCell<PlaylistManager> = OnceCell::new();

/// Registre global du cache audio
static AUDIO_CACHE: OnceCell<Arc<pmoaudiocache::Cache>> = OnceCell::new();

/// Structure interne du manager
struct ManagerInner {
    playlists: RwLock<HashMap<String, Arc<Playlist>>>,
    persistence: Option<Arc<PersistenceManager>>,
    callbacks: StdRwLock<HashMap<u64, Arc<dyn Fn(&PlaylistEvent) + Send + Sync>>>,
    cb_counter: AtomicU64,
    track_index: StdRwLock<HashMap<String, Vec<String>>>, // cache_pk -> playlists
    cache_subscriptions: StdRwLock<HashMap<String, CacheSubscription>>,
    event_tx: broadcast::Sender<PlaylistEventEnvelope>,
}

/// Type d'évènement émis par le PlaylistManager.
#[derive(Debug, Clone)]
pub struct PlaylistEvent {
    pub playlist_id: String,
    pub kind: PlaylistEventKind,
}

/// Variantes d'évènements playlist.
#[derive(Debug, Clone)]
pub enum PlaylistEventKind {
    /// La playlist a été modifiée (ajout/suppression/changement de config).
    Updated,
    /// Un morceau référencé par la playlist a été servi par le cache audio.
    TrackPlayed { cache_pk: String, qualifier: String },
}

/// Evènement enrichi pour diffusion (timestamp + source client éventuel).
#[derive(Debug, Clone)]
pub struct PlaylistEventEnvelope {
    pub event: PlaylistEvent,
    pub timestamp: std::time::SystemTime,
    pub source_client: Option<String>,
}

/// Gestionnaire central de playlists
pub struct PlaylistManager {
    inner: Arc<ManagerInner>,
}

impl PlaylistManager {
    /// Initialise le gestionnaire (� appeler une seule fois au d�marrage)
    fn init(db_path: PathBuf) -> Result<Self> {
        // Initialiser la persistance
        let persistence = Arc::new(PersistenceManager::new(&db_path)?);

        // Lancer la consolidation en arrière-plan
        let persistence_clone = persistence.clone();
        tokio::spawn(async move {
            if let Err(e) = persistence_clone.consolidate().await {
                tracing::warn!("Failed to consolidate playlist database on startup: {}", e);
            }
        });

        let manager = Self {
            inner: Arc::new(ManagerInner {
                playlists: RwLock::new(HashMap::new()),
                persistence: Some(persistence.clone()),
                callbacks: StdRwLock::new(HashMap::new()),
                cb_counter: AtomicU64::new(1),
                track_index: StdRwLock::new(HashMap::new()),
                cache_subscriptions: StdRwLock::new(HashMap::new()),
                event_tx: broadcast::channel(256).0,
            }),
        };

        // Lancer la task d'�viction en background
        let manager_clone = manager.clone();
        tokio::spawn(async move {
            manager_clone.eviction_task().await;
        });

        Ok(manager)
    }

    /// Initialise avec la configuration de pmoconfig
    #[cfg(feature = "pmoconfig")]
    fn init_with_config() -> Result<Self> {
        use crate::config_ext::PlaylistConfigExt;

        let config = pmoconfig::get_config();
        let db_path = config.playlist_db_path();

        Self::init(db_path)
    }

    /// Retourne le singleton
    pub fn get() -> &'static PlaylistManager {
        #[cfg(feature = "pmoconfig")]
        {
            PLAYLIST_MANAGER.get_or_init(|| {
                Self::init_with_config().expect("Failed to initialize PlaylistManager")
            })
        }

        #[cfg(not(feature = "pmoconfig"))]
        {
            PLAYLIST_MANAGER
                .get()
                .expect("PlaylistManager not initialized. Call init() first.")
        }
    }

    /// Cr�e une playlist persistante (erreur si existe d�j�)
    pub async fn create_persistent_playlist(&self, id: String) -> Result<WriteHandle> {
        let mut playlists = self.inner.playlists.write().await;

        if playlists.contains_key(&id) {
            return Err(crate::Error::PlaylistAlreadyExists(id));
        }

        let playlist = Arc::new(Playlist::new(
            id.clone(),
            id.clone(), // Titre = id par d�faut
            PlaylistConfig::default(),
            true, // persistent
        ));

        // Acqu�rir le write lock
        let write_token = playlist
            .acquire_write_lock()
            .await
            .map_err(|_| crate::Error::WriteLockHeld(id.clone()))?;

        playlists.insert(id.clone(), playlist.clone());
        drop(playlists);

        // Sauvegarder la structure vide
        if let Some(persistence) = &self.inner.persistence {
            let title = playlist.title().await;
            let core = playlist.core.read().await;
            persistence
                .save_playlist(&playlist.id, &title, &core.config, &core.tracks)
                .await?;
        }

        Ok(WriteHandle::new(playlist, write_token))
    }

    /// Enregistre un callback d'évènement playlist (update, track joué).
    ///
    /// Retourne un jeton (u64) pour désenregistrer plus tard.
    pub fn register_callback<F>(&self, cb: F) -> u64
    where
        F: Fn(&PlaylistEvent) + Send + Sync + 'static,
    {
        let token = self.inner.cb_counter.fetch_add(1, Ordering::Relaxed);
        let mut guard = self.inner.callbacks.write().unwrap();
        guard.insert(token, Arc::new(cb));
        token
    }

    /// Désenregistre un callback via son jeton.
    pub fn unregister_callback(&self, token: u64) {
        let mut guard = self.inner.callbacks.write().unwrap();
        guard.remove(&token);
    }

    /// Notifie tous les callbacks qu'une playlist a changé.
    pub(crate) fn notify_playlist_changed(&self, id: &str) {
        self.notify_playlist_event(
            id,
            PlaylistEventKind::Updated,
        );
    }

    /// Notifie les callbacks qu'un morceau a été joué pour une playlist donnée.
    pub(crate) fn notify_playlist_track_played(&self, playlist_id: &str, cache_pk: &str, qualifier: &str) {
        self.notify_playlist_event(
            playlist_id,
            PlaylistEventKind::TrackPlayed {
                cache_pk: cache_pk.to_string(),
                qualifier: qualifier.to_string(),
            },
        );
    }

    fn notify_playlist_event(&self, id: &str, kind: PlaylistEventKind) {
        let event = PlaylistEvent {
            playlist_id: id.to_string(),
            kind,
        };
        let envelope = PlaylistEventEnvelope {
            event: event.clone(),
            timestamp: std::time::SystemTime::now(),
            source_client: None,
        };

        let guard = self.inner.callbacks.read().unwrap();
        for cb in guard.values() {
            cb(&event);
        }

        // Diffusion via canal interne (ignoré si aucun abonné)
        let _ = self.inner.event_tx.send(envelope);
    }

    /// Ré-inscrit les abonnements cache pour tous les pk connus (utilisé au boot ou après enregistrement du cache audio).
    async fn sync_cache_subscriptions(&self) {
        let pks: Vec<String> = {
            let index = self.inner.track_index.read().unwrap();
            index.keys().cloned().collect()
        };

        if pks.is_empty() {
            return;
        }

        if let Ok(cache) = audio_cache() {
            for pk in pks {
                // Ne pas doubler les abonnements
                let already = {
                    let subs = self.inner.cache_subscriptions.read().unwrap();
                    subs.contains_key(&pk)
                };
                if already {
                    continue;
                }

                let manager = self.clone();
                let token = cache
                    .subscribe_broadcast(pk.clone(), move |event: &CacheBroadcastEvent| {
                        manager.handle_cache_broadcast(event);
                        let index = manager.inner.track_index.read().unwrap();
                        index.contains_key(&event.pk)
                    })
                    .await;

                self.inner
                    .cache_subscriptions
                    .write()
                    .unwrap()
                    .insert(pk, token);
            }
        }
    }

    /// Réconcilie l'index pk→playlists et les souscriptions cache pour une playlist donnée.
    pub(crate) async fn rebuild_track_index(
        &self,
        playlist_id: &str,
        records: &[Arc<crate::playlist::record::Record>],
    ) {
        // 1) Retirer la playlist de toutes les entrées
        let mut removed_pks = Vec::new();
        {
            let mut index = self.inner.track_index.write().unwrap();
            for (pk, playlists) in index.iter_mut() {
                playlists.retain(|p| p != playlist_id);
                if playlists.is_empty() {
                    removed_pks.push(pk.clone());
                }
            }
            for pk in &removed_pks {
                index.remove(pk);
            }
            // 2) Ajouter les nouveaux records
            for record in records {
                let entry = index.entry(record.cache_pk.clone()).or_default();
                if !entry.iter().any(|p| p == playlist_id) {
                    entry.push(playlist_id.to_string());
                }
            }
        }

        // 3) Se désabonner des pk qui ne sont plus référencés
        // Collecter les tokens à désinscrire sans bloquer pendant l'await
        let removed_tokens: Vec<CacheSubscription> = {
            if removed_pks.is_empty() {
                Vec::new()
            } else {
                let mut subs = self.inner.cache_subscriptions.write().unwrap();
                removed_pks
                    .into_iter()
                    .filter_map(|pk| subs.remove(&pk))
                    .collect()
            }
        };

        if !removed_tokens.is_empty() {
            if let Ok(cache) = audio_cache() {
                for token in removed_tokens {
                    cache.unsubscribe_broadcast(&token).await;
                }
            }
        }

        // 4) S'abonner aux nouveaux pk sans souscription
        let missing: Vec<String> = {
            let index = self.inner.track_index.read().unwrap();
            let subs = self.inner.cache_subscriptions.read().unwrap();
            index
                .iter()
                .filter_map(|(pk, playlists)| {
                    if playlists.contains(&playlist_id.to_string()) && !subs.contains_key(pk) {
                        Some(pk.clone())
                    } else {
                        None
                    }
                })
                .collect()
        };

        if !missing.is_empty() {
            if let Ok(cache) = audio_cache() {
                for pk in missing {
                    let manager = self.clone();
                    let token = cache
                        .subscribe_broadcast(pk.clone(), move |event: &CacheBroadcastEvent| {
                            manager.handle_cache_broadcast(event);
                            // Garder l'abonnement tant que le pk est référencé
                            let index = manager.inner.track_index.read().unwrap();
                            index.contains_key(&event.pk)
                        })
                        .await;
                    self.inner
                        .cache_subscriptions
                        .write()
                        .unwrap()
                        .insert(pk, token);
                }
            }
        }
    }

    fn handle_cache_broadcast(&self, event: &CacheBroadcastEvent) {
        let playlists = {
            let index = self.inner.track_index.read().unwrap();
            index.get(&event.pk).cloned()
        };

        if let Some(playlists) = playlists {
            for playlist_id in playlists {
                self.notify_playlist_track_played(&playlist_id, &event.pk, &event.qualifier);
            }
        }
    }

    /// R�cup�re un write handle (cr�e �ph�m�re si n'existe pas)
    pub async fn get_write_handle(&self, id: String) -> Result<WriteHandle> {
        let mut playlists = self.inner.playlists.write().await;

        if let Some(playlist) = playlists.get(&id) {
            // Playlist existe, tenter d'acqu�rir le lock
            let write_token = playlist
                .acquire_write_lock()
                .await
                .map_err(|_| crate::Error::WriteLockHeld(id.clone()))?;

            return Ok(WriteHandle::new(playlist.clone(), write_token));
        }

        // N'existe pas, cr�er �ph�m�re
        let playlist = Arc::new(Playlist::new(
            id.clone(),
            id.clone(),
            PlaylistConfig::default(),
            false, // �ph�m�re
        ));

        let write_token = playlist
            .acquire_write_lock()
            .await
            .map_err(|_| crate::Error::WriteLockHeld(id.clone()))?;

        playlists.insert(id, playlist.clone());
        drop(playlists);

        Ok(WriteHandle::new(playlist, write_token))
    }

    /// R�cup�re un write handle persistant (cr�e si n'existe pas)
    pub async fn get_persistent_write_handle(&self, id: String) -> Result<WriteHandle> {
        let playlists = self.inner.playlists.read().await;

        if let Some(playlist) = playlists.get(&id) {
            // Playlist existe en mémoire
            if !playlist.persistent {
                return Err(crate::Error::PlaylistNotPersistent(id));
            }

            let write_token = playlist
                .acquire_write_lock()
                .await
                .map_err(|_| crate::Error::WriteLockHeld(id.clone()))?;

            return Ok(WriteHandle::new(playlist.clone(), write_token));
        }

        drop(playlists);

        // Pas en mémoire, essayer de charger depuis la DB
        if let Some(persistence) = &self.inner.persistence {
            if let Some((title, config, tracks)) = persistence.load_playlist(&id).await? {
                // Reconstruire la playlist
                let mut playlists = self.inner.playlists.write().await;

                let playlist = Arc::new(Playlist::new(id.clone(), title.clone(), config, true));

                // Restaurer les tracks
                {
                    let mut core = playlist.core.write().await;
                    core.tracks = tracks;
                    let snapshot = core.snapshot();
                    drop(core);
                    self.rebuild_track_index(&id, &snapshot).await;
                }

                // Acquérir le write lock
                let write_token = playlist
                    .acquire_write_lock()
                    .await
                    .map_err(|_| crate::Error::WriteLockHeld(id.clone()))?;

                playlists.insert(id.clone(), playlist.clone());
                drop(playlists);

                return Ok(WriteHandle::new(playlist, write_token));
            }
        }

        // N'existe pas en DB, créer une nouvelle playlist persistante
        self.create_persistent_playlist(id).await
    }

    /// R�cup�re un read handle (ressuscite depuis DB si besoin)
    pub async fn get_read_handle(&self, id: &str) -> Result<ReadHandle> {
        let playlists = self.inner.playlists.read().await;

        if let Some(playlist) = playlists.get(id) {
            if !playlist.is_alive() {
                return Err(crate::Error::PlaylistDeleted(id.to_string()));
            }
            return Ok(ReadHandle::new(playlist.clone()));
        }

        drop(playlists);

        // Pas en m�moire, essayer de ressusciter depuis la DB
        if let Some(persistence) = &self.inner.persistence {
            if let Some((title, config, tracks)) = persistence.load_playlist(id).await? {
                // Reconstruire la playlist
                let mut playlists = self.inner.playlists.write().await;

                let playlist = Arc::new(Playlist::new(id.to_string(), title.clone(), config, true));

                // Restaurer les tracks
                {
                    let mut core = playlist.core.write().await;
                    core.tracks = tracks;
                    let snapshot = core.snapshot();
                    drop(core);
                    self.rebuild_track_index(id, &snapshot).await;
                }

                playlists.insert(id.to_string(), playlist.clone());
                drop(playlists);

                return Ok(ReadHandle::new(playlist));
            }
        }

        Err(crate::Error::PlaylistNotFound(id.to_string()))
    }

    /// Supprime une playlist d�finitivement
    pub async fn delete_playlist(&self, id: &str) -> Result<()> {
        let mut playlists = self.inner.playlists.write().await;

        if let Some(playlist) = playlists.remove(id) {
            playlist.mark_deleted();
        }

        drop(playlists);

        // Nettoyer l'index et les souscriptions
        self.rebuild_track_index(id, &[]).await;

        // Supprimer de la DB
        if let Some(persistence) = &self.inner.persistence {
            persistence.delete_playlist(id).await?;
        }

        Ok(())
    }

    /// Liste toutes les playlists
    pub async fn list_playlists(&self) -> Vec<String> {
        let playlists = self.inner.playlists.read().await;
        playlists.keys().cloned().collect()
    }

    /// V�rifie si une playlist existe
    pub async fn exists(&self, id: &str) -> bool {
        self.inner.playlists.read().await.contains_key(id)
    }

    /// Retourne la r�f�rence au PersistenceManager
    pub(crate) fn persistence(&self) -> Option<&Arc<PersistenceManager>> {
        self.inner.persistence.as_ref()
    }

    /// Task d'�viction en background
    async fn eviction_task(&self) {
        loop {
            tokio::time::sleep(Duration::from_secs(5)).await;

            let playlists = self.inner.playlists.read().await;

            for playlist in playlists.values() {
                if !playlist.is_alive() {
                    continue;
                }

                let mut core = playlist.core.write().await;
                let initial_len = core.len();
                core.evict();
                let new_len = core.len();
                drop(core);

                // Si des morceaux ont �t� �vict�s et la playlist est persistante
                if new_len < initial_len && playlist.persistent {
                    if let Some(persistence) = &self.inner.persistence {
                        let title = playlist.title().await;
                        let core = playlist.core.read().await;
                        let _ = persistence
                            .save_playlist(&playlist.id, &title, &core.config, &core.tracks)
                            .await;
                    }
                }
            }
        }
    }

    fn clone(&self) -> Self {
        Self {
            inner: self.inner.clone(),
        }
    }
}

/// Souscrit au flux d'évènements playlist (Updated / TrackPlayed) avec timestamp.
pub fn subscribe_events() -> broadcast::Receiver<PlaylistEventEnvelope> {
    PlaylistManager::get().inner.event_tx.subscribe()
}

/// Helper pour supprimer une playlist (appel� depuis WriteHandle)
pub(crate) async fn delete_playlist_internal(id: &str) -> Result<()> {
    PlaylistManager::get().delete_playlist(id).await
}

/// Enregistre le cache audio global
///
/// Cette fonction doit être appelée au démarrage de l'application
/// pour rendre le cache audio disponible au PlaylistManager.
///
/// # Examples
///
/// ```rust,ignore
/// use pmoplaylist::register_audio_cache;
/// use pmoaudiocache::Cache as AudioCache;
/// use std::sync::Arc;
///
/// let audio_cache = Arc::new(AudioCache::new("./cache", 1000)?);
/// register_audio_cache(audio_cache);
/// ```
pub fn register_audio_cache(cache: Arc<pmoaudiocache::Cache>) {
    let _ = AUDIO_CACHE.set(cache);

    // Si le PlaylistManager est déjà initialisé, synchroniser les abonnements
    if let Some(manager) = PLAYLIST_MANAGER.get() {
        let manager = manager.clone();
        tokio::spawn(async move {
            manager.sync_cache_subscriptions().await;
        });
    }
}

/// Helper pour acc�der au cache audio
pub(crate) fn audio_cache() -> Result<Arc<pmoaudiocache::Cache>> {
    AUDIO_CACHE
        .get()
        .cloned()
        .or_else(|| {
            // Fallback: essayer le registre global de pmoaudiocache
            pmoaudiocache::get_audio_cache()
        })
        .ok_or_else(|| crate::Error::ManagerNotInitialized)
}

/// Fonction raccourcie pour acc�der au singleton
pub fn PlaylistManager() -> &'static PlaylistManager {
    PlaylistManager::get()
}