//! Lease storage for TTL-based key expiration
//!
//! Manages lease lifecycle: grant, revoke, refresh, expiration.

use chainfire_types::error::StorageError;
use chainfire_types::lease::{Lease, LeaseData, LeaseId};
use dashmap::DashMap;
use std::sync::atomic::{AtomicI64, Ordering};
use std::sync::Arc;
use std::time::Duration;
use tokio::sync::mpsc;
use tracing::{debug, info};

/// Store for managing leases
pub struct LeaseStore {
    /// Active leases: lease_id -> Lease
    leases: DashMap<LeaseId, Lease>,
    /// ID generator for new leases
    next_id: AtomicI64,
    /// Channel to notify of expired leases (lease_id, keys_to_delete)
    expiration_tx: Option<mpsc::UnboundedSender<(LeaseId, Vec<Vec<u8>>)>>,
}

impl LeaseStore {
    /// Create a new lease store
    pub fn new() -> Self {
        Self {
            leases: DashMap::new(),
            next_id: AtomicI64::new(1),
            expiration_tx: None,
        }
    }

    /// Set the expiration notification channel
    pub fn set_expiration_sender(&mut self, tx: mpsc::UnboundedSender<(LeaseId, Vec<Vec<u8>>)>) {
        self.expiration_tx = Some(tx);
    }

    /// Grant a new lease
    pub fn grant(&self, id: LeaseId, ttl: i64) -> Result<Lease, StorageError> {
        let lease_id = if id == 0 {
            self.next_id.fetch_add(1, Ordering::SeqCst)
        } else {
            // Check if ID is already in use
            if self.leases.contains_key(&id) {
                return Err(StorageError::LeaseError(format!("Lease {} already exists", id)));
            }
            // Update next_id if necessary
            let _ = self.next_id.fetch_max(id + 1, Ordering::SeqCst);
            id
        };

        let lease = Lease::new(lease_id, ttl);
        self.leases.insert(lease_id, lease.clone());

        debug!(lease_id, ttl, "Lease granted");
        Ok(lease)
    }

    /// Revoke a lease and return keys to delete
    pub fn revoke(&self, id: LeaseId) -> Result<Vec<Vec<u8>>, StorageError> {
        match self.leases.remove(&id) {
            Some((_, lease)) => {
                info!(lease_id = id, keys_count = lease.keys.len(), "Lease revoked");
                Ok(lease.keys)
            }
            None => Err(StorageError::LeaseError(format!("Lease {} not found", id))),
        }
    }

    /// Refresh a lease (keep-alive)
    pub fn refresh(&self, id: LeaseId) -> Result<i64, StorageError> {
        match self.leases.get_mut(&id) {
            Some(mut lease) => {
                lease.refresh();
                let ttl = lease.ttl;
                debug!(lease_id = id, ttl, "Lease refreshed");
                Ok(ttl)
            }
            None => Err(StorageError::LeaseError(format!("Lease {} not found", id))),
        }
    }

    /// Get a lease by ID
    pub fn get(&self, id: LeaseId) -> Option<Lease> {
        self.leases.get(&id).map(|l| l.clone())
    }

    /// Get remaining TTL for a lease
    pub fn time_to_live(&self, id: LeaseId) -> Option<(i64, i64, Vec<Vec<u8>>)> {
        self.leases.get(&id).map(|lease| {
            (lease.remaining(), lease.ttl, lease.keys.clone())
        })
    }

    /// List all lease IDs
    pub fn list(&self) -> Vec<LeaseId> {
        self.leases.iter().map(|entry| *entry.key()).collect()
    }

    /// Attach a key to a lease
    pub fn attach_key(&self, lease_id: LeaseId, key: Vec<u8>) -> Result<(), StorageError> {
        match self.leases.get_mut(&lease_id) {
            Some(mut lease) => {
                lease.attach_key(key);
                Ok(())
            }
            None => Err(StorageError::LeaseError(format!("Lease {} not found", lease_id))),
        }
    }

    /// Detach a key from a lease
    pub fn detach_key(&self, lease_id: LeaseId, key: &[u8]) {
        if let Some(mut lease) = self.leases.get_mut(&lease_id) {
            lease.detach_key(key);
        }
    }

    /// Check for expired leases and return their IDs and keys
    pub fn collect_expired(&self) -> Vec<(LeaseId, Vec<Vec<u8>>)> {
        let mut expired = Vec::new();

        for entry in self.leases.iter() {
            if entry.is_expired() {
                expired.push((*entry.key(), entry.keys.clone()));
            }
        }

        // Remove expired leases
        for (id, _) in &expired {
            self.leases.remove(id);
        }

        expired
    }

    /// Export all leases for snapshot
    pub fn export(&self) -> Vec<LeaseData> {
        self.leases
            .iter()
            .map(|entry| LeaseData::from_lease(&entry))
            .collect()
    }

    /// Import leases from snapshot
    pub fn import(&self, leases: Vec<LeaseData>) {
        self.leases.clear();
        for data in leases {
            let id = data.id;
            let lease = data.to_lease();
            self.leases.insert(id, lease);
            // Update next_id
            let _ = self.next_id.fetch_max(id + 1, Ordering::SeqCst);
        }
    }
}

impl Default for LeaseStore {
    fn default() -> Self {
        Self::new()
    }
}

/// Background worker that checks for expired leases
pub struct LeaseExpirationWorker {
    store: Arc<LeaseStore>,
    interval: Duration,
    shutdown_rx: mpsc::Receiver<()>,
}

impl LeaseExpirationWorker {
    /// Create a new expiration worker
    pub fn new(
        store: Arc<LeaseStore>,
        interval: Duration,
        shutdown_rx: mpsc::Receiver<()>,
    ) -> Self {
        Self {
            store,
            interval,
            shutdown_rx,
        }
    }

    /// Run the expiration worker
    pub async fn run(mut self, expire_callback: impl Fn(LeaseId, Vec<Vec<u8>>) + Send + 'static) {
        let mut interval = tokio::time::interval(self.interval);

        loop {
            tokio::select! {
                _ = interval.tick() => {
                    let expired = self.store.collect_expired();
                    for (lease_id, keys) in expired {
                        info!(lease_id, keys_count = keys.len(), "Lease expired");
                        expire_callback(lease_id, keys);
                    }
                }
                _ = self.shutdown_rx.recv() => {
                    info!("Lease expiration worker shutting down");
                    break;
                }
            }
        }
    }
}

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

    #[test]
    fn test_lease_grant() {
        let store = LeaseStore::new();
        let lease = store.grant(0, 10).unwrap();
        assert!(lease.id > 0);
        assert_eq!(lease.ttl, 10);
    }

    #[test]
    fn test_lease_grant_with_id() {
        let store = LeaseStore::new();
        let lease = store.grant(42, 10).unwrap();
        assert_eq!(lease.id, 42);
    }

    #[test]
    fn test_lease_revoke() {
        let store = LeaseStore::new();
        let lease = store.grant(0, 10).unwrap();
        let id = lease.id;

        // Attach some keys
        store.attach_key(id, b"key1".to_vec()).unwrap();
        store.attach_key(id, b"key2".to_vec()).unwrap();

        let keys = store.revoke(id).unwrap();
        assert_eq!(keys.len(), 2);

        // Lease should be gone
        assert!(store.get(id).is_none());
    }

    #[test]
    fn test_lease_refresh() {
        let store = LeaseStore::new();
        let lease = store.grant(0, 10).unwrap();
        let id = lease.id;

        let ttl = store.refresh(id).unwrap();
        assert_eq!(ttl, 10);
    }

    #[test]
    fn test_lease_list() {
        let store = LeaseStore::new();
        store.grant(1, 10).unwrap();
        store.grant(2, 10).unwrap();
        store.grant(3, 10).unwrap();

        let ids = store.list();
        assert_eq!(ids.len(), 3);
    }

    #[test]
    fn test_lease_attach_detach() {
        let store = LeaseStore::new();
        let lease = store.grant(0, 10).unwrap();
        let id = lease.id;

        store.attach_key(id, b"key1".to_vec()).unwrap();
        store.attach_key(id, b"key2".to_vec()).unwrap();

        let lease = store.get(id).unwrap();
        assert_eq!(lease.keys.len(), 2);

        store.detach_key(id, b"key1");
        let lease = store.get(id).unwrap();
        assert_eq!(lease.keys.len(), 1);
    }
}