//! Persistence traits for data and routing table.
//!
//! The library defines the traits; applications
//! implement backends (SQLite, file, etc).

use crate::error::Error;
use crate::id::NodeId;
use std::net::SocketAddr;

/// Stored value record for persistence.
#[derive(Debug, Clone)]
pub struct StoredRecord {
    pub key: Vec<u8>,
    pub value: Vec<u8>,
    pub target_id: NodeId,
    pub source: NodeId,
    pub ttl: u16,
    pub is_unique: bool,
}

/// Contact record for routing table persistence.
#[derive(Debug, Clone)]
pub struct ContactRecord {
    pub id: NodeId,
    pub addr: SocketAddr,
}

/// Trait for persisting DHT stored values.
///
/// Implement this to survive restarts. The library
/// calls `save` periodically and `load` on startup.
pub trait DataPersistence {
    /// Save all stored values.
    fn save(&self, records: &[StoredRecord]) -> Result<(), Error>;

    /// Load previously saved values.
    fn load(&self) -> Result<Vec<StoredRecord>, Error>;
}

/// Trait for persisting the routing table.
///
/// Implement this for fast re-bootstrap after restart.
pub trait RoutingPersistence {
    /// Save known contacts.
    fn save_contacts(&self, contacts: &[ContactRecord]) -> Result<(), Error>;

    /// Load previously saved contacts.
    fn load_contacts(&self) -> Result<Vec<ContactRecord>, Error>;
}

/// No-op persistence (default — no persistence).
pub struct NoPersistence;

impl DataPersistence for NoPersistence {
    fn save(&self, _records: &[StoredRecord]) -> Result<(), Error> {
        Ok(())
    }
    fn load(&self) -> Result<Vec<StoredRecord>, Error> {
        Ok(Vec::new())
    }
}

impl RoutingPersistence for NoPersistence {
    fn save_contacts(&self, _contacts: &[ContactRecord]) -> Result<(), Error> {
        Ok(())
    }
    fn load_contacts(&self) -> Result<Vec<ContactRecord>, Error> {
        Ok(Vec::new())
    }
}

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

    #[test]
    fn no_persistence_save_load() {
        let p = NoPersistence;
        assert!(p.save(&[]).is_ok());
        assert!(p.load().unwrap().is_empty());
        assert!(p.save_contacts(&[]).is_ok());
        assert!(p.load_contacts().unwrap().is_empty());
    }
}