//! Type-safe WAL wrapper.
//!
//! [`TypedWal`] wraps a [`WalManager`] and ensures that only records of type `R`
//! can be written. This prevents accidentally mixing record types (e.g., LPG
//! and RDF) in the same WAL instance.
//!
//! Use [`LpgWal`] for the standard labeled property graph WAL.

use std::marker::PhantomData;
use std::path::{Path, PathBuf};

use grafeo_common::types::EpochId;
use grafeo_common::types::TransactionId;
use grafeo_common::utils::error::{Error, Result};

use super::WalRecord;
use super::log::{CheckpointMetadata, DurabilityMode, WalConfig, WalManager};
use super::record::WalEntry;

/// A type-safe wrapper around [`WalManager`] that constrains record types
/// at compile time.
///
/// `TypedWal<R>` ensures that only records implementing [`WalEntry`] with
/// the specific type `R` can be logged. This prevents accidentally writing
/// the wrong record type to a WAL instance.
///
/// # Example
///
/// ```no_run
/// use grafeo_adapters::storage::wal::{LpgWal, WalRecord};
/// use grafeo_common::types::NodeId;
///
/// # fn main() -> grafeo_common::utils::error::Result<()> {
/// let wal = LpgWal::open("wal_dir")?;
/// wal.log(&WalRecord::CreateNode {
///     id: NodeId::new(1),
///     labels: vec!["Person".to_string()],
/// })?;
/// # Ok(())
/// # }
/// ```
pub struct TypedWal<R: WalEntry> {
    manager: WalManager,
    _record: PhantomData<R>,
}

impl<R: WalEntry> TypedWal<R> {
    /// Opens or creates a typed WAL in the given directory.
    ///
    /// # Errors
    ///
    /// Returns an error if the directory cannot be created or accessed.
    pub fn open(dir: impl AsRef<Path>) -> Result<Self> {
        Ok(Self {
            manager: WalManager::open(dir)?,
            _record: PhantomData,
        })
    }

    /// Opens or creates a typed WAL with custom configuration.
    ///
    /// # Errors
    ///
    /// Returns an error if the directory cannot be created or accessed.
    pub fn with_config(dir: impl AsRef<Path>, config: WalConfig) -> Result<Self> {
        Ok(Self {
            manager: WalManager::with_config(dir, config)?,
            _record: PhantomData,
        })
    }

    /// Logs a typed record to the WAL.
    ///
    /// The record is serialized via bincode and written with a length prefix
    /// and CRC32 checksum. Durability handling (fsync) is determined by the
    /// record's [`WalEntry::requires_sync`] method.
    ///
    /// # Errors
    ///
    /// Returns an error if serialization or writing fails.
    pub fn log(&self, record: &R) -> Result<()> {
        let data = bincode::serde::encode_to_vec(record, bincode::config::standard())
            .map_err(|e| Error::Serialization(e.to_string()))?;
        let force_sync = record.requires_sync();
        self.manager.write_frame(&data, force_sync)
    }

    /// Writes a checkpoint marker and persists checkpoint metadata.
    ///
    /// Creates a checkpoint record via [`WalEntry::make_checkpoint`], logs it,
    /// then syncs and writes the checkpoint metadata file.
    ///
    /// # Errors
    ///
    /// Returns an error if the checkpoint cannot be written.
    pub fn checkpoint(&self, current_transaction: TransactionId, epoch: EpochId) -> Result<()> {
        let checkpoint_record = R::make_checkpoint(current_transaction);
        self.log(&checkpoint_record)?;
        self.manager.complete_checkpoint(current_transaction, epoch)
    }

    /// Syncs the WAL to disk (fsync).
    ///
    /// # Errors
    ///
    /// Returns an error if the sync fails.
    pub fn sync(&self) -> Result<()> {
        self.manager.sync()
    }

    /// Flushes the WAL buffer to disk.
    ///
    /// # Errors
    ///
    /// Returns an error if the flush fails.
    pub fn flush(&self) -> Result<()> {
        self.manager.flush()
    }

    /// Rotates to a new log file.
    ///
    /// # Errors
    ///
    /// Returns an error if rotation fails.
    pub fn rotate(&self) -> Result<()> {
        self.manager.rotate()
    }

    /// Returns the underlying [`WalManager`].
    ///
    /// Useful for accessing administrative methods or for passing to
    /// [`AdaptiveFlusher`](super::AdaptiveFlusher).
    #[must_use]
    pub fn manager(&self) -> &WalManager {
        &self.manager
    }

    /// Returns the total number of records written.
    #[must_use]
    pub fn record_count(&self) -> u64 {
        self.manager.record_count()
    }

    /// Returns the WAL directory path.
    #[must_use]
    pub fn dir(&self) -> &Path {
        self.manager.dir()
    }

    /// Returns the current durability mode.
    #[must_use]
    pub fn durability_mode(&self) -> DurabilityMode {
        self.manager.durability_mode()
    }

    /// Returns the total size of all WAL files in bytes.
    #[must_use]
    pub fn size_bytes(&self) -> usize {
        self.manager.size_bytes()
    }

    /// Returns the timestamp of the last checkpoint (Unix epoch seconds), if any.
    #[must_use]
    pub fn last_checkpoint_timestamp(&self) -> Option<u64> {
        self.manager.last_checkpoint_timestamp()
    }

    /// Returns the latest checkpoint epoch, if any.
    #[must_use]
    pub fn checkpoint_epoch(&self) -> Option<EpochId> {
        self.manager.checkpoint_epoch()
    }

    /// Returns all WAL log file paths in sequence order.
    pub fn log_files(&self) -> Result<Vec<PathBuf>> {
        self.manager.log_files()
    }

    /// Reads checkpoint metadata from disk.
    pub fn read_checkpoint_metadata(&self) -> Result<Option<CheckpointMetadata>> {
        self.manager.read_checkpoint_metadata()
    }

    /// Returns the path to the active WAL file.
    #[must_use]
    pub fn path(&self) -> PathBuf {
        self.manager.path()
    }
}

/// Type alias for the LPG (labeled property graph) WAL.
pub type LpgWal = TypedWal<WalRecord>;

#[cfg(test)]
mod tests {
    use super::*;
    use grafeo_common::types::NodeId;
    use tempfile::tempdir;

    #[test]
    fn test_typed_wal_write() {
        let dir = tempdir().unwrap();
        let wal: LpgWal = TypedWal::open(dir.path()).unwrap();

        let record = WalRecord::CreateNode {
            id: NodeId::new(1),
            labels: vec!["Person".to_string()],
        };

        wal.log(&record).unwrap();
        wal.flush().unwrap();
        assert_eq!(wal.record_count(), 1);
    }

    #[test]
    fn test_typed_wal_checkpoint() {
        let dir = tempdir().unwrap();
        let wal: LpgWal = TypedWal::open(dir.path()).unwrap();

        wal.log(&WalRecord::CreateNode {
            id: NodeId::new(1),
            labels: vec!["Test".to_string()],
        })
        .unwrap();

        wal.log(&WalRecord::TransactionCommit {
            transaction_id: TransactionId::new(1),
        })
        .unwrap();

        wal.checkpoint(TransactionId::new(1), EpochId::new(10))
            .unwrap();
        assert_eq!(wal.checkpoint_epoch(), Some(EpochId::new(10)));
    }

    #[test]
    fn test_typed_wal_recovery_compatible() {
        // Verify TypedWal writes are recoverable by existing WalRecovery
        let dir = tempdir().unwrap();

        {
            let wal: LpgWal = TypedWal::open(dir.path()).unwrap();
            wal.log(&WalRecord::CreateNode {
                id: NodeId::new(1),
                labels: vec!["Person".to_string()],
            })
            .unwrap();
            wal.log(&WalRecord::TransactionCommit {
                transaction_id: TransactionId::new(1),
            })
            .unwrap();
            wal.sync().unwrap();
        }

        let recovery = super::super::WalRecovery::new(dir.path());
        let records = recovery.recover().unwrap();
        assert_eq!(records.len(), 2);
    }

    #[test]
    fn test_typed_wal_delegates_admin_methods() {
        let dir = tempdir().unwrap();
        let wal: LpgWal = TypedWal::open(dir.path()).unwrap();

        // Verify delegation works
        assert_eq!(wal.record_count(), 0);
        assert_eq!(wal.dir(), dir.path());
        assert!(wal.size_bytes() > 0 || wal.size_bytes() == 0);
        assert!(wal.checkpoint_epoch().is_none());
        assert!(wal.last_checkpoint_timestamp().is_none());

        let files = wal.log_files().unwrap();
        assert!(!files.is_empty());

        let _path = wal.path();
        let _mode = wal.durability_mode();
    }
}
