//! Key-Value store operations

use crate::{cf, meta_keys, RocksStore};
use chainfire_types::error::StorageError;
use chainfire_types::kv::{KeyRange, KvEntry, Revision};
use rocksdb::WriteBatch;
use std::sync::atomic::{AtomicU64, Ordering};
use tracing::{debug, trace};

/// KV store built on RocksDB
pub struct KvStore {
    store: RocksStore,
    /// Current revision counter
    revision: AtomicU64,
}

impl KvStore {
    /// Create a new KV store
    pub fn new(store: RocksStore) -> Result<Self, StorageError> {
        let revision = Self::load_revision(&store)?;

        Ok(Self {
            store,
            revision: AtomicU64::new(revision),
        })
    }

    /// Load the current revision from storage
    fn load_revision(store: &RocksStore) -> Result<Revision, StorageError> {
        let cf = store
            .cf_handle(cf::META)
            .ok_or_else(|| StorageError::RocksDb("META cf not found".into()))?;

        match store
            .db()
            .get_cf(&cf, meta_keys::REVISION)
            .map_err(|e| StorageError::RocksDb(e.to_string()))?
        {
            Some(bytes) => {
                let revision: Revision = bincode::deserialize(&bytes)
                    .map_err(|e| StorageError::Serialization(e.to_string()))?;
                Ok(revision)
            }
            None => Ok(0),
        }
    }

    /// Get current revision
    pub fn current_revision(&self) -> Revision {
        self.revision.load(Ordering::SeqCst)
    }

    /// Increment and return new revision
    fn next_revision(&self) -> Revision {
        self.revision.fetch_add(1, Ordering::SeqCst) + 1
    }

    /// Persist current revision
    fn save_revision(&self, revision: Revision) -> Result<(), StorageError> {
        let cf = self
            .store
            .cf_handle(cf::META)
            .ok_or_else(|| StorageError::RocksDb("META cf not found".into()))?;

        let bytes =
            bincode::serialize(&revision).map_err(|e| StorageError::Serialization(e.to_string()))?;

        self.store
            .db()
            .put_cf(&cf, meta_keys::REVISION, bytes)
            .map_err(|e| StorageError::RocksDb(e.to_string()))?;

        Ok(())
    }

    /// Get a single key
    pub fn get(&self, key: &[u8]) -> Result<Option<KvEntry>, StorageError> {
        let cf = self
            .store
            .cf_handle(cf::KV)
            .ok_or_else(|| StorageError::RocksDb("KV cf not found".into()))?;

        match self
            .store
            .db()
            .get_cf(&cf, key)
            .map_err(|e| StorageError::RocksDb(e.to_string()))?
        {
            Some(bytes) => {
                let entry: KvEntry = bincode::deserialize(&bytes)
                    .map_err(|e| StorageError::Serialization(e.to_string()))?;
                Ok(Some(entry))
            }
            None => Ok(None),
        }
    }

    /// Put a key-value pair
    pub fn put(
        &self,
        key: Vec<u8>,
        value: Vec<u8>,
        lease_id: Option<i64>,
    ) -> Result<(Revision, Option<KvEntry>), StorageError> {
        let cf = self
            .store
            .cf_handle(cf::KV)
            .ok_or_else(|| StorageError::RocksDb("KV cf not found".into()))?;

        // Get previous entry
        let prev = self.get(&key)?;
        let revision = self.next_revision();

        // Create new entry
        let entry = match &prev {
            Some(old) => old.update(value, revision),
            None => {
                if let Some(lease) = lease_id {
                    KvEntry::with_lease(key.clone(), value, revision, lease)
                } else {
                    KvEntry::new(key.clone(), value, revision)
                }
            }
        };

        // Write to RocksDB
        let bytes =
            bincode::serialize(&entry).map_err(|e| StorageError::Serialization(e.to_string()))?;

        let mut batch = WriteBatch::default();
        batch.put_cf(&cf, &key, &bytes);

        // Also persist revision
        let meta_cf = self
            .store
            .cf_handle(cf::META)
            .ok_or_else(|| StorageError::RocksDb("META cf not found".into()))?;
        let rev_bytes = bincode::serialize(&revision)
            .map_err(|e| StorageError::Serialization(e.to_string()))?;
        batch.put_cf(&meta_cf, meta_keys::REVISION, &rev_bytes);

        self.store
            .db()
            .write(batch)
            .map_err(|e| StorageError::RocksDb(e.to_string()))?;

        debug!(key = ?String::from_utf8_lossy(&key), revision, "Put key");
        Ok((revision, prev))
    }

    /// Delete a single key
    pub fn delete(&self, key: &[u8]) -> Result<(Revision, Option<KvEntry>), StorageError> {
        let cf = self
            .store
            .cf_handle(cf::KV)
            .ok_or_else(|| StorageError::RocksDb("KV cf not found".into()))?;

        // Get previous entry
        let prev = self.get(key)?;

        if prev.is_none() {
            return Ok((self.current_revision(), None));
        }

        let revision = self.next_revision();

        // Delete from RocksDB
        let mut batch = WriteBatch::default();
        batch.delete_cf(&cf, key);

        // Persist revision
        let meta_cf = self
            .store
            .cf_handle(cf::META)
            .ok_or_else(|| StorageError::RocksDb("META cf not found".into()))?;
        let rev_bytes = bincode::serialize(&revision)
            .map_err(|e| StorageError::Serialization(e.to_string()))?;
        batch.put_cf(&meta_cf, meta_keys::REVISION, &rev_bytes);

        self.store
            .db()
            .write(batch)
            .map_err(|e| StorageError::RocksDb(e.to_string()))?;

        debug!(key = ?String::from_utf8_lossy(key), revision, "Deleted key");
        Ok((revision, prev))
    }

    /// Delete a range of keys
    pub fn delete_range(
        &self,
        start: &[u8],
        end: &[u8],
    ) -> Result<(Revision, Vec<KvEntry>), StorageError> {
        let cf = self
            .store
            .cf_handle(cf::KV)
            .ok_or_else(|| StorageError::RocksDb("KV cf not found".into()))?;

        // First, collect all keys to delete
        let entries = self.range(start, Some(end))?;

        if entries.is_empty() {
            return Ok((self.current_revision(), Vec::new()));
        }

        let revision = self.next_revision();

        // Delete all keys
        let mut batch = WriteBatch::default();
        for entry in &entries {
            batch.delete_cf(&cf, &entry.key);
        }

        // Persist revision
        let meta_cf = self
            .store
            .cf_handle(cf::META)
            .ok_or_else(|| StorageError::RocksDb("META cf not found".into()))?;
        let rev_bytes = bincode::serialize(&revision)
            .map_err(|e| StorageError::Serialization(e.to_string()))?;
        batch.put_cf(&meta_cf, meta_keys::REVISION, &rev_bytes);

        self.store
            .db()
            .write(batch)
            .map_err(|e| StorageError::RocksDb(e.to_string()))?;

        debug!(
            start = ?String::from_utf8_lossy(start),
            end = ?String::from_utf8_lossy(end),
            deleted = entries.len(),
            revision,
            "Deleted range"
        );

        Ok((revision, entries))
    }

    /// Scan a range of keys
    pub fn range(&self, start: &[u8], end: Option<&[u8]>) -> Result<Vec<KvEntry>, StorageError> {
        let cf = self
            .store
            .cf_handle(cf::KV)
            .ok_or_else(|| StorageError::RocksDb("KV cf not found".into()))?;

        let mut entries = Vec::new();

        let iter = self.store.db().iterator_cf(
            &cf,
            rocksdb::IteratorMode::From(start, rocksdb::Direction::Forward),
        );

        for item in iter {
            let (key, value) = item.map_err(|e| StorageError::RocksDb(e.to_string()))?;

            // Check if we've passed the end
            if let Some(end_key) = end {
                if key.as_ref() >= end_key {
                    break;
                }
            }

            let entry: KvEntry = bincode::deserialize(&value)
                .map_err(|e| StorageError::Serialization(e.to_string()))?;
            entries.push(entry);
        }

        trace!(
            start = ?String::from_utf8_lossy(start),
            count = entries.len(),
            "Range scan"
        );

        Ok(entries)
    }

    /// Scan keys with a prefix
    pub fn prefix(&self, prefix: &[u8]) -> Result<Vec<KvEntry>, StorageError> {
        let range = KeyRange::prefix(prefix);
        self.range(&range.start, range.end.as_deref())
    }

    /// Get the underlying store
    pub fn store(&self) -> &RocksStore {
        &self.store
    }
}

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

    fn create_test_store() -> KvStore {
        let dir = tempdir().unwrap();
        let store = RocksStore::new(dir.path()).unwrap();
        KvStore::new(store).unwrap()
    }

    #[test]
    fn test_put_and_get() {
        let kv = create_test_store();

        let (rev, prev) = kv.put(b"key1".to_vec(), b"value1".to_vec(), None).unwrap();
        assert_eq!(rev, 1);
        assert!(prev.is_none());

        let entry = kv.get(b"key1").unwrap().unwrap();
        assert_eq!(entry.key, b"key1");
        assert_eq!(entry.value, b"value1");
        assert_eq!(entry.version, 1);
    }

    #[test]
    fn test_update() {
        let kv = create_test_store();

        kv.put(b"key1".to_vec(), b"value1".to_vec(), None).unwrap();
        let (rev, prev) = kv.put(b"key1".to_vec(), b"value2".to_vec(), None).unwrap();

        assert_eq!(rev, 2);
        assert!(prev.is_some());
        assert_eq!(prev.unwrap().value, b"value1");

        let entry = kv.get(b"key1").unwrap().unwrap();
        assert_eq!(entry.value, b"value2");
        assert_eq!(entry.version, 2);
        assert_eq!(entry.create_revision, 1); // Unchanged
        assert_eq!(entry.mod_revision, 2);
    }

    #[test]
    fn test_delete() {
        let kv = create_test_store();

        kv.put(b"key1".to_vec(), b"value1".to_vec(), None).unwrap();
        let (rev, prev) = kv.delete(b"key1").unwrap();

        assert_eq!(rev, 2);
        assert!(prev.is_some());
        assert_eq!(prev.unwrap().value, b"value1");

        let entry = kv.get(b"key1").unwrap();
        assert!(entry.is_none());
    }

    #[test]
    fn test_delete_nonexistent() {
        let kv = create_test_store();

        let (rev, prev) = kv.delete(b"nonexistent").unwrap();
        assert_eq!(rev, 0);
        assert!(prev.is_none());
    }

    #[test]
    fn test_range() {
        let kv = create_test_store();

        kv.put(b"a".to_vec(), b"1".to_vec(), None).unwrap();
        kv.put(b"b".to_vec(), b"2".to_vec(), None).unwrap();
        kv.put(b"c".to_vec(), b"3".to_vec(), None).unwrap();
        kv.put(b"d".to_vec(), b"4".to_vec(), None).unwrap();

        let entries = kv.range(b"b", Some(b"d")).unwrap();
        assert_eq!(entries.len(), 2);
        assert_eq!(entries[0].key, b"b");
        assert_eq!(entries[1].key, b"c");
    }

    #[test]
    fn test_prefix() {
        let kv = create_test_store();

        kv.put(b"/nodes/1".to_vec(), b"node1".to_vec(), None)
            .unwrap();
        kv.put(b"/nodes/2".to_vec(), b"node2".to_vec(), None)
            .unwrap();
        kv.put(b"/tasks/1".to_vec(), b"task1".to_vec(), None)
            .unwrap();

        let entries = kv.prefix(b"/nodes/").unwrap();
        assert_eq!(entries.len(), 2);
    }

    #[test]
    fn test_delete_range() {
        let kv = create_test_store();

        kv.put(b"/nodes/1".to_vec(), b"node1".to_vec(), None)
            .unwrap();
        kv.put(b"/nodes/2".to_vec(), b"node2".to_vec(), None)
            .unwrap();
        kv.put(b"/tasks/1".to_vec(), b"task1".to_vec(), None)
            .unwrap();

        let (rev, deleted) = kv.delete_range(b"/nodes/", b"/nodes0").unwrap();
        assert_eq!(deleted.len(), 2);

        // Verify nodes are gone
        assert!(kv.get(b"/nodes/1").unwrap().is_none());
        assert!(kv.get(b"/nodes/2").unwrap().is_none());

        // Verify task still exists
        assert!(kv.get(b"/tasks/1").unwrap().is_some());
    }

    #[test]
    fn test_revision_persistence() {
        let dir = tempdir().unwrap();

        // Create store and write some data
        {
            let store = RocksStore::new(dir.path()).unwrap();
            let kv = KvStore::new(store).unwrap();
            kv.put(b"key1".to_vec(), b"value1".to_vec(), None).unwrap();
            kv.put(b"key2".to_vec(), b"value2".to_vec(), None).unwrap();
            assert_eq!(kv.current_revision(), 2);
        }

        // Reopen and verify revision is restored
        {
            let store = RocksStore::new(dir.path()).unwrap();
            let kv = KvStore::new(store).unwrap();
            assert_eq!(kv.current_revision(), 2);

            // Next write should continue from 3
            let (rev, _) = kv.put(b"key3".to_vec(), b"value3".to_vec(), None).unwrap();
            assert_eq!(rev, 3);
        }
    }
}