//! [`ManagedDb`] and [`StateSyncDb`] implementations for QMDB
//! [`any`](commonware_storage::qmdb::any) databases.
//!
//! Batch reads consult the database at the time of the read for keys their batch chain does not
//! write, and return a `StaleRead` error once the database is at no state of that chain.

use crate::stateful::db::{
    BatchContext, InitError, ManagedDb, Merkleized as MerkleizedTrait, Shared, StateSyncDb,
    SyncEngineConfig, Unmerkleized as UnmerkleizedTrait, sync_standard_db, validate_initialization,
};
use commonware_codec::{Codec, Read as CodecRead};
use commonware_cryptography::Hasher;
use commonware_parallel::Strategy;
use commonware_runtime::{Handle, Spawner};
use commonware_storage::{
    Context,
    index::{
        Ordered as OrderedIndex, Unordered as UnorderedIndex, unordered::Index as UnorderedIdx,
    },
    journal::contiguous::{
        Contiguous, Mutable, fixed::Journal as FixedJournal, variable::Journal as VariableJournal,
    },
    merkle::{Family, Location},
    qmdb::{
        Error,
        any::{
            FixedConfig, VariableConfig,
            batch::{MerkleizedBatch, Slot, Staged, UnmerkleizedBatch},
            db::Db,
            initial_root,
            operation::{Operation, Update},
            ordered, unordered,
            value::{self, FixedEncoding, ValueEncoding, VariableEncoding},
        },
        floor::Proportional,
        operation::Key,
        sync::{self, Target as AnySyncTarget},
    },
    translator::Translator,
};
use commonware_utils::{
    Array,
    channel::{mpsc, ring},
    non_empty_range,
};
use std::{
    ops::{Deref, Range},
    sync::Arc,
};

// Matches commonware_storage::qmdb::any::BITMAP_CHUNK_BYTES, which is crate-private.
const ANY_BITMAP_CHUNK_BYTES: usize = 64;

/// A speculative batch of updates and deletes over a shared `any` database.
pub struct AnyUnmerkleized<F, E, C, I, H, U, S>
where
    F: Family,
    E: Context,
    U: Update,
    C: Contiguous<Item = Operation<F, U>>,
    I: UnorderedIndex<Value = Location<F>>,
    H: Hasher,
    S: Strategy,
    Operation<F, U>: Codec,
{
    batch: UnmerkleizedBatch<F, H, U, S>,
    db: Shared<Db<F, E, C, I, H, U, ANY_BITMAP_CHUNK_BYTES, S>>,
    metadata: Option<U::Value>,
}

/// A staged batch returned by [`AnyUnmerkleized::stage`].
///
/// Like any speculative batch, this handle reads the shared database only while the database is
/// at a state of the batch's chain, and its reads return [`Error::StaleRead`] once the database
/// is at any other state (see [`MerkleizedBatch`]'s "Batch validity" docs).
pub struct AnyStaged<F, E, C, I, H, U, S>
where
    F: Family,
    E: Context,
    U: Update,
    C: Contiguous<Item = Operation<F, U>>,
    I: UnorderedIndex<Value = Location<F>>,
    H: Hasher,
    S: Strategy,
    Operation<F, U>: Codec,
{
    staged: Staged<F, H, U, S>,
    db: Shared<Db<F, E, C, I, H, U, ANY_BITMAP_CHUNK_BYTES, S>>,
    metadata: Option<U::Value>,
}

impl<F, E, C, I, H, U, S> AnyUnmerkleized<F, E, C, I, H, U, S>
where
    F: Family,
    E: Context,
    U: Update,
    C: Contiguous<Item = Operation<F, U>>,
    I: UnorderedIndex<Value = Location<F>> + 'static,
    H: Hasher,
    S: Strategy,
    Operation<F, U>: Codec,
{
    /// Sets the metadata committed by [`merkleize`](UnmerkleizedTrait::merkleize).
    ///
    /// The metadata carries over to a batch returned by [`Self::stage`].
    pub fn with_metadata(mut self, metadata: U::Value) -> Self {
        self.metadata = Some(metadata);
        self
    }

    /// Reads a value by key, falling back to applied state.
    pub async fn get(&self, key: &U::Key) -> Result<Option<U::Value>, Error<F>> {
        let db = self.db.read().await;
        self.batch.get(key, &db).await
    }

    /// Reads multiple values by key, falling back to applied state.
    ///
    /// Returns results in the same order as `keys`.
    pub async fn get_many(&self, keys: &[&U::Key]) -> Result<Vec<Option<U::Value>>, Error<F>> {
        let db = self.db.read().await;
        self.batch.get_many(keys, &db).await
    }

    /// Reads multiple values and returns a staged batch for the same keys.
    ///
    /// Returns results in the same order as `keys`.
    pub async fn stage(
        self,
        keys: &[&U::Key],
    ) -> Result<(Vec<Option<U::Value>>, AnyStaged<F, E, C, I, H, U, S>), Error<F>> {
        let Self {
            batch,
            db,
            metadata,
        } = self;
        let (values, staged) = {
            let guard = db.read().await;
            batch.stage(keys, &guard).await?
        };
        Ok((
            values,
            AnyStaged {
                staged,
                db,
                metadata,
            },
        ))
    }

    /// Records an upsert (`Some`) or a delete (`None`) of `key`.
    pub fn write(mut self, key: U::Key, value: Option<U::Value>) -> Self {
        self.batch = self.batch.write(key, value);
        self
    }
}

/// A sealed `any` batch with a computed root.
pub struct AnyMerkleized<F, E, C, I, H, U, S>
where
    F: Family,
    E: Context,
    U: Update,
    C: Contiguous<Item = Operation<F, U>>,
    I: UnorderedIndex<Value = Location<F>>,
    H: Hasher,
    S: Strategy,
    Operation<F, U>: Codec,
{
    inner: Arc<MerkleizedBatch<F, H::Digest, U, S>>,
    db: Shared<Db<F, E, C, I, H, U, ANY_BITMAP_CHUNK_BYTES, S>>,
}

impl<F, E, C, I, H, U, S> Clone for AnyMerkleized<F, E, C, I, H, U, S>
where
    F: Family,
    E: Context,
    U: Update,
    C: Contiguous<Item = Operation<F, U>>,
    I: UnorderedIndex<Value = Location<F>>,
    H: Hasher,
    S: Strategy,
    Operation<F, U>: Codec,
{
    fn clone(&self) -> Self {
        Self {
            inner: Arc::clone(&self.inner),
            db: self.db.clone(),
        }
    }
}

impl<F, E, C, I, H, U, S> Deref for AnyUnmerkleized<F, E, C, I, H, U, S>
where
    F: Family,
    E: Context,
    U: Update,
    C: Contiguous<Item = Operation<F, U>>,
    I: UnorderedIndex<Value = Location<F>>,
    H: Hasher,
    S: Strategy,
    Operation<F, U>: Codec,
{
    type Target = UnmerkleizedBatch<F, H, U, S>;

    fn deref(&self) -> &Self::Target {
        &self.batch
    }
}

impl<F, E, C, I, H, U, S> Deref for AnyMerkleized<F, E, C, I, H, U, S>
where
    F: Family,
    E: Context,
    U: Update,
    C: Contiguous<Item = Operation<F, U>>,
    I: UnorderedIndex<Value = Location<F>>,
    H: Hasher,
    S: Strategy,
    Operation<F, U>: Codec,
{
    type Target = MerkleizedBatch<F, H::Digest, U, S>;

    fn deref(&self) -> &Self::Target {
        &self.inner
    }
}

impl<F, E, C, I, H, U, S> AnyStaged<F, E, C, I, H, U, S>
where
    F: Family,
    E: Context,
    U: Update,
    C: Contiguous<Item = Operation<F, U>>,
    I: UnorderedIndex<Value = Location<F>> + 'static,
    H: Hasher,
    S: Strategy,
    Operation<F, U>: Codec,
{
    /// Sets the metadata committed by [`merkleize`](Self::merkleize), replacing any metadata set
    /// before staging.
    pub fn with_metadata(mut self, metadata: U::Value) -> Self {
        self.metadata = Some(metadata);
        self
    }

    /// The number of staged read slots: the keys passed to `stage` plus every
    /// [`expand`](Self::expand) range. [`merkleize`](Self::merkleize) takes one [`Slot`] per
    /// staged read.
    pub const fn len(&self) -> usize {
        self.staged.len()
    }

    /// Whether no reads are staged.
    pub const fn is_empty(&self) -> bool {
        self.staged.is_empty()
    }

    /// Expands this staged batch with more reads.
    ///
    /// Existing slots keep their positions. Newly read keys are appended to the staged read set
    /// and assigned the returned range of slots. Expansion does not deduplicate against previously
    /// staged keys and does not observe values computed for earlier staged slots but not yet
    /// passed to `merkleize`.
    pub async fn expand(
        self,
        keys: &[&U::Key],
    ) -> Result<(Range<usize>, Vec<Option<U::Value>>, Self), Error<F>> {
        let Self {
            staged,
            db,
            metadata,
        } = self;
        let (range, values, staged) = {
            let guard = db.read().await;
            staged.expand(keys, &guard).await?
        };
        Ok((
            range,
            values,
            Self {
                staged,
                db,
                metadata,
            },
        ))
    }
}

impl<F, E, C, I, H, K, V, S> AnyStaged<F, E, C, I, H, unordered::Update<K, V>, S>
where
    F: Family,
    E: Context,
    K: Key,
    V: ValueEncoding,
    C: Mutable<Item = Operation<F, unordered::Update<K, V>>>,
    I: UnorderedIndex<Value = Location<F>> + 'static,
    H: Hasher,
    S: Strategy,
    Operation<F, unordered::Update<K, V>>: Codec,
{
    /// Applies `slots` to staged reads and `unstaged` writes to unread keys, then merkleizes.
    ///
    /// `slots` holds one [`Slot`] per staged read, in the order of the keys passed to `stage`
    /// followed by each [`expand`](Self::expand) range. A key staged in several slots takes its
    /// last put or delete, and an unstaged write to a staged key wins. Metadata set through
    /// [`with_metadata`](Self::with_metadata), or before staging, is committed with the batch.
    ///
    /// # Panics
    ///
    /// Panics if `slots` does not hold one entry per staged read.
    pub async fn merkleize(
        self,
        slots: Vec<Slot<V::Value>>,
        unstaged: Vec<(K, Option<V::Value>)>,
    ) -> Result<AnyMerkleized<F, E, C, I, H, unordered::Update<K, V>, S>, Error<F>> {
        let Self {
            staged,
            db,
            metadata,
        } = self;
        let inner = {
            let guard = db.read().await;
            staged
                .merkleize(slots, unstaged, metadata, &guard, &mut Proportional)
                .await?
        };
        Ok(AnyMerkleized { inner, db })
    }
}

impl<F, E, C, I, H, K, V, S> AnyStaged<F, E, C, I, H, ordered::Update<K, V>, S>
where
    F: Family,
    E: Context,
    K: Key,
    V: ValueEncoding,
    C: Mutable<Item = Operation<F, ordered::Update<K, V>>>,
    I: OrderedIndex<Value = Location<F>> + 'static,
    H: Hasher,
    S: Strategy,
    Operation<F, ordered::Update<K, V>>: Codec,
{
    /// Applies `slots` to staged reads and `unstaged` writes to unread keys, then merkleizes.
    ///
    /// `slots` holds one [`Slot`] per staged read, in the order of the keys passed to `stage`
    /// followed by each [`expand`](Self::expand) range. A key staged in several slots takes its
    /// last put or delete, and an unstaged write to a staged key wins. Metadata set through
    /// [`with_metadata`](Self::with_metadata), or before staging, is committed with the batch.
    ///
    /// # Panics
    ///
    /// Panics if `slots` does not hold one entry per staged read.
    pub async fn merkleize(
        self,
        slots: Vec<Slot<V::Value>>,
        unstaged: Vec<(K, Option<V::Value>)>,
    ) -> Result<AnyMerkleized<F, E, C, I, H, ordered::Update<K, V>, S>, Error<F>> {
        let Self {
            staged,
            db,
            metadata,
        } = self;
        let inner = {
            let guard = db.read().await;
            staged
                .merkleize(slots, unstaged, metadata, &guard, &mut Proportional)
                .await?
        };
        Ok(AnyMerkleized { inner, db })
    }
}

impl<F, E, C, I, H, U, S> AnyMerkleized<F, E, C, I, H, U, S>
where
    F: Family,
    E: Context,
    U: Update,
    C: Contiguous<Item = Operation<F, U>>,
    I: UnorderedIndex<Value = Location<F>> + 'static,
    H: Hasher,
    S: Strategy,
    Operation<F, U>: Codec,
{
    /// Reads a value by key, falling back to applied state.
    pub async fn get(&self, key: &U::Key) -> Result<Option<U::Value>, Error<F>> {
        let db = self.db.read().await;
        self.inner.get(key, &db).await
    }

    /// Reads multiple values by key, falling back to applied state.
    ///
    /// Returns results in the same order as `keys`.
    pub async fn get_many(&self, keys: &[&U::Key]) -> Result<Vec<Option<U::Value>>, Error<F>> {
        let db = self.db.read().await;
        self.inner.get_many(keys, &db).await
    }
}

impl<F, E, C, I, H, K, V, S> UnmerkleizedTrait
    for AnyUnmerkleized<F, E, C, I, H, unordered::Update<K, V>, S>
where
    F: Family,
    E: Context,
    K: Key,
    V: ValueEncoding,
    C: Mutable<Item = Operation<F, unordered::Update<K, V>>>,
    I: UnorderedIndex<Value = Location<F>> + 'static,
    H: Hasher,
    S: Strategy,
    Operation<F, unordered::Update<K, V>>: Codec,
{
    type Merkleized = AnyMerkleized<F, E, C, I, H, unordered::Update<K, V>, S>;
    type Error = Error<F>;

    async fn merkleize(self) -> Result<Self::Merkleized, Error<F>> {
        let db = self.db.read().await;
        let merkleized = self
            .batch
            .merkleize(&db, self.metadata, &mut Proportional)
            .await?;
        Ok(AnyMerkleized {
            inner: merkleized,
            db: self.db.clone(),
        })
    }
}

impl<F, E, C, I, H, K, V, S> UnmerkleizedTrait
    for AnyUnmerkleized<F, E, C, I, H, ordered::Update<K, V>, S>
where
    F: Family,
    E: Context,
    K: Key,
    V: ValueEncoding,
    C: Mutable<Item = Operation<F, ordered::Update<K, V>>>,
    I: OrderedIndex<Value = Location<F>> + 'static,
    H: Hasher,
    S: Strategy,
    Operation<F, ordered::Update<K, V>>: Codec,
{
    type Merkleized = AnyMerkleized<F, E, C, I, H, ordered::Update<K, V>, S>;
    type Error = Error<F>;

    async fn merkleize(self) -> Result<Self::Merkleized, Error<F>> {
        let db = self.db.read().await;
        let merkleized = self
            .batch
            .merkleize(&db, self.metadata, &mut Proportional)
            .await?;
        Ok(AnyMerkleized {
            inner: merkleized,
            db: self.db.clone(),
        })
    }
}

impl<F, E, C, I, H, U, S> MerkleizedTrait for AnyMerkleized<F, E, C, I, H, U, S>
where
    F: Family,
    E: Context,
    U: Update,
    C: Mutable<Item = Operation<F, U>>,
    I: UnorderedIndex<Value = Location<F>> + 'static,
    H: Hasher,
    S: Strategy,
    Operation<F, U>: Codec,
    AnyUnmerkleized<F, E, C, I, H, U, S>: UnmerkleizedTrait,
{
    type Digest = H::Digest;
    type Unmerkleized = AnyUnmerkleized<F, E, C, I, H, U, S>;

    fn root(&self) -> H::Digest {
        self.inner.root()
    }

    fn new_batch(&self) -> Self::Unmerkleized {
        AnyUnmerkleized {
            batch: self.inner.new_batch::<H>(),
            db: self.db.clone(),
            metadata: None,
        }
    }
}

impl<F, E, K, V, H, T, S> ManagedDb<E>
    for Db<
        F,
        E,
        FixedJournal<E, Operation<F, unordered::Update<K, FixedEncoding<V>>>>,
        UnorderedIdx<T, Location<F>>,
        H,
        unordered::Update<K, FixedEncoding<V>>,
        ANY_BITMAP_CHUNK_BYTES,
        S,
    >
where
    F: Family,
    E: Context + Spawner,
    K: Array,
    V: value::FixedValue,
    H: Hasher,
    T: Translator,
    S: Strategy,
{
    type Unmerkleized = AnyUnmerkleized<
        F,
        E,
        FixedJournal<E, Operation<F, unordered::Update<K, FixedEncoding<V>>>>,
        UnorderedIdx<T, Location<F>>,
        H,
        unordered::Update<K, FixedEncoding<V>>,
        S,
    >;
    type Merkleized = AnyMerkleized<
        F,
        E,
        FixedJournal<E, Operation<F, unordered::Update<K, FixedEncoding<V>>>>,
        UnorderedIdx<T, Location<F>>,
        H,
        unordered::Update<K, FixedEncoding<V>>,
        S,
    >;
    type Error = Error<F>;
    type Config = FixedConfig<T, S>;
    type SyncTarget = AnySyncTarget<F, H::Digest>;

    async fn init(
        context: E,
        config: Self::Config,
        expected: Option<Self::SyncTarget>,
    ) -> Result<Self, InitError<Error<F>, Self::SyncTarget>> {
        let db = <Self>::init(
            context,
            config,
            expected.as_ref().map(|target| target.range.end()),
        )
        .await
        .map_err(InitError::Database)?;
        validate_initialization(db, expected)
    }

    fn initial_sync_target() -> Self::SyncTarget {
        AnySyncTarget::new(
            initial_root::<F, unordered::Update<K, FixedEncoding<V>>, H>(),
            non_empty_range!(Location::new(0), Location::new(1)),
        )
    }

    fn new_batch(database: BatchContext<'_, Self>) -> Self::Unmerkleized {
        let (database, shared) = database.into_parts();
        AnyUnmerkleized {
            batch: database.new_batch(),
            db: shared,
            metadata: None,
        }
    }

    fn matches_sync_target(batch: &Self::Merkleized, target: &Self::SyncTarget) -> bool {
        batch.root() == target.root
            && *target.range.start() == batch.bounds().inactivity_floor
            && *target.range.end() == batch.bounds().tip.size
    }

    async fn apply(self, batch: Self::Merkleized) -> Result<Self, Error<F>> {
        self.apply_batch(batch.inner).await
    }

    async fn finalize(self) -> Result<(Self, Handle<()>), Error<F>> {
        self.start_sync().await
    }

    async fn prune(self, target: &Self::SyncTarget) -> Result<Self, Error<F>> {
        self.prune((*target.range.start()).into()).await
    }

    fn sync_target(&self) -> Self::SyncTarget {
        let bounds = self.bounds();
        AnySyncTarget::new(
            self.root(),
            non_empty_range!(self.sync_boundary(), bounds.end),
        )
    }
}

impl<F, E, K, V, H, T, S> ManagedDb<E>
    for Db<
        F,
        E,
        VariableJournal<E, Operation<F, unordered::Update<K, VariableEncoding<V>>>>,
        UnorderedIdx<T, Location<F>>,
        H,
        unordered::Update<K, VariableEncoding<V>>,
        ANY_BITMAP_CHUNK_BYTES,
        S,
    >
where
    F: Family,
    E: Context + Spawner,
    K: Key,
    V: value::VariableValue,
    H: Hasher,
    T: Translator,
    S: Strategy,
{
    type Unmerkleized = AnyUnmerkleized<
        F,
        E,
        VariableJournal<E, Operation<F, unordered::Update<K, VariableEncoding<V>>>>,
        UnorderedIdx<T, Location<F>>,
        H,
        unordered::Update<K, VariableEncoding<V>>,
        S,
    >;
    type Merkleized = AnyMerkleized<
        F,
        E,
        VariableJournal<E, Operation<F, unordered::Update<K, VariableEncoding<V>>>>,
        UnorderedIdx<T, Location<F>>,
        H,
        unordered::Update<K, VariableEncoding<V>>,
        S,
    >;
    type Error = Error<F>;
    type Config = VariableConfig<
        T,
        <Operation<F, unordered::Update<K, VariableEncoding<V>>> as CodecRead>::Cfg,
        S,
    >;
    type SyncTarget = AnySyncTarget<F, H::Digest>;

    async fn init(
        context: E,
        config: Self::Config,
        expected: Option<Self::SyncTarget>,
    ) -> Result<Self, InitError<Error<F>, Self::SyncTarget>> {
        let db = <Self>::init(
            context,
            config,
            expected.as_ref().map(|target| target.range.end()),
        )
        .await
        .map_err(InitError::Database)?;
        validate_initialization(db, expected)
    }

    fn initial_sync_target() -> Self::SyncTarget {
        AnySyncTarget::new(
            initial_root::<F, unordered::Update<K, VariableEncoding<V>>, H>(),
            non_empty_range!(Location::new(0), Location::new(1)),
        )
    }

    fn new_batch(database: BatchContext<'_, Self>) -> Self::Unmerkleized {
        let (database, shared) = database.into_parts();
        AnyUnmerkleized {
            batch: database.new_batch(),
            db: shared,
            metadata: None,
        }
    }

    fn matches_sync_target(batch: &Self::Merkleized, target: &Self::SyncTarget) -> bool {
        batch.root() == target.root
            && *target.range.start() == batch.bounds().inactivity_floor
            && *target.range.end() == batch.bounds().tip.size
    }

    async fn apply(self, batch: Self::Merkleized) -> Result<Self, Error<F>> {
        self.apply_batch(batch.inner).await
    }

    async fn finalize(self) -> Result<(Self, Handle<()>), Error<F>> {
        self.start_sync().await
    }

    async fn prune(self, target: &Self::SyncTarget) -> Result<Self, Error<F>> {
        self.prune((*target.range.start()).into()).await
    }

    fn sync_target(&self) -> Self::SyncTarget {
        let bounds = self.bounds();
        AnySyncTarget::new(
            self.root(),
            non_empty_range!(self.sync_boundary(), bounds.end),
        )
    }
}

impl<F, E, K, V, H, T, S, R> StateSyncDb<E, R>
    for Db<
        F,
        E,
        FixedJournal<E, Operation<F, unordered::Update<K, FixedEncoding<V>>>>,
        UnorderedIdx<T, Location<F>>,
        H,
        unordered::Update<K, FixedEncoding<V>>,
        ANY_BITMAP_CHUNK_BYTES,
        S,
    >
where
    F: Family,
    E: Context + Spawner,
    K: Array,
    V: value::FixedValue,
    H: Hasher,
    T: Translator,
    S: Strategy,
    R: sync::SourceFor<Self>,
{
    type SyncError = sync::Error<F, R::Error, H::Digest>;

    async fn sync_db(
        context: E,
        config: Self::Config,
        source: R,
        target: Self::SyncTarget,
        tip_updates: ring::Receiver<Self::SyncTarget>,
        finish: Option<mpsc::Receiver<()>>,
        reached_target: Option<ring::Sender<Self::SyncTarget>>,
        sync_config: SyncEngineConfig,
    ) -> Result<Self, Self::SyncError> {
        sync_standard_db(
            context,
            config,
            source,
            target,
            tip_updates,
            finish,
            reached_target,
            sync_config,
        )
        .await
    }
}

impl<F, E, K, V, H, T, S, R> StateSyncDb<E, R>
    for Db<
        F,
        E,
        VariableJournal<E, Operation<F, unordered::Update<K, VariableEncoding<V>>>>,
        UnorderedIdx<T, Location<F>>,
        H,
        unordered::Update<K, VariableEncoding<V>>,
        ANY_BITMAP_CHUNK_BYTES,
        S,
    >
where
    F: Family,
    E: Context + Spawner,
    K: Key,
    V: value::VariableValue,
    H: Hasher,
    T: Translator,
    S: Strategy,
    R: sync::SourceFor<Self>,
{
    type SyncError = sync::Error<F, R::Error, H::Digest>;

    async fn sync_db(
        context: E,
        config: Self::Config,
        source: R,
        target: Self::SyncTarget,
        tip_updates: ring::Receiver<Self::SyncTarget>,
        finish: Option<mpsc::Receiver<()>>,
        reached_target: Option<ring::Sender<Self::SyncTarget>>,
        sync_config: SyncEngineConfig,
    ) -> Result<Self, Self::SyncError> {
        sync_standard_db(
            context,
            config,
            source,
            target,
            tip_updates,
            finish,
            reached_target,
            sync_config,
        )
        .await
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use commonware_cryptography::{Sha256, sha256::Digest};
    use commonware_parallel::Sequential;
    use commonware_runtime::{
        Runner as _, Supervisor as _,
        buffer::paged::CacheRef,
        deterministic,
        mocks::{DelayedSyncContext, PendingSyncs, drive_pending_syncs, release_pending_syncs},
    };
    use commonware_storage::{
        journal::contiguous::fixed::Config as FixedJournalConfig,
        merkle::{full::Config as MerkleConfig, mmr},
        qmdb::{self, any::unordered::fixed},
        translator::TwoCap,
    };
    use commonware_utils::{NZU16, NZU64, NZUsize};
    use std::num::{NonZeroU16, NonZeroUsize};

    type UnorderedFixedDb =
        fixed::Db<mmr::Family, deterministic::Context, Digest, Digest, Sha256, TwoCap, Sequential>;

    const PAGE_SIZE: NonZeroU16 = NZU16!(101);
    const PAGE_CACHE_SIZE: NonZeroUsize = NZUsize!(11);

    fn fixed_config(suffix: &str) -> FixedConfig<TwoCap, Sequential> {
        let page_cache = CacheRef::new(PAGE_SIZE, PAGE_CACHE_SIZE);
        FixedConfig {
            merkle_config: MerkleConfig {
                journal_partition: format!("stateful-any-journal-{suffix}"),
                metadata_partition: format!("stateful-any-metadata-{suffix}"),
                items_per_blob: NZU64!(11),
                write_buffer: NZUsize!(1024),
                replay_buffer: NZUsize!(1024),
                strategy: Sequential,
                page_cache: page_cache.clone(),
            },
            journal_config: FixedJournalConfig {
                partition: format!("stateful-any-log-{suffix}"),
                items_per_blob: NZU64!(7),
                page_cache,
                write_buffer: NZUsize!(1024),
                replay_buffer: NZUsize!(1024),
            },
            translator: TwoCap,
            init_cache: Some(NZUsize!(1024)),
            init_buffer: NZUsize!(1 << 21),
            init_concurrency: (),
        }
    }

    #[test]
    fn unmerkleized_batch_refuses_after_competing_finalization() {
        deterministic::Runner::default().start(|context| async move {
            let config = fixed_config("unordered-fixed-stale-refusal");
            let db = <UnorderedFixedDb as ManagedDb<_>>::init(context.child("db"), config, None)
                .await
                .unwrap();
            let db = Shared::new("test", db);

            let key = Sha256::hash(&[b"key"]);
            let value = Sha256::hash(&[b"winner"]);
            let pre_finalization = db.new_batch_for_test::<_>().await;
            let winner = db.new_batch_for_test::<_>().await.write(key, Some(value));
            let winner = crate::stateful::db::Unmerkleized::merkleize(winner)
                .await
                .unwrap();

            let (slot, database) = db.write().await;
            let database = <UnorderedFixedDb as ManagedDb<_>>::apply(database, winner)
                .await
                .unwrap();
            let (database, sync) = <UnorderedFixedDb as ManagedDb<_>>::finalize(database)
                .await
                .unwrap();
            slot.put(database);
            sync.await.expect("database sync failed");

            // `winner` is a sibling built on the same state, so applying it moves the database to
            // a state outside `pre_finalization`'s chain and reads through `pre_finalization`
            // return `StaleRead`.
            assert!(matches!(
                pre_finalization.get(&key).await,
                Err(qmdb::Error::StaleRead)
            ));
        });
    }

    /// The glue staged wrapper (`AnyUnmerkleized::stage` -> `AnyStaged::expand` ->
    /// `AnyStaged::merkleize`) must return the same values and root as an explicit `get_many` +
    /// `write` + `merkleize`, including a staged delete, an unstaged write, and metadata flow (both
    /// set on the staged handle via `with_metadata` and carried from before staging). This guards
    /// metadata flow and db-handle pairing through the wrapper.
    #[test]
    fn unordered_fixed_staged_merkleize_matches_explicit_writes() {
        deterministic::Runner::default().start(|context| async move {
            let config = fixed_config("unordered-fixed-glue-staged");
            let db = <UnorderedFixedDb as ManagedDb<_>>::init(context.child("db"), config, None)
                .await
                .unwrap();
            let db = Shared::new("test", db);

            let key = |i: u64| Sha256::hash(&[&i.to_be_bytes()]);
            let val = |i: u64| Sha256::hash(&[&(i + 10_000).to_be_bytes()]);
            let metadata = Sha256::hash(&[b"metadata"]);

            // Seed keys 0..50 and persist them.
            let mut seed = db.new_batch_for_test::<_>().await;
            for i in 0..50u64 {
                seed = seed.write(key(i), Some(val(i)));
            }
            let merkleized = crate::stateful::db::Unmerkleized::merkleize(seed)
                .await
                .unwrap();
            {
                let (slot, database) = db.write().await;
                let database = <UnorderedFixedDb as ManagedDb<_>>::apply(database, merkleized)
                    .await
                    .unwrap();
                let (database, sync) = <UnorderedFixedDb as ManagedDb<_>>::finalize(database)
                    .await
                    .unwrap();
                slot.put(database);
                sync.await.expect("database sync failed");
            }

            // Read set: key(1) updated, key(2) deleted, key(999) missing -> created.
            let read_keys = [key(1), key(2), key(999)];
            let keys: Vec<&Digest> = read_keys.iter().collect();
            let slots = vec![Slot::Put(val(1_000)), Slot::Delete, Slot::Put(val(1_001))];
            let unstaged = vec![(key(3), Some(val(1_002)))];

            // Explicit path.
            let mut explicit = db.new_batch_for_test::<_>().await;
            let explicit_values = explicit.get_many(&keys).await.unwrap();
            for (key, slot) in read_keys.iter().zip(&slots) {
                let value = match slot {
                    Slot::Put(value) => Some(*value),
                    Slot::Delete => None,
                    Slot::Keep => unreachable!("every staged read must be written"),
                };
                explicit = explicit.write(*key, value);
            }
            for (k, v) in &unstaged {
                explicit = explicit.write(*k, *v);
            }
            let explicit_root =
                crate::stateful::db::Unmerkleized::merkleize(explicit.with_metadata(metadata))
                    .await
                    .unwrap()
                    .root();

            // Staged path, with metadata set on the staged handle.
            let staged_batch = db.new_batch_for_test::<_>().await;
            let split = 2;
            let (mut staged_values, staged) = staged_batch.stage(&keys[..split]).await.unwrap();
            let (range, suffix_values, staged) = staged.expand(&keys[split..]).await.unwrap();
            assert_eq!(range, split..keys.len());
            assert_eq!(staged.len(), keys.len());
            assert!(!staged.is_empty());
            staged_values.extend(suffix_values);
            let staged_root = staged
                .with_metadata(metadata)
                .merkleize(slots.clone(), unstaged.clone())
                .await
                .unwrap()
                .root();

            assert_eq!(explicit_values, staged_values);
            assert_eq!(explicit_root, staged_root);

            // Metadata set before staging must be carried through to staged merkleize.
            let carried_batch = db.new_batch_for_test::<_>().await.with_metadata(metadata);
            let (carried_values, staged) = carried_batch.stage(&keys).await.unwrap();
            let carried_root = staged
                .merkleize(slots.clone(), unstaged.clone())
                .await
                .unwrap()
                .root();
            assert_eq!(explicit_values, carried_values);
            assert_eq!(explicit_root, carried_root);
        });
    }

    type DelayedFixedDb = fixed::Db<
        mmr::Family,
        DelayedSyncContext<deterministic::Context>,
        Digest,
        Digest,
        Sha256,
        TwoCap,
        Sequential,
    >;

    #[test]
    fn apply_does_not_finalize() {
        deterministic::Runner::default().start(|context| async move {
            let pending = PendingSyncs::default();
            let delayed = DelayedSyncContext {
                inner: context,
                pending: pending.clone(),
            };
            let config = fixed_config("unordered-fixed-deferred");
            let db = drive_pending_syncs(
                &pending,
                <DelayedFixedDb as ManagedDb<_>>::init(delayed.child("db"), config, None),
            )
            .await
            .unwrap();
            let db = Shared::new("test", db);

            let key = Sha256::hash(&[b"key"]);
            let value = Sha256::hash(&[b"value"]);
            let batch = db.new_batch_for_test::<_>().await.write(key, Some(value));
            let merkleized = crate::stateful::db::Unmerkleized::merkleize(batch)
                .await
                .unwrap();

            let starts = pending.starts();
            let (slot, database) = db.write().await;
            let database = <DelayedFixedDb as ManagedDb<_>>::apply(database, merkleized)
                .await
                .unwrap();
            slot.put(database);

            assert_eq!(pending.starts(), starts, "apply must not start durability");
            {
                let guard = db.read().await;
                assert_eq!(guard.get(&key).await.unwrap(), Some(value));
            }

            let (slot, database) = db.write().await;
            let (database, sync) = <DelayedFixedDb as ManagedDb<_>>::finalize(database)
                .await
                .unwrap();
            slot.put(database);
            assert!(
                pending.starts() > pending.completions(),
                "finalize must leave its flush parked",
            );

            release_pending_syncs(&pending);
            drive_pending_syncs(&pending, sync)
                .await
                .expect("flush must succeed once released");
        });
    }
}