//! Shared synchronization logic for [crate::qmdb::current] databases.
//!
//! Contains the implementation of [crate::qmdb::sync::Database] for
//! [Db](crate::qmdb::current::db::Db), covering every variant (ordered/unordered,
//! fixed/variable, any snapshot index).
//!
//! The canonical root of a `current` database combines the ops root, grafted root, and optional
//! pending and partial chunk digests into a single hash (see the [Root structure](super) section in
//! the module documentation). The sync engine operates on the **ops root**, not the canonical root:
//! it downloads operations and verifies each batch against the ops root using ops-tree range proofs
//! (identical to `any` sync). Callers that verify current ops proofs directly should use
//! [crate::qmdb::verify_proof]. [crate::qmdb::current::proof::OpsRootWitness] can be used by
//! callers that need to authenticate the synced ops root against a trusted canonical root; the sync
//! engine does not perform this check itself.
//!
//! After all operations are synced, the bitmap and grafted tree are reconstructed deterministically
//! from the operations. The canonical root is then computed from the ops root, the reconstructed
//! grafted root, and any pending or partial chunk digests.
//!
//! The [Database]`::`[root()](crate::qmdb::sync::Database::root) implementation returns the **ops
//! root** (not the canonical root) because that is what the sync engine verifies against.
//!
//! For pruned databases (`range.start > 0`), grafted pinned nodes for the pruned region are read
//! directly from the ops tree after it is built. This works because of the zero-chunk identity: for
//! all-zero bitmap chunks (which all pruned chunks are), the grafted leaf equals the ops subtree
//! root, making the grafted tree structurally identical to the ops tree at and above the grafting
//! height.

use crate::{
    Context,
    index::{Factory as IndexFactory, Unordered as UnorderedIndex},
    journal::{authenticated, contiguous::Mutable},
    merkle::{
        Graftable, Location,
        full::{self, Merkle},
    },
    qmdb::{
        self,
        any::{
            db::Db as AnyDb,
            operation::{Operation, update::Update},
        },
        bitmap::Shared,
        current::{db, grafting},
        metrics::Metrics as AnyMetrics,
        sync::{Database, DatabaseConfig as Config, Request, source},
    },
    translator::Translator,
};
use commonware_codec::Codec;
use commonware_cryptography::{DigestOf, Hasher};
use commonware_parallel::Strategy;
use commonware_runtime::Spawner;
use commonware_utils::{bitmap::Prunable as BitMap, range::NonEmptyRange};
use core::num::NonZeroUsize;
use std::{num::NonZeroU64, sync::Arc};

#[cfg(test)]
pub(crate) mod tests;

impl<T: Translator, J: Clone, S: Strategy, B> Config for super::Config<T, J, S, B> {
    type JournalConfig = J;

    fn journal_config(&self) -> Self::JournalConfig {
        self.journal_config.clone()
    }
}

/// Shared helper to build a `current::db::Db` from sync components.
///
/// This follows the same pattern as `any/sync/mod.rs::build_db` but additionally:
/// * Builds the activity bitmap by replaying the operations log.
/// * Extracts grafted pinned nodes from the ops tree (zero-chunk identity).
/// * Builds the grafted tree from the bitmap and ops tree.
/// * Computes and caches the canonical root.
#[allow(clippy::too_many_arguments)]
async fn build_db<F, E, U, I, H, J, const N: usize, S>(
    context: E,
    merkle_config: full::Config<S>,
    log: J,
    translator: I::Translator,
    pinned_nodes: Option<Vec<H::Digest>>,
    range: NonEmptyRange<Location<F>>,
    apply_batch_size: NonZeroU64,
    init_concurrency: <I as crate::qmdb::SnapshotBuild<F>>::Concurrency,
    init_buffer: NonZeroUsize,
    cache_size: Option<NonZeroUsize>,
    metadata_partition: String,
    strategy: S,
) -> Result<db::Db<F, E, J, I, H, U, N, S>, qmdb::Error<F>>
where
    F: Graftable,
    E: Context + Spawner,
    U: Update,
    I: IndexFactory + crate::qmdb::SnapshotBuild<F>,
    H: Hasher,
    J: Mutable<Item = Operation<F, U>> + 'static,
    S: Strategy,
    Operation<F, U>: Codec,
{
    // Build authenticated log.
    let merkle = Merkle::<F, _, _, S>::init_sync(
        context.child("merkle"),
        full::SyncConfig {
            config: merkle_config,
            range: range.clone(),
            pinned_nodes,
        },
    )
    .await?;
    let index = I::new(context.child("index"), translator);
    let log = authenticated::Journal::<F, _, _, _, S>::from_components(
        merkle,
        log,
        qmdb::hasher::<H>(),
        apply_batch_size,
    )
    .await?;

    // Initialize bitmap with pruned chunks.
    //
    // Floor division is intentional: chunks entirely below range.start are pruned.
    // If range.start is not chunk-aligned, the partial leading chunk is reconstructed by
    // init_from_log, which pads the gap between `pruned_chunks * CHUNK_SIZE_BITS` and the
    // journal's inactivity floor with inactive (false) bits.
    let pruned_chunks = (*range.start() / BitMap::<N>::CHUNK_SIZE_BITS) as usize;
    let bitmap = BitMap::<N>::new_with_pruned_chunks(pruned_chunks)
        .map_err(|_| qmdb::Error::<F>::DataCorrupted("pruned chunks overflow"))?;
    let bitmap = Arc::new(Shared::<N>::new(bitmap));

    // Build any::Db, handing it the pre-allocated bitmap. `init_from_log` populates the bitmap
    // during replay.
    let snapshot_context = context.child("any_snapshot");
    let any_metrics = AnyMetrics::new(context.child("any"));
    let any: AnyDb<F, E, J, I, H, U, N, S> = AnyDb::init_from_log(
        snapshot_context,
        index,
        log,
        Some(bitmap),
        init_concurrency,
        init_buffer,
        cache_size,
        any_metrics,
    )
    .await?;

    // Fetch grafted pinned nodes from the ops tree. For each position the grafted family
    // needs at its pruning boundary, source the digest from the ops tree via the zero-chunk
    // identity: when the covered chunks are all zero (which pruned chunks always are), the
    // ops-family digest at the mapped position equals the grafted digest.
    //
    // Requires `range.start <=` target's [`Db::sync_boundary`](db::Db::sync_boundary): that
    // bound guarantees every required ops-tree node is born at `range.end`.
    let grafted_pinned_nodes = {
        let grafted_boundary = Location::<F>::new(pruned_chunks as u64);
        let grafting_height = grafting::height::<N>();
        let mut pinned_nodes = Vec::new();
        for grafted_pos in F::nodes_to_pin(grafted_boundary) {
            let ops_pos = grafting::grafted_to_ops_pos::<F>(grafted_pos, grafting_height);
            let digest = any
                .log
                .merkle
                .get_node(ops_pos)
                .await?
                .ok_or(qmdb::Error::<F>::DataCorrupted("missing ops pinned node"))?;
            pinned_nodes.push(digest);
        }
        pinned_nodes
    };

    // Rebuild the grafted tree, graft roots, and canonical root from the synced `any` state.
    // The canonical root is deterministic because the engine authenticates the ops and the
    // bitmap is derived from them.
    let (grafted_tree, graft_roots, root) = db::rebuild_grafted_tree::<F, H, S, N>(
        any.bitmap.as_ref(),
        &grafted_pinned_nodes,
        &any.log.merkle,
        any.inactivity_floor_loc,
        any.root(),
        &strategy,
    )
    .await?;

    // Initialize metadata store and construct the Db.
    let (metadata, _, _) =
        db::init_metadata::<F, E, DigestOf<H>>(context.child("metadata"), &metadata_partition)
            .await?;

    let metrics = db::Metrics::new(context);
    let current_db = db::Db {
        any,
        grafted_tree: Arc::new(grafted_tree),
        graft_roots,
        metadata,
        strategy,
        root,
        metrics,
        #[cfg(test)]
        halt_before_prune_log: false,
    };
    current_db.update_metrics();

    // Persist metadata so the db can be reopened with init_fixed/init_variable.
    let current_db = current_db.sync_metadata().await?;

    Ok(current_db)
}

impl<F, E, C, I, H, U, const N: usize, S> Database for db::Db<F, E, C, I, H, U, N, S>
where
    F: Graftable,
    E: Context + Spawner,
    C: Mutable<Item = Operation<F, U>>
        + crate::qmdb::sync::Journal<F, Context = E, Op = Operation<F, U>>
        + 'static,
    I: IndexFactory + crate::qmdb::SnapshotBuild<F> + UnorderedIndex<Value = Location<F>>,
    H: Hasher,
    U: Update,
    S: Strategy,
    Operation<F, U>: Codec,
{
    type Family = F;
    type Context = E;
    type Op = Operation<F, U>;
    type Journal = C;
    type Hasher = H;
    type Config = super::Config<
        I::Translator,
        <C as crate::qmdb::sync::Journal<F>>::Config,
        S,
        <I as crate::qmdb::SnapshotBuild<F>>::Concurrency,
    >;
    type Digest = H::Digest;

    async fn from_sync_result(
        context: Self::Context,
        config: Self::Config,
        log: Self::Journal,
        pinned_nodes: Option<Vec<Self::Digest>>,
        range: NonEmptyRange<Location<F>>,
        apply_batch_size: NonZeroU64,
    ) -> Result<Self, qmdb::Error<F>> {
        let strategy = config.merkle_config.strategy.clone();
        build_db::<F, _, U, _, H, _, N, _>(
            context,
            config.merkle_config,
            log,
            config.translator,
            pinned_nodes,
            range,
            apply_batch_size,
            config.init_concurrency,
            config.init_buffer,
            config.init_cache,
            config.grafted_metadata_partition,
            strategy,
        )
        .await
    }

    async fn persist_sync_result(self) -> Result<Self, qmdb::Error<F>> {
        Ok(self)
    }

    async fn local_pinned_nodes(
        context: Self::Context,
        config: &Self::Config,
        target: &qmdb::sync::Target<Self::Family, Self::Digest>,
        journal: &Self::Journal,
    ) -> Result<Option<Vec<Self::Digest>>, qmdb::Error<F>> {
        if target.range.start() == Location::new(0)
            || !qmdb::sync::journal_covers_range(journal.bounds(), &target.range)
        {
            return Ok(None);
        }

        // The inactivity floor is carried by the last commit operation rather than
        // being the target range's start.
        let inactivity_floor =
            qmdb::find_inactivity_floor_at::<F, _>(journal, target.range.end()).await?;

        qmdb::sync::local_pinned_nodes::<F, _, H, S>(
            context,
            config.merkle_config.clone(),
            target,
            inactivity_floor,
        )
        .await
    }

    /// Returns the ops root (not the canonical root), since the sync engine verifies
    /// batches against the ops tree.
    fn root(&self) -> Self::Digest {
        self.any.root()
    }
}

/// A `current` database serves proofs from the `any` database it wraps. The sync engine
/// operates on the ops root, which is `any`'s root.
impl<F, E, C, I, H, U, const N: usize, S> crate::qmdb::sync::Source
    for db::Db<F, E, C, I, H, U, N, S>
where
    F: Graftable,
    E: Context,
    C: Mutable<Item = Operation<F, U>>,
    I: UnorderedIndex<Value = Location<F>>,
    H: Hasher,
    U: Update,
    S: Strategy,
    Operation<F, U>: Codec,
{
    type Family = F;
    type Digest = H::Digest;
    type Op = Operation<F, U>;
    type Error = qmdb::Error<F>;

    async fn serve(&self, request: Request<F>) -> source::Result<Self> {
        self.any.serve(request).await
    }
}