//! Reading note commitment trees.
//!
//! In the functions in this module:
//!
//! The block write task commits blocks to the finalized state before updating
//! `chain` with a cached copy of the best non-finalized chain from
//! `NonFinalizedState.chain_set`. Then the block commit task can commit additional blocks to
//! the finalized state after we've cloned the `chain`.
//!
//! This means that some blocks can be in both:
//! - the cached [`Chain`], and
//! - the shared finalized [`ZebraDb`] reference.

use std::sync::Arc;

use zebra_chain::{
    orchard, sapling,
    subtree::{NoteCommitmentSubtree, NoteCommitmentSubtreeIndex},
};

use crate::{
    service::{finalized_state::ZebraDb, non_finalized_state::Chain},
    HashOrHeight,
};

/// Returns the Sapling
/// [`NoteCommitmentTree`](sapling::tree::NoteCommitmentTree) specified by a
/// hash or height, if it exists in the non-finalized `chain` or finalized `db`.
pub fn sapling_tree<C>(
    chain: Option<C>,
    db: &ZebraDb,
    hash_or_height: HashOrHeight,
) -> Option<Arc<sapling::tree::NoteCommitmentTree>>
where
    C: AsRef<Chain>,
{
    // # Correctness
    //
    // Since sapling treestates are the same in the finalized and non-finalized
    // state, we check the most efficient alternative first. (`chain` is always
    // in memory, but `db` stores blocks on disk, with a memory cache.)
    chain
        .and_then(|chain| chain.as_ref().sapling_tree(hash_or_height))
        .or_else(|| db.sapling_tree_by_hash_or_height(hash_or_height))
}

/// Returns the Sapling
/// [`NoteCommitmentSubtree`](NoteCommitmentSubtree) specified by an
/// index, if it exists in the non-finalized `chain` or finalized `db`.
#[allow(unused)]
pub fn sapling_subtree<C>(
    chain: Option<C>,
    db: &ZebraDb,
    index: NoteCommitmentSubtreeIndex,
) -> Option<Arc<NoteCommitmentSubtree<sapling::tree::Node>>>
where
    C: AsRef<Chain>,
{
    // # Correctness
    //
    // Since sapling treestates are the same in the finalized and non-finalized
    // state, we check the most efficient alternative first. (`chain` is always
    // in memory, but `db` stores blocks on disk, with a memory cache.)
    chain
        .and_then(|chain| chain.as_ref().sapling_subtree_by_index(index))
        .or_else(|| db.sapling_subtree_by_index(index))
}

/// Returns the Orchard
/// [`NoteCommitmentTree`](orchard::tree::NoteCommitmentTree) specified by a
/// hash or height, if it exists in the non-finalized `chain` or finalized `db`.
pub fn orchard_tree<C>(
    chain: Option<C>,
    db: &ZebraDb,
    hash_or_height: HashOrHeight,
) -> Option<Arc<orchard::tree::NoteCommitmentTree>>
where
    C: AsRef<Chain>,
{
    // # Correctness
    //
    // Since orchard treestates are the same in the finalized and non-finalized
    // state, we check the most efficient alternative first. (`chain` is always
    // in memory, but `db` stores blocks on disk, with a memory cache.)
    chain
        .and_then(|chain| chain.as_ref().orchard_tree(hash_or_height))
        .or_else(|| db.orchard_tree_by_hash_or_height(hash_or_height))
}

/// Returns the Orchard
/// [`NoteCommitmentSubtree`](NoteCommitmentSubtree) specified by an
/// index, if it exists in the non-finalized `chain` or finalized `db`.
#[allow(unused)]
pub fn orchard_subtree<C>(
    chain: Option<C>,
    db: &ZebraDb,
    index: NoteCommitmentSubtreeIndex,
) -> Option<Arc<NoteCommitmentSubtree<orchard::tree::Node>>>
where
    C: AsRef<Chain>,
{
    // # Correctness
    //
    // Since orchard treestates are the same in the finalized and non-finalized
    // state, we check the most efficient alternative first. (`chain` is always
    // in memory, but `db` stores blocks on disk, with a memory cache.)
    chain
        .and_then(|chain| chain.as_ref().orchard_subtree_by_index(index))
        .or_else(|| db.orchard_subtree_by_index(index))
}

#[cfg(feature = "getblocktemplate-rpcs")]
/// Get the history tree of the provided chain.
pub fn history_tree<C>(
    chain: Option<C>,
    db: &ZebraDb,
    hash_or_height: HashOrHeight,
) -> Option<Arc<zebra_chain::history_tree::HistoryTree>>
where
    C: AsRef<Chain>,
{
    chain
        .and_then(|chain| chain.as_ref().history_tree(hash_or_height))
        .or_else(|| Some(db.history_tree()))
}