// SPDX-FileCopyrightText: Copyright (c) 2024-2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
// SPDX-License-Identifier: Apache-2.0

use async_trait::async_trait;

use super::{KvRouterError, WorkerTask};
use crate::protocols::*;

#[async_trait]
pub trait KvIndexerInterface {
    /// Find matches for a given sequence of `LocalBlockHash`es.
    ///
    /// ### Arguments
    ///
    /// * `sequence` - A vector of `LocalBlockHash` representing the sequence to match.
    ///
    /// ### Returns
    ///
    /// An `OverlapScores` representing the match scores.
    async fn find_matches(
        &self,
        sequence: Vec<LocalBlockHash>,
    ) -> Result<OverlapScores, KvRouterError>;

    /// Find matches for a given sequence of tokens.
    ///
    /// ### Arguments
    ///
    /// * `tokens` - A vector of `u32` tokens.
    /// * `lora_name` - Optional LoRA adapter name to include in block hash computation.
    ///
    /// ### Returns
    ///
    /// An `OverlapScores` representing the match scores.
    async fn find_matches_for_request(
        &self,
        tokens: &[u32],
        lora_name: Option<&str>,
    ) -> Result<OverlapScores, KvRouterError>;

    /// Apply a `RouterEvent` to the KV store.
    ///
    /// ### Arguments
    ///
    /// * `event` - The `RouterEvent` to apply.
    async fn apply_event(&self, event: RouterEvent);

    /// Remove a worker's entries from the trie.
    ///
    /// ### Arguments
    ///
    /// * `worker` - The worker to remove from the trie.
    async fn remove_worker(&self, worker: WorkerId);

    /// Remove a single dp_rank for a worker from the trie.
    ///
    /// Default implementation falls back to removing the entire worker.
    /// Indexers that track dp_rank-level granularity should override this.
    async fn remove_worker_dp_rank(&self, worker: WorkerId, _dp_rank: DpRank) {
        self.remove_worker(worker).await;
    }

    /// Shutdown the KV Indexer.
    fn shutdown(&self);

    /// Dump the entire tree as RouterEvents.
    ///
    /// ### Returns
    ///
    /// A vector of RouterEvents representing the current state of the tree.
    async fn dump_events(&self) -> Result<Vec<RouterEvent>, KvRouterError>;

    /// Process a routing decision for a request with tokens.
    ///
    /// Uses TokensWithHashes for lazy hash computation - if hashes were already
    /// computed (e.g., by find_best_match), they will be reused.
    ///
    /// ### Arguments
    ///
    /// * `tokens_with_hashes` - Tokens with lazily computed hashes.
    /// * `worker` - The worker (with dp_rank) that was selected.
    async fn process_routing_decision_for_request(
        &self,
        tokens_with_hashes: &mut TokensWithHashes,
        worker: WorkerWithDpRank,
    ) -> Result<(), KvRouterError>;

    /// Async task that returns when all pending events have been processed.
    /// For now, we assume that no requests or events are being sent in the meantime.
    /// Returns the amount of events still in the queue at the time of the flush.
    /// Used primarily for debugging.
    async fn flush(&self) -> usize;
}

// ============================================================================
// SyncIndexer trait
// ============================================================================

/// Trait for thread-safe data structures that support KV cache indexing operations.
///
/// All methods take `&self` and are synchronous. Implementations must be safe for
/// concurrent access (via internal locking, DashMap, etc).
///
/// This trait is used with [`ThreadPoolIndexer`](super::ThreadPoolIndexer), which wraps a `SyncIndexer` to
/// provide the async [`KvIndexerInterface`] with:
/// - Sticky event routing to N worker threads
/// - Inline reads on the caller's thread (no channel dispatch for find_matches)
pub trait SyncIndexer: Send + Sync + 'static {
    fn worker(&self, event_receiver: flume::Receiver<WorkerTask>) -> anyhow::Result<()>;

    /// Find matches for a sequence of block hashes.
    fn find_matches(&self, sequence: &[LocalBlockHash], early_exit: bool) -> OverlapScores;

    /// Dump events directly from the shared structure, bypassing worker channels.
    /// Returns `Some(events)` for backends whose tree state is fully shared (e.g.
    /// ConcurrentRadixTree). Returns `None` for backends that keep per-thread
    /// state and must dump via the worker channel.
    fn dump_events(&self) -> Option<Vec<RouterEvent>> {
        None
    }
}
