use super::mem_pool::MemoryChunkPool;
use crate::mem_pool::FileID;
use anyhow::Result;
use metrics::{Histogram, Sample};
use network::{NetworkMessage, NetworkSender};
use shared_types::{ChunkArray, FileProof};
use std::{sync::Arc, time::Instant};
use storage_async::{ShardConfig, Store};
use tokio::sync::mpsc::UnboundedReceiver;

lazy_static::lazy_static! {
    pub static ref FINALIZE_FILE_LATENCY: Arc<dyn Histogram> = Sample::ExpDecay(0.015).register("chunk_pool_finalize_file_latency", 1024);
}

/// Handle the cached file when uploaded completely and verified from blockchain.
/// Generally, the file will be persisted into log store.
pub struct ChunkPoolHandler {
    receiver: UnboundedReceiver<ChunkPoolMessage>,
    mem_pool: Arc<MemoryChunkPool>,
    log_store: Arc<Store>,
    sender: NetworkSender,
}

impl ChunkPoolHandler {
    pub(crate) fn new(
        receiver: UnboundedReceiver<ChunkPoolMessage>,
        mem_pool: Arc<MemoryChunkPool>,
        log_store: Arc<Store>,
        sender: NetworkSender,
    ) -> Self {
        ChunkPoolHandler {
            receiver,
            mem_pool,
            log_store,
            sender,
        }
    }

    async fn handle(&mut self) -> Result<bool> {
        match self.receiver.recv().await {
            Some(ChunkPoolMessage::FinalizeFile(file_id)) => self.handle_file_id(file_id).await,
            Some(ChunkPoolMessage::ChangeShardConfig(shard_config)) => {
                self.handle_change_shard_config(shard_config).await;
                Ok(true)
            }
            None => Ok(false),
        }
    }

    /// Writes memory cached chunks into store and finalize transaction.
    /// Note, a separate thread should be spawned to call this method.
    async fn handle_file_id(&mut self, id: FileID) -> Result<bool> {
        debug!(?id, "Received task to finalize transaction");

        // TODO(qhz): remove from memory pool after transaction finalized,
        // when store support to write chunks with reference.
        if let Some(file) = self.mem_pool.remove_cached_file(&id.root).await {
            // If there is still cache of chunks, write them into store
            let mut segments: Vec<(ChunkArray, FileProof)> = file.segments.into_values().collect();
            while let Some((seg, proof)) = segments.pop() {
                if !self
                    .log_store
                    .put_chunks_with_tx_hash(
                        id.tx_id.seq,
                        id.tx_id.hash,
                        seg,
                        Some(proof.try_into()?),
                    )
                    .await?
                {
                    return Ok(false);
                }
            }
        }

        let start = Instant::now();
        if !self
            .log_store
            .finalize_tx_with_hash(id.tx_id.seq, id.tx_id.hash)
            .await?
        {
            return Ok(false);
        }

        let elapsed = start.elapsed();
        debug!(?id, ?elapsed, "Transaction finalized");
        FINALIZE_FILE_LATENCY.update_since(start);

        // always remove file from pool after transaction finalized
        self.mem_pool.remove_file(&id.root).await;

        let msg = NetworkMessage::AnnounceLocalFile { tx_id: id.tx_id };
        if let Err(e) = self.sender.send(msg) {
            error!(
                "Failed to send NetworkMessage::AnnounceLocalFile message, tx_seq={}, err={}",
                id.tx_id.seq, e
            );
        }

        Ok(true)
    }

    async fn handle_change_shard_config(&self, shard_config: ShardConfig) {
        self.mem_pool.set_shard_config(shard_config).await
    }

    pub async fn run(mut self) {
        info!("Worker started to finalize transactions");

        loop {
            if let Err(e) = self.handle().await {
                warn!("Failed to write chunks or finalize transaction, {:?}", e);
            }
        }
    }
}

pub enum ChunkPoolMessage {
    FinalizeFile(FileID),
    ChangeShardConfig(ShardConfig),
}