use std::{net::SocketAddr, sync::Arc, time::Duration};

use anyhow::{Context as _, Result, anyhow};
use bytesize::ByteSize;
use common::transaction::NSSATransaction;
use futures::never::Never;
use jsonrpsee::server::ServerHandle;
#[cfg(not(feature = "standalone"))]
use log::warn;
use log::{error, info};
use mempool::MemPoolHandle;
#[cfg(feature = "standalone")]
use sequencer_core::SequencerCoreWithMockClients as SequencerCore;
pub use sequencer_core::config::*;
#[cfg(not(feature = "standalone"))]
use sequencer_core::{SequencerCore, block_settlement_client::BlockSettlementClientTrait as _};
use sequencer_service_rpc::RpcServer as _;
use tokio::{sync::Mutex, task::JoinHandle};

pub mod service;

const REQUEST_BODY_MAX_SIZE: ByteSize = ByteSize::mib(10);

/// Handle to manage the sequencer and its tasks.
///
/// Implements `Drop` to ensure all tasks are aborted and the RPC server is stopped when dropped.
pub struct SequencerHandle {
    addr: SocketAddr,
    /// Option because of `Drop` which forbids to simply move out of `self` in `stopped()`.
    server_handle: Option<ServerHandle>,
    main_loop_handle: JoinHandle<Result<Never>>,
    retry_pending_blocks_loop_handle: JoinHandle<Result<Never>>,
    listen_for_bedrock_blocks_loop_handle: JoinHandle<Result<Never>>,
}

impl SequencerHandle {
    const fn new(
        addr: SocketAddr,
        server_handle: ServerHandle,
        main_loop_handle: JoinHandle<Result<Never>>,
        retry_pending_blocks_loop_handle: JoinHandle<Result<Never>>,
        listen_for_bedrock_blocks_loop_handle: JoinHandle<Result<Never>>,
    ) -> Self {
        Self {
            addr,
            server_handle: Some(server_handle),
            main_loop_handle,
            retry_pending_blocks_loop_handle,
            listen_for_bedrock_blocks_loop_handle,
        }
    }

    /// Wait for any of the sequencer tasks to fail and return the error.
    #[expect(
        clippy::integer_division_remainder_used,
        reason = "Generated by select! macro, can't be easily rewritten to avoid this lint"
    )]
    pub async fn failed(mut self) -> Result<Never> {
        let Self {
            addr: _,
            server_handle,
            main_loop_handle,
            retry_pending_blocks_loop_handle,
            listen_for_bedrock_blocks_loop_handle,
        } = &mut self;

        let server_handle = server_handle.take().expect("Server handle is set");

        tokio::select! {
            () = server_handle.stopped() => {
                Err(anyhow!("RPC Server stopped"))
            }
            res = main_loop_handle => {
                res
                   .context("Main loop task panicked")?
                   .context("Main loop exited unexpectedly")
            }
            res = retry_pending_blocks_loop_handle => {
                res
                   .context("Retry pending blocks loop task panicked")?
                   .context("Retry pending blocks loop exited unexpectedly")
            }
            res = listen_for_bedrock_blocks_loop_handle => {
                res
                   .context("Listen for bedrock blocks loop task panicked")?
                   .context("Listen for bedrock blocks loop exited unexpectedly")
            }
        }
    }

    /// Check if all Sequencer tasks are still running.
    ///
    /// Return `false` if any of the tasks has failed and `true` otherwise.
    /// Error of the failed task can be retrieved by awaiting on [`Self::failed()`].
    #[must_use]
    pub fn is_healthy(&self) -> bool {
        let Self {
            addr: _,
            server_handle,
            main_loop_handle,
            retry_pending_blocks_loop_handle,
            listen_for_bedrock_blocks_loop_handle,
        } = self;

        let stopped = server_handle.as_ref().is_none_or(ServerHandle::is_stopped)
            || main_loop_handle.is_finished()
            || retry_pending_blocks_loop_handle.is_finished()
            || listen_for_bedrock_blocks_loop_handle.is_finished();
        !stopped
    }

    #[must_use]
    pub const fn addr(&self) -> SocketAddr {
        self.addr
    }
}

impl Drop for SequencerHandle {
    fn drop(&mut self) {
        let Self {
            addr: _,
            server_handle,
            main_loop_handle,
            retry_pending_blocks_loop_handle,
            listen_for_bedrock_blocks_loop_handle,
        } = self;

        main_loop_handle.abort();
        retry_pending_blocks_loop_handle.abort();
        listen_for_bedrock_blocks_loop_handle.abort();

        let Some(handle) = server_handle else {
            return;
        };

        if let Err(err) = handle.stop() {
            error!("An error occurred while stopping Sequencer RPC server: {err}");
        }
    }
}

pub async fn run(config: SequencerConfig, port: u16) -> Result<SequencerHandle> {
    let block_timeout = config.block_create_timeout;
    let retry_pending_blocks_timeout = config.retry_pending_blocks_timeout;
    let max_block_size = config.max_block_size;

    let (sequencer_core, mempool_handle) = SequencerCore::start_from_config(config).await;

    info!("Sequencer core set up");

    let seq_core_wrapped = Arc::new(Mutex::new(sequencer_core));

    let (server_handle, addr) = run_server(
        Arc::clone(&seq_core_wrapped),
        mempool_handle,
        port,
        max_block_size.as_u64(),
    )
    .await?;
    info!("RPC server started");

    #[cfg(not(feature = "standalone"))]
    {
        info!("Submitting stored pending blocks");
        retry_pending_blocks(&seq_core_wrapped)
            .await
            .expect("Failed to submit pending blocks on startup");
    }

    info!("Starting main sequencer loop");
    let main_loop_handle = tokio::spawn(main_loop(Arc::clone(&seq_core_wrapped), block_timeout));

    info!("Starting pending block retry loop");
    let retry_pending_blocks_loop_handle = tokio::spawn(retry_pending_blocks_loop(
        Arc::clone(&seq_core_wrapped),
        retry_pending_blocks_timeout,
    ));

    info!("Starting bedrock block listening loop");
    let listen_for_bedrock_blocks_loop_handle =
        tokio::spawn(listen_for_bedrock_blocks_loop(seq_core_wrapped));

    Ok(SequencerHandle::new(
        addr,
        server_handle,
        main_loop_handle,
        retry_pending_blocks_loop_handle,
        listen_for_bedrock_blocks_loop_handle,
    ))
}

async fn run_server(
    sequencer: Arc<Mutex<SequencerCore>>,
    mempool_handle: MemPoolHandle<NSSATransaction>,
    port: u16,
    max_block_size: u64,
) -> Result<(ServerHandle, SocketAddr)> {
    let server = jsonrpsee::server::ServerBuilder::with_config(
        jsonrpsee::server::ServerConfigBuilder::new()
            .max_request_body_size(
                u32::try_from(REQUEST_BODY_MAX_SIZE.as_u64())
                    .expect("REQUEST_BODY_MAX_SIZE should be less than u32::MAX"),
            )
            .build(),
    )
    .build(SocketAddr::from(([0, 0, 0, 0], port)))
    .await
    .context("Failed to build RPC server")?;

    let addr = server
        .local_addr()
        .context("Failed to get local address of RPC server")?;

    info!("Starting Sequencer Service RPC server on {addr}");

    let service = service::SequencerService::new(sequencer, mempool_handle, max_block_size);
    let handle = server.start(service.into_rpc());
    Ok((handle, addr))
}

async fn main_loop(seq_core: Arc<Mutex<SequencerCore>>, block_timeout: Duration) -> Result<Never> {
    loop {
        tokio::time::sleep(block_timeout).await;

        info!("Collecting transactions from mempool, block creation");

        let id = {
            let mut state = seq_core.lock().await;

            state.produce_new_block().await?
        };

        info!("Block with id {id} created");

        info!("Waiting for new transactions");
    }
}

#[cfg(not(feature = "standalone"))]
async fn retry_pending_blocks(seq_core: &Arc<Mutex<SequencerCore>>) -> Result<()> {
    use std::time::Instant;

    use log::debug;

    let (mut pending_blocks, block_settlement_client) = {
        let sequencer_core = seq_core.lock().await;
        let client = sequencer_core.block_settlement_client();
        let pending_blocks = sequencer_core
            .get_pending_blocks()
            .expect("Sequencer should be able to retrieve pending blocks");
        (pending_blocks, client)
    };

    pending_blocks.sort_by(|block1, block2| block1.header.block_id.cmp(&block2.header.block_id));

    if !pending_blocks.is_empty() {
        info!(
            "Resubmitting blocks from {} to {}",
            pending_blocks.first().unwrap().header.block_id,
            pending_blocks.last().unwrap().header.block_id
        );
    }

    for block in &pending_blocks {
        debug!(
            "Resubmitting pending block with id {}",
            block.header.block_id
        );
        // TODO: We could cache the inscribe tx for each pending block to avoid re-creating it
        // on every retry.
        let now = Instant::now();
        let (tx, _msg_id) = block_settlement_client
            .create_inscribe_tx(block)
            .context("Failed to create inscribe tx for pending block")?;

        debug!("Create inscribe: {:?}", now.elapsed());

        let now = Instant::now();
        if let Err(e) = block_settlement_client
            .submit_inscribe_tx_to_bedrock(tx)
            .await
        {
            warn!(
                "Failed to resubmit block with id {} with error {e:#}",
                block.header.block_id
            );
        }
        debug!("Post: {:?}", now.elapsed());
    }
    Ok(())
}

#[cfg(not(feature = "standalone"))]
async fn retry_pending_blocks_loop(
    seq_core: Arc<Mutex<SequencerCore>>,
    retry_pending_blocks_timeout: Duration,
) -> Result<Never> {
    loop {
        tokio::time::sleep(retry_pending_blocks_timeout).await;
        retry_pending_blocks(&seq_core).await?;
    }
}

#[cfg(not(feature = "standalone"))]
async fn listen_for_bedrock_blocks_loop(seq_core: Arc<Mutex<SequencerCore>>) -> Result<Never> {
    use indexer_service_rpc::RpcClient as _;

    let indexer_client = seq_core.lock().await.indexer_client();

    let retry_delay = Duration::from_secs(5);

    loop {
        // TODO: Subscribe from the first pending block ID?
        let mut subscription = indexer_client
            .subscribe_to_finalized_blocks()
            .await
            .context("Failed to subscribe to finalized blocks")?;

        while let Some(block_id) = subscription.next().await {
            let block_id = block_id.context("Failed to get next block from subscription")?;

            info!("Received new L2 block with ID {block_id}");

            seq_core
                .lock()
                .await
                .clean_finalized_blocks_from_db(block_id)
                .with_context(|| {
                    format!("Failed to clean finalized blocks from DB for block ID {block_id}")
                })?;
        }

        warn!(
            "Block subscription closed unexpectedly, reason: {:?}, retrying after {retry_delay:?}",
            subscription.close_reason()
        );
        tokio::time::sleep(retry_delay).await;
    }
}

#[cfg(feature = "standalone")]
async fn listen_for_bedrock_blocks_loop(_seq_core: Arc<Mutex<SequencerCore>>) -> Result<Never> {
    std::future::pending::<Result<Never>>().await
}

#[cfg(feature = "standalone")]
async fn retry_pending_blocks_loop(
    _seq_core: Arc<Mutex<SequencerCore>>,
    _retry_pending_blocks_timeout: Duration,
) -> Result<Never> {
    std::future::pending::<Result<Never>>().await
}