use std::pin::Pin;

use dashmap::DashMap;
use eyre::Result;
use time::OffsetDateTime;
use tokio_stream::Stream;
use tonic::{Request, Response, Status};
use tracing::{Level, instrument};

use crate::{
    aclient::{
        history::{History, HistoryId, store::HistoryStore},
        settings::Settings,
    },
    api::{
        DAEMON_PROTOCOL_VERSION,
        generated::history::{
            EndHistoryReply, EndHistoryRequest, HistoryEntry, HistoryEventKind, StartHistoryReply,
            StartHistoryRequest, TailHistoryReply, TailHistoryRequest,
            history_server::{History as HistorySvc, HistoryServer},
        },
    },
    daemon::DaemonHandle,
    events::DaemonEvent,
};

/// The gRPC service implementation.
///
/// This is a thin wrapper that delegates to the component's shared state.
pub(crate) struct HistoryService {
    /// Commands currently running (not yet completed).
    running: DashMap<HistoryId, History>,

    /// Handle to the daemon (set during start).
    pub(crate) handle: DaemonHandle,

    /// History store for pushing records (set during start).
    pub(crate) history_store: HistoryStore,
}

impl HistoryService {
    pub(crate) async fn new(handle: DaemonHandle) -> Result<Self> {
        let host_id = Settings::host_id().await?;
        let history_store =
            HistoryStore::new(handle.store().clone(), host_id, *handle.encryption_key());

        Ok(Self {
            running: DashMap::new(),
            handle,
            history_store,
        })
    }

    /// Get a tonic server for this service.
    pub(crate) fn into_server(self) -> HistoryServer<Self> {
        HistoryServer::new(self)
    }
}

fn history_to_tail_reply(kind: HistoryEventKind, history: History) -> TailHistoryReply {
    TailHistoryReply {
        kind: kind as i32,
        history: Some(HistoryEntry {
            timestamp: history.timestamp.unix_timestamp_nanos() as u64,
            id: history.id.0,
            command: history.command,
            cwd: history.cwd,
            session: history.session,
            hostname: history.hostname,
            author: history.author,
            intent: history.intent.unwrap_or_default(),
            exit: history.exit,
            duration: history.duration,
        }),
    }
}

#[tonic::async_trait]
impl HistorySvc for HistoryService {
    type TailHistoryStream = Pin<Box<dyn Stream<Item = Result<TailHistoryReply, Status>> + Send>>;

    #[instrument(skip_all, level = Level::INFO)]
    async fn start_history(
        &self,
        request: Request<StartHistoryRequest>,
    ) -> Result<Response<StartHistoryReply>, Status> {
        let req = request.into_inner();

        let timestamp = OffsetDateTime::from_unix_timestamp_nanos(i128::from(req.timestamp))
            .map_err(|_| {
                Status::invalid_argument(
                    "failed to parse timestamp as unix time (expected nanos since epoch)",
                )
            })?;

        let h: History = History::daemon()
            .timestamp(timestamp)
            .command(req.command)
            .cwd(req.cwd)
            .session(req.session)
            .hostname(req.hostname)
            .author(req.author)
            .intent(req.intent)
            .build()
            .into();

        self.handle.emit(DaemonEvent::HistoryStarted(h.clone()));

        let id = h.id.clone();
        tracing::info!(id = id.to_string(), "start history");
        self.running.insert(id.clone(), h);

        let reply = StartHistoryReply {
            id: id.to_string(),
            version: env!("CARGO_PKG_VERSION").to_string(),
            protocol: DAEMON_PROTOCOL_VERSION,
        };

        Ok(Response::new(reply))
    }

    #[instrument(skip_all, level = Level::INFO)]
    #[expect(clippy::significant_drop_tightening, reason = "Would be a logic-bug")]
    async fn end_history(
        &self,
        request: Request<EndHistoryRequest>,
    ) -> Result<Response<EndHistoryReply>, Status> {
        let req = request.into_inner();
        let id = HistoryId(req.id);

        if let Some((_, mut history)) = self.running.remove(&id) {
            history.exit = req.exit;
            history.duration = match req.duration {
                0 => i64::try_from(
                    (OffsetDateTime::now_utc() - history.timestamp).whole_nanoseconds(),
                )
                .expect("failed to convert calculated duration to i64"),
                value => i64::try_from(value).expect("failed to get i64 duration"),
            };

            self.handle
                .history_db()
                .save(&history)
                .await
                .map_err(|e| Status::internal(format!("failed to write to db: {e:?}")))?;

            tracing::info!(id = id.0, duration = history.duration, "end history");

            let (record_id, idx) = self
                .history_store
                .push(history.clone())
                .await
                .map_err(|e| Status::internal(format!("failed to push record to store: {e:?}")))?;

            self.handle.emit(DaemonEvent::HistoryEnded(history));

            let reply = EndHistoryReply {
                id: record_id.0.to_string(),
                idx,
                version: env!("CARGO_PKG_VERSION").to_string(),
                protocol: DAEMON_PROTOCOL_VERSION,
            };

            return Ok(Response::new(reply));
        }

        Err(Status::not_found(format!(
            "could not find history with id: {id}"
        )))
    }

    #[instrument(skip_all, level = Level::INFO)]
    #[expect(clippy::significant_drop_tightening, reason = "Would be a logic-bug")]
    async fn tail_history(
        &self,
        _request: Request<TailHistoryRequest>,
    ) -> Result<Response<Self::TailHistoryStream>, Status> {
        let mut rx = self.handle.subscribe();
        let (tx, out_rx) = tokio::sync::mpsc::channel::<Result<TailHistoryReply, Status>>(128);

        tokio::spawn(async move {
            loop {
                let event = match rx.recv().await {
                    Ok(event) => event,
                    Err(tokio::sync::broadcast::error::RecvError::Lagged(skipped)) => {
                        drop(
                            tx.send(Err(Status::resource_exhausted(format!(
                                "tail stream lagged behind and dropped {skipped} events"
                            ))))
                            .await,
                        );
                        break;
                    }
                    Err(tokio::sync::broadcast::error::RecvError::Closed) => break,
                };

                let reply = match event {
                    DaemonEvent::HistoryStarted(history) => {
                        Some(history_to_tail_reply(HistoryEventKind::Started, history))
                    }
                    DaemonEvent::HistoryEnded(history) => {
                        Some(history_to_tail_reply(HistoryEventKind::Ended, history))
                    }
                    _ => None,
                };

                if let Some(reply) = reply
                    && tx.send(Ok(reply)).await.is_err()
                {
                    break;
                }
            }
        });

        let stream = tokio_stream::wrappers::ReceiverStream::new(out_rx);
        Ok(Response::new(Box::pin(stream)))
    }
}