//! UI event helpers used by peer command and service code.

use std::{
    collections::{BTreeMap, HashMap},
    sync::Arc,
};

use lanspread_db::content_manifest::ContentId;
use tokio::sync::{RwLock, mpsc::UnboundedSender};

use crate::{
    ActiveOperation,
    ActiveOperationKind,
    PeerEvent,
    RemoteGameAvailability,
    RemoteLibraryView,
    context::OperationKind,
    peer_db::PeerGameDB,
};

pub fn send(tx_notify_ui: &UnboundedSender<PeerEvent>, event: PeerEvent) {
    if let Err(err) = tx_notify_ui.send(event) {
        let kind: &'static str = (&err.0).into();
        log::error!("Failed to send {kind} event: channel closed");
    }
}

pub(crate) fn active_operation_snapshot_from_map(
    active_operations: &HashMap<String, OperationKind>,
) -> Vec<ActiveOperation> {
    let mut snapshot = active_operations
        .iter()
        .map(|(id, operation)| ActiveOperation {
            id: id.clone(),
            operation: active_operation_kind(*operation),
        })
        .collect::<Vec<_>>();
    snapshot.sort_by(|left, right| left.id.cmp(&right.id));
    snapshot
}

pub(crate) fn send_active_operations_snapshot(
    tx_notify_ui: &UnboundedSender<PeerEvent>,
    active_operations: &HashMap<String, OperationKind>,
) {
    send(
        tx_notify_ui,
        PeerEvent::ActiveOperationsChanged {
            active_operations: active_operation_snapshot_from_map(active_operations),
        },
    );
}

pub(crate) async fn emit_active_operations(
    active_operations: &Arc<RwLock<HashMap<String, OperationKind>>>,
    tx_notify_ui: &UnboundedSender<PeerEvent>,
) {
    let active_operations = active_operations.read().await;
    send_active_operations_snapshot(tx_notify_ui, &active_operations);
}

fn active_operation_kind(operation: OperationKind) -> ActiveOperationKind {
    match operation {
        OperationKind::Downloading => ActiveOperationKind::Downloading,
        OperationKind::Installing => ActiveOperationKind::Installing,
        OperationKind::Updating => ActiveOperationKind::Updating,
        OperationKind::Uninstalling => ActiveOperationKind::Uninstalling,
        OperationKind::RemovingDownload => ActiveOperationKind::RemovingDownload,
    }
}

pub async fn emit_peer_game_list(
    peer_game_db: &Arc<RwLock<PeerGameDB>>,
    tx_notify_ui: &UnboundedSender<PeerEvent>,
) {
    let db = peer_game_db.read().await;
    send_remote_library_view_locked(&db, tx_notify_ui);
}

fn send_remote_library_view_locked(
    peer_game_db: &PeerGameDB,
    tx_notify_ui: &UnboundedSender<PeerEvent>,
) {
    send(
        tx_notify_ui,
        PeerEvent::RemoteLibraryView(remote_library_view(peer_game_db)),
    );
}

pub(crate) fn remote_library_view(peer_game_db: &PeerGameDB) -> RemoteLibraryView {
    let mut counts = BTreeMap::<(String, ContentId), u32>::new();
    for game in peer_game_db
        .peer_snapshots()
        .into_iter()
        .flat_map(|peer| peer.games)
    {
        let count = counts.entry((game.game_id, game.content_id)).or_default();
        *count = count.saturating_add(1);
    }
    RemoteLibraryView {
        games: counts
            .into_iter()
            .map(
                |((game_id, content_id), peer_count)| RemoteGameAvailability {
                    game_id,
                    content_id,
                    peer_count,
                },
            )
            .collect(),
    }
}

pub async fn emit_peer_count(
    peer_game_db: &Arc<RwLock<PeerGameDB>>,
    tx_notify_ui: &UnboundedSender<PeerEvent>,
) {
    let db = peer_game_db.read().await;
    let peer_count = db.peer_endpoints().len();
    send(tx_notify_ui, PeerEvent::PeerCountUpdated(peer_count));
}

#[cfg(test)]
mod tests {
    use super::*;

    #[tokio::test]
    async fn remote_library_view_is_enqueued_before_a_waiting_writer_can_commit() {
        let peer_game_db = Arc::new(RwLock::new(PeerGameDB::new()));
        let guard = peer_game_db.read().await;
        let writer_db = Arc::clone(&peer_game_db);
        let writer = tokio::spawn(async move {
            let _guard = writer_db.write().await;
        });
        tokio::task::yield_now().await;
        assert!(!writer.is_finished(), "writer must wait for the read guard");

        let (tx, mut rx) = tokio::sync::mpsc::unbounded_channel();
        send_remote_library_view_locked(&guard, &tx);
        assert!(matches!(
            rx.try_recv(),
            Ok(PeerEvent::RemoteLibraryView(RemoteLibraryView { games })) if games.is_empty()
        ));
        assert!(
            !writer.is_finished(),
            "the view must be enqueued while the read guard still orders writers"
        );

        drop(guard);
        tokio::time::timeout(std::time::Duration::from_secs(1), writer)
            .await
            .expect("writer should acquire after the view is enqueued")
            .expect("writer task should finish");
    }
}