//! Command handlers for peer commands.

use std::{net::SocketAddr, path::PathBuf, sync::Arc};

use lanspread_db::db::GameFileDescription;
use tokio::sync::{RwLock, mpsc::UnboundedSender};

use crate::{
    PeerEvent,
    context::Ctx,
    download::download_game_files,
    events,
    identity::FEATURE_LIBRARY_DELTA,
    local_games::{
        LocalLibraryScan,
        get_game_file_descriptions,
        local_download_available,
        scan_local_library,
    },
    network::{announce_games_to_peer, request_game_details_from_peer, send_library_delta},
    peer_db::PeerGameDB,
    remote_peer::ensure_peer_id_for_addr,
};

// =============================================================================
// Command handlers
// =============================================================================

/// Handles the `ListGames` command.
pub async fn handle_list_games_command(ctx: &Ctx, tx_notify_ui: &UnboundedSender<PeerEvent>) {
    log::info!("ListGames command received");
    events::emit_peer_game_list(&ctx.peer_game_db, tx_notify_ui).await;
}

/// Tries to serve a game from local files.
async fn try_serve_local_game(
    ctx: &Ctx,
    tx_notify_ui: &UnboundedSender<PeerEvent>,
    id: &str,
) -> bool {
    let game_dir = { ctx.game_dir.read().await.clone() };

    let downloading = ctx.downloading_games.read().await;
    if !local_download_available(&game_dir, id, &downloading).await {
        return false;
    }
    drop(downloading);

    match get_game_file_descriptions(id, &game_dir).await {
        Ok(file_descriptions) => {
            log::info!("Serving game {id} from local files");
            if let Err(e) = tx_notify_ui.send(PeerEvent::GotGameFiles {
                id: id.to_string(),
                file_descriptions,
            }) {
                log::error!("Failed to send GotGameFiles event: {e}");
            }
            true
        }
        Err(e) => {
            log::error!("Failed to enumerate local file descriptions for {id}: {e}");
            false
        }
    }
}

/// Handles the `GetGame` command.
pub async fn handle_get_game_command(
    ctx: &Ctx,
    tx_notify_ui: &UnboundedSender<PeerEvent>,
    id: String,
) {
    if try_serve_local_game(ctx, tx_notify_ui, &id).await {
        return;
    }

    log::info!("Requesting game from peers: {id}");
    let peers = { ctx.peer_game_db.read().await.peers_with_game(&id) };
    if peers.is_empty() {
        log::warn!("No peers have game {id}");
        if let Err(e) = tx_notify_ui.send(PeerEvent::NoPeersHaveGame { id: id.clone() }) {
            log::error!("Failed to send NoPeersHaveGame event: {e}");
        }
        return;
    }

    let peer_game_db = ctx.peer_game_db.clone();
    let tx_notify_ui = tx_notify_ui.clone();
    tokio::spawn(async move {
        let mut fetched_any = false;
        for peer_addr in peers {
            match request_game_details_and_update(peer_addr, &id, peer_game_db.clone()).await {
                Ok(_) => {
                    log::info!("Fetched game file list for {id} from peer {peer_addr}");
                    fetched_any = true;
                }
                Err(e) => {
                    log::error!("Failed to fetch game files for {id} from {peer_addr}: {e}");
                }
            }
        }

        if fetched_any {
            let aggregated_files = { peer_game_db.read().await.aggregated_game_files(&id) };

            if let Err(e) = tx_notify_ui.send(PeerEvent::GotGameFiles {
                id: id.clone(),
                file_descriptions: aggregated_files,
            }) {
                log::error!("Failed to send GotGameFiles event: {e}");
            }
        } else {
            log::warn!("Failed to retrieve game files for {id} from any peer");
        }
    });
}

/// Requests game details from a peer and updates the peer game database.
async fn request_game_details_and_update(
    peer_addr: SocketAddr,
    game_id: &str,
    peer_game_db: Arc<RwLock<PeerGameDB>>,
) -> eyre::Result<Vec<GameFileDescription>> {
    let (file_descriptions, _) = request_game_details_from_peer(peer_addr, game_id).await?;
    let peer_id = ensure_peer_id_for_addr(&peer_game_db, peer_addr).await;

    {
        let mut db = peer_game_db.write().await;
        db.update_peer_game_files(&peer_id, game_id, file_descriptions.clone());
    }

    Ok(file_descriptions)
}

/// Handles the `DownloadGameFiles` command.
#[allow(clippy::too_many_lines)]
pub async fn handle_download_game_files_command(
    ctx: &Ctx,
    tx_notify_ui: &UnboundedSender<PeerEvent>,
    id: String,
    file_descriptions: Vec<GameFileDescription>,
) {
    log::info!("Got PeerCommand::DownloadGameFiles");
    let games_folder = { ctx.game_dir.read().await.clone() };

    // Use majority validation to get trusted file descriptions and peer whitelist
    let (validated_descriptions, peer_whitelist, file_peer_map) = {
        match ctx
            .peer_game_db
            .read()
            .await
            .validate_file_sizes_majority(&id)
        {
            Ok((files, peers, file_peer_map)) => {
                log::info!(
                    "Majority validation: {} validated files, {} trusted peers for game {id}",
                    files.len(),
                    peers.len()
                );
                (files, peers, file_peer_map)
            }
            Err(e) => {
                log::error!("File size majority validation failed for {id}: {e}");
                if let Err(send_err) =
                    tx_notify_ui.send(PeerEvent::DownloadGameFilesFailed { id: id.clone() })
                {
                    log::error!("Failed to send DownloadGameFilesFailed event: {send_err}");
                }
                return;
            }
        }
    };

    let resolved_descriptions = if file_descriptions.is_empty() {
        validated_descriptions
    } else {
        // If user provided specific descriptions, still validate them against majority
        // but keep user's selection (they might want specific files)
        file_descriptions
    };

    if resolved_descriptions.is_empty() {
        log::error!(
            "No validated file descriptions available to download game {id}; request metadata first"
        );
        return;
    }

    let local_dl_available = {
        let downloading = ctx.downloading_games.read().await;
        local_download_available(&games_folder, &id, &downloading).await
    };

    if peer_whitelist.is_empty() {
        if local_dl_available {
            log::info!("Using locally downloaded files for game {id}; skipping peer transfer");
            if let Err(e) = tx_notify_ui.send(PeerEvent::DownloadGameFilesBegin { id: id.clone() })
            {
                log::error!("Failed to send DownloadGameFilesBegin event: {e}");
            }
            if let Err(e) =
                tx_notify_ui.send(PeerEvent::DownloadGameFilesFinished { id: id.clone() })
            {
                log::error!("Failed to send DownloadGameFilesFinished event: {e}");
            }
        } else {
            log::error!("No trusted peers available after majority validation for game {id}");
        }
        return;
    }

    {
        let mut in_progress = ctx.downloading_games.write().await;
        if !in_progress.insert(id.clone()) {
            log::warn!("Download for {id} already in progress; ignoring new request");
            return;
        }
    }

    let downloading_games = ctx.downloading_games.clone();
    let active_downloads = ctx.active_downloads.clone();
    let tx_notify_ui_clone = tx_notify_ui.clone();
    let download_id = id.clone();

    let handle = tokio::spawn(async move {
        let result = download_game_files(
            &download_id,
            resolved_descriptions,
            games_folder,
            peer_whitelist,
            file_peer_map,
            tx_notify_ui_clone.clone(),
        )
        .await;

        {
            let mut guard = downloading_games.write().await;
            guard.remove(&download_id);
        }

        if let Err(e) = result {
            log::error!("Download failed for {download_id}: {e}");
            if let Err(send_err) = tx_notify_ui_clone.send(PeerEvent::DownloadGameFilesFailed {
                id: download_id.clone(),
            }) {
                log::error!("Failed to send DownloadGameFilesFailed event: {send_err}");
            }
        }

        let _ = active_downloads.write().await.remove(&download_id);
    });

    ctx.active_downloads.write().await.insert(id, handle);
}

/// Handles the `SetGameDir` command.
pub async fn handle_set_game_dir_command(
    ctx: &Ctx,
    tx_notify_ui: &UnboundedSender<PeerEvent>,
    game_dir: PathBuf,
) {
    *ctx.game_dir.write().await = game_dir.clone();
    log::info!("Game directory set to: {}", game_dir.display());

    let tx_notify_ui = tx_notify_ui.clone();
    let ctx_clone = ctx.clone();

    tokio::spawn(async move {
        match load_local_library(&ctx_clone, &tx_notify_ui).await {
            Ok(()) => log::info!("Local game database loaded successfully"),
            Err(e) => {
                log::error!("Failed to load local game database: {e}");
            }
        }
    });
}

/// Loads the configured local library and announces the result.
pub async fn load_local_library(
    ctx: &Ctx,
    tx_notify_ui: &UnboundedSender<PeerEvent>,
) -> eyre::Result<()> {
    let game_dir = { ctx.game_dir.read().await.clone() };
    let scan = scan_local_library(&game_dir).await?;
    update_and_announce_games(ctx, tx_notify_ui, scan).await;
    Ok(())
}

/// Handles the `GetPeerCount` command.
pub async fn handle_get_peer_count_command(ctx: &Ctx, tx_notify_ui: &UnboundedSender<PeerEvent>) {
    log::info!("GetPeerCount command received");
    events::emit_peer_count(&ctx.peer_game_db, tx_notify_ui).await;
}

// =============================================================================
// Game announcement helpers
// =============================================================================

/// Updates the local game database and announces changes to peers.
pub async fn update_and_announce_games(
    ctx: &Ctx,
    tx_notify_ui: &UnboundedSender<PeerEvent>,
    scan: LocalLibraryScan,
) {
    let LocalLibraryScan {
        game_db,
        summaries,
        revision,
    } = scan;

    let delta = {
        let mut library_guard = ctx.local_library.write().await;
        library_guard.update_from_scan(summaries, revision)
    };

    let Some(delta) = delta else {
        return;
    };

    {
        let mut db_guard = ctx.local_game_db.write().await;
        *db_guard = Some(game_db.clone());
    }

    let all_games = game_db.all_games().into_iter().cloned().collect::<Vec<_>>();

    if let Err(e) = tx_notify_ui.send(PeerEvent::LocalGamesUpdated(all_games.clone())) {
        log::error!("Failed to send LocalGamesUpdated event: {e}");
    }

    let peer_targets = {
        let db = ctx.peer_game_db.read().await;
        db.peer_identities()
            .into_iter()
            .map(|(peer_id, addr)| {
                let features = db.peer_features(&peer_id);
                (peer_id, addr, features)
            })
            .collect::<Vec<_>>()
    };

    for (_peer_id, peer_addr, features) in peer_targets {
        if features
            .iter()
            .any(|feature| feature == FEATURE_LIBRARY_DELTA)
        {
            let delta = delta.clone();
            tokio::spawn(async move {
                if let Err(e) = send_library_delta(peer_addr, delta).await {
                    log::warn!("Failed to send library delta to {peer_addr}: {e}");
                }
            });
        } else {
            let games_clone = all_games.clone();
            tokio::spawn(async move {
                if let Err(e) = announce_games_to_peer(peer_addr, games_clone).await {
                    log::warn!("Failed to announce games to {peer_addr}: {e}");
                }
            });
        }
    }
}