use std::{
    collections::BTreeMap,
    path::PathBuf,
    sync::{Arc, RwLock},
    thread,
    time::Duration,
};

use fuser::INodeNo;
use sea_orm::{DatabaseConnection, EntityTrait};
use tokio::sync::Notify;
use tokio_stream::StreamExt;

use crate::item::Item;
use crate::origins::network::transport::NetworkTransport;
use crate::origins::{FileWatcher, WatcherHandle};
use crate::proto::ManifestEntry as ProtoManifestEntry;
use tracing::{info, warn};

const INITIAL_RETRY_DELAY: Duration = Duration::from_secs(1);
const MAX_RETRY_DELAY: Duration = Duration::from_secs(30);

pub struct NetworkOriginFileWatcher {
    transport: NetworkTransport,
    runtime_handle: tokio::runtime::Handle,
    client: DatabaseConnection,
    destination: PathBuf,
    latest_manifest: Arc<RwLock<BTreeMap<u64, ProtoManifestEntry>>>,
}

impl NetworkOriginFileWatcher {
    #[allow(clippy::too_many_arguments)]
    pub fn new(
        transport: NetworkTransport,
        runtime_handle: tokio::runtime::Handle,
        client: DatabaseConnection,
        destination: PathBuf,
        latest_manifest: Arc<RwLock<BTreeMap<u64, ProtoManifestEntry>>>,
    ) -> Self {
        return NetworkOriginFileWatcher {
            transport,
            runtime_handle,
            client,
            destination,
            latest_manifest,
        };
    }
}

impl FileWatcher for NetworkOriginFileWatcher {
    fn watch(&self, files: Arc<std::sync::Mutex<BTreeMap<INodeNo, Item>>>) -> WatcherHandle {
        let runtime_handle = self.runtime_handle.clone();
        let shutdown = Arc::new(Notify::new());
        let state = WatcherState {
            transport: self.transport.clone(),
            client: self.client.clone(),
            destination: self.destination.clone(),
            latest_manifest: self.latest_manifest.clone(),
            files,
        };
        let loop_shutdown = shutdown.clone();
        let join = thread::spawn(move || {
            runtime_handle.block_on(state.run_loop(loop_shutdown));
        });
        return WatcherHandle::new(move || {
            shutdown.notify_one();
            let _ = join.join();
        });
    }
}

#[derive(Clone)]
struct WatcherState {
    transport: NetworkTransport,
    client: DatabaseConnection,
    destination: PathBuf,
    latest_manifest: Arc<RwLock<BTreeMap<u64, ProtoManifestEntry>>>,
    files: Arc<std::sync::Mutex<BTreeMap<INodeNo, Item>>>,
}

impl WatcherState {
    async fn run_loop(self, shutdown: Arc<Notify>) {
        let mut retry_delay = INITIAL_RETRY_DELAY;
        loop {
            let subscribed = tokio::select! {
                biased;
                _ = shutdown.notified() => return,
                s = self.transport.subscribe_events() => s,
            };
            match subscribed {
                Ok(mut stream) => {
                    info!("network watcher: subscribed to /events");
                    retry_delay = INITIAL_RETRY_DELAY;
                    loop {
                        let item = tokio::select! {
                            biased;
                            _ = shutdown.notified() => return,
                            item = stream.next() => item,
                        };
                        match item {
                            Some(Ok(_event)) => {
                                if let Err(e) = self.reconcile_once().await {
                                    warn!(error = %e, "network watcher: reconcile after event failed");
                                }
                            }
                            Some(Err(e)) => {
                                warn!(error = %e, "network watcher: stream error; reconnecting");
                                break;
                            }
                            None => break,
                        }
                    }
                }
                Err(e) => {
                    warn!(error = %e, "network watcher: subscribe failed; will retry");
                }
            }
            tokio::select! {
                biased;
                _ = shutdown.notified() => return,
                _ = tokio::time::sleep(retry_delay) => {}
            }
            retry_delay = (retry_delay * 2).min(MAX_RETRY_DELAY);
            if let Err(e) = self.reconcile_once().await {
                warn!(error = %e, "network watcher: poll reconcile failed");
            }
        }
    }

    async fn reconcile_once(&self) -> anyhow::Result<()> {
        let client_entries: Vec<(u64, u64)> = crate::db::entities::Entity::find()
            .all(&self.client)
            .await?
            .into_iter()
            .map(|m| (m.inode as u64, m.hash as u64))
            .collect();

        let response = self.transport.reconcile(client_entries).await?;

        let mut changed_or_deleted: Vec<i64> =
            response.changed.iter().map(|ih| ih.inode as i64).collect();
        changed_or_deleted.extend(response.deleted.iter().map(|i| *i as i64));
        crate::db::cache::delete_cached_bytes_for(&changed_or_deleted, &self.client).await;

        let wanted: Vec<u64> = response.changed.iter().map(|ih| ih.inode).collect();
        let mut current_manifest = self.latest_manifest.read().unwrap().clone();
        if !wanted.is_empty() {
            let entries = self.transport.get_metadata(wanted).await?;
            for entry in entries {
                current_manifest.insert(entry.id, entry);
            }
        }
        for inode in &response.deleted {
            current_manifest.remove(inode);
        }
        *self.latest_manifest.write().unwrap() = current_manifest.clone();

        let new_snapshot =
            super::build_snapshot_from_manifest(&current_manifest, &self.destination, &self.client)
                .await?;

        {
            let mut files = self.files.lock().unwrap();
            files.retain(|ino, _| new_snapshot.contains_key(ino));
            for (ino, new_item) in &new_snapshot {
                match files.get(ino) {
                    Some(existing) if existing.hash == new_item.hash => {}
                    _ => {
                        files.insert(*ino, new_item.clone());
                    }
                }
            }
        }

        info!(
            changed = response.changed.len(),
            deleted = response.deleted.len(),
            total = current_manifest.len(),
            "network watcher: reconcile applied"
        );

        return Ok(());
    }
}