use crate::server_folder::folder_pad::{FolderOperations, FolderRevisionSynchronizer};
use crate::server_folder::ServerFolder;
use async_stream::stream;
use flowy_sync::errors::{internal_sync_error, SyncError, SyncResult};
use flowy_sync::ext::FolderCloudPersistence;
use flowy_sync::{RevisionSyncResponse, RevisionUser};
use folder_model::FolderInfo;
use futures::stream::StreamExt;
use revision_model::Revision;
use std::{collections::HashMap, sync::Arc};
use tokio::{
  sync::{mpsc, oneshot, RwLock},
  task::spawn_blocking,
};
use ws_model::ws_revision::{ClientRevisionWSData, ServerRevisionWSDataBuilder};

pub struct ServerFolderManager {
  folder_handlers: Arc<RwLock<HashMap<String, Arc<OpenFolderHandler>>>>,
  persistence: Arc<dyn FolderCloudPersistence>,
}

impl ServerFolderManager {
  pub fn new(persistence: Arc<dyn FolderCloudPersistence>) -> Self {
    Self {
      folder_handlers: Arc::new(RwLock::new(HashMap::new())),
      persistence,
    }
  }

  pub async fn handle_client_revisions(
    &self,
    user: Arc<dyn RevisionUser>,
    client_data: ClientRevisionWSData,
  ) -> Result<(), SyncError> {
    let cloned_user = user.clone();
    let ack_id = client_data.rev_id;
    let folder_id = client_data.object_id;
    let user_id = user.user_id();

    let result = match self.get_folder_handler(&user_id, &folder_id).await {
      None => {
        let _ = self
          .create_folder(&user_id, &folder_id, client_data.revisions)
          .await
          .map_err(|e| {
            SyncError::internal().context(format!("Server create folder failed: {:?}", e))
          })?;
        Ok(())
      },
      Some(handler) => {
        handler.apply_revisions(user, client_data.revisions).await?;
        Ok(())
      },
    };

    if result.is_ok() {
      cloned_user.receive(RevisionSyncResponse::Ack(
        ServerRevisionWSDataBuilder::build_ack_message(&folder_id, ack_id),
      ));
    }
    result
  }

  pub async fn handle_client_ping(
    &self,
    user: Arc<dyn RevisionUser>,
    client_data: ClientRevisionWSData,
  ) -> Result<(), SyncError> {
    let user_id = user.user_id();
    let rev_id = client_data.rev_id;
    let folder_id = client_data.object_id.clone();
    match self.get_folder_handler(&user_id, &folder_id).await {
      None => {
        tracing::trace!("Folder:{} doesn't exist, ignore client ping", folder_id);
        Ok(())
      },
      Some(handler) => {
        handler.apply_ping(rev_id, user).await?;
        Ok(())
      },
    }
  }

  async fn get_folder_handler(
    &self,
    user_id: &str,
    folder_id: &str,
  ) -> Option<Arc<OpenFolderHandler>> {
    let folder_id = folder_id.to_owned();
    if let Some(handler) = self.folder_handlers.read().await.get(&folder_id).cloned() {
      return Some(handler);
    }

    let mut write_guard = self.folder_handlers.write().await;
    match self.persistence.read_folder(user_id, &folder_id).await {
      Ok(folder_info) => {
        let handler = self
          .create_folder_handler(folder_info)
          .await
          .map_err(internal_sync_error)
          .unwrap();
        write_guard.insert(folder_id, handler.clone());
        drop(write_guard);
        Some(handler)
      },
      Err(_) => None,
    }
  }

  async fn create_folder_handler(
    &self,
    folder_info: FolderInfo,
  ) -> Result<Arc<OpenFolderHandler>, SyncError> {
    let persistence = self.persistence.clone();
    let handle = spawn_blocking(|| OpenFolderHandler::new(folder_info, persistence))
      .await
      .map_err(|e| SyncError::internal().context(format!("Create folder handler failed: {}", e)))?;
    Ok(Arc::new(handle?))
  }

  #[tracing::instrument(level = "debug", skip(self, revisions), err)]
  async fn create_folder(
    &self,
    user_id: &str,
    folder_id: &str,
    revisions: Vec<Revision>,
  ) -> Result<Arc<OpenFolderHandler>, SyncError> {
    match self
      .persistence
      .create_folder(user_id, folder_id, revisions)
      .await?
    {
      Some(folder_info) => {
        let handler = self.create_folder_handler(folder_info).await?;
        self
          .folder_handlers
          .write()
          .await
          .insert(folder_id.to_owned(), handler.clone());
        Ok(handler)
      },
      None => Err(SyncError::internal().context(String::new())),
    }
  }
}

struct OpenFolderHandler {
  folder_id: String,
  sender: mpsc::Sender<FolderCommand>,
}

impl OpenFolderHandler {
  fn new(
    folder_info: FolderInfo,
    persistence: Arc<dyn FolderCloudPersistence>,
  ) -> SyncResult<Self> {
    let (sender, receiver) = mpsc::channel(1000);
    let folder_id = folder_info.folder_id.clone();
    let operations = FolderOperations::from_bytes(&folder_info.text)?;
    let sync_object = ServerFolder::from_operations(&folder_id, operations);
    let synchronizer = Arc::new(FolderRevisionSynchronizer::new(
      folder_info.rev_id,
      sync_object,
      persistence,
    ));

    let queue = FolderCommandRunner::new(&folder_id, receiver, synchronizer);
    tokio::task::spawn(queue.run());

    Ok(Self { folder_id, sender })
  }

  #[tracing::instrument(
    name = "server_folder_apply_revision",
    level = "trace",
    skip(self, user, revisions),
    err
  )]
  async fn apply_revisions(
    &self,
    user: Arc<dyn RevisionUser>,
    revisions: Vec<Revision>,
  ) -> SyncResult<()> {
    let (ret, rx) = oneshot::channel();
    let msg = FolderCommand::ApplyRevisions {
      user,
      revisions,
      ret,
    };

    self.send(msg, rx).await?
  }

  async fn apply_ping(&self, rev_id: i64, user: Arc<dyn RevisionUser>) -> Result<(), SyncError> {
    let (ret, rx) = oneshot::channel();
    let msg = FolderCommand::Ping { user, rev_id, ret };
    self.send(msg, rx).await?
  }

  async fn send<T>(&self, msg: FolderCommand, rx: oneshot::Receiver<T>) -> SyncResult<T> {
    self
      .sender
      .send(msg)
      .await
      .map_err(|e| SyncError::internal().context(format!("Send folder command failed: {}", e)))?;
    rx.await.map_err(internal_sync_error)
  }
}

impl std::ops::Drop for OpenFolderHandler {
  fn drop(&mut self) {
    tracing::trace!("{} OpenFolderHandler was dropped", self.folder_id);
  }
}

enum FolderCommand {
  ApplyRevisions {
    user: Arc<dyn RevisionUser>,
    revisions: Vec<Revision>,
    ret: oneshot::Sender<SyncResult<()>>,
  },
  Ping {
    user: Arc<dyn RevisionUser>,
    rev_id: i64,
    ret: oneshot::Sender<SyncResult<()>>,
  },
}

struct FolderCommandRunner {
  folder_id: String,
  receiver: Option<mpsc::Receiver<FolderCommand>>,
  synchronizer: Arc<FolderRevisionSynchronizer>,
}
impl FolderCommandRunner {
  fn new(
    folder_id: &str,
    receiver: mpsc::Receiver<FolderCommand>,
    synchronizer: Arc<FolderRevisionSynchronizer>,
  ) -> Self {
    Self {
      folder_id: folder_id.to_owned(),
      receiver: Some(receiver),
      synchronizer,
    }
  }

  async fn run(mut self) {
    let mut receiver = self
      .receiver
      .take()
      .expect("FolderCommandRunner's receiver should only take one time");

    let stream = stream! {
      while let Some(msg) = receiver.recv().await {
        yield msg;
      }
    };
    stream.for_each(|msg| self.handle_message(msg)).await;
  }

  async fn handle_message(&self, msg: FolderCommand) {
    match msg {
      FolderCommand::ApplyRevisions {
        user,
        revisions,
        ret,
      } => {
        let result = self
          .synchronizer
          .sync_revisions(user, revisions)
          .await
          .map_err(internal_sync_error);
        let _ = ret.send(result);
      },
      FolderCommand::Ping { user, rev_id, ret } => {
        let result = self
          .synchronizer
          .pong(user, rev_id)
          .await
          .map_err(internal_sync_error);
        let _ = ret.send(result);
      },
    }
  }
}

impl std::ops::Drop for FolderCommandRunner {
  fn drop(&mut self) {
    tracing::trace!("{} FolderCommandRunner was dropped", self.folder_id);
  }
}