// Copyright 2024 The NativeLink Authors. All rights reserved.

//

// Licensed under the Functional Source License, Version 1.1, Apache 2.0 Future License (the "License");

// you may not use this file except in compliance with the License.

// You may obtain a copy of the License at

//

//    See LICENSE file for details

//

// Unless required by applicable law or agreed to in writing, software

// distributed under the License is distributed on an "AS IS" BASIS,

// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

// See the License for the specific language governing permissions and

// limitations under the License.

use core::convert::Into;

use core::pin::Pin;

use core::time::Duration;

use std::collections::HashMap;

use std::sync::Arc;

use std::time::{SystemTime, UNIX_EPOCH};

use futures::stream::unfold;

use futures::{Stream, StreamExt};

use nativelink_config::cas_server::WorkerApiConfig;

use nativelink_error::{make_err, Code, Error, ResultExt};

use nativelink_proto::com::github::trace_machina::nativelink::remote_execution::update_for_scheduler::Update;

use nativelink_proto::com::github::trace_machina::nativelink::remote_execution::worker_api_server::{

    WorkerApi, WorkerApiServer as Server,

};

use nativelink_proto::com::github::trace_machina::nativelink::remote_execution::{

    execute_result, ExecuteComplete, ExecuteResult, GoingAwayRequest, KeepAliveRequest, UpdateForScheduler, UpdateForWorker

};

use nativelink_scheduler::worker::Worker;

use nativelink_scheduler::worker_scheduler::WorkerScheduler;

use nativelink_util::background_spawn;

use nativelink_util::action_messages::{OperationId, WorkerId};

use nativelink_util::operation_state_manager::UpdateOperationType;

use nativelink_util::platform_properties::PlatformProperties;

use rand::RngCore;

use tokio::sync::mpsc;

use tokio::time::interval;

use tonic::{Response, Status};

use tracing::{debug, error, warn, instrument, Level};

use uuid::Uuid;

pub type ConnectWorkerStream =

    Pin<Box<dyn Stream<Item = Result<UpdateForWorker, Status>> + Send + Sync + 'static>>;

pub type NowFn = Box<dyn Fn() -> Result<Duration, Error> + Send + Sync>;

pub struct WorkerApiServer {

    scheduler: Arc<dyn WorkerScheduler>,

    now_fn: Arc<NowFn>,

    node_id: [u8; 6],

}

impl core::fmt::Debug for WorkerApiServer {

    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {

        f.debug_struct("WorkerApiServer")

            .field("node_id", &self.node_id)

            .finish_non_exhaustive()

    }

}

impl WorkerApiServer {

    pub fn new(

        config: &WorkerApiConfig,

        schedulers: &HashMap<String, Arc<dyn WorkerScheduler>>,

    ) -> Result<Self, Error> {

        let node_id = {

            let mut out = [0; 6];

            rand::rng().fill_bytes(&mut out);

            out

        };

        for scheduler in schedulers.values() {

            // This will protect us from holding a reference to the scheduler forever in the

            // event our ExecutionServer dies. Our scheduler is a weak ref, so the spawn will

            // eventually see the Arc went away and return.

            let weak_scheduler = Arc::downgrade(scheduler);

            background_spawn!("worker_api_server", async move {

                let mut ticker = interval(Duration::from_secs(1));

                loop {

                    ticker.tick().await;

                    let timestamp = SystemTime::now()

                        .duration_since(UNIX_EPOCH)

                        .expect("Error: system time is now behind unix epoch");

                    match weak_scheduler.upgrade() {

                        Some(scheduler) => {

                            if let Err(err) =

                                scheduler.remove_timedout_workers(timestamp.as_secs()).await

                            {

                                error!(?err, "Failed to remove_timedout_workers",);

                            }

                        }

                        // If we fail to upgrade, our service is probably destroyed, so return.

                        None => return,

                    }

                }

            });

        }

        Self::new_with_now_fn(

            config,

            schedulers,

            Box::new(move || {

                SystemTime::now().duration_since(UNIX_EPOCH).map_err(|err| {

                    Error::from_std_err(Code::Internal, &err)

                        .append("System time is now behind unix epoch")

                })

            }),

            node_id,

        )

    }

    /// Same as `new()`, but you can pass a custom `now_fn`, that returns a Duration since `UNIX_EPOCH`

    /// representing the current time. Used mostly in  unit tests.

    pub fn new_with_now_fn(

        config: &WorkerApiConfig,

        schedulers: &HashMap<String, Arc<dyn WorkerScheduler>>,

        now_fn: NowFn,

        node_id: [u8; 6],

    ) -> Result<Self, Error> {

        let scheduler = schedulers

            .get(&config.scheduler)

            .err_tip(|| 
{0

                format!(

                    "Scheduler needs config for '{}' because it exists in worker_api",

                    config.scheduler

                )

            })?

            .clone();

        Ok(Self {

            scheduler,

            now_fn: Arc::new(now_fn),

            node_id,

        })

    }

    pub fn into_service(self) -> Server<Self> {

        Server::new(self)

    }

    async fn inner_connect_worker(

        &self,

        mut update_stream: impl Stream<Item = Result<UpdateForScheduler, Status>>

        + Unpin

        + Send

        + 'static,

    ) -> Result<Response<ConnectWorkerStream>, Error> {

        let first_message = update_stream

            .next()

            .await

            .err_tip(|| "Missing first message for connect_worker")
?0

            .err_tip(|| "Error reading first message for connect_worker")
?0
;

        let Some(Update::ConnectWorkerRequest(connect_worker_request)) = first_message.update

        else {

            return Err(make_err!(

                Code::Internal,

                "First message was not a ConnectWorkerRequest"

            ));

        };

        let (tx, rx) = mpsc::unbounded_channel();

        // First convert our proto platform properties into one our scheduler understands.

        let platform_properties = {

            let mut platform_properties = PlatformProperties::default();

            for 
property0
 in connect_worker_request.properties {

                let platform_property_value = self

                    .scheduler

                    .get_platform_property_manager()

                    .make_prop_value(&property.name, &property.value)

                    .err_tip(|| "Bad Property during connect_worker()")?;

                platform_properties

                    .properties

                    .insert(property.name.clone(), platform_property_value);

            }

            platform_properties

        };

        // Now register the worker with the scheduler.

        let worker_id = {

            let worker_id = WorkerId(format!(

                "{}{}",

                connect_worker_request.worker_id_prefix,

                Uuid::now_v6(&self.node_id).hyphenated()

            ));

            let worker = Worker::new(

                worker_id.clone(),

                platform_properties,

                tx,

                (self.now_fn)()
?0
.as_secs(),

                connect_worker_request.max_inflight_tasks,

            );

            self.scheduler

                .add_worker(worker)

                .await

                .err_tip(|| "Failed to add worker in inner_connect_worker()")
?0
;

            worker_id

        };

        WorkerConnection::start(

            self.scheduler.clone(),

            self.now_fn.clone(),

            worker_id.clone(),

            update_stream,

        );

        Ok(Response::new(Box::pin(unfold(

            (rx, worker_id),

            move |state| async move {

                let (mut rx, worker_id) = state;

                if let Some(update_for_worker) = rx.recv().await {

                    return Some((Ok(update_for_worker), (rx, worker_id)));

                }

                warn!(

                    ?worker_id,

                    "UpdateForWorker channel was closed, thus closing connection to worker node",

                );

                None

            },

        ))))

    }

    pub async fn inner_connect_worker_for_testing(

        &self,

        update_stream: impl Stream<Item = Result<UpdateForScheduler, Status>> + Unpin + Send + 'static,

    ) -> Result<Response<ConnectWorkerStream>, Error> {

        self.inner_connect_worker(update_stream).await

    }

}

#[tonic::async_trait]

impl WorkerApi for WorkerApiServer {

    type ConnectWorkerStream = ConnectWorkerStream;

    #[instrument(

        err,

        level = Level::ERROR,

        skip_all,

        fields(request = ?grpc_request.get_ref())

    )]

    async fn connect_worker(

        &self,

        grpc_request: tonic::Request<tonic::Streaming<UpdateForScheduler>>,

    ) -> Result<Response<Self::ConnectWorkerStream>, Status> {

        let resp = self

            .inner_connect_worker(grpc_request.into_inner())

            .await

            .map_err(Into::into);

        if resp.is_ok() {

            debug!(return = "Ok(<stream>)");

        }

        resp

    }

}

struct WorkerConnection {

    scheduler: Arc<dyn WorkerScheduler>,

    now_fn: Arc<NowFn>,

    worker_id: WorkerId,

}

impl WorkerConnection {

    fn start(

        scheduler: Arc<dyn WorkerScheduler>,

        now_fn: Arc<NowFn>,

        worker_id: WorkerId,

        mut connection: impl Stream<Item = Result<UpdateForScheduler, Status>> + Unpin + Send + 'static,

    ) {

        let instance = Self {

            scheduler,

            now_fn,

            worker_id,

        };

        background_spawn!("worker_api", async move 
{2

            let mut had_going_away = false;

            while let Some(
maybe_update2
) = connection.next().await {

                let update = match maybe_update.map(|u| u.update) {

                    Ok(Some(update)) => update,

                    Ok(None) => {

                        tracing::warn!(worker_id=?instance.worker_id, "Empty update");

                        continue;

                    }

                    Err(err) => {

                        tracing::warn!(worker_id=?instance.worker_id, ?err, "Error from worker");

                        break;

                    }

                };

                let 
result1
 = match update {

                    Update::ConnectWorkerRequest(_connect_worker_request) => Err(make_err!(

                        Code::Internal,

                        "Got ConnectWorkerRequest after initial message for {}",

                        instance.worker_id

                    )),

                    Update::KeepAliveRequest(keep_alive_request) => {

                        instance.inner_keep_alive(keep_alive_request).await

                    }

                    Update::GoingAwayRequest(going_away_request) => {

                        had_going_away = true;

                        instance.inner_going_away(going_away_request).await

                    }

                    Update::ExecuteResult(execute_result) => {

                        instance.inner_execution_response(execute_result).await

                    }

                    Update::ExecuteComplete(execute_complete) => {

                        instance.execution_complete(execute_complete).await

                    }

                };

                if let Err(
err0
) = result {

                    tracing::warn!(worker_id=?instance.worker_id, ?err, "Error processing worker message");

                }

            }

            tracing::debug!(worker_id=?instance.worker_id, "Update for scheduler dropped");

            if !had_going_away {

                drop(instance.scheduler.remove_worker(&instance.worker_id).await);

            }

        });

    }

    async fn inner_keep_alive(&self, _keep_alive_request: KeepAliveRequest) -> Result<(), Error> {

        self.scheduler

            .worker_keep_alive_received(&self.worker_id, (self.now_fn)()
?0
.as_secs())

            .await

            .err_tip(|| "Could not process keep_alive from worker in inner_keep_alive()")
?0
;

        Ok(())

    }

    async fn inner_going_away(&self, _going_away_request: GoingAwayRequest) -> Result<(), Error> {

        self.scheduler

            .remove_worker(&self.worker_id)

            .await

            .err_tip(|| "While calling WorkerApiServer::inner_going_away")?;

        Ok(())

    }

    async fn inner_execution_response(&self, execute_result: ExecuteResult) -> Result<(), Error> {

        let operation_id = OperationId::from(execute_result.operation_id);

        match execute_result

            .result

            .err_tip(|| "Expected result to exist in ExecuteResult")
?0

        {

            execute_result::Result::ExecuteResponse(finished_result) => {

                let action_stage = finished_result

                    .try_into()

                    .err_tip(|| "Failed to convert ExecuteResponse into an ActionStage")
?0
;

                self.scheduler

                    .update_action(

                        &self.worker_id,

                        &operation_id,

                        UpdateOperationType::UpdateWithActionStage(action_stage),

                    )

                    .await

                    .err_tip(|| format!("Failed to operation {operation_id}"))?;

            }

            execute_result::Result::InternalError(e) => {

                self.scheduler

                    .update_action(

                        &self.worker_id,

                        &operation_id,

                        UpdateOperationType::UpdateWithError(e.into()),

                    )

                    .await

                    .err_tip(|| format!("Failed to operation {operation_id}"))?;

            }

        }

        Ok(())

    }

    async fn execution_complete(&self, execute_complete: ExecuteComplete) -> Result<(), Error> {

        let operation_id = OperationId::from(execute_complete.operation_id);

        self.scheduler

            .update_action(

                &self.worker_id,

                &operation_id,

                UpdateOperationType::ExecutionComplete,

            )

            .await

            .err_tip(|| format!("Failed to operation {operation_id}"))?;

        Ok(())

    }

}