// Copyright (C) 2019-2020 Zilliz. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance
// with the License. You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// 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.

package datacoord

import (
	"context"
	"sync"
	"time"

	grpcdatanodeclient "github.com/milvus-io/milvus/internal/distributed/datanode/client"
	"github.com/milvus-io/milvus/internal/log"
	"github.com/milvus-io/milvus/internal/proto/datapb"
	"github.com/milvus-io/milvus/internal/types"
	"go.uber.org/zap"
)

const flushTimeout = 5 * time.Second

// SessionManager provides the grpc interfaces of cluster
type SessionManager struct {
	sessions struct {
		sync.RWMutex
		data map[int64]*Session
	}
	sessionCreator dataNodeCreatorFunc
}

// SessionOpt provides a way to set params in SessionManager
type SessionOpt func(c *SessionManager)

func withSessionCreator(creator dataNodeCreatorFunc) SessionOpt {
	return func(c *SessionManager) { c.sessionCreator = creator }
}

func defaultSessionCreator() dataNodeCreatorFunc {
	return func(ctx context.Context, addr string) (types.DataNode, error) {
		return grpcdatanodeclient.NewClient(ctx, addr)
	}
}

// NewSessionManager creates a new SessionManager
func NewSessionManager(options ...SessionOpt) *SessionManager {
	m := &SessionManager{
		sessions: struct {
			sync.RWMutex
			data map[int64]*Session
		}{data: make(map[int64]*Session)},
		sessionCreator: defaultSessionCreator(),
	}
	for _, opt := range options {
		opt(m)
	}
	return m
}

// AddSession creates a new session
func (c *SessionManager) AddSession(node *NodeInfo) {
	c.sessions.Lock()
	defer c.sessions.Unlock()

	session := NewSession(node, c.sessionCreator)
	c.sessions.data[node.NodeID] = session
}

// DeleteSession removes the node session
func (c *SessionManager) DeleteSession(node *NodeInfo) {
	c.sessions.Lock()
	defer c.sessions.Unlock()

	if session, ok := c.sessions.data[node.NodeID]; ok {
		session.Dispose()
		delete(c.sessions.data, node.NodeID)
	}
}

// GetSessions gets all node sessions
func (c *SessionManager) GetSessions() []*Session {
	c.sessions.RLock()
	defer c.sessions.RUnlock()

	ret := make([]*Session, 0, len(c.sessions.data))
	for _, s := range c.sessions.data {
		ret = append(ret, s)
	}
	return ret
}

// Flush is a grpc interface. It will send req to nodeID asynchronously
func (c *SessionManager) Flush(ctx context.Context, nodeID int64, req *datapb.FlushSegmentsRequest) {
	go c.execFlush(ctx, nodeID, req)
}

func (c *SessionManager) execFlush(ctx context.Context, nodeID int64, req *datapb.FlushSegmentsRequest) {
	c.sessions.RLock()
	session, ok := c.sessions.data[nodeID]
	c.sessions.RUnlock()

	if !ok {
		return
	}

	cli, err := session.GetOrCreateClient(ctx)
	if err != nil {
		log.Warn("unable to connect to node", zap.Int64("node", nodeID), zap.Error(err))
		return
	}

	ctx, cancel := context.WithTimeout(ctx, flushTimeout)
	defer cancel()

	resp, err := cli.FlushSegments(ctx, req)
	if err := VerifyResponse(resp, err); err != nil {
		log.Warn("failed to flush", zap.Int64("node", nodeID), zap.Error(err))
		return
	}

	log.Debug("success to flush", zap.Int64("node", nodeID), zap.Any("segments", req))
}

// Close release sessions
func (c *SessionManager) Close() {
	c.sessions.Lock()
	defer c.sessions.Unlock()

	for _, s := range c.sessions.data {
		s.Dispose()
	}
	c.sessions.data = nil
}