// 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 dataservice

import (
	"github.com/milvus-io/milvus/internal/log"
	"github.com/milvus-io/milvus/internal/proto/datapb"
	"go.uber.org/zap"
)

type vchannel struct {
	CollectionID UniqueID
	DmlChannel   string
	DdlChannel   string
}

// positionProvider provides vchannel pair related position pairs
type positionProvider interface {
	GetVChanPositions(vchans []vchannel) ([]*datapb.VchannelPair, error)
	GetDdlChannel() string
}

type dummyPosProvider struct{}

//GetVChanPositions implements positionProvider
func (dp dummyPosProvider) GetVChanPositions(vchans []vchannel) ([]*datapb.VchannelPair, error) {
	pairs := make([]*datapb.VchannelPair, len(vchans))
	for _, vchan := range vchans {
		dmlPos := &datapb.PositionPair{}
		ddlPos := &datapb.PositionPair{}
		pairs = append(pairs, &datapb.VchannelPair{
			CollectionID:    vchan.CollectionID,
			DmlVchannelName: vchan.DmlChannel,
			DdlVchannelName: vchan.DmlChannel,
			DdlPosition:     ddlPos,
			DmlPosition:     dmlPos,
		})
	}
	return pairs, nil
}

//GetDdlChannel implements positionProvider
func (dp dummyPosProvider) GetDdlChannel() string {
	return "dummy_ddl"
}

//GetDdlChannel implements positionProvider
func (s *Server) GetDdlChannel() string {
	return s.ddChannelName
}

// getAllActiveVChannels get all vchannels with unflushed segments
func (s *Server) getAllActiveVChannels() []vchannel {
	segments := s.meta.GetUnFlushedSegments()

	mChanCol := make(map[string]UniqueID)
	for _, segment := range segments {
		ocid, has := mChanCol[segment.InsertChannel]
		if has && ocid != segment.CollectionID {
			log.Error("col:vchan not 1:N",
				zap.Int64("colid 1", ocid),
				zap.Int64("colid 2", segment.CollectionID),
				zap.String("channel", segment.InsertChannel))
		}
		mChanCol[segment.InsertChannel] = segment.CollectionID
	}

	vchans := make([]vchannel, 0, len(mChanCol))
	for dmChan, colID := range mChanCol {
		vchans = append(vchans, vchannel{
			CollectionID: colID,
			DmlChannel:   dmChan,
			DdlChannel:   s.ddChannelName,
		})
	}
	return vchans
}