package shell

import (
	"context"
	"flag"
	"fmt"
	"io"

	"google.golang.org/grpc"

	"github.com/chrislusf/seaweedfs/weed/operation"
	"github.com/chrislusf/seaweedfs/weed/pb/master_pb"
	"github.com/chrislusf/seaweedfs/weed/pb/volume_server_pb"
	"github.com/chrislusf/seaweedfs/weed/storage/erasure_coding"
	"github.com/chrislusf/seaweedfs/weed/storage/needle"
)

func init() {
	Commands = append(Commands, &commandEcDecode{})
}

type commandEcDecode struct {
}

func (c *commandEcDecode) Name() string {
	return "ec.decode"
}

func (c *commandEcDecode) Help() string {
	return `decode a erasure coded volume into a normal volume

	ec.decode [-collection=""] [-volumeId=<volume_id>]

`
}

func (c *commandEcDecode) Do(args []string, commandEnv *CommandEnv, writer io.Writer) (err error) {

	encodeCommand := flag.NewFlagSet(c.Name(), flag.ContinueOnError)
	volumeId := encodeCommand.Int("volumeId", 0, "the volume id")
	collection := encodeCommand.String("collection", "", "the collection name")
	if err = encodeCommand.Parse(args); err != nil {
		return nil
	}

	ctx := context.Background()
	vid := needle.VolumeId(*volumeId)

	// collect topology information
	topologyInfo, err := collectTopologyInfo(ctx, commandEnv)
	if err != nil {
		return err
	}

	// volumeId is provided
	if vid != 0 {
		return doEcDecode(ctx, commandEnv, topologyInfo, *collection, vid)
	}

	// apply to all volumes in the collection
	volumeIds := collectEcShardIds(topologyInfo, *collection)
	fmt.Printf("ec encode volumes: %v\n", volumeIds)
	for _, vid := range volumeIds {
		if err = doEcDecode(ctx, commandEnv, topologyInfo, *collection, vid); err != nil {
			return err
		}
	}

	return nil
}

func doEcDecode(ctx context.Context, commandEnv *CommandEnv, topoInfo *master_pb.TopologyInfo, collection string, vid needle.VolumeId) (err error) {
	// find volume location
	nodeToEcIndexBits := collectEcNodeShardBits(topoInfo, vid)

	fmt.Printf("ec volume %d shard locations: %+v\n", vid, nodeToEcIndexBits)

	// collect ec shards to the server with most space
	targetNodeLocation, err := collectEcShards(ctx, commandEnv, nodeToEcIndexBits, collection, vid)
	if err != nil {
		return fmt.Errorf("collectEcShards for volume %d: %v", vid, err)
	}

	// generate a normal volume
	err = generateNormalVolume(ctx, commandEnv.option.GrpcDialOption, needle.VolumeId(vid), collection, targetNodeLocation)
	if err != nil {
		return fmt.Errorf("generate normal volume %d on %s: %v", vid, targetNodeLocation, err)
	}

	// delete the previous ec shards
	err = mountVolumeAndDeleteEcShards(ctx, commandEnv.option.GrpcDialOption, collection, targetNodeLocation, nodeToEcIndexBits, vid)
	if err != nil {
		return fmt.Errorf("delete ec shards for volume %d: %v", vid, err)
	}

	return nil
}

func mountVolumeAndDeleteEcShards(ctx context.Context, grpcDialOption grpc.DialOption, collection, targetNodeLocation string, nodeToEcIndexBits map[string]erasure_coding.ShardBits, vid needle.VolumeId) error {

	// mount volume
	if err := operation.WithVolumeServerClient(targetNodeLocation, grpcDialOption, func(ctx context.Context, volumeServerClient volume_server_pb.VolumeServerClient) error {
		_, mountErr := volumeServerClient.VolumeMount(ctx, &volume_server_pb.VolumeMountRequest{
			VolumeId: uint32(vid),
		})
		return mountErr
	}); err != nil {
		return fmt.Errorf("mountVolumeAndDeleteEcShards mount volume %d on %s: %v", vid, targetNodeLocation, err)
	}

	// unmount ec shards
	for location, ecIndexBits := range nodeToEcIndexBits {
		fmt.Printf("unmount ec volume %d on %s has shards: %+v\n", vid, location, ecIndexBits.ShardIds())
		err := unmountEcShards(ctx, grpcDialOption, vid, location, ecIndexBits.ToUint32Slice())
		if err != nil {
			return fmt.Errorf("mountVolumeAndDeleteEcShards unmount ec volume %d on %s: %v", vid, location, err)
		}
	}
	// delete ec shards
	for location, ecIndexBits := range nodeToEcIndexBits {
		fmt.Printf("delete ec volume %d on %s has shards: %+v\n", vid, location, ecIndexBits.ShardIds())
		err := sourceServerDeleteEcShards(ctx, grpcDialOption, collection, vid, location, ecIndexBits.ToUint32Slice())
		if err != nil {
			return fmt.Errorf("mountVolumeAndDeleteEcShards delete ec volume %d on %s: %v", vid, location, err)
		}
	}

	return nil
}

func generateNormalVolume(ctx context.Context, grpcDialOption grpc.DialOption, vid needle.VolumeId, collection string, sourceVolumeServer string) error {

	fmt.Printf("generateNormalVolume from ec volume %d on %s\n", vid, sourceVolumeServer)

	err := operation.WithVolumeServerClient(sourceVolumeServer, grpcDialOption, func(ctx context.Context, volumeServerClient volume_server_pb.VolumeServerClient) error {
		_, genErr := volumeServerClient.VolumeEcShardsToVolume(ctx, &volume_server_pb.VolumeEcShardsToVolumeRequest{
			VolumeId:   uint32(vid),
			Collection: collection,
		})
		return genErr
	})

	return err

}

func collectEcShards(ctx context.Context, commandEnv *CommandEnv, nodeToEcIndexBits map[string]erasure_coding.ShardBits, collection string, vid needle.VolumeId) (targetNodeLocation string, err error) {

	maxShardCount := 0
	var exisitngEcIndexBits erasure_coding.ShardBits
	for loc, ecIndexBits := range nodeToEcIndexBits {
		toBeCopiedShardCount := ecIndexBits.MinusParityShards().ShardIdCount()
		if toBeCopiedShardCount > maxShardCount {
			maxShardCount = toBeCopiedShardCount
			targetNodeLocation = loc
			exisitngEcIndexBits = ecIndexBits
		}
	}

	fmt.Printf("collectEcShards: ec volume %d collect shards to %s from: %+v\n", vid, targetNodeLocation, nodeToEcIndexBits)

	var copiedEcIndexBits erasure_coding.ShardBits
	for loc, ecIndexBits := range nodeToEcIndexBits {
		if loc == targetNodeLocation {
			continue
		}

		needToCopyEcIndexBits := ecIndexBits.Minus(exisitngEcIndexBits).MinusParityShards()
		if needToCopyEcIndexBits.ShardIdCount() == 0 {
			continue
		}

		err = operation.WithVolumeServerClient(targetNodeLocation, commandEnv.option.GrpcDialOption, func(ctx context.Context, volumeServerClient volume_server_pb.VolumeServerClient) error {

			fmt.Printf("copy %d.%v %s => %s\n", vid, needToCopyEcIndexBits.ShardIds(), loc, targetNodeLocation)

			_, copyErr := volumeServerClient.VolumeEcShardsCopy(ctx, &volume_server_pb.VolumeEcShardsCopyRequest{
				VolumeId:       uint32(vid),
				Collection:     collection,
				ShardIds:       needToCopyEcIndexBits.ToUint32Slice(),
				CopyEcxFile:    false,
				CopyEcjFile:    true,
				CopyVifFile:    true,
				SourceDataNode: loc,
			})
			if copyErr != nil {
				return fmt.Errorf("copy %d.%v %s => %s : %v\n", vid, needToCopyEcIndexBits.ShardIds(), loc, targetNodeLocation, copyErr)
			}

			return nil
		})

		if err != nil {
			break
		}

		copiedEcIndexBits = copiedEcIndexBits.Plus(needToCopyEcIndexBits)

	}

	nodeToEcIndexBits[targetNodeLocation] = exisitngEcIndexBits.Plus(copiedEcIndexBits)

	return targetNodeLocation, err

}

func collectTopologyInfo(ctx context.Context, commandEnv *CommandEnv) (topoInfo *master_pb.TopologyInfo, err error) {

	var resp *master_pb.VolumeListResponse
	err = commandEnv.MasterClient.WithClient(ctx, func(client master_pb.SeaweedClient) error {
		resp, err = client.VolumeList(ctx, &master_pb.VolumeListRequest{})
		return err
	})
	if err != nil {
		return
	}

	return resp.TopologyInfo, nil

}

func collectEcShardInfos(topoInfo *master_pb.TopologyInfo, selectedCollection string, vid needle.VolumeId) (ecShardInfos []*master_pb.VolumeEcShardInformationMessage) {

	eachDataNode(topoInfo, func(dc string, rack RackId, dn *master_pb.DataNodeInfo) {
		for _, v := range dn.EcShardInfos {
			if v.Collection == selectedCollection && v.Id == uint32(vid) {
				ecShardInfos = append(ecShardInfos, v)
			}
		}
	})

	return
}

func collectEcShardIds(topoInfo *master_pb.TopologyInfo, selectedCollection string) (vids []needle.VolumeId) {

	vidMap := make(map[uint32]bool)
	eachDataNode(topoInfo, func(dc string, rack RackId, dn *master_pb.DataNodeInfo) {
		for _, v := range dn.EcShardInfos {
			if v.Collection == selectedCollection {
				vidMap[v.Id] = true
			}
		}
	})

	for vid := range vidMap {
		vids = append(vids, needle.VolumeId(vid))
	}

	return
}

func collectEcNodeShardBits(topoInfo *master_pb.TopologyInfo, vid needle.VolumeId) map[string]erasure_coding.ShardBits {

	nodeToEcIndexBits := make(map[string]erasure_coding.ShardBits)
	eachDataNode(topoInfo, func(dc string, rack RackId, dn *master_pb.DataNodeInfo) {
		for _, v := range dn.EcShardInfos {
			if v.Id == uint32(vid) {
				nodeToEcIndexBits[dn.Id] = erasure_coding.ShardBits(v.EcIndexBits)
			}
		}
	})

	return nodeToEcIndexBits
}
