package weed_server

import (
	"context"
	"fmt"
	"io"
	"math"
	"os"
	"path"
	"path/filepath"
	"strings"
	"time"

	"github.com/seaweedfs/seaweedfs/weed/glog"
	"github.com/seaweedfs/seaweedfs/weed/operation"
	"github.com/seaweedfs/seaweedfs/weed/pb"
	"github.com/seaweedfs/seaweedfs/weed/pb/volume_server_pb"
	"github.com/seaweedfs/seaweedfs/weed/storage"
	"github.com/seaweedfs/seaweedfs/weed/storage/erasure_coding"
	"github.com/seaweedfs/seaweedfs/weed/storage/needle"
	"github.com/seaweedfs/seaweedfs/weed/storage/types"
	"github.com/seaweedfs/seaweedfs/weed/storage/volume_info"
	"github.com/seaweedfs/seaweedfs/weed/util"
)

/*

Steps to apply erasure coding to .dat .idx files
0. ensure the volume is readonly
1. client call VolumeEcShardsGenerate to generate the .ecx and .ec00 ~ .ec13 files
2. client ask master for possible servers to hold the ec files
3. client call VolumeEcShardsCopy on above target servers to copy ec files from the source server
4. target servers report the new ec files to the master
5.   master stores vid -> [14]*DataNode
6. client checks master. If all 14 slices are ready, delete the original .idx, .idx files

*/

// isGenerationCompatible checks if requested and actual generations are compatible
// for mixed-version cluster support
func isGenerationCompatible(actualGeneration, requestedGeneration uint32) bool {
	// Exact match is always compatible
	if actualGeneration == requestedGeneration {
		return true
	}

	// Mixed-version compatibility: if client requests generation 0 (default/legacy),
	// allow access to any generation for backward compatibility
	if requestedGeneration == 0 {
		return true
	}

	// If client requests specific generation but volume has different generation,
	// this is not compatible (strict generation matching)
	return false
}

// VolumeEcShardsGenerate generates the .ecx and .ec00 ~ .ec13 files
func (vs *VolumeServer) VolumeEcShardsGenerate(ctx context.Context, req *volume_server_pb.VolumeEcShardsGenerateRequest) (*volume_server_pb.VolumeEcShardsGenerateResponse, error) {

	glog.V(0).Infof("VolumeEcShardsGenerate volume %d generation %d collection %s",
		req.VolumeId, req.Generation, req.Collection)

	v := vs.store.GetVolume(needle.VolumeId(req.VolumeId))
	if v == nil {
		return nil, fmt.Errorf("volume %d not found", req.VolumeId)
	}

	if v.Collection != req.Collection {
		return nil, fmt.Errorf("existing collection:%v unexpected input: %v", v.Collection, req.Collection)
	}

	// Generate output filenames with generation suffix
	generation := req.Generation
	// Extract base names by removing file extensions
	dataFileName := v.DataFileName()   // e.g., "/data/collection_123.dat"
	indexFileName := v.IndexFileName() // e.g., "/index/collection_123.idx"

	// Remove the .dat and .idx extensions to get base filenames
	dataBaseName := dataFileName[:len(dataFileName)-4]    // removes ".dat"
	indexBaseName := indexFileName[:len(indexFileName)-4] // removes ".idx"

	// Apply generation naming
	dataBaseFileName := erasure_coding.EcShardFileNameWithGeneration(v.Collection, filepath.Dir(dataBaseName), int(req.VolumeId), generation)
	indexBaseFileName := erasure_coding.EcShardFileNameWithGeneration(v.Collection, filepath.Dir(indexBaseName), int(req.VolumeId), generation)

	glog.V(1).Infof("VolumeEcShardsGenerate: generating EC shards with generation %d: data=%s, index=%s",
		generation, dataBaseFileName, indexBaseFileName)

	shouldCleanup := true
	defer func() {
		if !shouldCleanup {
			return
		}
		// Clean up generation-specific files on error
		for i := 0; i < erasure_coding.TotalShardsCount; i++ {
			os.Remove(fmt.Sprintf("%s.ec%02d", dataBaseFileName, i))
		}
		os.Remove(indexBaseFileName + ".ecx")
		os.Remove(dataBaseFileName + ".vif")
	}()

	// write .ec00 ~ .ec13 files with generation-specific names
	if err := erasure_coding.WriteEcFiles(dataBaseFileName); err != nil {
		return nil, fmt.Errorf("WriteEcFiles %s: %v", dataBaseFileName, err)
	}

	// write .ecx file with generation-specific name
	if err := erasure_coding.WriteSortedFileFromIdxToTarget(v.IndexFileName(), indexBaseFileName+".ecx"); err != nil {
		return nil, fmt.Errorf("WriteSortedFileFromIdxToTarget %s: %v", indexBaseFileName, err)
	}

	// write .vif files
	var expireAtSec uint64
	if v.Ttl != nil {
		ttlSecond := v.Ttl.ToSeconds()
		if ttlSecond > 0 {
			expireAtSec = uint64(time.Now().Unix()) + ttlSecond //calculated expiration time
		}
	}
	volumeInfo := &volume_server_pb.VolumeInfo{Version: uint32(v.Version())}
	volumeInfo.ExpireAtSec = expireAtSec

	datSize, _, _ := v.FileStat()
	volumeInfo.DatFileSize = int64(datSize)
	if err := volume_info.SaveVolumeInfo(dataBaseFileName+".vif", volumeInfo); err != nil {
		return nil, fmt.Errorf("SaveVolumeInfo %s: %v", dataBaseFileName, err)
	}

	shouldCleanup = false

	return &volume_server_pb.VolumeEcShardsGenerateResponse{}, nil
}

// VolumeEcShardsRebuild generates the any of the missing .ec00 ~ .ec13 files
func (vs *VolumeServer) VolumeEcShardsRebuild(ctx context.Context, req *volume_server_pb.VolumeEcShardsRebuildRequest) (*volume_server_pb.VolumeEcShardsRebuildResponse, error) {

	glog.V(0).Infof("VolumeEcShardsRebuild: %v", req)

	baseFileName := erasure_coding.EcShardBaseFileName(req.Collection, int(req.VolumeId))

	var rebuiltShardIds []uint32

	for _, location := range vs.store.Locations {
		_, _, existingShardCount, err := checkEcVolumeStatus(baseFileName, location)
		if err != nil {
			return nil, err
		}

		if existingShardCount == 0 {
			continue
		}

		if util.FileExists(path.Join(location.IdxDirectory, baseFileName+".ecx")) {
			// write .ec00 ~ .ec13 files
			dataBaseFileName := path.Join(location.Directory, baseFileName)
			if generatedShardIds, err := erasure_coding.RebuildEcFiles(dataBaseFileName); err != nil {
				return nil, fmt.Errorf("RebuildEcFiles %s: %v", dataBaseFileName, err)
			} else {
				rebuiltShardIds = generatedShardIds
			}

			indexBaseFileName := path.Join(location.IdxDirectory, baseFileName)
			if err := erasure_coding.RebuildEcxFile(indexBaseFileName); err != nil {
				return nil, fmt.Errorf("RebuildEcxFile %s: %v", dataBaseFileName, err)
			}

			break
		}
	}

	return &volume_server_pb.VolumeEcShardsRebuildResponse{
		RebuiltShardIds: rebuiltShardIds,
	}, nil
}

// VolumeEcShardsCopy copy the .ecx and some ec data slices
func (vs *VolumeServer) VolumeEcShardsCopy(ctx context.Context, req *volume_server_pb.VolumeEcShardsCopyRequest) (*volume_server_pb.VolumeEcShardsCopyResponse, error) {

	glog.V(0).Infof("VolumeEcShardsCopy volume %d generation %d shards %v from %s collection %s",
		req.VolumeId, req.Generation, req.ShardIds, req.SourceDataNode, req.Collection)

	var location *storage.DiskLocation

	// Use disk_id if provided (disk-aware storage)
	if req.DiskId > 0 || (req.DiskId == 0 && len(vs.store.Locations) > 0) {
		// Validate disk ID is within bounds
		if int(req.DiskId) >= len(vs.store.Locations) {
			return nil, fmt.Errorf("invalid disk_id %d: only have %d disks", req.DiskId, len(vs.store.Locations))
		}

		// Use the specific disk location
		location = vs.store.Locations[req.DiskId]
		glog.V(1).Infof("Using disk %d for EC shard copy: %s", req.DiskId, location.Directory)
	} else {
		// Fallback to old behavior for backward compatibility
		if req.CopyEcxFile {
			location = vs.store.FindFreeLocation(func(location *storage.DiskLocation) bool {
				return location.DiskType == types.HardDriveType
			})
		} else {
			location = vs.store.FindFreeLocation(func(location *storage.DiskLocation) bool {
				return true
			})
		}
		if location == nil {
			return nil, fmt.Errorf("no space left")
		}
	}

	// Generate target filenames with generation awareness
	generation := req.Generation
	dataBaseFileName := erasure_coding.EcShardFileNameWithGeneration(req.Collection, location.Directory, int(req.VolumeId), generation)
	indexBaseFileName := erasure_coding.EcShardFileNameWithGeneration(req.Collection, location.IdxDirectory, int(req.VolumeId), generation)

	glog.V(1).Infof("VolumeEcShardsCopy: copying EC shards with generation %d: data=%s, index=%s",
		generation, dataBaseFileName, indexBaseFileName)

	err := operation.WithVolumeServerClient(true, pb.ServerAddress(req.SourceDataNode), vs.grpcDialOption, func(client volume_server_pb.VolumeServerClient) error {

		// copy ec data slices with generation awareness
		for _, shardId := range req.ShardIds {
			if _, err := vs.doCopyFileWithGeneration(client, true, req.Collection, req.VolumeId, math.MaxUint32, math.MaxInt64, dataBaseFileName, erasure_coding.ToExt(int(shardId)), false, false, nil, generation); err != nil {
				return err
			}
		}

		if req.CopyEcxFile {
			// copy ecx file with generation awareness
			if _, err := vs.doCopyFileWithGeneration(client, true, req.Collection, req.VolumeId, math.MaxUint32, math.MaxInt64, indexBaseFileName, ".ecx", false, false, nil, generation); err != nil {
				return err
			}
		}

		if req.CopyEcjFile {
			// copy ecj file with generation awareness
			if _, err := vs.doCopyFileWithGeneration(client, true, req.Collection, req.VolumeId, math.MaxUint32, math.MaxInt64, indexBaseFileName, ".ecj", true, true, nil, generation); err != nil {
				return err
			}
		}

		if req.CopyVifFile {
			// copy vif file with generation awareness
			if _, err := vs.doCopyFileWithGeneration(client, true, req.Collection, req.VolumeId, math.MaxUint32, math.MaxInt64, dataBaseFileName, ".vif", false, true, nil, generation); err != nil {
				return err
			}
		}
		return nil
	})
	if err != nil {
		return nil, fmt.Errorf("VolumeEcShardsCopy volume %d: %v", req.VolumeId, err)
	}

	return &volume_server_pb.VolumeEcShardsCopyResponse{}, nil
}

// VolumeEcShardsDelete local delete the .ecx and some ec data slices if not needed
// the shard should not be mounted before calling this.
func (vs *VolumeServer) VolumeEcShardsDelete(ctx context.Context, req *volume_server_pb.VolumeEcShardsDeleteRequest) (*volume_server_pb.VolumeEcShardsDeleteResponse, error) {

	bName := erasure_coding.EcShardBaseFileName(req.Collection, int(req.VolumeId))

	glog.V(0).Infof("ec volume %s shard delete %v", bName, req.ShardIds)

	for _, location := range vs.store.Locations {
		if err := deleteEcShardIdsForEachLocation(bName, location, req.ShardIds); err != nil {
			glog.Errorf("deleteEcShards from %s %s.%v: %v", location.Directory, bName, req.ShardIds, err)
			return nil, err
		}
	}

	return &volume_server_pb.VolumeEcShardsDeleteResponse{}, nil
}

func deleteEcShardIdsForEachLocation(bName string, location *storage.DiskLocation, shardIds []uint32) error {

	found := false

	indexBaseFilename := path.Join(location.IdxDirectory, bName)
	dataBaseFilename := path.Join(location.Directory, bName)

	if util.FileExists(path.Join(location.IdxDirectory, bName+".ecx")) {
		for _, shardId := range shardIds {
			shardFileName := dataBaseFilename + erasure_coding.ToExt(int(shardId))
			if util.FileExists(shardFileName) {
				found = true
				os.Remove(shardFileName)
			}
		}
	}

	if !found {
		return nil
	}

	hasEcxFile, hasIdxFile, existingShardCount, err := checkEcVolumeStatus(bName, location)
	if err != nil {
		return err
	}

	if hasEcxFile && existingShardCount == 0 {
		if err := os.Remove(indexBaseFilename + ".ecx"); err != nil {
			return err
		}
		os.Remove(indexBaseFilename + ".ecj")

		if !hasIdxFile {
			// .vif is used for ec volumes and normal volumes
			os.Remove(dataBaseFilename + ".vif")
		}
	}

	return nil
}

func checkEcVolumeStatus(bName string, location *storage.DiskLocation) (hasEcxFile bool, hasIdxFile bool, existingShardCount int, err error) {
	// check whether to delete the .ecx and .ecj file also
	fileInfos, err := os.ReadDir(location.Directory)
	if err != nil {
		return false, false, 0, err
	}
	if location.IdxDirectory != location.Directory {
		idxFileInfos, err := os.ReadDir(location.IdxDirectory)
		if err != nil {
			return false, false, 0, err
		}
		fileInfos = append(fileInfos, idxFileInfos...)
	}
	for _, fileInfo := range fileInfos {
		if fileInfo.Name() == bName+".ecx" || fileInfo.Name() == bName+".ecj" {
			hasEcxFile = true
			continue
		}
		if fileInfo.Name() == bName+".idx" {
			hasIdxFile = true
			continue
		}
		if strings.HasPrefix(fileInfo.Name(), bName+".ec") {
			existingShardCount++
		}
	}
	return hasEcxFile, hasIdxFile, existingShardCount, nil
}

func (vs *VolumeServer) VolumeEcShardsMount(ctx context.Context, req *volume_server_pb.VolumeEcShardsMountRequest) (*volume_server_pb.VolumeEcShardsMountResponse, error) {

	glog.V(0).Infof("VolumeEcShardsMount volume %d generation %d shards %v collection %s",
		req.VolumeId, req.Generation, req.ShardIds, req.Collection)

	for _, shardId := range req.ShardIds {
		err := vs.store.MountEcShards(req.Collection, needle.VolumeId(req.VolumeId), erasure_coding.ShardId(shardId), req.Generation)

		if err != nil {
			glog.Errorf("ec shard mount %d.%d generation %d: %v", req.VolumeId, shardId, req.Generation, err)
		} else {
			glog.V(2).Infof("ec shard mount %d.%d generation %d success", req.VolumeId, shardId, req.Generation)
		}

		if err != nil {
			return nil, fmt.Errorf("mount %d.%d: %v", req.VolumeId, shardId, err)
		}
	}

	return &volume_server_pb.VolumeEcShardsMountResponse{}, nil
}

func (vs *VolumeServer) VolumeEcShardsUnmount(ctx context.Context, req *volume_server_pb.VolumeEcShardsUnmountRequest) (*volume_server_pb.VolumeEcShardsUnmountResponse, error) {

	glog.V(0).Infof("VolumeEcShardsUnmount volume %d generation %d shards %v",
		req.VolumeId, req.Generation, req.ShardIds)

	for _, shardId := range req.ShardIds {
		err := vs.store.UnmountEcShards(needle.VolumeId(req.VolumeId), erasure_coding.ShardId(shardId), req.Generation)

		if err != nil {
			glog.Errorf("ec shard unmount %d.%d generation %d: %v", req.VolumeId, shardId, req.Generation, err)
		} else {
			glog.V(2).Infof("ec shard unmount %d.%d generation %d success", req.VolumeId, shardId, req.Generation)
		}

		if err != nil {
			return nil, fmt.Errorf("unmount %d.%d: %v", req.VolumeId, shardId, err)
		}
	}

	return &volume_server_pb.VolumeEcShardsUnmountResponse{}, nil
}

func (vs *VolumeServer) VolumeEcShardRead(req *volume_server_pb.VolumeEcShardReadRequest, stream volume_server_pb.VolumeServer_VolumeEcShardReadServer) error {

	ecVolume, found := vs.store.FindEcVolume(needle.VolumeId(req.VolumeId))
	if !found {
		return fmt.Errorf("VolumeEcShardRead not found ec volume id %d (requested generation %d)", req.VolumeId, req.Generation)
	}

	// Validate generation matches with mixed-version compatibility
	requestedGeneration := req.Generation
	if !isGenerationCompatible(ecVolume.Generation, requestedGeneration) {
		return fmt.Errorf("VolumeEcShardRead volume %d generation mismatch: requested %d, found %d",
			req.VolumeId, requestedGeneration, ecVolume.Generation)
	}
	ecShard, found := ecVolume.FindEcVolumeShard(erasure_coding.ShardId(req.ShardId))
	if !found {
		return fmt.Errorf("not found ec shard %d.%d generation %d", req.VolumeId, req.ShardId, ecVolume.Generation)
	}

	if req.FileKey != 0 {
		_, size, _ := ecVolume.FindNeedleFromEcx(types.Uint64ToNeedleId(req.FileKey))
		if size.IsDeleted() {
			return stream.Send(&volume_server_pb.VolumeEcShardReadResponse{
				IsDeleted: true,
			})
		}
	}

	bufSize := req.Size
	if bufSize > BufferSizeLimit {
		bufSize = BufferSizeLimit
	}
	buffer := make([]byte, bufSize)

	startOffset, bytesToRead := req.Offset, req.Size

	for bytesToRead > 0 {
		// min of bytesToRead and bufSize
		bufferSize := bufSize
		if bufferSize > bytesToRead {
			bufferSize = bytesToRead
		}
		bytesread, err := ecShard.ReadAt(buffer[0:bufferSize], startOffset)

		// println("read", ecShard.FileName(), "startOffset", startOffset, bytesread, "bytes, with target", bufferSize)
		if bytesread > 0 {

			if int64(bytesread) > bytesToRead {
				bytesread = int(bytesToRead)
			}
			err = stream.Send(&volume_server_pb.VolumeEcShardReadResponse{
				Data: buffer[:bytesread],
			})
			if err != nil {
				// println("sending", bytesread, "bytes err", err.Error())
				return err
			}

			startOffset += int64(bytesread)
			bytesToRead -= int64(bytesread)

		}

		if err != nil {
			if err != io.EOF {
				return err
			}
			return nil
		}

	}

	return nil

}

func (vs *VolumeServer) VolumeEcBlobDelete(ctx context.Context, req *volume_server_pb.VolumeEcBlobDeleteRequest) (*volume_server_pb.VolumeEcBlobDeleteResponse, error) {

	glog.V(0).Infof("VolumeEcBlobDelete: %v", req)

	resp := &volume_server_pb.VolumeEcBlobDeleteResponse{}

	for _, location := range vs.store.Locations {
		if localEcVolume, found := location.FindEcVolume(needle.VolumeId(req.VolumeId)); found {

			_, size, _, err := localEcVolume.LocateEcShardNeedle(types.NeedleId(req.FileKey), needle.Version(req.Version))
			if err != nil {
				return nil, fmt.Errorf("locate in local ec volume: %w", err)
			}
			if size.IsDeleted() {
				return resp, nil
			}

			err = localEcVolume.DeleteNeedleFromEcx(types.NeedleId(req.FileKey))
			if err != nil {
				return nil, err
			}

			break
		}
	}

	return resp, nil
}

// VolumeEcShardsToVolume generates the .idx, .dat files from .ecx, .ecj and .ec01 ~ .ec14 files
func (vs *VolumeServer) VolumeEcShardsToVolume(ctx context.Context, req *volume_server_pb.VolumeEcShardsToVolumeRequest) (*volume_server_pb.VolumeEcShardsToVolumeResponse, error) {

	glog.V(0).Infof("VolumeEcShardsToVolume: %v", req)

	// collect .ec00 ~ .ec09 files
	shardFileNames := make([]string, erasure_coding.DataShardsCount)
	v, found := vs.store.CollectEcShards(needle.VolumeId(req.VolumeId), shardFileNames)
	if !found {
		return nil, fmt.Errorf("ec volume %d not found", req.VolumeId)
	}

	if v.Collection != req.Collection {
		return nil, fmt.Errorf("existing collection:%v unexpected input: %v", v.Collection, req.Collection)
	}

	for shardId := 0; shardId < erasure_coding.DataShardsCount; shardId++ {
		if shardFileNames[shardId] == "" {
			return nil, fmt.Errorf("ec volume %d missing shard %d", req.VolumeId, shardId)
		}
	}

	dataBaseFileName, indexBaseFileName := v.DataBaseFileName(), v.IndexBaseFileName()
	// calculate .dat file size
	datFileSize, err := erasure_coding.FindDatFileSize(dataBaseFileName, indexBaseFileName)
	if err != nil {
		return nil, fmt.Errorf("FindDatFileSize %s: %v", dataBaseFileName, err)
	}

	// write .dat file from .ec00 ~ .ec09 files
	if err := erasure_coding.WriteDatFile(dataBaseFileName, datFileSize, shardFileNames); err != nil {
		return nil, fmt.Errorf("WriteDatFile %s: %v", dataBaseFileName, err)
	}

	// write .idx file from .ecx and .ecj files
	if err := erasure_coding.WriteIdxFileFromEcIndex(indexBaseFileName); err != nil {
		return nil, fmt.Errorf("WriteIdxFileFromEcIndex %s: %v", v.IndexBaseFileName(), err)
	}

	return &volume_server_pb.VolumeEcShardsToVolumeResponse{}, nil
}

func (vs *VolumeServer) VolumeEcShardsInfo(ctx context.Context, req *volume_server_pb.VolumeEcShardsInfoRequest) (*volume_server_pb.VolumeEcShardsInfoResponse, error) {
	glog.V(0).Infof("VolumeEcShardsInfo: volume %d", req.VolumeId)

	var ecShardInfos []*volume_server_pb.EcShardInfo

	// Find the EC volume
	for _, location := range vs.store.Locations {
		if v, found := location.FindEcVolume(needle.VolumeId(req.VolumeId)); found {
			// Get shard details from the EC volume
			shardDetails := v.ShardDetails()
			for _, shardDetail := range shardDetails {
				ecShardInfo := &volume_server_pb.EcShardInfo{
					ShardId:    uint32(shardDetail.ShardId),
					Size:       int64(shardDetail.Size),
					Collection: v.Collection,
				}
				ecShardInfos = append(ecShardInfos, ecShardInfo)
			}
			break
		}
	}

	return &volume_server_pb.VolumeEcShardsInfoResponse{
		EcShardInfos: ecShardInfos,
	}, nil
}