package erasure_coding

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

	"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/pb/worker_pb"
	"github.com/seaweedfs/seaweedfs/weed/storage/erasure_coding"
	"github.com/seaweedfs/seaweedfs/weed/storage/needle"
	"github.com/seaweedfs/seaweedfs/weed/storage/volume_info"
	"github.com/seaweedfs/seaweedfs/weed/worker/types"
	"github.com/seaweedfs/seaweedfs/weed/worker/types/base"
	"google.golang.org/grpc"
)

// ErasureCodingTask implements the Task interface
type ErasureCodingTask struct {
	*base.BaseTask
	server     string
	volumeID   uint32
	collection string
	workDir    string
	progress   float64

	// EC parameters
	dataShards      int32
	parityShards    int32
	targets         []*worker_pb.TaskTarget // Unified targets for EC shards
	sources         []*worker_pb.TaskSource // Unified sources for cleanup
	shardAssignment map[string][]string     // destination -> assigned shard types
}

// NewErasureCodingTask creates a new unified EC task instance
func NewErasureCodingTask(id string, server string, volumeID uint32, collection string) *ErasureCodingTask {
	return &ErasureCodingTask{
		BaseTask:     base.NewBaseTask(id, types.TaskType("erasure_coding")),
		server:       server,
		volumeID:     volumeID,
		collection:   collection,
		dataShards:   erasure_coding.DataShardsCount,   // Default values
		parityShards: erasure_coding.ParityShardsCount, // Default values
	}
}

// Execute implements the UnifiedTask interface
func (t *ErasureCodingTask) Execute(ctx context.Context, params *worker_pb.TaskParams) error {
	if params == nil {
		return fmt.Errorf("task parameters are required")
	}

	ecParams := params.GetErasureCodingParams()
	if ecParams == nil {
		return fmt.Errorf("erasure coding parameters are required")
	}

	t.dataShards = ecParams.DataShards
	t.parityShards = ecParams.ParityShards
	t.workDir = ecParams.WorkingDir
	t.targets = params.Targets // Get unified targets
	t.sources = params.Sources // Get unified sources

	// Log detailed task information
	t.LogInfo("Starting erasure coding task", map[string]interface{}{
		"data_shards":   t.dataShards,
		"parity_shards": t.parityShards,
		"total_shards":  t.dataShards + t.parityShards,
		"targets":       len(t.targets),
		"sources":       len(t.sources),
	})

	// Log detailed target server assignments
	for i, target := range t.targets {
		t.LogInfo("Target server shard assignment", map[string]interface{}{
			"target_index": i,
			"server":       target.Node,
			"shard_count":  len(target.ShardIds),
		})
	}

	// Log source information
	for i, source := range t.sources {
		t.LogInfo("Source server information", map[string]interface{}{
			"source_index": i,
			"server":       source.Node,
		})
	}

	// Use the working directory from task parameters, or fall back to a default
	baseWorkDir := t.workDir

	// Create unique working directory for this task
	taskWorkDir := filepath.Join(baseWorkDir, fmt.Sprintf("vol_%d_%d", t.volumeID, time.Now().Unix()))
	if err := os.MkdirAll(taskWorkDir, 0755); err != nil {
		return fmt.Errorf("failed to create task working directory %s: %v", taskWorkDir, err)
	}
	t.LogInfo("Created working directory", map[string]interface{}{
		"working_dir": taskWorkDir,
	})

	// Update the task's working directory to the specific instance directory
	t.workDir = taskWorkDir

	// Ensure cleanup of working directory (but preserve logs)
	defer func() {
		// Clean up volume files and EC shards, but preserve the directory structure and any logs
		patterns := []string{"*.dat", "*.idx", "*.ec*", "*.vif"}
		for _, pattern := range patterns {
			matches, err := filepath.Glob(filepath.Join(taskWorkDir, pattern))
			if err != nil {
				continue
			}
			for _, match := range matches {
				if err := os.Remove(match); err != nil {
					t.LogWarning("Could not remove file during cleanup", map[string]interface{}{
						"file": match,
					})
				}
			}
		}
		t.LogInfo("Cleaned up volume files from working directory")
	}()

	// Step 1: Mark volume readonly
	t.ReportProgressWithStage(10.0, "Marking volume readonly")
	if err := t.markVolumeReadonly(); err != nil {
		return fmt.Errorf("failed to mark volume readonly: %v", err)
	}

	// Step 2: Copy volume files to worker
	t.ReportProgressWithStage(25.0, "Copying volume files to worker")
	localFiles, err := t.copyVolumeFilesToWorker(taskWorkDir)
	if err != nil {
		return fmt.Errorf("failed to copy volume files: %v", err)
	}

	// Step 3: Generate EC shards locally
	t.ReportProgressWithStage(40.0, "Generating EC shards locally")
	shardFiles, err := t.generateEcShardsLocally(localFiles, taskWorkDir)
	if err != nil {
		return fmt.Errorf("failed to generate EC shards: %v", err)
	}

	// Step 4: Distribute shards to destinations
	t.ReportProgressWithStage(60.0, "Distributing EC shards to destinations")
	if err := t.distributeEcShards(shardFiles); err != nil {
		return fmt.Errorf("failed to distribute EC shards: %v", err)
	}

	// Step 5: Mount EC shards
	t.ReportProgressWithStage(80.0, "Mounting EC shards")
	if err := t.mountEcShards(); err != nil {
		return fmt.Errorf("failed to mount EC shards: %v", err)
	}

	// Step 6: Delete original volume
	t.ReportProgressWithStage(90.0, "Deleting original volume")
	if err := t.deleteOriginalVolume(); err != nil {
		return fmt.Errorf("failed to delete original volume: %v", err)
	}

	t.ReportProgressWithStage(100.0, "EC processing complete")
	t.LogInfo("EC task completed successfully", map[string]interface{}{
		"shards_distributed": len(shardFiles),
	})

	return nil
}

// Validate implements the UnifiedTask interface
func (t *ErasureCodingTask) Validate(params *worker_pb.TaskParams) error {
	if params == nil {
		return fmt.Errorf("task parameters are required")
	}

	ecParams := params.GetErasureCodingParams()
	if ecParams == nil {
		return fmt.Errorf("erasure coding parameters are required")
	}

	if params.VolumeId != t.volumeID {
		return fmt.Errorf("volume ID mismatch: expected %d, got %d", t.volumeID, params.VolumeId)
	}

	// Validate that at least one source matches our server
	found := false
	for _, source := range params.Sources {
		if source.Node == t.server {
			found = true
			break
		}
	}
	if !found {
		return fmt.Errorf("no source matches expected server %s", t.server)
	}

	if ecParams.DataShards < 1 {
		return fmt.Errorf("invalid data shards: %d (must be >= 1)", ecParams.DataShards)
	}

	if ecParams.ParityShards < 1 {
		return fmt.Errorf("invalid parity shards: %d (must be >= 1)", ecParams.ParityShards)
	}

	if len(params.Targets) < int(ecParams.DataShards+ecParams.ParityShards) {
		return fmt.Errorf("insufficient targets: got %d, need %d", len(params.Targets), ecParams.DataShards+ecParams.ParityShards)
	}

	return nil
}

// EstimateTime implements the UnifiedTask interface
func (t *ErasureCodingTask) EstimateTime(params *worker_pb.TaskParams) time.Duration {
	// Basic estimate based on simulated steps
	return 20 * time.Second // Sum of all step durations
}

// GetProgress returns current progress
func (t *ErasureCodingTask) GetProgress() float64 {
	return t.progress
}

// Helper methods for actual EC operations

// markVolumeReadonly marks the volume as readonly on the source server
func (t *ErasureCodingTask) markVolumeReadonly() error {
	return operation.WithVolumeServerClient(false, pb.ServerAddress(t.server), grpc.WithInsecure(),
		func(client volume_server_pb.VolumeServerClient) error {
			_, err := client.VolumeMarkReadonly(context.Background(), &volume_server_pb.VolumeMarkReadonlyRequest{
				VolumeId: t.volumeID,
			})
			return err
		})
}

// copyVolumeFilesToWorker copies .dat and .idx files from source server to local worker
func (t *ErasureCodingTask) copyVolumeFilesToWorker(workDir string) (map[string]string, error) {
	localFiles := make(map[string]string)

	t.LogInfo("Starting volume file copy from source server")

	// Copy .dat file
	datFile := filepath.Join(workDir, fmt.Sprintf("%d.dat", t.volumeID))
	if err := t.copyFileFromSource(".dat", datFile); err != nil {
		return nil, fmt.Errorf("failed to copy .dat file: %v", err)
	}
	localFiles["dat"] = datFile

	// Copy .idx file
	idxFile := filepath.Join(workDir, fmt.Sprintf("%d.idx", t.volumeID))
	if err := t.copyFileFromSource(".idx", idxFile); err != nil {
		return nil, fmt.Errorf("failed to copy .idx file: %v", err)
	}
	localFiles["idx"] = idxFile

	t.LogInfo("Volume files copied successfully")

	return localFiles, nil
}

// copyFileFromSource copies a file from source server to local path using gRPC streaming
func (t *ErasureCodingTask) copyFileFromSource(ext, localPath string) error {
	return operation.WithVolumeServerClient(false, pb.ServerAddress(t.server), grpc.WithInsecure(),
		func(client volume_server_pb.VolumeServerClient) error {
			stream, err := client.CopyFile(context.Background(), &volume_server_pb.CopyFileRequest{
				VolumeId:           t.volumeID,
				Collection:         t.collection,
				Ext:                ext,
				StopOffset:         uint64(math.MaxInt64),
				CompactionRevision: math.MaxUint32, // Bypass compaction revision check to handle volumes compacted after task creation
			})
			if err != nil {
				return fmt.Errorf("failed to initiate file copy: %v", err)
			}

			// Create local file
			localFile, err := os.Create(localPath)
			if err != nil {
				return fmt.Errorf("failed to create local file %s: %v", localPath, err)
			}
			defer localFile.Close()

			// Stream data and write to local file
			totalBytes := int64(0)
			for {
				resp, err := stream.Recv()
				if err == io.EOF {
					break
				}
				if err != nil {
					return fmt.Errorf("failed to receive file data: %v", err)
				}

				if len(resp.FileContent) > 0 {
					written, writeErr := localFile.Write(resp.FileContent)
					if writeErr != nil {
						return fmt.Errorf("failed to write to local file: %v", writeErr)
					}
					totalBytes += int64(written)
				}
			}

			// File copying is already logged at higher level
			return nil
		})
}

// generateEcShardsLocally generates EC shards from local volume files
func (t *ErasureCodingTask) generateEcShardsLocally(localFiles map[string]string, workDir string) (map[string]string, error) {
	datFile := localFiles["dat"]
	idxFile := localFiles["idx"]

	if datFile == "" || idxFile == "" {
		return nil, fmt.Errorf("missing required volume files: dat=%s, idx=%s", datFile, idxFile)
	}

	// Get base name without extension for EC operations
	baseName := strings.TrimSuffix(datFile, ".dat")
	shardFiles := make(map[string]string)

	t.LogInfo("Generating EC shards from local files")

	// Generate EC shard files (.ec00 ~ .ec13)
	if err := erasure_coding.WriteEcFiles(baseName); err != nil {
		return nil, fmt.Errorf("failed to generate EC shard files: %v", err)
	}

	// Generate .ecx file from .idx (use baseName, not full idx path)
	if err := erasure_coding.WriteSortedFileFromIdx(baseName, ".ecx"); err != nil {
		return nil, fmt.Errorf("failed to generate .ecx file: %v", err)
	}

	// Collect generated shard file paths and log details
	var generatedShards []string
	var totalShardSize int64

	for i := 0; i < erasure_coding.TotalShardsCount; i++ {
		shardFile := fmt.Sprintf("%s.ec%02d", baseName, i)
		if info, err := os.Stat(shardFile); err == nil {
			shardKey := fmt.Sprintf("ec%02d", i)
			shardFiles[shardKey] = shardFile
			generatedShards = append(generatedShards, shardKey)
			totalShardSize += info.Size()
		}
	}

	// Add metadata files
	ecxFile := baseName + ".ecx"
	if _, err := os.Stat(ecxFile); err == nil {
		shardFiles["ecx"] = ecxFile
	}

	// Generate .vif file (volume info)
	vifFile := baseName + ".vif"
	volumeInfo := &volume_server_pb.VolumeInfo{
		Version: uint32(needle.GetCurrentVersion()),
	}
	if err := volume_info.SaveVolumeInfo(vifFile, volumeInfo); err != nil {
		t.LogWarning("Failed to create VIF file")
	} else {
		shardFiles["vif"] = vifFile
	}

	// Log summary of generation
	t.LogInfo("EC shard generation completed", map[string]interface{}{
		"total_shards": len(generatedShards),
		"total_mb":     float64(totalShardSize) / (1024 * 1024),
	})
	return shardFiles, nil
}

// distributeEcShards distributes locally generated EC shards to destination servers
// using pre-assigned shard IDs from planning phase
func (t *ErasureCodingTask) distributeEcShards(shardFiles map[string]string) error {
	if len(t.targets) == 0 {
		return fmt.Errorf("no targets specified for EC shard distribution")
	}

	if len(shardFiles) == 0 {
		return fmt.Errorf("no shard files available for distribution")
	}

	// Build shard assignment from pre-assigned target shard IDs (from planning phase)
	shardAssignment := make(map[string][]string)

	for _, target := range t.targets {
		if len(target.ShardIds) == 0 {
			continue // Skip targets with no assigned shards
		}

		var assignedShards []string

		// Convert shard IDs to shard file names (e.g., 0 → "ec00", 1 → "ec01")
		for _, shardId := range target.ShardIds {
			shardType := fmt.Sprintf("ec%02d", shardId)
			assignedShards = append(assignedShards, shardType)
		}

		// Add metadata files (.ecx, .vif) to targets that have shards
		if len(assignedShards) > 0 {
			if _, hasEcx := shardFiles["ecx"]; hasEcx {
				assignedShards = append(assignedShards, "ecx")
			}
			if _, hasVif := shardFiles["vif"]; hasVif {
				assignedShards = append(assignedShards, "vif")
			}
		}

		shardAssignment[target.Node] = assignedShards
	}

	if len(shardAssignment) == 0 {
		return fmt.Errorf("no shard assignments found from planning phase")
	}

	// Store assignment for use during mounting
	t.shardAssignment = shardAssignment

	// Send assigned shards to each destination
	for destNode, assignedShards := range shardAssignment {
		t.LogInfo("Distributing shards to destination", map[string]interface{}{
			"destination": destNode,
			"shard_count": len(assignedShards),
		})

		// Send only the assigned shards to this destination
		var transferredBytes int64
		for _, shardType := range assignedShards {
			filePath, exists := shardFiles[shardType]
			if !exists {
				return fmt.Errorf("shard file %s not found for destination %s", shardType, destNode)
			}

			if info, err := os.Stat(filePath); err == nil {
				transferredBytes += info.Size()
			}

			if err := t.sendShardFileToDestination(destNode, filePath, shardType); err != nil {
				return fmt.Errorf("failed to send %s to %s: %v", shardType, destNode, err)
			}
		}

		t.LogInfo("Shards distributed to destination", map[string]interface{}{
			"destination": destNode,
			"shard_count": len(assignedShards),
			"total_mb":    float64(transferredBytes) / (1024 * 1024),
		})
	}

	t.LogInfo("Successfully distributed EC shards", map[string]interface{}{
		"destinations": len(shardAssignment),
	})
	return nil
}

// sendShardFileToDestination sends a single shard file to a destination server using ReceiveFile API
func (t *ErasureCodingTask) sendShardFileToDestination(destServer, filePath, shardType string) error {
	return operation.WithVolumeServerClient(false, pb.ServerAddress(destServer), grpc.WithInsecure(),
		func(client volume_server_pb.VolumeServerClient) error {
			// Open the local shard file
			file, err := os.Open(filePath)
			if err != nil {
				return fmt.Errorf("failed to open shard file %s: %v", filePath, err)
			}
			defer file.Close()

			// Get file size
			fileInfo, err := file.Stat()
			if err != nil {
				return fmt.Errorf("failed to get file info for %s: %v", filePath, err)
			}

			// Determine file extension and shard ID
			var ext string
			var shardId uint32
			if shardType == "ecx" {
				ext = ".ecx"
				shardId = 0 // ecx file doesn't have a specific shard ID
			} else if shardType == "vif" {
				ext = ".vif"
				shardId = 0 // vif file doesn't have a specific shard ID
			} else if strings.HasPrefix(shardType, "ec") && len(shardType) == 4 {
				// EC shard file like "ec00", "ec01", etc.
				ext = "." + shardType
				fmt.Sscanf(shardType[2:], "%d", &shardId)
			} else {
				return fmt.Errorf("unknown shard type: %s", shardType)
			}

			// Create streaming client
			stream, err := client.ReceiveFile(context.Background())
			if err != nil {
				return fmt.Errorf("failed to create receive stream: %v", err)
			}

			// Send file info first
			err = stream.Send(&volume_server_pb.ReceiveFileRequest{
				Data: &volume_server_pb.ReceiveFileRequest_Info{
					Info: &volume_server_pb.ReceiveFileInfo{
						VolumeId:   t.volumeID,
						Ext:        ext,
						Collection: t.collection,
						IsEcVolume: true,
						ShardId:    shardId,
						FileSize:   uint64(fileInfo.Size()),
						Generation: 0, // EC encoding always uses generation 0
					},
				},
			})
			if err != nil {
				return fmt.Errorf("failed to send file info: %v", err)
			}

			// Send file content in chunks
			buffer := make([]byte, 64*1024) // 64KB chunks
			for {
				n, readErr := file.Read(buffer)
				if n > 0 {
					err = stream.Send(&volume_server_pb.ReceiveFileRequest{
						Data: &volume_server_pb.ReceiveFileRequest_FileContent{
							FileContent: buffer[:n],
						},
					})
					if err != nil {
						return fmt.Errorf("failed to send file content: %v", err)
					}
				}
				if readErr == io.EOF {
					break
				}
				if readErr != nil {
					return fmt.Errorf("failed to read file: %v", readErr)
				}
			}

			// Close stream and get response
			resp, err := stream.CloseAndRecv()
			if err != nil {
				return fmt.Errorf("failed to close stream: %v", err)
			}

			if resp.Error != "" {
				return fmt.Errorf("server error: %s", resp.Error)
			}

			// Individual shard transfers are logged at higher level
			return nil
		})
}

// mountEcShards mounts EC shards on destination servers
func (t *ErasureCodingTask) mountEcShards() error {
	if t.shardAssignment == nil {
		return fmt.Errorf("shard assignment not available for mounting")
	}

	// Mount only assigned shards on each destination
	for destNode, assignedShards := range t.shardAssignment {
		// Convert shard names to shard IDs for mounting
		var shardIds []uint32
		var metadataFiles []string

		for _, shardType := range assignedShards {
			// Skip metadata files (.ecx, .vif) - only mount EC shards
			if strings.HasPrefix(shardType, "ec") && len(shardType) == 4 {
				// Parse shard ID from "ec00", "ec01", etc.
				var shardId uint32
				if _, err := fmt.Sscanf(shardType[2:], "%d", &shardId); err == nil {
					shardIds = append(shardIds, shardId)
				}
			} else {
				metadataFiles = append(metadataFiles, shardType)
			}
		}

		if len(shardIds) == 0 {
			continue // No shards to mount, only metadata
		}

		err := operation.WithVolumeServerClient(false, pb.ServerAddress(destNode), grpc.WithInsecure(),
			func(client volume_server_pb.VolumeServerClient) error {
				_, mountErr := client.VolumeEcShardsMount(context.Background(), &volume_server_pb.VolumeEcShardsMountRequest{
					VolumeId:   t.volumeID,
					Collection: t.collection,
					ShardIds:   shardIds,
					Generation: 0, // EC encoding always uses generation 0
				})
				return mountErr
			})

		if err != nil {
			t.LogWarning("Failed to mount EC shards", map[string]interface{}{
				"destination": destNode,
				"shard_count": len(shardIds),
			})
		}
	}

	return nil
}

// deleteOriginalVolume deletes the original volume and all its replicas from all servers
func (t *ErasureCodingTask) deleteOriginalVolume() error {
	// Get replicas from task parameters (set during detection)
	replicas := t.getReplicas()

	if len(replicas) == 0 {
		replicas = []string{t.server}
	}

	t.LogInfo("Deleting original volume from replicas", map[string]interface{}{
		"replica_count": len(replicas),
	})

	// Delete volume from all replica locations
	var deleteErrors []string
	successCount := 0

	for _, replicaServer := range replicas {

		err := operation.WithVolumeServerClient(false, pb.ServerAddress(replicaServer), grpc.WithInsecure(),
			func(client volume_server_pb.VolumeServerClient) error {
				_, err := client.VolumeDelete(context.Background(), &volume_server_pb.VolumeDeleteRequest{
					VolumeId:  t.volumeID,
					OnlyEmpty: false, // Force delete since we've created EC shards
				})
				return err
			})

		if err != nil {
			deleteErrors = append(deleteErrors, fmt.Sprintf("failed to delete volume %d from %s: %v", t.volumeID, replicaServer, err))
			t.LogError("Failed to delete volume from replica server", map[string]interface{}{
				"server": replicaServer,
				"error":  err.Error(),
			})
		} else {
			successCount++
			// Only log individual successes for small replica sets
			if len(replicas) <= 3 {
				t.LogInfo("Successfully deleted volume from replica server", map[string]interface{}{
					"server": replicaServer,
				})
			}
		}
	}

	// Report results
	if len(deleteErrors) > 0 {
		t.LogWarning("Some volume deletions failed", map[string]interface{}{
			"successful":     successCount,
			"failed":         len(deleteErrors),
			"total_replicas": len(replicas),
			"success_rate":   float64(successCount) / float64(len(replicas)) * 100,
			"errors":         deleteErrors,
		})
		// Don't return error - EC task should still be considered successful if shards are mounted
	} else {
		t.LogInfo("Successfully deleted volume from all replica servers", map[string]interface{}{
			"replica_count":   len(replicas),
			"replica_servers": replicas,
		})
	}

	return nil
}

// getReplicas extracts replica servers from unified sources
func (t *ErasureCodingTask) getReplicas() []string {
	var replicas []string
	for _, source := range t.sources {
		// Only include volume replica sources (not EC shard sources)
		// Assumption: VolumeId == 0 is considered invalid and should be excluded.
		// If volume ID 0 is valid in some contexts, update this check accordingly.
		if source.VolumeId > 0 {
			replicas = append(replicas, source.Node)
		}
	}
	return replicas
}