package filer

import (
	"context"
	"fmt"
	"strings"
	"sync"
	"time"

	"github.com/seaweedfs/seaweedfs/weed/storage"
	"github.com/seaweedfs/seaweedfs/weed/util"

	"github.com/seaweedfs/seaweedfs/weed/glog"
	"github.com/seaweedfs/seaweedfs/weed/operation"
	"github.com/seaweedfs/seaweedfs/weed/pb/filer_pb"
	"github.com/seaweedfs/seaweedfs/weed/wdclient"
)

const (
	// Maximum number of retry attempts for failed deletions
	MaxRetryAttempts = 10
	// Initial retry delay (will be doubled with each attempt)
	InitialRetryDelay = 5 * time.Minute
	// Maximum retry delay
	MaxRetryDelay = 6 * time.Hour
)

// DeletionRetryItem represents a file deletion that failed and needs to be retried
type DeletionRetryItem struct {
	FileId      string
	RetryCount  int
	NextRetryAt time.Time
	LastError   string
}

// DeletionRetryQueue manages the queue of failed deletions that need to be retried
type DeletionRetryQueue struct {
	items     []*DeletionRetryItem
	itemsLock sync.RWMutex
}

// NewDeletionRetryQueue creates a new retry queue
func NewDeletionRetryQueue() *DeletionRetryQueue {
	return &DeletionRetryQueue{
		items: make([]*DeletionRetryItem, 0),
	}
}

// AddOrUpdate adds a new failed deletion or updates an existing one
func (q *DeletionRetryQueue) AddOrUpdate(fileId string, errorMsg string) {
	q.itemsLock.Lock()
	defer q.itemsLock.Unlock()

	// Check if item already exists
	for _, item := range q.items {
		if item.FileId == fileId {
			item.RetryCount++
			item.LastError = errorMsg
			// Calculate next retry time with exponential backoff
			delay := InitialRetryDelay * time.Duration(1<<uint(item.RetryCount-1))
			if delay > MaxRetryDelay {
				delay = MaxRetryDelay
			}
			item.NextRetryAt = time.Now().Add(delay)
			glog.V(2).Infof("updated retry for %s: attempt %d, next retry in %v", fileId, item.RetryCount, delay)
			return
		}
	}

	// Add new item
	delay := InitialRetryDelay
	newItem := &DeletionRetryItem{
		FileId:      fileId,
		RetryCount:  1,
		NextRetryAt: time.Now().Add(delay),
		LastError:   errorMsg,
	}
	q.items = append(q.items, newItem)
	glog.V(2).Infof("added retry for %s: next retry in %v", fileId, delay)
}

// GetReadyItems returns items that are ready to be retried and removes them from the queue
func (q *DeletionRetryQueue) GetReadyItems(maxItems int) []*DeletionRetryItem {
	q.itemsLock.Lock()
	defer q.itemsLock.Unlock()

	now := time.Now()
	var readyItems []*DeletionRetryItem
	var remainingItems []*DeletionRetryItem

	for _, item := range q.items {
		if len(readyItems) < maxItems && item.NextRetryAt.Before(now) {
			if item.RetryCount < MaxRetryAttempts {
				readyItems = append(readyItems, item)
			} else {
				// Max attempts reached, log and discard
				glog.Warningf("max retry attempts (%d) reached for %s, last error: %s", MaxRetryAttempts, item.FileId, item.LastError)
			}
		} else {
			// Keep items that are not ready yet or if the batch is full
			remainingItems = append(remainingItems, item)
		}
	}

	q.items = remainingItems
	return readyItems
}

// Size returns the current size of the retry queue
func (q *DeletionRetryQueue) Size() int {
	q.itemsLock.RLock()
	defer q.itemsLock.RUnlock()
	return len(q.items)
}

func LookupByMasterClientFn(masterClient *wdclient.MasterClient) func(vids []string) (map[string]*operation.LookupResult, error) {
	return func(vids []string) (map[string]*operation.LookupResult, error) {
		m := make(map[string]*operation.LookupResult)
		for _, vid := range vids {
			locs, _ := masterClient.GetVidLocations(vid)
			var locations []operation.Location
			for _, loc := range locs {
				locations = append(locations, operation.Location{
					Url:       loc.Url,
					PublicUrl: loc.PublicUrl,
					GrpcPort:  loc.GrpcPort,
				})
			}
			m[vid] = &operation.LookupResult{
				VolumeOrFileId: vid,
				Locations:      locations,
			}
		}
		return m, nil
	}
}

func (f *Filer) loopProcessingDeletion() {

	lookupFunc := LookupByMasterClientFn(f.MasterClient)

	DeletionBatchSize := 100000 // roughly 20 bytes cost per file id.

	// Create retry queue
	retryQueue := NewDeletionRetryQueue()

	// Start retry processor in a separate goroutine
	go f.loopProcessingDeletionRetry(lookupFunc, retryQueue)

	var deletionCount int
	for {
		deletionCount = 0
		f.fileIdDeletionQueue.Consume(func(fileIds []string) {
			for len(fileIds) > 0 {
				var toDeleteFileIds []string
				if len(fileIds) > DeletionBatchSize {
					toDeleteFileIds = fileIds[:DeletionBatchSize]
					fileIds = fileIds[DeletionBatchSize:]
				} else {
					toDeleteFileIds = fileIds
					fileIds = fileIds[:0]
				}
				deletionCount = len(toDeleteFileIds)
				results := operation.DeleteFileIdsWithLookupVolumeId(f.GrpcDialOption, toDeleteFileIds, lookupFunc)

				// Process individual results for better error tracking
				var successCount, notFoundCount, retryableErrorCount, permanentErrorCount int
				var errorDetails []string

				for _, result := range results {
					if result.Error == "" {
						successCount++
					} else if result.Error == "not found" || strings.Contains(result.Error, storage.ErrorDeleted.Error()) {
						// Already deleted - acceptable
						notFoundCount++
					} else if isRetryableError(result.Error) {
						// Retryable error - add to retry queue
						retryableErrorCount++
						retryQueue.AddOrUpdate(result.FileId, result.Error)
						if retryableErrorCount <= 10 {
							errorDetails = append(errorDetails, result.FileId+": "+result.Error+" (will retry)")
						}
					} else {
						// Permanent error - log but don't retry
						permanentErrorCount++
						if permanentErrorCount <= 10 {
							errorDetails = append(errorDetails, result.FileId+": "+result.Error+" (permanent)")
						}
					}
				}

				if successCount > 0 || notFoundCount > 0 {
					glog.V(2).Infof("deleted %d files successfully, %d already deleted (not found)", successCount, notFoundCount)
				}

				totalErrors := retryableErrorCount + permanentErrorCount
				if totalErrors > 0 {
					logMessage := fmt.Sprintf("failed to delete %d/%d files (%d retryable, %d permanent)",
						totalErrors, len(toDeleteFileIds), retryableErrorCount, permanentErrorCount)
					if totalErrors > 10 {
						logMessage += " (showing first 10)"
					}
					glog.V(0).Infof("%s: %v", logMessage, strings.Join(errorDetails, "; "))
				}

				if retryQueue.Size() > 0 {
					glog.V(2).Infof("retry queue size: %d", retryQueue.Size())
				}
			}
		})

		if deletionCount == 0 {
			time.Sleep(1123 * time.Millisecond)
		}
	}
}

// isRetryableError determines if an error is retryable
func isRetryableError(errorMsg string) bool {
	// Errors that indicate temporary conditions
	retryablePatterns := []string{
		"is read only",
		"error reading from server",
		"connection reset by peer",
		"closed network connection",
	}

	errorLower := strings.ToLower(errorMsg)
	for _, pattern := range retryablePatterns {
		if strings.Contains(errorLower, pattern) {
			return true
		}
	}
	return false
}

// loopProcessingDeletionRetry processes the retry queue for failed deletions
func (f *Filer) loopProcessingDeletionRetry(lookupFunc func([]string) (map[string]*operation.LookupResult, error), retryQueue *DeletionRetryQueue) {

	ticker := time.NewTicker(1 * time.Minute)
	defer ticker.Stop()

	for range ticker.C {
		// Get items that are ready to retry
		readyItems := retryQueue.GetReadyItems(1000)

		if len(readyItems) == 0 {
			continue
		}

		glog.V(1).Infof("retrying deletion of %d files", len(readyItems))

		// Extract file IDs from retry items
		var fileIds []string
		itemsByFileId := make(map[string]*DeletionRetryItem)
		for _, item := range readyItems {
			fileIds = append(fileIds, item.FileId)
			itemsByFileId[item.FileId] = item
		}

		// Attempt deletion
		results := operation.DeleteFileIdsWithLookupVolumeId(f.GrpcDialOption, fileIds, lookupFunc)

		// Process results
		var successCount, notFoundCount, retryCount int
		for _, result := range results {
			item := itemsByFileId[result.FileId]

			if result.Error == "" {
				successCount++
				glog.V(2).Infof("retry successful for %s after %d attempts", result.FileId, item.RetryCount)
			} else if result.Error == "not found" || strings.Contains(result.Error, storage.ErrorDeleted.Error()) {
				// Already deleted - success
				notFoundCount++
			} else if isRetryableError(result.Error) {
				// Still failing, add back to retry queue
				retryCount++
				retryQueue.AddOrUpdate(result.FileId, result.Error)
			} else {
				// Permanent error on retry - give up
				glog.Warningf("permanent error on retry for %s after %d attempts: %s", result.FileId, item.RetryCount, result.Error)
			}
		}

		if successCount > 0 || notFoundCount > 0 {
			glog.V(1).Infof("retry: deleted %d files successfully, %d already deleted", successCount, notFoundCount)
		}
		if retryCount > 0 {
			glog.V(1).Infof("retry: %d files still failing, will retry again later", retryCount)
		}
	}
}

func (f *Filer) DeleteUncommittedChunks(ctx context.Context, chunks []*filer_pb.FileChunk) {
	f.doDeleteChunks(ctx, chunks)
}

func (f *Filer) DeleteChunks(ctx context.Context, fullpath util.FullPath, chunks []*filer_pb.FileChunk) {
	rule := f.FilerConf.MatchStorageRule(string(fullpath))
	if rule.DisableChunkDeletion {
		return
	}
	f.doDeleteChunks(ctx, chunks)
}

func (f *Filer) doDeleteChunks(ctx context.Context, chunks []*filer_pb.FileChunk) {
	for _, chunk := range chunks {
		if !chunk.IsChunkManifest {
			f.fileIdDeletionQueue.EnQueue(chunk.GetFileIdString())
			continue
		}
		dataChunks, manifestResolveErr := ResolveOneChunkManifest(ctx, f.MasterClient.LookupFileId, chunk)
		if manifestResolveErr != nil {
			glog.V(0).InfofCtx(ctx, "failed to resolve manifest %s: %v", chunk.FileId, manifestResolveErr)
		}
		for _, dChunk := range dataChunks {
			f.fileIdDeletionQueue.EnQueue(dChunk.GetFileIdString())
		}
		f.fileIdDeletionQueue.EnQueue(chunk.GetFileIdString())
	}
}

func (f *Filer) DeleteChunksNotRecursive(chunks []*filer_pb.FileChunk) {
	for _, chunk := range chunks {
		f.fileIdDeletionQueue.EnQueue(chunk.GetFileIdString())
	}
}

func (f *Filer) deleteChunksIfNotNew(ctx context.Context, oldEntry, newEntry *Entry) {
	var oldChunks, newChunks []*filer_pb.FileChunk
	if oldEntry != nil {
		oldChunks = oldEntry.GetChunks()
	}
	if newEntry != nil {
		newChunks = newEntry.GetChunks()
	}

	toDelete, err := MinusChunks(ctx, f.MasterClient.GetLookupFileIdFunction(), oldChunks, newChunks)
	if err != nil {
		glog.ErrorfCtx(ctx, "Failed to resolve old entry chunks when delete old entry chunks. new: %s, old: %s", newChunks, oldChunks)
		return
	}
	f.DeleteChunksNotRecursive(toDelete)
}