package sync

import (
	"context"
	"fmt"
	"time"

	"go.uber.org/zap"

	"codeberg.org/mapleopentech/monorepo/cloud/maplefile-backend/pkg/maplefile/client"
	collectionDomain "codeberg.org/mapleopentech/monorepo/native/desktop/maplefile/internal/domain/collection"
	"codeberg.org/mapleopentech/monorepo/native/desktop/maplefile/internal/domain/syncstate"
)

// CollectionSyncService defines the interface for collection synchronization
type CollectionSyncService interface {
	Execute(ctx context.Context, input *SyncInput) (*SyncResult, error)
}

type collectionSyncService struct {
	logger       *zap.Logger
	apiClient    *client.Client
	repoProvider RepositoryProvider
}

// ProvideCollectionSyncService creates a new collection sync service for Wire
func ProvideCollectionSyncService(
	logger *zap.Logger,
	apiClient *client.Client,
	repoProvider RepositoryProvider,
) CollectionSyncService {
	return &collectionSyncService{
		logger:       logger.Named("CollectionSyncService"),
		apiClient:    apiClient,
		repoProvider: repoProvider,
	}
}

// getCollectionRepo returns the collection repository, or an error if not initialized
func (s *collectionSyncService) getCollectionRepo() (collectionDomain.Repository, error) {
	if !s.repoProvider.IsInitialized() {
		return nil, fmt.Errorf("storage not initialized - user must be logged in")
	}
	repo := s.repoProvider.GetCollectionRepository()
	if repo == nil {
		return nil, fmt.Errorf("collection repository not available")
	}
	return repo, nil
}

// getSyncStateRepo returns the sync state repository, or an error if not initialized
func (s *collectionSyncService) getSyncStateRepo() (syncstate.Repository, error) {
	if !s.repoProvider.IsInitialized() {
		return nil, fmt.Errorf("storage not initialized - user must be logged in")
	}
	repo := s.repoProvider.GetSyncStateRepository()
	if repo == nil {
		return nil, fmt.Errorf("sync state repository not available")
	}
	return repo, nil
}

// Execute synchronizes collections from the cloud to local storage
func (s *collectionSyncService) Execute(ctx context.Context, input *SyncInput) (*SyncResult, error) {
	s.logger.Info("Starting collection synchronization")

	// Get repositories (will fail if user not logged in)
	syncStateRepo, err := s.getSyncStateRepo()
	if err != nil {
		s.logger.Error("Cannot sync - storage not initialized", zap.Error(err))
		return nil, err
	}

	// Set defaults
	if input == nil {
		input = &SyncInput{}
	}
	if input.BatchSize <= 0 {
		input.BatchSize = DefaultBatchSize
	}
	if input.MaxBatches <= 0 {
		input.MaxBatches = DefaultMaxBatches
	}

	// Get current sync state
	state, err := syncStateRepo.Get()
	if err != nil {
		s.logger.Error("Failed to get sync state", zap.Error(err))
		return nil, err
	}

	result := &SyncResult{}
	batchCount := 0

	// Sync loop - fetch and process batches until done or max reached
	for batchCount < input.MaxBatches {
		// Prepare API request
		syncInput := &client.SyncInput{
			Cursor: state.CollectionCursor,
			Limit:  input.BatchSize,
		}

		// Fetch batch from cloud
		resp, err := s.apiClient.SyncCollections(ctx, syncInput)
		if err != nil {
			s.logger.Error("Failed to fetch collections from cloud", zap.Error(err))
			result.Errors = append(result.Errors, "failed to fetch collections: "+err.Error())
			break
		}

		// Process each collection in the batch
		for _, cloudCol := range resp.Collections {
			if err := s.processCollection(ctx, cloudCol, input.Password, result); err != nil {
				s.logger.Error("Failed to process collection",
					zap.String("id", cloudCol.ID),
					zap.Error(err))
				result.Errors = append(result.Errors, "failed to process collection "+cloudCol.ID+": "+err.Error())
			}
			result.CollectionsProcessed++
		}

		// Update sync state with new cursor
		state.UpdateCollectionSync(resp.NextCursor, resp.HasMore)
		if err := syncStateRepo.Save(state); err != nil {
			s.logger.Error("Failed to save sync state", zap.Error(err))
			result.Errors = append(result.Errors, "failed to save sync state: "+err.Error())
		}

		batchCount++

		// Check if we're done
		if !resp.HasMore {
			s.logger.Info("Collection sync completed - no more items")
			break
		}
	}

	s.logger.Info("Collection sync finished",
		zap.Int("processed", result.CollectionsProcessed),
		zap.Int("added", result.CollectionsAdded),
		zap.Int("updated", result.CollectionsUpdated),
		zap.Int("deleted", result.CollectionsDeleted),
		zap.Int("errors", len(result.Errors)))

	return result, nil
}

// processCollection handles a single collection from the cloud
// Note: ctx and password are reserved for future use (on-demand content decryption)
func (s *collectionSyncService) processCollection(_ context.Context, cloudCol *client.Collection, _ string, result *SyncResult) error {
	// Get collection repository
	collectionRepo, err := s.getCollectionRepo()
	if err != nil {
		return err
	}

	// Check if collection exists locally
	localCol, err := collectionRepo.Get(cloudCol.ID)
	if err != nil {
		return err
	}

	// Handle deleted collections
	if cloudCol.State == collectionDomain.StateDeleted {
		if localCol != nil {
			if err := collectionRepo.Delete(cloudCol.ID); err != nil {
				return err
			}
			result.CollectionsDeleted++
		}
		return nil
	}

	// The collection name comes from the API already decrypted for owned collections.
	// For shared collections, it would need decryption using the key chain.
	// For now, we use the name as-is from the API response.
	collectionName := cloudCol.Name

	// Create or update local collection
	if localCol == nil {
		// Create new local collection
		newCol := s.mapCloudToLocal(cloudCol, collectionName)
		if err := collectionRepo.Create(newCol); err != nil {
			return err
		}
		result.CollectionsAdded++
	} else {
		// Update existing collection
		updatedCol := s.mapCloudToLocal(cloudCol, collectionName)
		updatedCol.SyncStatus = localCol.SyncStatus // Preserve local sync status
		updatedCol.LastSyncedAt = time.Now()
		if err := collectionRepo.Update(updatedCol); err != nil {
			return err
		}
		result.CollectionsUpdated++
	}

	return nil
}

// mapCloudToLocal converts a cloud collection to local domain model
func (s *collectionSyncService) mapCloudToLocal(cloudCol *client.Collection, decryptedName string) *collectionDomain.Collection {
	return &collectionDomain.Collection{
		ID:                     cloudCol.ID,
		ParentID:               cloudCol.ParentID,
		OwnerID:                cloudCol.UserID,
		EncryptedCollectionKey: cloudCol.EncryptedCollectionKey.Ciphertext,
		Nonce:                  cloudCol.EncryptedCollectionKey.Nonce,
		Name:                   decryptedName,
		Description:            cloudCol.Description,
		CustomIcon:             cloudCol.CustomIcon, // Custom icon (emoji or "icon:<id>")
		TotalFiles:             cloudCol.TotalFiles,
		TotalSizeInBytes:       cloudCol.TotalSizeInBytes,
		PermissionLevel:        cloudCol.PermissionLevel,
		IsOwner:                cloudCol.IsOwner,
		OwnerName:              cloudCol.OwnerName,
		OwnerEmail:             cloudCol.OwnerEmail,
		SyncStatus:             collectionDomain.SyncStatusCloudOnly,
		LastSyncedAt:           time.Now(),
		State:                  cloudCol.State,
		CreatedAt:              cloudCol.CreatedAt,
		ModifiedAt:             cloudCol.ModifiedAt,
	}
}