// Package service provides business logic implementations for WeKnora application
// This package contains service layer implementations that coordinate between
// repositories and handlers, applying business rules and transaction management
package service

import (
	"context"
	"fmt"

	"github.com/Tencent/WeKnora/internal/application/service/retriever"
	"github.com/Tencent/WeKnora/internal/logger"
	"github.com/Tencent/WeKnora/internal/types"
	"github.com/Tencent/WeKnora/internal/types/interfaces"
)

// chunkService implements the ChunkService interface
// It provides operations for managing document chunks in the knowledge base
// Chunks are segments of documents that have been processed and prepared for indexing
type chunkService struct {
	chunkRepository interfaces.ChunkRepository // Repository for chunk data persistence
	kbRepository    interfaces.KnowledgeBaseRepository
	modelService    interfaces.ModelService
	retrieveEngine  interfaces.RetrieveEngineRegistry
}

// NewChunkService creates a new chunk service
// It initializes a service with the provided chunk repository
// Parameters:
//   - chunkRepository: Repository for chunk operations
//
// Returns:
//   - interfaces.ChunkService: Initialized chunk service implementation
func NewChunkService(
	chunkRepository interfaces.ChunkRepository,
	kbRepository interfaces.KnowledgeBaseRepository,
	modelService interfaces.ModelService,
	retrieveEngine interfaces.RetrieveEngineRegistry,
) interfaces.ChunkService {
	return &chunkService{
		chunkRepository: chunkRepository,
		kbRepository:    kbRepository,
		modelService:    modelService,
		retrieveEngine:  retrieveEngine,
	}
}

// GetRepository gets the chunk repository
// Parameters:
//   - ctx: Context with authentication and request information
//
// Returns:
//   - interfaces.ChunkRepository: Chunk repository
func (s *chunkService) GetRepository() interfaces.ChunkRepository {
	return s.chunkRepository
}

// CreateChunks creates multiple chunks
// This method persists a batch of document chunks to the repository
// Parameters:
//   - ctx: Context with authentication and request information
//   - chunks: Slice of document chunks to create
//
// Returns:
//   - error: Any error encountered during chunk creation
func (s *chunkService) CreateChunks(ctx context.Context, chunks []*types.Chunk) error {
	err := s.chunkRepository.CreateChunks(ctx, chunks)
	if err != nil {
		logger.ErrorWithFields(ctx, err, map[string]interface{}{
			"chunk_count": len(chunks),
		})
		return err
	}

	logger.Infof(ctx, "Add %d chunks successfully", len(chunks))
	return nil
}

// GetChunkByID retrieves a chunk by its ID
// This method fetches a specific chunk using its ID and validates tenant access
// Parameters:
//   - ctx: Context with authentication and request information
//   - knowledgeID: ID of the knowledge document containing the chunk
//   - id: ID of the chunk to retrieve
//
// Returns:
//   - *types.Chunk: Retrieved chunk if found
//   - error: Any error encountered during retrieval
func (s *chunkService) GetChunkByID(ctx context.Context, id string) (*types.Chunk, error) {
	tenantID := ctx.Value(types.TenantIDContextKey).(uint64)
	logger.Infof(ctx, "Getting chunk by ID, ID: %s, tenant ID: %d", id, tenantID)
	chunk, err := s.chunkRepository.GetChunkByID(ctx, tenantID, id)
	if err != nil {
		logger.ErrorWithFields(ctx, err, map[string]interface{}{
			"tenant_id": tenantID,
		})
		return nil, err
	}

	logger.Info(ctx, "Chunk retrieved successfully")
	return chunk, nil
}

// ListChunksByKnowledgeID lists all chunks for a knowledge ID
// This method retrieves all chunks belonging to a specific knowledge document
// Parameters:
//   - ctx: Context with authentication and request information
//   - knowledgeID: ID of the knowledge document
//
// Returns:
//   - []*types.Chunk: List of chunks belonging to the knowledge document
//   - error: Any error encountered during retrieval
func (s *chunkService) ListChunksByKnowledgeID(ctx context.Context, knowledgeID string) ([]*types.Chunk, error) {
	logger.Info(ctx, "Start listing chunks by knowledge ID")
	logger.Infof(ctx, "Knowledge ID: %s", knowledgeID)

	tenantID := ctx.Value(types.TenantIDContextKey).(uint64)
	logger.Infof(ctx, "Tenant ID: %d", tenantID)

	chunks, err := s.chunkRepository.ListChunksByKnowledgeID(ctx, tenantID, knowledgeID)
	if err != nil {
		logger.ErrorWithFields(ctx, err, map[string]interface{}{
			"knowledge_id": knowledgeID,
			"tenant_id":    tenantID,
		})
		return nil, err
	}

	logger.Infof(ctx, "Retrieved %d chunks successfully", len(chunks))
	return chunks, nil
}

// ListPagedChunksByKnowledgeID lists chunks for a knowledge ID with pagination
// This method retrieves chunks with pagination support for better performance with large datasets
// Parameters:
//   - ctx: Context with authentication and request information
//   - knowledgeID: ID of the knowledge document
//   - page: Pagination parameters including page number and page size
//
// Returns:
//   - *types.PageResult: Paginated result containing chunks and pagination metadata
//   - error: Any error encountered during retrieval
func (s *chunkService) ListPagedChunksByKnowledgeID(ctx context.Context,
	knowledgeID string, page *types.Pagination, chunkType []types.ChunkType,
) (*types.PageResult, error) {
	tenantID := ctx.Value(types.TenantIDContextKey).(uint64)
	chunks, total, err := s.chunkRepository.ListPagedChunksByKnowledgeID(
		ctx,
		tenantID,
		knowledgeID,
		page,
		chunkType,
		"",
		"",
	)
	if err != nil {
		logger.ErrorWithFields(ctx, err, map[string]interface{}{
			"knowledge_id": knowledgeID,
			"tenant_id":    tenantID,
		})
		return nil, err
	}

	logger.Infof(ctx, "Retrieved %d chunks out of %d total chunks", len(chunks), total)
	return types.NewPageResult(total, page, chunks), nil
}

// updateChunk updates a chunk
// This method updates an existing chunk in the repository
// Parameters:
//   - ctx: Context with authentication and request information
//   - chunk: Chunk with updated fields
//
// Returns:
//   - error: Any error encountered during update
//
// This method handles the actual update logic for a chunk, including updating the vector database representation
func (s *chunkService) UpdateChunk(ctx context.Context, chunk *types.Chunk) error {
	logger.Infof(ctx, "Updating chunk, ID: %s, knowledge ID: %s", chunk.ID, chunk.KnowledgeID)

	// Update the chunk in the repository
	err := s.chunkRepository.UpdateChunk(ctx, chunk)
	if err != nil {
		logger.ErrorWithFields(ctx, err, map[string]interface{}{
			"chunk_id":     chunk.ID,
			"knowledge_id": chunk.KnowledgeID,
		})
		return err
	}

	logger.Info(ctx, "Chunk updated successfully")
	return nil
}

// UpdateChunks updates chunks in batch
func (s *chunkService) UpdateChunks(ctx context.Context, chunks []*types.Chunk) error {
	if len(chunks) == 0 {
		return nil
	}
	logger.Infof(ctx, "Updating %d chunks in batch", len(chunks))

	// Update the chunks in the repository
	err := s.chunkRepository.UpdateChunks(ctx, chunks)
	if err != nil {
		logger.ErrorWithFields(ctx, err, map[string]interface{}{
			"chunk_count": len(chunks),
		})
		return err
	}

	logger.Infof(ctx, "Successfully updated %d chunks", len(chunks))
	return nil
}

// DeleteChunk deletes a chunk by ID
// This method removes a specific chunk from the repository
// Parameters:
//   - ctx: Context with authentication and request information
//   - id: ID of the chunk to delete
//
// Returns:
//   - error: Any error encountered during deletion
func (s *chunkService) DeleteChunk(ctx context.Context, id string) error {
	tenantID := ctx.Value(types.TenantIDContextKey).(uint64)
	err := s.chunkRepository.DeleteChunk(ctx, tenantID, id)
	if err != nil {
		logger.ErrorWithFields(ctx, err, map[string]interface{}{
			"tenant_id": tenantID,
		})
		return err
	}
	logger.Info(ctx, "Chunk deleted successfully")
	return nil
}

// DeleteChunks deletes chunks by IDs in batch
// This method removes multiple chunks from the repository in a single operation
// Parameters:
//   - ctx: Context with authentication and request information
//   - ids: Slice of chunk IDs to delete
//
// Returns:
//   - error: Any error encountered during batch deletion
func (s *chunkService) DeleteChunks(ctx context.Context, ids []string) error {
	if len(ids) == 0 {
		return nil
	}
	logger.Info(ctx, "Start deleting chunks in batch")
	logger.Infof(ctx, "Deleting %d chunks", len(ids))

	tenantID := ctx.Value(types.TenantIDContextKey).(uint64)
	logger.Infof(ctx, "Tenant ID: %d", tenantID)

	err := s.chunkRepository.DeleteChunks(ctx, tenantID, ids)
	if err != nil {
		logger.ErrorWithFields(ctx, err, map[string]interface{}{
			"chunk_ids": ids,
			"tenant_id": tenantID,
		})
		return err
	}

	logger.Infof(ctx, "Successfully deleted %d chunks", len(ids))
	return nil
}

// DeleteChunksByKnowledgeID deletes all chunks for a knowledge ID
// This method removes all chunks belonging to a specific knowledge document
// Parameters:
//   - ctx: Context with authentication and request information
//   - knowledgeID: ID of the knowledge document
//
// Returns:
//   - error: Any error encountered during bulk deletion
func (s *chunkService) DeleteChunksByKnowledgeID(ctx context.Context, knowledgeID string) error {
	logger.Info(ctx, "Start deleting all chunks by knowledge ID")
	logger.Infof(ctx, "Knowledge ID: %s", knowledgeID)

	tenantID := ctx.Value(types.TenantIDContextKey).(uint64)
	logger.Infof(ctx, "Tenant ID: %d", tenantID)

	err := s.chunkRepository.DeleteChunksByKnowledgeID(ctx, tenantID, knowledgeID)
	if err != nil {
		logger.ErrorWithFields(ctx, err, map[string]interface{}{
			"knowledge_id": knowledgeID,
			"tenant_id":    tenantID,
		})
		return err
	}

	logger.Info(ctx, "All chunks under knowledge deleted successfully")
	return nil
}

func (s *chunkService) DeleteByKnowledgeList(ctx context.Context, ids []string) error {
	logger.Info(ctx, "Start deleting all chunks by knowledge IDs")
	logger.Infof(ctx, "Knowledge IDs: %v", ids)

	tenantID := ctx.Value(types.TenantIDContextKey).(uint64)
	logger.Infof(ctx, "Tenant ID: %d", tenantID)

	err := s.chunkRepository.DeleteByKnowledgeList(ctx, tenantID, ids)
	if err != nil {
		logger.ErrorWithFields(ctx, err, map[string]interface{}{
			"knowledge_id": ids,
			"tenant_id":    tenantID,
		})
		return err
	}

	logger.Info(ctx, "All chunks under knowledge deleted successfully")
	return nil
}

func (s *chunkService) ListChunkByParentID(
	ctx context.Context,
	tenantID uint64,
	parentID string,
) ([]*types.Chunk, error) {
	logger.Info(ctx, "Start listing chunk by parent ID")
	logger.Infof(ctx, "Parent ID: %s", parentID)

	chunks, err := s.chunkRepository.ListChunkByParentID(ctx, tenantID, parentID)
	if err != nil {
		logger.ErrorWithFields(ctx, err, map[string]interface{}{
			"parent_id": parentID,
			"tenant_id": tenantID,
		})
		return nil, err
	}

	logger.Info(ctx, "Chunk listed successfully")
	return chunks, nil
}

// DeleteGeneratedQuestion deletes a single generated question from a chunk by question ID
// This updates the chunk metadata and removes the corresponding vector index
func (s *chunkService) DeleteGeneratedQuestion(ctx context.Context, chunkID string, questionID string) error {
	logger.Infof(ctx, "Deleting generated question, chunk ID: %s, question ID: %s", chunkID, questionID)

	tenantID := ctx.Value(types.TenantIDContextKey).(uint64)

	// 1. Get the chunk
	chunk, err := s.chunkRepository.GetChunkByID(ctx, tenantID, chunkID)
	if err != nil {
		logger.ErrorWithFields(ctx, err, map[string]interface{}{
			"chunk_id":  chunkID,
			"tenant_id": tenantID,
		})
		return fmt.Errorf("failed to get chunk: %w", err)
	}

	// 2. Parse the metadata
	meta, err := chunk.DocumentMetadata()
	if err != nil {
		logger.ErrorWithFields(ctx, err, map[string]interface{}{
			"chunk_id": chunkID,
		})
		return fmt.Errorf("failed to parse chunk metadata: %w", err)
	}

	if meta == nil || len(meta.GeneratedQuestions) == 0 {
		return fmt.Errorf("no generated questions found for chunk %s", chunkID)
	}

	// 3. Find the question by ID
	questionIndex := -1
	for i, q := range meta.GeneratedQuestions {
		if q.ID == questionID {
			questionIndex = i
			break
		}
	}

	if questionIndex == -1 {
		return fmt.Errorf("question with ID %s not found in chunk %s", questionID, chunkID)
	}

	// 4. Get knowledge base to get embedding model
	kb, err := s.kbRepository.GetKnowledgeBaseByID(ctx, chunk.KnowledgeBaseID)
	if err != nil {
		logger.ErrorWithFields(ctx, err, map[string]interface{}{
			"knowledge_base_id": chunk.KnowledgeBaseID,
		})
		return fmt.Errorf("failed to get knowledge base: %w", err)
	}

	// 5. Delete the vector index for this question
	// The source_id format is: {chunk_id}-{question_id}
	sourceID := fmt.Sprintf("%s-%s", chunkID, questionID)

	tenantInfo := ctx.Value(types.TenantInfoContextKey).(*types.Tenant)
	retrieveEngine, err := retriever.NewCompositeRetrieveEngine(s.retrieveEngine, tenantInfo.RetrieverEngines.Engines)
	if err != nil {
		logger.ErrorWithFields(ctx, err, map[string]interface{}{
			"chunk_id": chunkID,
		})
		return fmt.Errorf("failed to create retrieve engine: %w", err)
	}

	embeddingModel, err := s.modelService.GetEmbeddingModel(ctx, kb.EmbeddingModelID)
	if err != nil {
		logger.ErrorWithFields(ctx, err, map[string]interface{}{
			"embedding_model_id": kb.EmbeddingModelID,
		})
		return fmt.Errorf("failed to get embedding model: %w", err)
	}

	// Delete the vector index by source ID
	if err := retrieveEngine.DeleteBySourceIDList(ctx, []string{sourceID}, embeddingModel.GetDimensions()); err != nil {
		logger.Warnf(ctx, "Failed to delete vector index for question (may not exist): %v", err)
		// Continue even if vector deletion fails - the question might not have been indexed
	}

	// 6. Remove the question from metadata
	newQuestions := make([]types.GeneratedQuestion, 0, len(meta.GeneratedQuestions)-1)
	for i, q := range meta.GeneratedQuestions {
		if i != questionIndex {
			newQuestions = append(newQuestions, q)
		}
	}

	// 7. Update chunk metadata
	meta.GeneratedQuestions = newQuestions
	if err := chunk.SetDocumentMetadata(meta); err != nil {
		return fmt.Errorf("failed to set chunk metadata: %w", err)
	}

	if err := s.chunkRepository.UpdateChunk(ctx, chunk); err != nil {
		logger.ErrorWithFields(ctx, err, map[string]interface{}{
			"chunk_id": chunkID,
		})
		return fmt.Errorf("failed to update chunk: %w", err)
	}

	logger.Infof(ctx, "Successfully deleted generated question %s from chunk %s", questionID, chunkID)
	return nil
}