package service

import (
	"context"
	"fmt"

	"github.com/gochat/gochat/internal/channel"
	"github.com/gochat/gochat/internal/llm"
	"github.com/gochat/gochat/internal/model"
	"github.com/gochat/gochat/internal/repository"
	"github.com/gochat/gochat/internal/search"
	applogger "github.com/gochat/gochat/pkg/logger"
	pkgvalidator "github.com/gochat/gochat/pkg/validator"
)

// MessageService implements business logic for Message operations.
// Reference: Chatwoot app/controllers/api/v1/messages_controller.rb
type MessageService struct {
	repo          *repository.MessageRepo
	dispatcher    *channel.Dispatcher
	searchIndexer SearchIndexer
	llmProvider   llm.Provider
}

// NewMessageService creates a new Message service.
func NewMessageService(repo *repository.MessageRepo, dispatcher *channel.Dispatcher, llmProvider llm.Provider) *MessageService {
	return &MessageService{repo: repo, dispatcher: dispatcher, llmProvider: llmProvider}
}

func (s *MessageService) SetSearchIndexer(indexer SearchIndexer) {
	s.searchIndexer = indexer
}

func (s *MessageService) indexMessage(ctx context.Context, message *model.Message) {
	if s.searchIndexer != nil {
		logSearchIndexError("message", message.ID, s.searchIndexer.IndexMessage(ctx, message))
	}
}

func (s *MessageService) deleteMessageIndex(ctx context.Context, accountID uint, id uint) {
	if s.searchIndexer != nil {
		logSearchIndexError("message", id, s.searchIndexer.DeleteMessage(ctx, accountID, id))
	}
}

// dispatchMessageEvent is a helper to build and dispatch a message event.
func (s *MessageService) dispatchMessageEvent(ctx context.Context, eventType channel.EventType, message *model.Message) {
	event := channel.NewChannelEvent(eventType, channel.ChannelAPI, message.AccountID, message.InboxID)
	event.ConversationID = message.ConversationID
	if message.SenderID != nil {
		event.UserID = *message.SenderID
	}
	event.Data["message"] = message
	applogger.L().Infof("dispatching event %s for message %d", eventType, message.ID)
	if err := s.dispatcher.Dispatch(ctx, event); err != nil {
		applogger.L().Errorf("failed to dispatch event %s for message %d: %v", eventType, message.ID, err)
	}
}

// ListByConversation retrieves all messages for a conversation.
func (s *MessageService) ListByConversation(ctx context.Context, conversationID uint, offset, limit int) ([]model.Message, int64, error) {
	return s.repo.FindByConversation(ctx, conversationID, offset, limit)
}

// GetByID retrieves a single message.
func (s *MessageService) GetByID(ctx context.Context, id uint) (*model.Message, error) {
	return s.repo.FindByID(ctx, id)
}

// GetByAccountAndID retrieves a message scoped to an account.
func (s *MessageService) GetByAccountAndID(ctx context.Context, accountID, id uint) (*model.Message, error) {
	return s.repo.FindByAccountAndID(ctx, accountID, id)
}

// GetByConversationAndID retrieves a message scoped to a conversation.
func (s *MessageService) GetByConversationAndID(ctx context.Context, conversationID, id uint) (*model.Message, error) {
	return s.repo.FindByConversationAndID(ctx, conversationID, id)
}

// Search searches messages by content within an account.
func (s *MessageService) Search(ctx context.Context, accountID uint, query string, offset, limit int, searchMode search.SearchMode) ([]model.Message, int64, error) {
	return s.repo.Search(ctx, accountID, query, offset, limit, searchMode)
}

// CreateMessageRequest is the DTO for creating a message.
// Reference: Chatwoot app/controllers/api/v1/accounts/conversations/messages_controller.rb #create
type CreateMessageRequest struct {
	ConversationID uint   `json:"conversation_id" validate:"required"`
	Content        string `json:"content" validate:"required,min=1"`
	MessageType    string `json:"message_type" validate:"required,oneof=outgoing incoming activity template private_note"`
	ContentType    string `json:"content_type,omitempty" validate:"omitempty,oneof=text input_text input_email input_phone select card private_note"`
	Private        bool   `json:"private,omitempty"`
	SourceID       string `json:"source_id,omitempty"` // Chatwoot: source_id for message origin (user/agent/bot)
}

// Create creates a new message.
func (s *MessageService) Create(ctx context.Context, accountID uint, userID uint, req CreateMessageRequest) (*model.Message, error) {
	if err := pkgvalidator.ValidateStruct(req); err != nil {
		return nil, err
	}

	message := &model.Message{
		AccountID:      accountID,
		ConversationID: req.ConversationID,
		Content:        req.Content,
		MessageType:    req.MessageType,
		ContentType:    req.ContentType,
		SenderID:       &userID,
		SenderType:     "user",
		Private:        req.Private,
		SourceID:       req.SourceID,
	}

	if req.ContentType == "" {
		message.ContentType = "text"
	}

	// Chatwoot: when message_type is "private_note", force Private=true and ContentType="private_note"
	if req.MessageType == "private_note" {
		message.Private = true
		if message.ContentType == "text" {
			message.ContentType = "private_note"
		}
	}

	if err := s.repo.Create(ctx, message); err != nil {
		applogger.L().Errorf("Failed to create message: %v", err)
		return nil, err
	}

	// Dispatch EventMessageCreated
	s.dispatchMessageEvent(ctx, channel.EventMessageCreated, message)
	s.indexMessage(ctx, message)

	// Dispatch additional event based on message type
	if req.MessageType == "incoming" {
		s.dispatchMessageEvent(ctx, channel.EventMessageIncoming, message)
	} else if req.MessageType == "outgoing" {
		s.dispatchMessageEvent(ctx, channel.EventMessageOutgoing, message)
	}

	return message, nil
}

// UpdateMessageRequest is the DTO for updating a message.
type UpdateMessageRequest struct {
	Content string `json:"content,omitempty" validate:"omitempty,min=1"`
}

// Update modifies an existing message.
func (s *MessageService) Update(ctx context.Context, accountID, id uint, req UpdateMessageRequest) (*model.Message, error) {
	if err := pkgvalidator.ValidateStruct(req); err != nil {
		return nil, err
	}

	message, err := s.repo.FindByAccountAndID(ctx, accountID, id)
	if err != nil {
		return nil, err
	}

	if req.Content != "" {
		message.Content = req.Content
	}

	if err := s.repo.Update(ctx, message); err != nil {
		return nil, err
	}

	// Dispatch EventMessageUpdated
	s.dispatchMessageEvent(ctx, channel.EventMessageUpdated, message)
	s.indexMessage(ctx, message)

	return message, nil
}

// Delete soft-deletes a message and dispatches EventMessageDeleted.
func (s *MessageService) Delete(ctx context.Context, accountID, id uint) error {
	message, err := s.repo.FindByAccountAndID(ctx, accountID, id)
	if err != nil {
		return err
	}

	if err := s.repo.Delete(ctx, message.ID); err != nil {
		return err
	}

	// Dispatch EventMessageDeleted
	s.dispatchMessageEvent(ctx, channel.EventMessageDeleted, message)
	s.deleteMessageIndex(ctx, accountID, message.ID)

	return nil
}

// UpdateStatus updates the delivery status of a message and dispatches EventMessageStatusUpdated.
func (s *MessageService) UpdateStatus(ctx context.Context, id uint, status string) (*model.Message, error) {
	message, err := s.repo.FindByID(ctx, id)
	if err != nil {
		return nil, err
	}

	message.Status = status

	if err := s.repo.Update(ctx, message); err != nil {
		return nil, err
	}

	// Dispatch EventMessageStatusUpdated
	event := channel.NewChannelEvent(channel.EventMessageStatusUpdated, channel.ChannelAPI, message.AccountID, message.InboxID)
	event.ConversationID = message.ConversationID
	if message.SenderID != nil {
		event.UserID = *message.SenderID
	}
	event.Data["message_id"] = message.ID
	event.Data["status"] = status
	applogger.L().Infof("dispatching event %s for message %d, status=%s", channel.EventMessageStatusUpdated, message.ID, status)
	if err := s.dispatcher.Dispatch(ctx, event); err != nil {
		applogger.L().Errorf("failed to dispatch event %s for message %d: %v", channel.EventMessageStatusUpdated, message.ID, err)
	}
	s.indexMessage(ctx, message)

	return message, nil
}

// Retry retries a failed message by resetting its delivery status.
func (s *MessageService) Retry(ctx context.Context, accountID, id uint) (*model.Message, error) {
	message, err := s.repo.FindByAccountAndID(ctx, accountID, id)
	if err != nil {
		return nil, err
	}

	// Reset status to indicate retry
	message.Status = "retrying"

	if err := s.repo.Update(ctx, message); err != nil {
		return nil, err
	}

	// Dispatch EventMessageStatusUpdated with "retrying" status
	event := channel.NewChannelEvent(channel.EventMessageStatusUpdated, channel.ChannelAPI, message.AccountID, message.InboxID)
	event.ConversationID = message.ConversationID
	if message.SenderID != nil {
		event.UserID = *message.SenderID
	}
	event.Data["message_id"] = message.ID
	event.Data["status"] = "retrying"
	applogger.L().Infof("dispatching retry event for message %d", message.ID)
	if err := s.dispatcher.Dispatch(ctx, event); err != nil {
		applogger.L().Errorf("failed to dispatch retry event for message %d: %v", message.ID, err)
	}
	s.indexMessage(ctx, message)

	return message, nil
}

// CountByConversation returns the total message count in a conversation.
func (s *MessageService) CountByConversation(ctx context.Context, conversationID uint) (int64, error) {
	return s.repo.CountByConversation(ctx, conversationID)
}

// TranslateMessageRequest is the DTO for translating a message.
type TranslateMessageRequest struct {
	TargetLanguage string `json:"target_language" validate:"required"`
}

// TranslateMessageResult holds the translated message content.
type TranslateMessageResult struct {
	ID                uint   `json:"id"`
	OriginalContent   string `json:"original_content"`
	TranslatedContent string `json:"translated_content"`
	SourceLanguage    string `json:"source_language,omitempty"`
	TargetLanguage    string `json:"target_language"`
}

// Translate translates a message's content to the target language using LLM.
func (s *MessageService) Translate(ctx context.Context, accountID, id uint, req TranslateMessageRequest) (*TranslateMessageResult, error) {
	if err := pkgvalidator.ValidateStruct(req); err != nil {
		return nil, err
	}

	message, err := s.repo.FindByAccountAndID(ctx, accountID, id)
	if err != nil {
		return nil, err
	}

	llmResp, err := s.llmProvider.ChatCompletion(ctx, llm.ChatRequest{
		Messages: []llm.ChatMessage{
			{Role: "system", Content: fmt.Sprintf("You are a translator. Translate the user's message to %s. Return only the translated text, nothing else.", req.TargetLanguage)},
			{Role: "user", Content: message.Content},
		},
	})
	if err != nil {
		applogger.L().Errorf("Translate message LLM: %v", err)
		return nil, fmt.Errorf("translate message: %w", err)
	}

	translated := ""
	if len(llmResp.Choices) > 0 {
		translated = llmResp.Choices[0].Message.Content
	}

	return &TranslateMessageResult{
		ID:                message.ID,
		OriginalContent:   message.Content,
		TranslatedContent: translated,
		TargetLanguage:    req.TargetLanguage,
	}, nil
}

// ListAttachments returns paginated attachments for all messages in a conversation.
// Reference: Chatwoot conversations_controller.rb #attachments (member route)
func (s *MessageService) ListAttachments(ctx context.Context, accountID, conversationID uint, offset, limit int) ([]model.Attachment, int64, error) {
	var attachments []model.Attachment
	var total int64

	db := s.repo.DB()
	err := db.WithContext(ctx).
		Where("account_id = ? AND message_id IN (SELECT id FROM messages WHERE conversation_id = ?)", accountID, conversationID).
		Order("id ASC").
		Find(&attachments).Error
	if err != nil {
		return nil, 0, err
	}

	total = int64(len(attachments))
	start := offset
	if start > len(attachments) {
		start = len(attachments)
	}
	end := start + limit
	if end > len(attachments) {
		end = len(attachments)
	}

	return attachments[start:end], total, nil
}