package service

import (
	"context"
	"fmt"

	"github.com/gochat/gochat/internal/model"
	"github.com/gochat/gochat/internal/repository"
	applogger "github.com/gochat/gochat/pkg/logger"
)

// ConversationParticipantService implements business logic for ConversationParticipant operations.
// Reference: Chatwoot app/controllers/api/v1/accounts/conversations/participants_controller.rb
// Chatwoot validates inbox access via assignable_agents before allowing participants.
type ConversationParticipantService struct {
	repo              *repository.ConversationParticipantRepo
	conversationRepo  *repository.ConversationRepo
	assignableAgentSvc *AssignableAgentService
}

// NewConversationParticipantService creates a new ConversationParticipant service.
func NewConversationParticipantService(repo *repository.ConversationParticipantRepo, conversationRepo *repository.ConversationRepo) *ConversationParticipantService {
	return &ConversationParticipantService{repo: repo, conversationRepo: conversationRepo}
}

// SetAssignableAgentService injects the assignable agent service for inbox access validation.
func (s *ConversationParticipantService) SetAssignableAgentService(svc *AssignableAgentService) {
	s.assignableAgentSvc = svc
}

// List retrieves all participants for a conversation.
// Chatwoot: @participants = @conversation.conversation_participants
func (s *ConversationParticipantService) List(ctx context.Context, accountID, conversationID uint) ([]model.ConversationParticipant, error) {
	if _, err := s.conversationRepo.FindByAccountAndID(ctx, accountID, conversationID); err != nil {
		return nil, err
	}
	return s.repo.FindByConversationID(ctx, conversationID)
}

// Add adds a participant to a conversation.
// Chatwoot: find_or_create_by(user_id), validates inbox access via assignable_agents
func (s *ConversationParticipantService) Add(ctx context.Context, accountID, conversationID, userID uint, role string) (*model.ConversationParticipant, error) {
	conversation, err := s.conversationRepo.FindByAccountAndID(ctx, accountID, conversationID)
	if err != nil {
		return nil, err
	}

	// Chatwoot: validates :ensure_inbox_access — user must be in assignable_agents
	if s.assignableAgentSvc != nil {
		if err := s.validateInboxAccess(ctx, accountID, conversation.InboxID, userID); err != nil {
			return nil, err
		}
	}

	// Chatwoot: before_validation :ensure_account_id — auto-sets account_id from conversation
	// find_or_create_by pattern
	existing, err := s.repo.FindByConversationAndUserID(ctx, conversationID, userID)
	if err == nil && existing != nil {
		return existing, nil
	}

	participant := &model.ConversationParticipant{
		AccountID:      accountID,
		ConversationID: conversationID,
		UserID:         userID,
		Role:           role,
	}
	if err := s.repo.Create(ctx, participant); err != nil {
		applogger.L().Errorf("ConversationParticipantService.Add: %v", err)
		return nil, err
	}
	return participant, nil
}

// Update updates a participant's role in a conversation.
func (s *ConversationParticipantService) Update(ctx context.Context, accountID, conversationID, userID uint, role string) (*model.ConversationParticipant, error) {
	if _, err := s.conversationRepo.FindByAccountAndID(ctx, accountID, conversationID); err != nil {
		return nil, err
	}
	if err := s.repo.UpdateRole(ctx, conversationID, userID, role); err != nil {
		applogger.L().Errorf("ConversationParticipantService.Update: %v", err)
		return nil, err
	}
	return s.repo.FindByConversationAndUserID(ctx, conversationID, userID)
}

// Remove removes a participant from a conversation.
// Chatwoot: conversation_participants.find_by(user_id: user_id)&.destroy
func (s *ConversationParticipantService) Remove(ctx context.Context, accountID, conversationID, userID uint) error {
	if _, err := s.conversationRepo.FindByAccountAndID(ctx, accountID, conversationID); err != nil {
		return err
	}
	return s.repo.DeleteByConversationAndUserID(ctx, conversationID, userID)
}

// BatchUpdate adds and removes participants in bulk.
// Chatwoot: update action — adds via find_or_create_by, removes via destroy
func (s *ConversationParticipantService) BatchUpdate(ctx context.Context, accountID, conversationID uint, addUserIDs []uint, removeUserIDs []uint, role string) ([]model.ConversationParticipant, error) {
	conversation, err := s.conversationRepo.FindByAccountAndID(ctx, accountID, conversationID)
	if err != nil {
		return nil, err
	}

	// Add new participants (find_or_create_by pattern)
	for _, userID := range addUserIDs {
		if s.assignableAgentSvc != nil {
			if err := s.validateInboxAccess(ctx, accountID, conversation.InboxID, userID); err != nil {
				return nil, err
			}
		}
		existing, _ := s.repo.FindByConversationAndUserID(ctx, conversationID, userID)
		if existing != nil {
			continue
		}
		participant := &model.ConversationParticipant{
			AccountID:      accountID,
			ConversationID: conversationID,
			UserID:         userID,
			Role:           role,
		}
		if err := s.repo.Create(ctx, participant); err != nil {
			applogger.L().Errorf("BatchUpdate add: %v", err)
		}
	}

	// Remove old participants
	for _, userID := range removeUserIDs {
		if err := s.repo.DeleteByConversationAndUserID(ctx, conversationID, userID); err != nil {
			applogger.L().Errorf("BatchUpdate remove user %d: %v", userID, err)
		}
	}

	return s.repo.FindByConversationID(ctx, conversationID)
}

// validateInboxAccess checks that a user has access to the conversation's inbox.
// Chatwoot: errors.add(:user, 'must have inbox access') if conversation.inbox.assignable_agents.exclude?(user)
func (s *ConversationParticipantService) validateInboxAccess(ctx context.Context, accountID, inboxID, userID uint) error {
	agents, err := s.assignableAgentSvc.FindAssignableAgents(ctx, accountID, []uint{inboxID})
	if err != nil {
		return fmt.Errorf("failed to verify inbox access: %w", err)
	}
	for _, agent := range agents {
		if agent.ID == userID {
			return nil
		}
	}
	return fmt.Errorf("user %d must have inbox access", userID)
}