package service

import (
	"context"
	"errors"

	"gorm.io/gorm"

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

// DeliveryStatusService implements business logic for message delivery status operations.
// Reference: Chatwoot message delivery tracking per recipient (per-contact status tracking)
type DeliveryStatusService struct {
	messageRepo         *repository.MessageRepo
	deliveryStatusRepo  *repository.DeliveryStatusRepo
}

// NewDeliveryStatusService creates a new DeliveryStatus service.
func NewDeliveryStatusService(messageRepo *repository.MessageRepo, deliveryStatusRepo *repository.DeliveryStatusRepo) *DeliveryStatusService {
	return &DeliveryStatusService{messageRepo: messageRepo, deliveryStatusRepo: deliveryStatusRepo}
}

// ListByMessage retrieves all delivery statuses for a given message.
// Validates that the message belongs to the specified account and conversation.
func (s *DeliveryStatusService) ListByMessage(ctx context.Context, accountID uint, conversationID uint, messageID uint) ([]model.DeliveryStatus, error) {
	// Verify message exists and belongs to the account and conversation
	msg, err := s.messageRepo.FindByAccountAndID(ctx, accountID, messageID)
	if err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, errors.New("message not found")
		}
		applogger.L().Errorf("DeliveryStatusService.ListByMessage: failed to find message: %v", err)
		return nil, errors.New("message not found")
	}
	if msg.ConversationID != conversationID {
		return nil, errors.New("message does not belong to the specified conversation")
	}

	return s.deliveryStatusRepo.FindByMessage(ctx, messageID)
}

// CreateDeliveryStatusRequest is the DTO for creating a delivery status record.
type CreateDeliveryStatusRequest struct {
	MessageID  uint            `json:"message_id" validate:"required"`
	InboxID    uint            `json:"inbox_id" validate:"required"`
	ContactID  uint            `json:"contact_id" validate:"required"`
	Status     model.MessageStatus `json:"status" validate:"required,oneof=sent delivered read failed"`
}

// Create inserts a new delivery status record for a message.
func (s *DeliveryStatusService) Create(ctx context.Context, accountID uint, req CreateDeliveryStatusRequest) (*model.DeliveryStatus, error) {
	// Verify message exists and belongs to the account
	msg, err := s.messageRepo.FindByAccountAndID(ctx, accountID, req.MessageID)
	if err != nil {
		return nil, errors.New("message not found")
	}

	status := &model.DeliveryStatus{
		MessageID: msg.ID,
		InboxID:   req.InboxID,
		ContactID: req.ContactID,
		Status:    req.Status,
	}

	if err := s.deliveryStatusRepo.Create(ctx, status); err != nil {
		applogger.L().Errorf("DeliveryStatusService.Create: failed to create delivery status: %v", err)
		return nil, errors.New("failed to create delivery status")
	}

	return status, nil
}

// UpdateDeliveryStatusRequest is the DTO for updating a delivery status.
type UpdateDeliveryStatusRequest struct {
	Status     model.MessageStatus `json:"status" validate:"required,oneof=sent delivered read failed"`
	DeliveredAt *string            `json:"delivered_at,omitempty"`
	ReadAt      *string            `json:"read_at,omitempty"`
}

// Update modifies an existing delivery status record.
func (s *DeliveryStatusService) Update(ctx context.Context, accountID uint, id uint, req UpdateDeliveryStatusRequest) (*model.DeliveryStatus, error) {
	status, err := s.deliveryStatusRepo.FindByID(ctx, id)
	if err != nil {
		return nil, errors.New("delivery status not found")
	}

	// Verify the message belongs to the account
	_, err = s.messageRepo.FindByAccountAndID(ctx, accountID, status.MessageID)
	if err != nil {
		return nil, errors.New("delivery status not found")
	}

	status.Status = req.Status
	if err := s.deliveryStatusRepo.Update(ctx, status); err != nil {
		applogger.L().Errorf("DeliveryStatusService.Update: failed to update delivery status: %v", err)
		return nil, errors.New("failed to update delivery status")
	}

	return status, nil
}