package service

import (
	"context"
	"encoding/json"
	"fmt"

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

// CategoryService implements business logic for Category CRUD.
type CategoryService struct {
	repo          *repository.CategoryRepo
	relatedRepo   *repository.RelatedCategoryRepo
}

func NewCategoryService(repo *repository.CategoryRepo, relatedRepo *repository.RelatedCategoryRepo) *CategoryService {
	return &CategoryService{repo: repo, relatedRepo: relatedRepo}
}

// CreateCategoryRequest is the DTO for creating a category.
type CreateCategoryRequest struct {
	Name                string          `json:"name" validate:"required,min=2"`
	Slug                string          `json:"slug" validate:"required"`
	Description         string          `json:"description"`
	Icon                string          `json:"icon"`
	Position            int             `json:"position"`
	Locale              string          `json:"locale"`
	ParentID            *uint           `json:"parent_id"`
	AssociatedCategoryID *uint          `json:"associated_category_id"`
	RelatedCategoryIDs  []uint          `json:"related_category_ids"`
	CustomAttributes    json.RawMessage `json:"custom_attributes"`
}

// UpdateCategoryRequest is the DTO for updating a category.
type UpdateCategoryRequest struct {
	Name                string          `json:"name"`
	Description         string          `json:"description"`
	Icon                string          `json:"icon"`
	Position            *int            `json:"position"`
	Locale              string          `json:"locale"`
	ParentID            *uint           `json:"parent_id"`
	AssociatedCategoryID *uint          `json:"associated_category_id"`
	RelatedCategoryIDs  []uint          `json:"related_category_ids"`
	CustomAttributes    json.RawMessage `json:"custom_attributes"`
}

func (s *CategoryService) Create(ctx context.Context, portalID uint, accountID uint, req *CreateCategoryRequest) (*model.Category, error) {
	category := &model.Category{
		AccountID:           accountID,
		PortalID:            portalID,
		Name:                req.Name,
		Slug:                req.Slug,
		Description:         req.Description,
		Icon:                req.Icon,
		Position:            req.Position,
		Locale:              req.Locale,
		ParentID:            req.ParentID,
		AssociatedCategoryID: req.AssociatedCategoryID,
		CustomAttributes:    req.CustomAttributes,
	}

	if err := s.repo.Create(ctx, category); err != nil {
		return nil, fmt.Errorf("create category: %w", err)
	}

	// Handle related categories
	if len(req.RelatedCategoryIDs) > 0 {
		if err := s.relatedRepo.ReplaceAll(ctx, category.ID, req.RelatedCategoryIDs); err != nil {
			applogger.L().Warnf("Failed to set related categories for category %d: %v", category.ID, err)
		}
	}

	return category, nil
}

func (s *CategoryService) GetByID(ctx context.Context, id uint) (*model.Category, error) {
	category, err := s.repo.GetByID(ctx, id)
	if err != nil {
		return nil, fmt.Errorf("get category: %w", err)
	}
	return category, nil
}

func (s *CategoryService) Update(ctx context.Context, id uint, req *UpdateCategoryRequest) (*model.Category, error) {
	category, err := s.repo.GetByID(ctx, id)
	if err != nil {
		return nil, fmt.Errorf("find category: %w", err)
	}

	if req.Name != "" {
		category.Name = req.Name
	}
	if req.Description != "" {
		category.Description = req.Description
	}
	if req.Icon != "" {
		category.Icon = req.Icon
	}
	if req.Position != nil {
		category.Position = *req.Position
	}
	if req.Locale != "" {
		category.Locale = req.Locale
	}
	if req.ParentID != nil {
		category.ParentID = req.ParentID
	}
	if req.AssociatedCategoryID != nil {
		category.AssociatedCategoryID = req.AssociatedCategoryID
	}
	if req.CustomAttributes != nil {
		category.CustomAttributes = req.CustomAttributes
	}

	if err := s.repo.Update(ctx, category); err != nil {
		return nil, fmt.Errorf("update category: %w", err)
	}

	// Handle related categories — replace all if provided
	if req.RelatedCategoryIDs != nil {
		if err := s.relatedRepo.ReplaceAll(ctx, category.ID, req.RelatedCategoryIDs); err != nil {
			applogger.L().Warnf("Failed to update related categories for category %d: %v", category.ID, err)
		}
	}

	return category, nil
}

func (s *CategoryService) Delete(ctx context.Context, id uint) error {
	// Check existence first — GORM Delete() returns nil even for non-existent IDs
	if _, err := s.repo.GetByID(ctx, id); err != nil {
		return fmt.Errorf("find category for delete: %w", err)
	}

	// Clean up related categories first
	if err := s.relatedRepo.DeleteByCategoryID(ctx, id); err != nil {
		applogger.L().Warnf("Failed to delete related categories for category %d: %v", id, err)
	}

	if err := s.repo.Delete(ctx, id); err != nil {
		return fmt.Errorf("delete category: %w", err)
	}
	return nil
}

// ListByPortalID returns categories for a portal with pagination.
func (s *CategoryService) ListByPortalID(ctx context.Context, portalID uint, locale string, page, perPage int) ([]model.Category, int64, error) {
	offset := (page - 1) * perPage
	if locale != "" {
		return s.repo.FindByPortalIDAndLocale(ctx, portalID, locale, offset, perPage)
	}
	return s.repo.FindByPortalID(ctx, portalID, offset, perPage)
}

// Reorder batch-updates category positions.
func (s *CategoryService) Reorder(ctx context.Context, positions map[uint]int) error {
	if err := s.repo.UpdatePositions(ctx, positions); err != nil {
		return fmt.Errorf("reorder categories: %w", err)
	}
	return nil
}