package repository

import (
	"errors"
	"fmt"

	"accounting-app/internal/models"

	"gorm.io/gorm"
)

// Category repository errors
var (
	ErrCategoryNotFound    = errors.New("category not found")
	ErrCategoryInUse       = errors.New("category is in use and cannot be deleted")
	ErrCategoryHasChildren = errors.New("category has children and cannot be deleted")
)

// CategoryRepository handles database operations for categories
type CategoryRepository struct {
	db *gorm.DB
}

// NewCategoryRepository creates a new CategoryRepository instance
func NewCategoryRepository(db *gorm.DB) *CategoryRepository {
	return &CategoryRepository{db: db}
}

// Create creates a new category in the database
func (r *CategoryRepository) Create(category *models.Category) error {
	if err := r.db.Create(category).Error; err != nil {
		return fmt.Errorf("failed to create category: %w", err)
	}
	return nil
}

// GetByID retrieves a category by its ID
func (r *CategoryRepository) GetByID(userID uint, id uint) (*models.Category, error) {
	var category models.Category
	if err := r.db.Where("user_id = ?", userID).First(&category, id).Error; err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, ErrCategoryNotFound
		}
		return nil, fmt.Errorf("failed to get category: %w", err)
	}
	return &category, nil
}

// GetAll retrieves all categories for a user
func (r *CategoryRepository) GetAll(userID uint) ([]models.Category, error) {
	var categories []models.Category
	if err := r.db.Where("user_id = ?", userID).Order("sort_order ASC, created_at ASC").Find(&categories).Error; err != nil {
		return nil, fmt.Errorf("failed to get categories: %w", err)
	}
	return categories, nil
}

// GetByType retrieves all categories of a specific type (income or expense) for a user
func (r *CategoryRepository) GetByType(userID uint, categoryType models.CategoryType) ([]models.Category, error) {
	var categories []models.Category
	if err := r.db.Where("user_id = ? AND type = ?", userID, categoryType).Order("sort_order ASC, created_at ASC").Find(&categories).Error; err != nil {
		return nil, fmt.Errorf("failed to get categories by type: %w", err)
	}
	return categories, nil
}

// GetRootCategories retrieves all categories without a parent (top-level categories) for a user
func (r *CategoryRepository) GetRootCategories(userID uint) ([]models.Category, error) {
	var categories []models.Category
	if err := r.db.Where("user_id = ? AND parent_id IS NULL", userID).Order("sort_order ASC, created_at ASC").Find(&categories).Error; err != nil {
		return nil, fmt.Errorf("failed to get root categories: %w", err)
	}
	return categories, nil
}

// GetChildren retrieves all child categories of a given parent category
func (r *CategoryRepository) GetChildren(userID uint, parentID uint) ([]models.Category, error) {
	var categories []models.Category
	if err := r.db.Where("user_id = ? AND parent_id = ?", userID, parentID).Order("sort_order ASC, created_at ASC").Find(&categories).Error; err != nil {
		return nil, fmt.Errorf("failed to get child categories: %w", err)
	}
	return categories, nil
}

// GetWithChildren retrieves a category with its children preloaded
func (r *CategoryRepository) GetWithChildren(userID uint, id uint) (*models.Category, error) {
	var category models.Category
	if err := r.db.Preload("Children", func(db *gorm.DB) *gorm.DB {
		return db.Order("sort_order ASC, created_at ASC")
	}).Where("user_id = ?", userID).First(&category, id).Error; err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, ErrCategoryNotFound
		}
		return nil, fmt.Errorf("failed to get category with children: %w", err)
	}
	return &category, nil
}

// GetWithParent retrieves a category with its parent preloaded
func (r *CategoryRepository) GetWithParent(userID uint, id uint) (*models.Category, error) {
	var category models.Category
	if err := r.db.Preload("Parent").Where("user_id = ?", userID).First(&category, id).Error; err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, ErrCategoryNotFound
		}
		return nil, fmt.Errorf("failed to get category with parent: %w", err)
	}
	return &category, nil
}

// Update updates an existing category in the database
func (r *CategoryRepository) Update(category *models.Category) error {
	// First check if the category exists
	var existing models.Category
	if err := r.db.Where("user_id = ?", category.UserID).First(&existing, category.ID).Error; err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return ErrCategoryNotFound
		}
		return fmt.Errorf("failed to check category existence: %w", err)
	}

	// Update the category
	if err := r.db.Save(category).Error; err != nil {
		return fmt.Errorf("failed to update category: %w", err)
	}
	return nil
}

// Delete deletes a category by its ID
func (r *CategoryRepository) Delete(userID uint, id uint) error {
	// First check if the category exists
	var category models.Category
	if err := r.db.Where("user_id = ?", userID).First(&category, id).Error; err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return ErrCategoryNotFound
		}
		return fmt.Errorf("failed to check category existence: %w", err)
	}

	// Check if there are any child categories
	var childCount int64
	if err := r.db.Model(&models.Category{}).Where("parent_id = ?", id).Count(&childCount).Error; err != nil {
		return fmt.Errorf("failed to check child categories: %w", err)
	}
	if childCount > 0 {
		return ErrCategoryHasChildren
	}

	// Check if there are any transactions associated with this category
	var transactionCount int64
	if err := r.db.Model(&models.Transaction{}).Where("category_id = ?", id).Count(&transactionCount).Error; err != nil {
		return fmt.Errorf("failed to check category transactions: %w", err)
	}
	if transactionCount > 0 {
		return ErrCategoryInUse
	}

	// Check if there are any budgets associated with this category
	var budgetCount int64
	if err := r.db.Model(&models.Budget{}).Where("category_id = ?", id).Count(&budgetCount).Error; err != nil {
		return fmt.Errorf("failed to check category budgets: %w", err)
	}
	if budgetCount > 0 {
		return ErrCategoryInUse
	}

	// Check if there are any recurring transactions associated with this category
	var recurringCount int64
	if err := r.db.Model(&models.RecurringTransaction{}).Where("category_id = ?", id).Count(&recurringCount).Error; err != nil {
		return fmt.Errorf("failed to check category recurring transactions: %w", err)
	}
	if recurringCount > 0 {
		return ErrCategoryInUse
	}

	// Delete the category (hard delete since Category doesn't have DeletedAt)
	if err := r.db.Delete(&category).Error; err != nil {
		return fmt.Errorf("failed to delete category: %w", err)
	}
	return nil
}

// ExistsByID checks if a category with the given ID exists
func (r *CategoryRepository) ExistsByID(userID uint, id uint) (bool, error) {
	var count int64
	if err := r.db.Model(&models.Category{}).Where("user_id = ? AND id = ?", userID, id).Count(&count).Error; err != nil {
		return false, fmt.Errorf("failed to check category existence: %w", err)
	}
	return count > 0, nil
}

// ExistsByName checks if a category with the given name exists for a user
func (r *CategoryRepository) ExistsByName(userID uint, name string) (bool, error) {
	var count int64
	if err := r.db.Model(&models.Category{}).Where("user_id = ? AND name = ?", userID, name).Count(&count).Error; err != nil {
		return false, fmt.Errorf("failed to check category name existence: %w", err)
	}
	return count > 0, nil
}

// ExistsByNameAndType checks if a category with the given name and type exists for a user
func (r *CategoryRepository) ExistsByNameAndType(userID uint, name string, categoryType models.CategoryType) (bool, error) {
	var count int64
	if err := r.db.Model(&models.Category{}).Where("user_id = ? AND name = ? AND type = ?", userID, name, categoryType).Count(&count).Error; err != nil {
		return false, fmt.Errorf("failed to check category name and type existence: %w", err)
	}
	return count > 0, nil
}

// ExistsByNameExcludingID checks if a category with the given name exists, excluding a specific ID, for a user
func (r *CategoryRepository) ExistsByNameExcludingID(userID uint, name string, excludeID uint) (bool, error) {
	var count int64
	if err := r.db.Model(&models.Category{}).Where("user_id = ? AND name = ? AND id != ?", userID, name, excludeID).Count(&count).Error; err != nil {
		return false, fmt.Errorf("failed to check category name existence: %w", err)
	}
	return count > 0, nil
}

// GetRootCategoriesByType retrieves all root categories of a specific type for a user
func (r *CategoryRepository) GetRootCategoriesByType(userID uint, categoryType models.CategoryType) ([]models.Category, error) {
	var categories []models.Category
	if err := r.db.Where("user_id = ? AND parent_id IS NULL AND type = ?", userID, categoryType).Order("sort_order ASC, created_at ASC").Find(&categories).Error; err != nil {
		return nil, fmt.Errorf("failed to get root categories by type: %w", err)
	}
	return categories, nil
}

// GetAllWithChildren retrieves all categories with their children preloaded for a user
func (r *CategoryRepository) GetAllWithChildren(userID uint) ([]models.Category, error) {
	var categories []models.Category
	if err := r.db.Preload("Children", func(db *gorm.DB) *gorm.DB {
		return db.Order("sort_order ASC, created_at ASC")
	}).Where("user_id = ? AND parent_id IS NULL", userID).Order("sort_order ASC, created_at ASC").Find(&categories).Error; err != nil {
		return nil, fmt.Errorf("failed to get categories with children: %w", err)
	}
	return categories, nil
}

// CountByType returns the count of categories by type for a user
func (r *CategoryRepository) CountByType(userID uint, categoryType models.CategoryType) (int64, error) {
	var count int64
	if err := r.db.Model(&models.Category{}).Where("user_id = ? AND type = ?", userID, categoryType).Count(&count).Error; err != nil {
		return 0, fmt.Errorf("failed to count categories by type: %w", err)
	}
	return count, nil
}

// GetByName retrieves a category by its name for a user
func (r *CategoryRepository) GetByName(userID uint, name string) (*models.Category, error) {
	var category models.Category
	if err := r.db.Where("user_id = ? AND name = ?", userID, name).First(&category).Error; err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, ErrCategoryNotFound
		}
		return nil, fmt.Errorf("failed to get category by name: %w", err)
	}
	return &category, nil
}