package repository

import (
	"errors"
	"fmt"

	"accounting-app/internal/models"

	"gorm.io/gorm"
)

// Common ledger repository errors
var (
	ErrLedgerNotFound = errors.New("ledger not found")
	ErrLedgerInUse    = errors.New("ledger is in use and cannot be deleted")
)

// LedgerRepository handles database operations for ledgers
type LedgerRepository struct {
	db *gorm.DB
}

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

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

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

// GetAll retrieves all ledgers from the database (excluding soft-deleted)
func (r *LedgerRepository) GetAll(userID uint) ([]models.Ledger, error) {
	var ledgers []models.Ledger
	if err := r.db.Where("user_id = ?", userID).Order("sort_order ASC, created_at DESC").Find(&ledgers).Error; err != nil {
		return nil, fmt.Errorf("failed to get ledgers: %w", err)
	}
	return ledgers, nil
}

// Update updates an existing ledger in the database
func (r *LedgerRepository) Update(userID uint, ledger *models.Ledger) error {
	// First check if the ledger exists and belongs to the user
	var existing models.Ledger
	if err := r.db.Where("id = ? AND user_id = ?", ledger.ID, userID).First(&existing).Error; err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return ErrLedgerNotFound
		}
		return fmt.Errorf("failed to check ledger existence: %w", err)
	}

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

// Delete soft-deletes a ledger by its ID
func (r *LedgerRepository) Delete(userID uint, id uint) error {
	// First check if the ledger exists and belongs to the user
	var ledger models.Ledger
	if err := r.db.Where("id = ? AND user_id = ?", id, userID).First(&ledger).Error; err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return ErrLedgerNotFound
		}
		return fmt.Errorf("failed to check ledger existence: %w", err)
	}

	// Soft delete the ledger
	if err := r.db.Delete(&ledger).Error; err != nil {
		return fmt.Errorf("failed to delete ledger: %w", err)
	}
	return nil
}

// Count returns the total number of ledgers (excluding soft-deleted)
func (r *LedgerRepository) Count(userID uint) (int64, error) {
	var count int64
	if err := r.db.Model(&models.Ledger{}).Where("user_id = ?", userID).Count(&count).Error; err != nil {
		return 0, fmt.Errorf("failed to count ledgers: %w", err)
	}
	return count, nil
}

// GetDefault retrieves the default ledger
func (r *LedgerRepository) GetDefault(userID uint) (*models.Ledger, error) {
	var ledger models.Ledger
	if err := r.db.Where("user_id = ? AND is_default = ?", userID, true).First(&ledger).Error; err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, ErrLedgerNotFound
		}
		return nil, fmt.Errorf("failed to get default ledger: %w", err)
	}
	return &ledger, nil
}

// SetDefault sets a ledger as the default ledger
func (r *LedgerRepository) SetDefault(userID uint, id uint) error {
	// Start a transaction
	return r.db.Transaction(func(tx *gorm.DB) error {
		// First, unset all other default ledgers for this user
		if err := tx.Model(&models.Ledger{}).Where("user_id = ? AND is_default = ?", userID, true).Update("is_default", false).Error; err != nil {
			return fmt.Errorf("failed to unset default ledgers: %w", err)
		}

		// Then set the specified ledger as default (must belong to the user)
		result := tx.Model(&models.Ledger{}).Where("id = ? AND user_id = ?", id, userID).Update("is_default", true)
		if result.Error != nil {
			return fmt.Errorf("failed to set default ledger: %w", result.Error)
		}
		if result.RowsAffected == 0 {
			return ErrLedgerNotFound
		}

		return nil
	})
}

// GetDeleted retrieves all soft-deleted ledgers
// Feature: accounting-feature-upgrade
// Validates: Requirements 3.9
// GetDeleted retrieves all soft-deleted ledgers
func (r *LedgerRepository) GetDeleted(userID uint) ([]models.Ledger, error) {
	var ledgers []models.Ledger
	if err := r.db.Unscoped().Where("user_id = ? AND deleted_at IS NOT NULL", userID).Order("deleted_at DESC").Find(&ledgers).Error; err != nil {
		return nil, fmt.Errorf("failed to get deleted ledgers: %w", err)
	}
	return ledgers, nil
}

// Restore restores a soft-deleted ledger by its ID
// Feature: accounting-feature-upgrade
// Validates: Requirements 3.9
// Restore restores a soft-deleted ledger by its ID
func (r *LedgerRepository) Restore(userID uint, id uint) error {
	// First check if the ledger exists and is deleted and belongs to the user
	var ledger models.Ledger
	if err := r.db.Unscoped().Where("id = ? AND user_id = ?", id, userID).First(&ledger).Error; err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return ErrLedgerNotFound
		}
		return fmt.Errorf("failed to check ledger existence: %w", err)
	}

	// Check if the ledger is actually deleted
	if ledger.DeletedAt.Time.IsZero() {
		return fmt.Errorf("ledger is not deleted")
	}

	// Restore the ledger by setting deleted_at to NULL
	if err := r.db.Unscoped().Model(&ledger).Update("deleted_at", nil).Error; err != nil {
		return fmt.Errorf("failed to restore ledger: %w", err)
	}
	return nil
}