package units

import (
	"context"
	"errors"

	"github.com/google/uuid"
	"github.com/jackc/pgx/v5/pgconn"
	"gorm.io/gorm"
)

var (
	ErrNotFound    = errors.New("unit not found")
	ErrSymbolTaken = errors.New("symbol already in use")
	ErrInUse       = errors.New("unit is referenced by existing price tiers")
)

type Repository interface {
	Create(ctx context.Context, u *Unit) error
	FindByID(ctx context.Context, id uuid.UUID) (*Unit, error)
	List(ctx context.Context) ([]*Unit, error)
	Update(ctx context.Context, u *Unit) error
	Delete(ctx context.Context, id uuid.UUID) error
}

type gormRepository struct {
	db *gorm.DB
}

func NewRepository(db *gorm.DB) Repository {
	return &gormRepository{db: db}
}

func (r *gormRepository) Create(ctx context.Context, u *Unit) error {
	if err := r.db.WithContext(ctx).Create(u).Error; err != nil {
		if isUniqueViolation(err) {
			return ErrSymbolTaken
		}
		return err
	}
	return nil
}

func (r *gormRepository) FindByID(ctx context.Context, id uuid.UUID) (*Unit, error) {
	var u Unit
	err := r.db.WithContext(ctx).Where("id = ?", id).First(&u).Error
	if errors.Is(err, gorm.ErrRecordNotFound) {
		return nil, ErrNotFound
	}
	if err != nil {
		return nil, err
	}
	return &u, nil
}

func (r *gormRepository) List(ctx context.Context) ([]*Unit, error) {
	var list []*Unit
	if err := r.db.WithContext(ctx).Order("name asc").Find(&list).Error; err != nil {
		return nil, err
	}
	return list, nil
}

func (r *gormRepository) Update(ctx context.Context, u *Unit) error {
	err := r.db.WithContext(ctx).Save(u).Error
	if isUniqueViolation(err) {
		return ErrSymbolTaken
	}
	return err
}

func (r *gormRepository) Delete(ctx context.Context, id uuid.UUID) error {
	res := r.db.WithContext(ctx).Delete(&Unit{}, "id = ?", id)
	if res.Error != nil {
		if isForeignKeyViolation(res.Error) {
			return ErrInUse
		}
		return res.Error
	}
	if res.RowsAffected == 0 {
		return ErrNotFound
	}
	return nil
}

func isUniqueViolation(err error) bool {
	var pgErr *pgconn.PgError
	return errors.As(err, &pgErr) && pgErr.Code == "23505"
}

func isForeignKeyViolation(err error) bool {
	var pgErr *pgconn.PgError
	return errors.As(err, &pgErr) && pgErr.Code == "23503"
}