Validation

-- A native ENUM rejects an invalid status at the type level, before a
-- CHECK constraint would even run. It also documents the legal set in
-- \d flats output for anyone poking around with psql.
CREATE TYPE flat_status AS ENUM ('vacant', 'occupied', 'under_maintenance', 'blocked');

ALTER TABLE flats
    ALTER COLUMN status DROP DEFAULT,
    ALTER COLUMN status TYPE flat_status USING status::flat_status,
    ALTER COLUMN status SET DEFAULT 'vacant';

ALTER TABLE flats
    ADD CONSTRAINT flats_area_sqft_positive CHECK (area_sqft > 0),
    ADD CONSTRAINT flats_floor_number_non_negative CHECK (floor_number >= 0);

ALTER TABLE flats
    DROP CONSTRAINT IF EXISTS flats_area_sqft_positive,
    DROP CONSTRAINT IF EXISTS flats_floor_number_non_negative;

ALTER TABLE flats
    ALTER COLUMN status DROP DEFAULT,
    ALTER COLUMN status TYPE TEXT,
    ALTER COLUMN status SET DEFAULT 'vacant';

DROP TYPE IF EXISTS flat_status;

package validate

import "fmt"

type FieldError struct {
	Field   string
	Message string
}

func (e FieldError) Error() string {
	return fmt.Sprintf("%s: %s", e.Field, e.Message)
}

// Flat mirrors the database constraints from migration 0004 exactly. If
// a rule changes here, it must change there too — that duplication is
// the point of this lesson, not an oversight.
func Flat(unitNumber string, floorNumber int, areaSqft float64) []FieldError {
	var errs []FieldError
	if unitNumber == "" {
		errs = append(errs, FieldError{"unit_number", "must not be empty"})
	}
	if floorNumber < 0 {
		errs = append(errs, FieldError{"floor_number", "must be zero or greater"})
	}
	if areaSqft <= 0 {
		errs = append(errs, FieldError{"area_sqft", "must be greater than zero"})
	}
	return errs
}

func (r *FlatRepository) Create(ctx context.Context, f domain.Flat) (domain.Flat, error) {
	const q = `
		INSERT INTO flats (tenant_id, building_id, unit_number, floor_number, area_sqft, status)
		VALUES ($1, $2, $3, $4, $5, $6)
		RETURNING id, created_at, updated_at`

	row := r.pool.QueryRow(ctx, q, f.TenantID, f.BuildingID, f.UnitNumber, f.FloorNumber, f.AreaSqft, f.Status)
	if err := row.Scan(&f.ID, &f.CreatedAt, &f.UpdatedAt); err != nil {
		var pgErr *pgconn.PgError
		if errors.As(err, &pgErr) {
			switch pgErr.Code {
			case "23505": // unique_violation
				return domain.Flat{}, domain.ErrDuplicateUnitNumber
			case "23514": // check_violation
				return domain.Flat{}, domain.ErrInvalidFlat
			case "23503": // foreign_key_violation
				return domain.Flat{}, domain.ErrBuildingNotFound
			}
		}
		return domain.Flat{}, err
	}
	return f, nil
}