import {Canonical, CanonicalDefinition} from './Canonical.ts'
import Instantiable, {isInstantiable} from '../../../di/src/type/Instantiable.ts'

/**
 * Error thrown when the item returned from a canonical definition file is not the expected item.
 * @extends Error
 */
export class InvalidCanonicalExportError extends Error {
    constructor(name: string) {
        super(`Unable to import canonical item from "${name}". The default export of this file is invalid.`)
    }
}

/**
 * Base class for Canonical units which return instantiated versions of the classes
 * defined in those files. The files should export default clases which are Instantiable.
 * @extends Canonical
 */
export class InstantiableCanonical<T> extends Canonical<Instantiable<T>> {
    public async init_canonical_item(def: CanonicalDefinition): Promise<Instantiable<T>> {
        if ( isInstantiable(def.imported.default) ) {
            return this.make(def.imported.default)
        }

        throw new InvalidCanonicalExportError(def.original_name)
    }
}