import { Item_Unresolvable } from '@efforting.tech/errors';

export class Abstract_Resolver {
	resolve(item) {
		const handler = this.resolve_handler(item);
		if (!handler) {
			throw new Item_Unresolvable({ resolver: this, item });
		}
		return handler({ resolver: this, item });
	}
}

export class Chained_Resolver extends Abstract_Resolver {
	constructor(chain_links) {
		super();
		Object.assign(this, { chain_links });
	}

	resolve_handler(item) {
		const { chain_links } = this;
		for (const link of chain_links) {
			const handler = link.resolve_handler(item);
			if (handler) {
				return handler;
			}
		}
	}
}


export class Mapping_Resolver extends Abstract_Resolver {
	constructor(rules=new Map(), key_function=null) {
		Object.assign(this, { rules, key_function });
	}

	resolve_handler(item) {
		const { key_function, rules } = this;
		const key = key_function ? key_function(item) : item;
		return rules.get(key);
	}

}