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


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 });
	}
}

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;
			}
		}
	}
}


class Mapping_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);
	}

}



const vr = new Mapping_Resolver();
const tr = new Mapping_Resolver(new Map(), item => typeof item);

const cr = new Chained_Resolver([vr, tr]);


vr.rules.set('HELLO', () => 'WORLD');
tr.rules.set('string', () => 'World');

console.log(cr.resolve('HELLO'));
console.log(cr.resolve('hello'));
console.log(cr.resolve(123));