//================================================================
/**
 * @packageDocumentation
 * @module std
 */
//================================================================
import { Singleton } from "./Singleton";
import { HashMap } from "../container/HashMap";
import { hash } from "../functional/hash";
import { equal } from "../ranges/algorithm/iterations";

/**
 * Variadic singleton generator.
 *
 * @author Jeongho Nam - https://github.comm/samchon
 */
export class VariadicSingleton<T, Args extends any[]> {
    private readonly closure_: (...args: Args) => T;
    private readonly dict_: HashMap<Args, Singleton<T, Args>>;

    public constructor(
        closure: (...args: Args) => T,
        hashFunc: (args: Args) => number = (args) => hash(...args),
        pred: (x: Args, y: Args) => boolean = equal,
    ) {
        this.closure_ = closure;
        this.dict_ = new HashMap(hashFunc, pred);
    }

    public get(...args: Args): T {
        let it: HashMap.Iterator<Args, Singleton<T, Args>> = this.dict_.find(
            args,
        );
        if (it.equals(this.dict_.end()) == true)
            it = this.dict_.emplace(args, new Singleton(this.closure_)).first;
        return it.second.get(...args);
    }
}