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

/**
 * Variadic mutable singleton generator.
 *
 * @author Jeongho Nam - https://github.com/samchon
 */
export class VariadicMutableSingleton<T, Args extends any[]> {
    /**
     * @hidden
     */
    private readonly closure_: (...args: Args) => Promise<T>;

    /**
     * @hidden
     */
    private readonly dict_: HashMap<Args, MutableSingleton<T, Args>>;

    /* ---------------------------------------------------------------
        CONSTRUCTORS
    --------------------------------------------------------------- */
    public constructor(
        closure: (...args: Args) => Promise<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 set(...items: [...Args, T]): Promise<void> {
        const args: Args = items.slice(0, items.length - 1) as Args;
        const value: T = items[items.length - 1];

        return this._Get_singleton(args).set(value);
    }

    public reload(...args: Args): Promise<T> {
        return this._Get_singleton(args).reload(...args);
    }

    public clear(): Promise<void>;
    public clear(...args: Args): Promise<void>;
    public async clear(...args: Args): Promise<void> {
        if (args.length === 0) this.dict_.clear();
        else await this._Get_singleton(args).clear();
    }

    /* ---------------------------------------------------------------
        ACCESSORS
    --------------------------------------------------------------- */
    public get(...args: Args): Promise<T> {
        return this._Get_singleton(args).get(...args);
    }

    public is_loaded(...args: Args): Promise<boolean> {
        return this._Get_singleton(args).is_loaded();
    }

    /**
     * @hidden
     */
    private _Get_singleton(args: Args): MutableSingleton<T, Args> {
        let it: HashMap.Iterator<
            Args,
            MutableSingleton<T, Args>
        > = this.dict_.find(args);
        if (it.equals(this.dict_.end()) === true)
            it = this.dict_.emplace(
                args,
                new MutableSingleton(this.closure_),
            ).first;
        return it.second;
    }
}