//================================================================
/**
 * @packageDocumentation
 * @module std
 */
//================================================================
import { IPair } from "./IPair";
import { IComparable } from "../functional/IComparable";

import { hash } from "../functional/hash";
import { less, equal_to } from "../functional/comparators";

/**
 * Pair of two elements.
 *
 * @author Jeongho Nam - https://github.com/samchon
 */
export class Pair<First, Second>
    implements IPair<First, Second>, IComparable<Pair<First, Second>>
{
    /**
     * @inheritDoc
     */
    public first: First;

    /**
     * @inheritDoc
     */
    public second: Second;

    /* ---------------------------------------------------------
        CONSTRUCTORS
    --------------------------------------------------------- */
    /**
     * Initializer Constructor.
     *
     * @param first The first element.
     * @param second The second element.
     */
    public constructor(first: First, second: Second) {
        this.first = first;
        this.second = second;
    }

    /* ---------------------------------------------------------
        COMPARISON
    --------------------------------------------------------- */
    /**
     * @inheritDoc
     */
    public equals<U1 extends First, U2 extends Second>(
        pair: Pair<U1, U2>,
    ): boolean {
        return (
            equal_to(this.first, pair.first) &&
            equal_to(this.second, pair.second)
        );
    }

    /**
     * @inheritDoc
     */
    public less<U1 extends First, U2 extends Second>(
        pair: Pair<U1, U2>,
    ): boolean {
        if (equal_to(this.first, pair.first) === false)
            return less(this.first, pair.first);
        else return less(this.second, pair.second);
    }

    /**
     * @inheritDoc
     */
    public hashCode(): number {
        return hash(this.first, this.second);
    }
}

/**
 * Create a {@link Pair}.
 *
 * @param first The 1st element.
 * @param second The 2nd element.
 *
 * @return A {@link Pair} object.
 */
export function make_pair<First, Second>(
    first: First,
    second: Second,
): Pair<First, Second> {
    return new Pair<First, Second>(first, second);
}