//================================================================
/**
 * @packageDocumentation
 * @module std
 */
//================================================================
import { IComparable } from "./IComparable";
import { get_uid } from "./uid";

/**
 * Hash function.
 *
 * @param itemList The items to be hashed.
 * @return The hash code.
 */
export function hash(...itemList: any[]): number {
    let ret: number = INIT_VALUE;

    for (let item of itemList) {
        item = item ? item.valueOf() : item;
        const type: string = typeof item;

        if (type === "boolean")
            // BOOLEAN -> 1 BYTE
            ret = _Hash_boolean(item, ret);
        else if (type === "number" || type === "bigint")
            // NUMBER -> 8 BYTES
            ret = _Hash_number(item, ret);
        else if (type === "string")
            // STRING -> {LENGTH} BYTES
            ret = _Hash_string(item, ret);
        else if (
            item instanceof Object &&
            ((<any>item) as IComparable<{}>).hashCode instanceof Function
        ) {
            const hashed: number = ((<any>item) as IComparable<{}>).hashCode();
            if (itemList.length === 1) return hashed;
            else {
                ret = ret ^ hashed;
                ret *= MULTIPLIER;
            }
        } // object | null | undefined
        else ret = _Hash_number(get_uid(item), ret);
    }
    return Math.abs(ret);
}

function _Hash_boolean(val: boolean, ret: number): number {
    ret ^= val ? 1 : 0;
    ret *= MULTIPLIER;

    return ret;
}

function _Hash_number(val: number, ret: number): number {
    return _Hash_string(val.toString(), ret);
    // // ------------------------------------------
    // //    IN C++
    // //        CONSIDER A NUMBER AS A STRING
    // //        HASH<STRING>((CHAR*)&VAL, 8)
    // // ------------------------------------------
    // // CONSTRUCT BUFFER AND BYTE_ARRAY
    // const buffer: ArrayBuffer = new ArrayBuffer(8);
    // const byteArray: Int8Array = new Int8Array(buffer);
    // const valueArray: Float64Array = new Float64Array(buffer);
    // valueArray[0] = val;

    // for (let i: number = 0; i < byteArray.length; ++i)
    // {
    //     const byte = (byteArray[i] < 0) ? byteArray[i] + 256 : byteArray[i];

    //     ret ^= byte;
    //     ret *= _HASH_MULTIPLIER;
    // }
    // return Math.abs(ret);
}

function _Hash_string(str: string, ret: number): number {
    for (let i: number = 0; i < str.length; ++i) {
        ret ^= str.charCodeAt(i);
        ret *= MULTIPLIER;
    }
    return Math.abs(ret);
}

/* ---------------------------------------------------------
    RESERVED ITEMS
--------------------------------------------------------- */
const INIT_VALUE: number = 2166136261;
const MULTIPLIER: number = 16777619;