import crypto from 'crypto'

let SHA256_cache = {}

function _SHA256(str) {
    return crypto.createHash('sha256').update(str).digest('base64')
}

/**
 * hashes with the secure hashing algorithm 256
 * @param       {string} str   string to hash
 * @param       {any} salt  salt to apply to string
 * @param       {number} num   amount of times to hash, defaults to 1
 * @returns     {string}    base64 digested hash
 */
function SHA256(str, salt, num) {
    if (!num && num !== 0) num = 1
    if (!str) return
    let identifier = _SHA256(str + salt + num.toString())
    if (SHA256_cache[identifier] != undefined) {
        return SHA256_cache[identifier]
    }
    let ret = str
    for (let i = 0; i < num; i++) {
        ret = _SHA256(ret + salt)
    }
    SHA256_cache[identifier] = ret
    setTimeout(() => {
        SHA256_cache[identifier] = undefined
    }, 10000) //cache for 10s
    return ret
}
export { SHA256 }
export default {
    SHA256: SHA256,
}