import {IConfig, DateYMD} from "./types"
import Crypto from "crypto-js";

type WordArray = Crypto.lib.WordArray;
export default class Signature {
    public static getSignature(config: IConfig, date: DateYMD, policyBase64: string): string {
        const getSignatureKey = (key: string, dateStamp: DateYMD, regionName: string): WordArray => {
            const kDate: WordArray = Crypto.HmacSHA256(dateStamp, "AWS4" + key);
            const kRegion: WordArray = Crypto.HmacSHA256(regionName, kDate);
            const kService: WordArray = Crypto.HmacSHA256("s3", kRegion);
            const kSigning: WordArray = Crypto.HmacSHA256("aws4_request", kService);
            return kSigning;
        };
        const signature = (policyEncoded: string): string => {
            return Crypto.HmacSHA256(
                policyEncoded,
                getSignatureKey(config.secretAccessKey, date, config.region)
            ).toString(Crypto.enc.Hex);
        };
        return signature(policyBase64);
    }
}