import { ensure0x, strip0x } from './common';
import { keccak256 } from '@ethersproject/keccak256';
import { hexlify, hexZeroPad } from '@ethersproject/bytes';
import {
  BigInteger,
  blind as _blind,
  Point,
  pointFromHex as _pointFromHex,
  signatureFromHex as _signatureFromHex,
  signatureToHex as _signatureToHex,
  unblind as _unblind,
  UnblindedSignature,
  UserSecretData,
  verify as _verify,
} from 'blindsecp256k1';
import { VoteCore } from '../core/vote';

export function getBlindedPayload(electionId: string, hexTokenR: string, address: string) {
  const tokenR = CensusBlind.decodePoint(hexTokenR);
  const caBundle = VoteCore.cspCaBundle(electionId, address);

  // hash(bundle)
  const hexCaBundle = hexlify(VoteCore.encodeCspCaBundle(caBundle));
  const hexCaHashedBundle = strip0x(keccak256(hexCaBundle));

  const { hexBlinded, userSecretData } = CensusBlind.blind(hexCaHashedBundle, tokenR);
  return { hexBlinded, userSecretData };
}

export namespace CensusBlind {
  /** Decodes the given hex-encoded point */
  export function decodePoint(hexPoint: string): Point {
    return _pointFromHex(hexPoint);
  }

  /** Blinds the given hex string using the given R point and returns the secret data to unblind an eventual blinded signature */
  export function blind(hexMessage: string, signerR: Point): { hexBlinded: string; userSecretData: UserSecretData } {
    const msg = BigInteger.fromHex(hexMessage);
    const { mBlinded, userSecretData } = _blind(msg, signerR);

    return { hexBlinded: hexZeroPad(ensure0x(mBlinded.toString(16)), 32).slice(2), userSecretData };
  }

  /** Unblinds the given blinded signature and returns it as a hex string */
  export function unblind(hexBlindedSignature: string, userSecretData: UserSecretData): string {
    const sBlind = BigInteger.fromHex(hexBlindedSignature);
    const unblindedSignature = _unblind(sBlind, userSecretData);

    return _signatureToHex(unblindedSignature);
  }

  /** Verifies that the given blind signature is valid */
  export function verify(hexMsg: string, hexUnblindedSignature: string, pk: Point) {
    const msg = BigInteger.fromHex(hexMsg);

    const unblindedSignature = signatureFromHex(hexUnblindedSignature);

    return _verify(msg, unblindedSignature, pk);
  }

  /** Deserializes the given hex Signature */
  export function signatureFromHex(hexSignature: string) {
    return _signatureFromHex(hexSignature);
  }

  /** Serializes the given signature into a hex string */
  export function signatureToHex(signature: UnblindedSignature) {
    return _signatureToHex(signature);
  }
}