/*! micro-eth-signer - MIT License (c) 2021 Paul Miller (paulmillr.com) */
import { secp256k1 } from '@noble/curves/secp256k1';
import { keccak_256 } from '@noble/hashes/sha3';
import { bytesToHex } from '@noble/hashes/utils';
import { add0x, astr, ethHex, strip0x } from './utils.ts';

export const addr = {
  RE: /^(0[xX])?([0-9a-fA-F]{40})?$/ satisfies RegExp as RegExp,
  parse: (
    address: string,
    allowEmpty = false
  ): {
    hasPrefix: boolean;
    data: string;
  } => {
    astr(address);
    // NOTE: empty address allowed for 'to', but would be mistake for other address fields.
    // '0x' instead of null/undefined because we don't want to send contract creation tx if user
    // accidentally missed 'to' field.
    if (allowEmpty && address === '0x') return { hasPrefix: true, data: '' };
    const res = address.match(addr.RE) || [];
    const hasPrefix = res[1] != null;
    const data = res[2];
    if (!data) {
      const len = hasPrefix ? 42 : 40;
      throw new Error(`address must be ${len}-char hex, got ${address.length}-char ${address}`);
    }
    return { hasPrefix, data };
  },

  /**
   * Address checksum is calculated by hashing with keccak_256.
   * It hashes *string*, not a bytearray: keccak('beef') not keccak([0xbe, 0xef])
   * @param nonChecksummedAddress
   * @param allowEmpty - allows '0x'
   * @returns checksummed address
   */
  addChecksum: (nonChecksummedAddress: string, allowEmpty = false): string => {
    const low = addr.parse(nonChecksummedAddress, allowEmpty).data.toLowerCase();
    const hash = bytesToHex(keccak_256(low));
    let checksummed = '';
    for (let i = 0; i < low.length; i++) {
      const hi = Number.parseInt(hash[i], 16);
      const li = low[i];
      checksummed += hi <= 7 ? li : li.toUpperCase(); // if char is 9-f, upcase it
    }
    return add0x(checksummed);
  },

  /**
   * Creates address from secp256k1 public key.
   */
  fromPublicKey: (key: string | Uint8Array): string => {
    if (!key) throw new Error('invalid public key: ' + key);
    const pub65b = secp256k1.ProjectivePoint.fromHex(key).toRawBytes(false);
    const hashed = keccak_256(pub65b.subarray(1, 65));
    const address = bytesToHex(hashed).slice(24); // slice 24..64
    return addr.addChecksum(address);
  },

  /**
   * Creates address from ETH private key in hex or ui8a format.
   */
  fromPrivateKey: (key: string | Uint8Array): string => {
    if (typeof key === 'string') key = strip0x(key);
    return addr.fromPublicKey(secp256k1.getPublicKey(key, false));
  },

  /**
   * Generates hex string with new random private key and address. Uses CSPRNG internally.
   */
  random(): { privateKey: string; address: string } {
    const privateKey = ethHex.encode(secp256k1.utils.randomPrivateKey());
    return { privateKey, address: addr.fromPrivateKey(privateKey) };
  },

  /**
   * Verifies checksum if the address is checksummed.
   * Always returns true when the address is not checksummed.
   * @param allowEmpty - allows '0x'
   */
  isValid: (checksummedAddress: string, allowEmpty = false): boolean => {
    let parsed: { hasPrefix: boolean; data: string };
    try {
      parsed = addr.parse(checksummedAddress, allowEmpty);
    } catch (error) {
      return false;
    }
    const { data: address, hasPrefix } = parsed;
    if (!hasPrefix) return false;
    const low = address.toLowerCase();
    const upp = address.toUpperCase();
    if (address === low || address === upp) return true;
    return addr.addChecksum(low, allowEmpty) === checksummedAddress;
  },
};