gistfile1.txt

import * as name from '../key-did-provider-secp256r1/dist/index.js'
import u8a from 'uint8arrays'
import  multicodec from 'multicodec'
import  multibase from 'multibase'
//import  toString from 'uint8arrays/to-string'
//import fromString from 'uint8arrays/from-string'
import  base64url from 'base64url' // this converts a text string to base64url, it does not take a uint8 array??
import  base64url_universal from 'base64url-universal'
import  bs58 from 'bs58'

const publicKey = 'zrurwcJZss4ruepVNu1H3xmSirvNbzgBk9qrCktB6kaewXnJAhYWwtP3bxACqBpzjZdN7TyHNzzGGSSH5qvZsSDir9z'
//const publicKey = 'zrusAFgBbf84b8mBz8Cmy8UoFWKV52EaeRnK86vnLo4Z5QoRypE6hXVPN2urevZMAMtcTaCDFLWBaE1Q3jmdb1FHgve'
//const publicKey = 'zXwpDcwhs3ryJCCM3vYz9nJ7jB7Mbp8ioihWmRkNjy1XPjTqMEn5MvjaH3i1qsegxku36mBUc5fQ5NEW5JfHRr6i3TVf'
//const publicKey = 'zJss7xQxaumG3JviQ6XF4MefAeJrYmD2dGk6BaZSueRx2zFeWNg6aCc5biu1mY72rgj7aNbaGkvtYX1sxx2XFn6PFpar3QKpgNKkikEwp6MhP4GaffSadvVxiCzb7XrT6VpK5osS6YmgzksSd7ugNvf8TeUEN2EK2v7rjzVYhg9tEMBHGhq8ByCE2'

const buf = multibase.decode(publicKey)

console.log(buf);

const bb = u8a.toString(buf,'base16')

console.log(bb);

const bbb = bb.slice(4)

console.log('hex key: '+bbb)

console.log(bbb.length)

// this is the regular length public key
console.log(encodeDIDfromHexString(bbb));

// compresedKeyInHex(publicKeyHex: string)

const compressedKey = compresedKeyInHex(bbb)

console.log(encodeDIDfromHexString(compressedKey))

export function compresedKeyInHex(publicKeyHex) {
  const xHex = publicKeyHex.slice(0,publicKeyHex.length/2);
  const yHex = publicKeyHex.slice(publicKeyHex.length/2,publicKeyHex.length);

  const xOctet = u8a.fromString(xHex,'base16')
  const yOctet = u8a.fromString(yHex,'base16');

  const compressedPoint = ECPointCompress( xOctet , yOctet );
  const compressedPointHex = u8a.toString(compressedPoint,'base16');
  return compressedPointHex;
}

// compress a public key with points x,y expressed as UintArrays
// source: https://stackoverflow.com/questions/17171542/algorithm-for-elliptic-curve-point-compression
export function ECPointCompress( x, y )
{
    const out = new Uint8Array( x.length + 1 );

    out[0] = 2 + ( y[ y.length-1 ] & 1 );
    out.set( x, 1 );

    return out;
}

export function encodeDIDfromHexString(publicKeyHex) {
    const publicKey = u8a.fromString(publicKeyHex,'base16');
    const didKey = encodeDID(publicKey)
    return didKey;
}

export function encodeDID(publicKey) {
          const publicKeywPrefix = multicodec.addPrefix('p256-pub',publicKey)
          const buf = multibase.encode('base58btc',publicKeywPrefix)
          const bufAsString = u8a.toString(buf)
          return `did:key:${bufAsString}`
}

ToDo: Use https://github.com/bshambaugh/did-key-creator to rewrite this.