#!/usr/bin/env node
let multihashes = require('multihashes')

let address = 'QmbWGdzNEed8JEgmfKTysjNAxNG6UEJpv3sBCVctBXAEsJ'

let raw_address = multihashes.fromB58String(address)
let hash_info = multihashes.decode(raw_address)
let digest = hash_info.digest
if (hash_info.name !== 'sha2-256') {
    console.error("ERR: IPFS address isn't a SHA256")
    process.exit(1)
}

// After verifying if the algorithm is SHA256, "digest" can be passed
// to the contract as a bytes32 field (probably encoded as a hexstring
// because of Web3).
let hexDigest = '0x' + digest.toString('hex')
console.log(hexDigest)



// Having a bytes32 encoded (by Web3) as a hex string, we can rebuild
// the IPFS address using the following procedure.
if (!hexDigest.startsWith('0x')) {
    // This is just a sanity test, Web3 should give us a hex string
    // beginning with "0x...".
    console.error("ERR: Invalid hex string received")
    process.exit(1)
}


let str_digest = Buffer.from(hexDigest.substr(2), 'hex')
let multi_digest = multihashes.encode(str_digest, 'sha2-256')
let ipfs_address = multihashes.toB58String(multi_digest)
console.log(ipfs_address)
console.log(ipfs_address === address)