/**
 * Richard Holland, XRPL Labs, 2021
 * Originally part of https://github.com/RichardAH/xpop-generator/tree/master
 */

import elliptic from 'elliptic'
const ed25519 = elliptic.eddsa('ed25519')
import fetch from 'node-fetch'
import address from 'ripple-address-codec'

const fetchUnl = (url, master_public_key) => {
  return new Promise(async (resolve, reject) => {
    const codec = { address, }
    const assert = (c, m) => {
      if (!c) reject("Invalid manifest: " + (m ? m : ""));
    }

    const parse_manifest = buf => {
      let man = {}
      let upto = 0

      let verify_fields = [Buffer.from('MAN\x00', 'utf-8')];
      let last_signing = 0;

      // sequence number
      assert(buf[upto++] == 0x24, "Missing Sequence Number")
      man['Sequence'] = (buf[upto] << 24) + (buf[upto+1] << 16) + (buf[upto+2] << 8) + buf[upto+3]
      upto += 4

      // public key
      assert(buf[upto++] == 0x71, "Missing Public Key")       // type 7 = VL, 1 = PublicKey
      assert(buf[upto++] == 33, "Missing Public Key size")    // one byte size
      man['PublicKey'] = buf.slice(upto, upto + 33).toString('hex')
      upto += 33

      // signing public key
      assert(buf[upto++] == 0x73, "Missing Signing Public Key")       // type 7 = VL, 3 = SigningPubKey
      assert(buf[upto++] == 33, "Missing Signing Public Key size")    // one byte size
      man['SigningPubKey'] = buf.slice(upto, upto + 33).toString('hex')
      upto += 33

      // signature
      verify_fields.push(buf.slice(last_signing, upto))
      assert(buf[upto++] == 0x76, "Missing Signature")    // type 7 = VL, 6 = Signature
      let signature_size = buf[upto++];
      man['Signature'] = buf.slice(upto, upto + signature_size).toString('hex')
      upto += signature_size
      last_signing = upto

      // domain field | optional
      if (buf[upto] == 0x77) {
        upto++
        let domain_size = buf[upto++]
        man['Domain'] = buf.slice(upto, upto + domain_size).toString('utf-8')
        upto += domain_size
      }

      // master signature
      verify_fields.push(buf.slice(last_signing, upto))
      assert(buf[upto++] == 0x70, "Missing Master Signature lead byte")   // type 7 = VL, 0 = uncommon field
      assert(buf[upto++] == 0x12, "Missing Master Signature follow byte") // un field = 0x12 master signature
      let master_size = buf[upto++];
      man['MasterSignature'] = buf.slice(upto, upto + master_size).toString('hex')
      upto += master_size
      last_signing = upto // here in case more fields ever added below

      assert(upto == buf.length, "Extra bytes after end of manifest")

      // for signature verification
      man.without_signing_fields = Buffer.concat(verify_fields)
      return man;
    }

    const unlData = await fetch(url)
    const json = await unlData.json()

    // initial json validation
    assert(json.public_key !== undefined, "public key missing from vl")
    assert(json.signature !== undefined, "signature missing from vl")
    assert(json.version !== undefined, "version missing from vl")
    assert(json.manifest !== undefined, "manifest missing from vl")
    assert(json.blob !== undefined, "blob missing from vl")
    assert(json.version == 1, "vl version != 1")

    // check key is recognised
    if (master_public_key)
        assert(json.public_key.toUpperCase() == master_public_key.toUpperCase(),
            "Provided VL key does not match")
    else
        master_public_key = json.public_key.toUpperCase()

    // parse blob
    let blob = Buffer.from(json.blob, 'base64')

    // parse manifest
    const manifest = parse_manifest(Buffer.from(json.manifest, 'base64'))

    // verify manifest signature and payload signature
    const master_key = ed25519.keyFromPublic(master_public_key.slice(2), 'hex')
    assert(master_key.verify(manifest.without_signing_fields, manifest.MasterSignature),
        "Master signature in master manifest does not match vl key")
    let signing_key = ed25519.keyFromPublic(manifest.SigningPubKey.slice(2), 'hex')
    assert(signing_key.verify(blob.toString('hex'), json.signature),
        "Payload signature in mantifest failed verification")
    blob = JSON.parse(blob)

    assert(blob.validators !== undefined, "validators missing from blob")

    // parse manifests inside blob (actual validator list)
    let unl = {}
    for (let idx in blob.validators) {
      assert(blob.validators[idx].manifest !== undefined,
        "validators list in blob contains invalid entry (missing manifest)")
      assert(blob.validators[idx].validation_public_key !== undefined,
        "validators list in blob contains invalid entry (missing validation public key)")
    
      let manifest = parse_manifest(Buffer.from(blob.validators[idx].manifest, 'base64'))

      // verify signature
      signing_key = ed25519.keyFromPublic(blob.validators[idx].validation_public_key.slice(2), 'hex')

      assert(signing_key.verify(manifest.without_signing_fields, manifest.MasterSignature),
        "Validation manifest " + idx + " signature verification failed")

      blob.validators[idx].validation_public_key = Buffer.from(blob.validators[idx].validation_public_key, 'hex')
      blob.validators[idx].manifest = manifest
      
      let nodepub = codec.address.encodeNodePublic(Buffer.from(manifest.SigningPubKey, 'hex'))
      unl[nodepub] = manifest.SigningPubKey
    }

    resolve({unl: {...unl}, vl: json})
  })
}

export {
  fetchUnl,
}