import { sha256 } from "@noble/hashes/sha2.js"
import { bytesToHex, utf8ToBytes } from "@noble/hashes/utils.js"

export interface NostrPowEvent {
  id: string
  pubkey: string
  created_at: number
  kind: number
  tags: Array<Array<string>>
  content: string
  sig: string
}

export function minePow(e: NostrPowEvent, target: number) {
  let ctr = 0

  let nonceTagIdx = e.tags.findIndex(a => a[0] === "nonce")
  if (nonceTagIdx === -1) {
    nonceTagIdx = e.tags.length
    e.tags.push(["nonce", ctr.toString(), target.toString()])
  }
  do {
    e.tags[nonceTagIdx][1] = (++ctr).toString()
    e.id = createId(e)
  } while (countLeadingZeros(e.id) < target)

  return e
}

function createId(e: NostrPowEvent) {
  const payload = [0, e.pubkey, e.created_at, e.kind, e.tags, e.content]
  return bytesToHex(sha256(utf8ToBytes(JSON.stringify(payload))))
}

export function countLeadingZeros(hex: string) {
  let count = 0

  for (let i = 0; i < hex.length; i++) {
    const nibble = parseInt(hex[i], 16)
    if (nibble === 0) {
      count += 4
    } else {
      count += Math.clz32(nibble) - 28
      break
    }
  }

  return count
}