ForkId

import * as ForkId from '@voltaire/primitives/ForkId'

const forkId = ForkId.from({
  hash: new Uint8Array([0xfc, 0x64, 0xec, 0x04]),
  next: 1920000n,  // DAO fork block
})

type ForkIdType = {
  readonly hash: Uint8Array  // CRC32 checksum (4 bytes)
  readonly next: BlockNumberType  // Next fork block (0 if none)
}

// From Uint8Array
const forkId1 = ForkId.from({
  hash: new Uint8Array([0xfc, 0x64, 0xec, 0x04]),
  next: 1920000n,
})

// From hex string
const forkId2 = ForkId.from({
  hash: "0xfc64ec04",
  next: 1920000n,
})

// From number
const forkId3 = ForkId.from({
  hash: 0xfc64ec04,
  next: 0n,  // No upcoming forks
})

const bytes = ForkId.toBytes({
  hash: new Uint8Array([0xfc, 0x64, 0xec, 0x04]),
  next: 1920000n,
})

console.log(bytes.length) // 12
// Format: hash (4 bytes) || next (8 bytes big-endian)

const local = ForkId.from({
  hash: new Uint8Array([0xfc, 0x64, 0xec, 0x04]),
  next: 1920000n,
})

const remote = ForkId.from({
  hash: new Uint8Array([0xfc, 0x64, 0xec, 0x04]),
  next: 1920000n,
})

if (ForkId.matches(local, remote)) {
  console.log('Peers are compatible')
} else {
  console.log('Fork incompatible - disconnect peer')
}

// Case 1: Identical
const a = ForkId.from({ hash: 0xfc64ec04, next: 1920000n })
const b = ForkId.from({ hash: 0xfc64ec04, next: 1920000n })
ForkId.matches(a, b) // true

// Case 2: Remote doesn't know about future forks
const local = ForkId.from({ hash: 0xfc64ec04, next: 2000000n })
const remote = ForkId.from({ hash: 0xfc64ec04, next: 0n })
ForkId.matches(local, remote) // true

// Case 3: Incompatible forks
const mainnet = ForkId.from({ hash: 0xfc64ec04, next: 1920000n })
const classic = ForkId.from({ hash: 0x12345678, next: 0n })
ForkId.matches(mainnet, classic) // false

// During peer connection
const localForkId = ForkId.from({
  hash: calculateForkHash(chainConfig, headBlock),
  next: getNextForkBlock(chainConfig),
})

const remoteForkId = parseStatusMessage(peerStatus)

if (!ForkId.matches(localForkId, remoteForkId)) {
  disconnectPeer(peer, 'Incompatible fork')
}