updateAccessChangeLog.ts

async function updateAccessChangeLog(
  type: 'user' | 'collection',
  currentUser: UserWithKeys,
  now: number,
  // Old item
  oldItem: Item,
  // New userAccess
  newItem: Item
) {
  // collectionAccess: Item belongs to collections
  // userAccess: Item can be edited by users
  const newAccess =
    type === 'user' ? newItem.userAccess : newItem.collectionAccess
  const oldAccess =
    type === 'user' ? oldItem.userAccess : oldItem.collectionAccess
  const oldIds = Object.keys(oldAccess)
  const newIds = Object.keys(newAccess)
  const add = newIds.filter(k => !oldAccess[k])
  const remove = oldIds.filter(k => !newAccess[k])
  const update = newIds.filter(
    k =>
      oldAccess[k] &&
      JSON.stringify(newAccess[k]) !== JSON.stringify(oldAccess[k])
  )
  const ops = { add, update, remove }

  // Create accessLog entries
  let previous = oldItem.id
  let accessChangeLog: AccessChangeLogEntry[] = []
  if (newItem.accessChangeLog) {
    accessChangeLog = newItem.accessChangeLog.slice()
    const last = accessChangeLog.slice(-1)[0]
    if (last) {
      const { signature64 } = extractJWT(last.operation)
      previous = signature64
    }
  }
  newItem.accessChangeLog = accessChangeLog

  const opsKeys = Object.keys(ops) as (keyof typeof ops)[]
  for (let i = 0; i < opsKeys.length; i++) {
    const opType = opsKeys[i]
    const ids = ops[opType]
    for (let j = 0; j < ids.length; j++) {
      const id = ids[j]
      const value = newAccess[id]
      const op: AccessChangeOperation = {
        // Changed timestamp.
        changedAt: now,
        // Signature of previous operation. Contains itemId for first operation.
        previous,
        // Type of access operation.
        type,
        // Concerned field in userAccess or collectionAccess.
        id,
        // Operation name.
        operation: opType,
      }

      if (type === 'user' && opType !== 'remove') {
        const val = value as CollectionUserAccess['id']
        // Changed access.
        op.access = val.access
        if (opType === 'add' && val.invite) {
          op.operation = 'invite'
        } else if (currentUser.user.id === id) {
          op.operation = 'join'
        }
      }

      const signedOperation = await sign(currentUser.signKey, op)
      previous = extractJWT(signedOperation).signature64
      accessChangeLog.push({
        changedBy: currentUser.user.id,
        operation: signedOperation,
      })
    }
  }
}