function applyChanges()

in backend/new.js [1516:1557]

• 36 lines of code
• 14 McCabe index (conditional complexity)

function applyChanges(patches, decodedChanges, docState, objectIds) {
  let heads = new Set(docState.heads), changeHashes = new Set()
  let clock = copyObject(docState.clock)
  let applied = [], enqueued = []

  for (let change of decodedChanges) {
    // Skip any duplicate changes that we have already seen
    if (docState.changeIndexByHash[change.hash] !== undefined || changeHashes.has(change.hash)) continue

    let causallyReady = true
    for (let dep of change.deps) {
      const depIndex = docState.changeIndexByHash[dep]
      if ((depIndex === undefined || depIndex === -1) && !changeHashes.has(dep)) {
        causallyReady = false
      }
    }

    if (causallyReady) {
      const expectedSeq = (clock[change.actor] || 0) + 1
      if (change.seq !== expectedSeq) {
        throw new RangeError(`Expected seq ${expectedSeq}, got seq ${change.seq} from actor ${change.actor}`)
      }
      clock[change.actor] = change.seq
      changeHashes.add(change.hash)
      for (let dep of change.deps) heads.delete(dep)
      heads.add(change.hash)
      applied.push(change)
    } else {
      enqueued.push(change)
    }
  }

  if (applied.length > 0) {
    let changeState = {changes: applied, changeIndex: -1, objectIds}
    readNextChangeOp(docState, changeState)
    while (!changeState.done) applyOps(patches, changeState, docState)

    docState.heads = [...heads].sort()
    docState.clock = clock
  }
  return [applied, enqueued]
}