import { getHandlers } from "./event.js"

let operationGroup = null

export function pushOperation(op) {
  if (operationGroup) {
    operationGroup.ops.push(op)
  } else {
    op.ownsGroup = operationGroup = {
      ops: [op],
      delayedCallbacks: []
    }
  }
}

function fireCallbacksForOps(group) {
  // Calls delayed callbacks and cursorActivity handlers until no
  // new ones appear
  let callbacks = group.delayedCallbacks, i = 0
  do {
    for (; i < callbacks.length; i++)
      callbacks[i].call(null)
    for (let j = 0; j < group.ops.length; j++) {
      let op = group.ops[j]
      if (op.cursorActivityHandlers)
        while (op.cursorActivityCalled < op.cursorActivityHandlers.length)
          op.cursorActivityHandlers[op.cursorActivityCalled++].call(null, op.cm)
    }
  } while (i < callbacks.length)
}

export function finishOperation(op, endCb) {
  let group = op.ownsGroup
  if (!group) return

  try { fireCallbacksForOps(group) }
  finally {
    operationGroup = null
    endCb(group)
  }
}

let orphanDelayedCallbacks = null

// Often, we want to signal events at a point where we are in the
// middle of some work, but don't want the handler to start calling
// other methods on the editor, which might be in an inconsistent
// state or simply not expect any other events to happen.
// signalLater looks whether there are any handlers, and schedules
// them to be executed when the last operation ends, or, if no
// operation is active, when a timeout fires.
export function signalLater(emitter, type /*, values...*/) {
  let arr = getHandlers(emitter, type)
  if (!arr.length) return
  let args = Array.prototype.slice.call(arguments, 2), list
  if (operationGroup) {
    list = operationGroup.delayedCallbacks
  } else if (orphanDelayedCallbacks) {
    list = orphanDelayedCallbacks
  } else {
    list = orphanDelayedCallbacks = []
    setTimeout(fireOrphanDelayed, 0)
  }
  for (let i = 0; i < arr.length; ++i)
    list.push(() => arr[i].apply(null, args))
}

function fireOrphanDelayed() {
  let delayed = orphanDelayedCallbacks
  orphanDelayedCallbacks = null
  for (let i = 0; i < delayed.length; ++i) delayed[i]()
}