import { set } from "mobx"
import { isArray } from "../utils"
import { ModelPool } from "../utils/ModelPool"
import { fromSnapshot } from "./fromSnapshot"
import { detachIfNeeded, reconcileSnapshot, registerReconciler } from "./reconcileSnapshot"
import type { SnapshotInOfObject } from "./SnapshotOf"
import { SnapshotterAndReconcilerPriority } from "./SnapshotterAndReconcilerPriority"

function reconcileArraySnapshot(
  value: any,
  sn: SnapshotInOfObject<any[]>,
  modelPool: ModelPool
): any[] {
  if (!isArray(value)) {
    // no reconciliation possible
    return fromSnapshot(sn)
  }

  // remove excess items
  if (value.length > sn.length) {
    value.splice(sn.length, value.length - sn.length)
  }

  // reconcile present items
  for (let i = 0; i < value.length; i++) {
    const oldValue = value[i]
    const newValue = reconcileSnapshot(oldValue, sn[i], modelPool)

    detachIfNeeded(newValue, oldValue, modelPool)

    set(value, i as any, newValue)
  }

  // add excess items
  for (let i = value.length; i < sn.length; i++) {
    value.push(reconcileSnapshot(undefined, sn[i], modelPool))
  }

  return value
}

registerReconciler(SnapshotterAndReconcilerPriority.Array, (value, sn, modelPool) => {
  if (isArray(sn)) {
    return reconcileArraySnapshot(value, sn, modelPool)
  }
  return undefined
})