/**
 * class designed to store actor modification instructions, to apply them in a single operation, and have the ability to revert these
 */
export class ActorImpacts {
  constructor(actorToken) {
    this.actorToken = actorToken
    this.updates = []
    this.deltas = []
    this.itemCreates = []
    this.itemUpdates = []
    this.itemDeletes = []
  }

  addActorUpdate(path, value) {
    this.updates.push([path, value])
  }

  addActorDelta(path, value) {
    const intValue = Number.parseInt(value)
    if (Number.isInteger(intValue) && intValue != 0) {
      const delta = [path, intValue]
      this.deltas.push(delta)
    }
    else {
      console.error('Cannot use non integer value {} for delta update', value)
    }
  }

  addDeletedItem(item) {
    this.itemDeletes.push(item)
  }
  addCreatedItem(item) {
    this.itemCreates.push(item)
  }

  addItemUpdate(item, path, value) {
    const existing = this.itemUpdates.find(it => it.id == item.id)
    const update = [path, value]
    if (existing) {
      existing.updates.push(update)
    }
    else {
      this.itemUpdates.push({ id: item.id, updates: [update], deltas: [] })
    }
  }

  addItemDelta(item, path, value) {
    const intValue = Number.parseInt(value)
    if (Number.isInteger(intValue) && intValue != 0) {
      const delta = [path, intValue]
      const existing = this.itemUpdates.find(it => it.id == item.id)
      if (existing) {
        existing.deltas.push(delta)
      }
      else {
        this.itemUpdates.push({ id: item.id, updates: [], deltas: [delta] })
      }
    }
    else {
      console.error('Cannot use non integer value {} for delta update', value)
    }
  }

  reverseImpacts() {
    const reverse = ActorImpacts.$computeReverts(new ActorImpacts(this.actorToken), this, __ => this.actorToken.actor)
    reverse.itemCreates = this.itemDeletes.map(it => foundry.utils.duplicate(it))
    reverse.itemDeletes = this.itemCreates.map(it => { return { id: it.id } })
    reverse.itemUpdates = this.itemUpdates.map(it => ActorImpacts.$computeReverts({ id: it.id }, it, id => this.$getActorItem(id)))
    return reverse
  }

  toStorable() {
    delete this.actorToken
    return this
  }

  async applyImpacts() {
    const actor = this.actorToken.actor
    const isItemsDelete = this.itemDeletes.length > 0
    const isItemsCreate = this.itemCreates.length > 0
    const isItemsUpdate = this.itemUpdates.length > 0
    const isActorUpdate = this.updates.length > 0 || this.deltas.length > 0

    if (isItemsDelete) {
      const deletes = this.itemDeletes.map(it => it.id)
      await actor.deleteEmbeddedDocuments('Item', deletes, { render: !(isItemsCreate || isItemsUpdate || isActorUpdate) })
    }

    if (isItemsCreate) {
      const creates = this.itemCreates
      const created = await actor.createEmbeddedDocuments('Item', creates, { render: !(isItemsUpdate || isActorUpdate)})
      for (let i=0; i<creates.length; i++){
        creates[i].createdId = created[i].id
      }
    }

    if (isItemsUpdate) {
      const updates = this.itemUpdates.map(u => ActorImpacts.$computeUpdates(u, id => this.$getActorItem(id)))
      await actor.updateEmbeddedDocuments('Item', updates, { render: !isActorUpdate })
    }

    if (isActorUpdate) {
      const updates = ActorImpacts.$computeUpdates(this, id => actor)
      await actor.update(updates, { render: true })
    }
  }

  $getActorItem(id) {
    return this.actorToken.actor.items.get(id)
  }

  static $computeUpdates(u, getSource) {
    const source = getSource(u.id)
    const instruction = { _id: u.id }
    u.updates.forEach(u => instruction[u[0]] = u[1])
    u.deltas.forEach(u => instruction[u[0]] = foundry.utils.getProperty(source, u[0]) + u[1])
    return instruction
  }

  static $computeReverts(target, u, getSource) {
    const source = getSource(u.id)
    target.updates = u.updates.map(u => [u[0], foundry.utils.getProperty(source, u[0])])
    target.deltas = u.deltas.map(d => [d[0], -d[1]])
    return target
  }

}