fvtt-celestopol/module/applications/sheets/base-actor-sheet.mjs

const { HandlebarsApplicationMixin } = foundry.applications.api

export default class CelestopolActorSheet extends HandlebarsApplicationMixin(foundry.applications.sheets.ActorSheetV2) {
  static SHEET_MODES = { EDIT: 0, PLAY: 1 }

  constructor(options = {}) {
    super(options)
    this.#dragDrop = this.#createDragDropHandlers()
  }

  #dragDrop

  /** @override */
  static DEFAULT_OPTIONS = {
    classes: ["fvtt-celestopol", "actor"],
    position: { width: 900, height: "auto" },
    form: { submitOnChange: true },
    window: { resizable: true },
    dragDrop: [{ dragSelector: '[data-drag="true"], .rollable', dropSelector: null }],
    actions: {
      editImage:    CelestopolActorSheet.#onEditImage,
      toggleSheet:  CelestopolActorSheet.#onToggleSheet,
      edit:         CelestopolActorSheet.#onItemEdit,
      delete:       CelestopolActorSheet.#onItemDelete,
    },
  }

  _sheetMode = this.constructor.SHEET_MODES.PLAY

  get isPlayMode() { return this._sheetMode === this.constructor.SHEET_MODES.PLAY }
  get isEditMode() { return this._sheetMode === this.constructor.SHEET_MODES.EDIT }

  /** @override */
  async _prepareContext() {
    return {
      fields:       this.document.schema.fields,
      systemFields: this.document.system.schema.fields,
      actor:        this.document,
      system:       this.document.system,
      source:       this.document.toObject(),
      isEditMode:   this.isEditMode,
      isPlayMode:   this.isPlayMode,
      isEditable:   this.isEditable,
    }
  }

  /** @override */
  _onRender(context, options) {
    this.#dragDrop.forEach(d => d.bind(this.element))
    this.element.querySelectorAll(".rollable").forEach(el => {
      el.addEventListener("click", this._onRoll.bind(this))
    })
  }

  async _onRoll(event) {
    if (!this.isPlayMode) return
    const el = event.currentTarget
    const statId  = el.dataset.statId
    const skillId = el.dataset.skillId
    if (!statId || !skillId) return
    await this.document.system.roll(statId, skillId)
  }

  #createDragDropHandlers() {
    return this.options.dragDrop.map(d => {
      d.permissions = {
        dragstart: this._canDragStart.bind(this),
        drop:      this._canDragDrop.bind(this),
      }
      d.callbacks = {
        dragover: this._onDragOver.bind(this),
        drop:     this._onDrop.bind(this),
      }
      return new foundry.applications.ux.DragDrop.implementation(d)
    })
  }

  _canDragStart()  { return this.isEditable }
  _canDragDrop()   { return true }
  _onDragOver()    {}

  async _onDrop(event) {
    if (!this.isEditable) return
    const data = foundry.applications.ux.TextEditor.implementation.getDragEventData(event)
    if (data.type === "Item") {
      const item = await fromUuid(data.uuid)
      if (item) return this._onDropItem(item)
    }
  }

  async _onDropItem(item) {
    await this.document.createEmbeddedDocuments("Item", [item.toObject()], { renderSheet: false })
  }

  static async #onEditImage(event, target) {
    const attr    = target.dataset.edit
    const current = foundry.utils.getProperty(this.document, attr)
    const fp = new FilePicker({
      current,
      type: "image",
      callback: (path) => this.document.update({ [attr]: path }),
      top:  this.position.top + 40,
      left: this.position.left + 10,
    })
    return fp.browse()
  }

  static #onToggleSheet() {
    const modes = this.constructor.SHEET_MODES
    this._sheetMode = this.isEditMode ? modes.PLAY : modes.EDIT
    this.render()
  }

  static async #onItemEdit(event, target) {
    const uuid = target.getAttribute("data-item-uuid")
    const id   = target.getAttribute("data-item-id")
    const item = uuid ? await fromUuid(uuid) : this.document.items.get(id)
    item?.sheet.render(true)
  }

  static async #onItemDelete(event, target) {
    const uuid = target.getAttribute("data-item-uuid")
    const item = await fromUuid(uuid)
    await item?.deleteDialog()
  }
}