fvtt-hamalron/module/applications/sheets/base-item-sheet.mjs

const { HandlebarsApplicationMixin } = foundry.applications.api

export default class HamalronItemSheet extends HandlebarsApplicationMixin(foundry.applications.sheets.ItemSheetV2) {
  /**
   * Different sheet modes.
   * @enum {number}
   */
  static SHEET_MODES = { EDIT: 0, PLAY: 1 }

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

  #dragDrop

  /** @override */
  static DEFAULT_OPTIONS = {
    classes: ["fvtt-hamalron", "item"],
    position: {
      width: 600,
      height: "auto",
    },
    form: {
      submitOnChange: true,
    },
    window: {
      resizable: true,
    },
    dragDrop: [{ dragSelector: "[data-drag]", dropSelector: null }],
    actions: {
      toggleSheet: HamalronItemSheet.#onToggleSheet,
      editImage: HamalronItemSheet.#onEditImage,
    },
  }

  /**
   * The current sheet mode.
   * @type {number}
   */
  _sheetMode = this.constructor.SHEET_MODES.PLAY

  /**
   * Is the sheet currently in 'Play' mode?
   * @type {boolean}
   */
  get isPlayMode() {
    return this._sheetMode === this.constructor.SHEET_MODES.PLAY
  }

  /**
   * Is the sheet currently in 'Edit' mode?
   * @type {boolean}
   */
  get isEditMode() {
    return this._sheetMode === this.constructor.SHEET_MODES.EDIT
  }

  /** @override */
  async _prepareContext() {
    const context = {
      fields: this.document.schema.fields,
      systemFields: this.document.system.schema.fields,
      item: this.document,
      system: this.document.system,
      source: this.document.toObject(),
      enrichedDescription: await foundry.applications.ux.TextEditor.implementation.enrichHTML(this.document.system.description, { async: true }),
      isEditMode: this.isEditMode,
      isPlayMode: this.isPlayMode,
      isEditable: this.isEditable,
    }
    return context
  }

  /** @override */
  _onRender(context, options) {
    this.#dragDrop.forEach((d) => d.bind(this.element))
  }

  // #region Drag-and-Drop Workflow
  /**
   * Create drag-and-drop workflow handlers for this Application
   * @returns {DragDrop[]}     An array of DragDrop handlers
   * @private
   */
  #createDragDropHandlers() {
    return this.options.dragDrop.map((d) => {
      d.permissions = {
        dragstart: this._canDragStart.bind(this),
        drop: this._canDragDrop.bind(this),
      }
      d.callbacks = {
        dragstart: this._onDragStart.bind(this),
        dragover: this._onDragOver.bind(this),
        drop: this._onDrop.bind(this),
      }
      return new foundry.applications.ux.DragDrop.implementation(d)
    })
  }

  /**
   * Define whether a user is able to begin a dragstart workflow for a given drag selector
   * @param {string} selector       The candidate HTML selector for dragging
   * @returns {boolean}             Can the current user drag this selector?
   * @protected
   */
  _canDragStart(selector) {
    return this.isEditable
  }

  /**
   * Define whether a user is able to conclude a drag-and-drop workflow for a given drop selector
   * @param {string} selector       The candidate HTML selector for the drop target
   * @returns {boolean}             Can the current user drop on this selector?
   * @protected
   */
  _canDragDrop(selector) {
    return this.isEditable && this.document.isOwner
  }

  /**
   * Callback actions which occur at the beginning of a drag start workflow.
   * @param {DragEvent} event       The originating DragEvent
   * @protected
   */
  _onDragStart(event) {
    const el = event.currentTarget
    if ("link" in event.target.dataset) return

    const itemId = el.dataset.itemId
    if (!itemId) return

    const item = this.document.items.get(itemId)
    if (!item) return

    const dragData = item.toDragData()
    event.dataTransfer.setData("text/plain", JSON.stringify(dragData))
  }

  /**
   * Callback actions which occur when a dragged element is over a drop target.
   * @param {DragEvent} event       The originating DragEvent
   * @protected
   */
  _onDragOver(event) { }

  /**
   * Callback actions which occur when a dragged element is dropped on a target.
   * @param {DragEvent} event       The originating DragEvent
   * @protected
   */
  async _onDrop(event) { }

  // #endregion

  // #region Actions
  /**
   * Handle toggling between Edit and Play mode.
   * @param {Event} event             The initiating click event.
   * @param {HTMLElement} target      The current target of the event listener.
   */
  static #onToggleSheet(event, target) {
    const modes = this.constructor.SHEET_MODES
    this._sheetMode = this.isEditMode ? modes.PLAY : modes.EDIT
    this.render()
  }

  /**
   * Handle changing a Document's image.
   *
   * @this CthulhuEternalCharacterSheet
   * @param {PointerEvent} event   The originating click event
   * @param {HTMLElement} target   The capturing HTML element which defined a [data-action]
   * @returns {Promise}
   * @private
   */
  static async #onEditImage(event, target) {
    const attr = target.dataset.edit
    const current = foundry.utils.getProperty(this.document, attr)
    const { img } = this.document.constructor.getDefaultArtwork?.(this.document.toObject()) ?? {}
    const fp = new FilePicker({
      current,
      type: "image",
      redirectToRoot: img ? [img] : [],
      callback: (path) => {
        this.document.update({ [attr]: path })
      },
      top: this.position.top + 40,
      left: this.position.left + 10,
    })
    return fp.browse()
  }
  // #endregion
}