@thi.ng/atom/cursor.js

Mutable wrappers for nested immutable values with optional undo/redo history and transaction support

import { defGetterUnsafe } from "@thi.ng/paths/getter";
import { defSetterUnsafe } from "@thi.ng/paths/setter";
import { Atom } from "./atom.js";
import { nextID } from "./idgen.js";
function defCursor(parent, path, opts) {
  return new Cursor(parent, path, opts);
}
function defCursorUnsafe(parent, path, opts) {
  return new Cursor(parent, path, opts);
}
class Cursor {
  id;
  parent;
  local;
  selfUpdate;
  constructor(parent, path, opts = {}) {
    const validate = opts.validate;
    const lookup = defGetterUnsafe(path);
    const update = defSetterUnsafe(path);
    this.parent = parent;
    this.id = opts.id || `cursor-${nextID()}`;
    this.selfUpdate = false;
    this.local = new Atom(lookup(parent.deref()), validate);
    this.local.addWatch(this.id, (_, prev, curr) => {
      if (prev !== curr) {
        this.selfUpdate = true;
        parent.swap((state) => update(state, curr));
        this.selfUpdate = false;
      }
    });
    parent.addWatch(this.id, (_, prev, curr) => {
      if (!this.selfUpdate) {
        const cval = lookup(curr);
        if (cval !== lookup(prev)) {
          this.local.reset(cval);
        }
      }
    });
  }
  get value() {
    return this.deref();
  }
  set value(val) {
    this.reset(val);
  }
  deref() {
    return this.local.deref();
  }
  release() {
    this.local.release();
    this.parent.removeWatch(this.id);
    delete this.local;
    delete this.parent;
    return true;
  }
  reset(val) {
    return this.local.reset(val);
  }
  resetIn(path, val) {
    return this.local.resetInUnsafe(path, val);
  }
  resetInUnsafe(path, val) {
    return this.local.resetInUnsafe(path, val);
  }
  swap(fn, ...args) {
    return this.local.swap(fn, ...args);
  }
  swapIn(path, fn, ...args) {
    return this.local.swapInUnsafe(path, fn, ...args);
  }
  swapInUnsafe(path, fn, ...args) {
    return this.local.swapInUnsafe(path, fn, ...args);
  }
  addWatch(id, fn) {
    return this.local.addWatch(id, fn);
  }
  removeWatch(id) {
    return this.local.removeWatch(id);
  }
  notifyWatches(oldState, newState) {
    return this.local.notifyWatches(oldState, newState);
  }
}
export {
  Cursor,
  defCursor,
  defCursorUnsafe
};