@winged/core/src/viewModel/Observable.ts

Morden webapp framekwork made only for ts developers. (UNDER DEVELOPMENT, PLEASE DO NOT USE)

import { ModificationTree } from '../types'

type WatcherCallback = (modificationTree: ModificationTree) => void

export abstract class Observable {
  private static idCounter = 0
  public readonly _observableId = ++Observable.idCounter

  protected _watchedTargets: {
    [id: string]: { target: Observable, watcherCount: number }
  } = {}
  protected _watchers: Array<{
    context: any;
    callback: WatcherCallback;
  }> = []

  public _watchBy(context: any, callback: WatcherCallback) {
    this._watchers.push({ context, callback } as any)
  }

  public _stopWatchBy(context: any) {
    this._watchers = this._watchers.filter((w) => w.context !== context)
  }

  protected _emitValueChange(modificationTree: ModificationTree) {
    for (const { callback } of this._watchers) {
      callback(modificationTree)
    }
  }

  protected _registerChild(field: () => string | string, child: Observable) {
    const id = child._observableId
    if (!child._watchedTargets[id]) {
      child._watchedTargets[id] = {
        target: child,
        watcherCount: 0
      }
    }
    child._watchedTargets[id].watcherCount++
    child._watchBy(this, (modificationTree) => {
      let s: string
      if (typeof field === 'function') {
        s = field()
      } else {
        s = field
      }
      this._emitValueChange({ [s]: modificationTree })
    })
  }

  protected _unregisterChild(childOrChildId: Observable | string) {
    let id: string
    if (childOrChildId instanceof Observable) {
      id = childOrChildId._observableId + ''
    } else {
      id = childOrChildId
    }
    const watchInfo = this._watchedTargets[id]
    if (watchInfo.watcherCount > 1) {
      watchInfo.watcherCount--
    } else {
      this._watchedTargets[id].target._stopWatchBy(this)
      delete this._watchedTargets[id]
    }
  }
}