@girders-elements/core/src/update/impl.js

Girders Elements is an architectural framework that assists with building data-driven apps with React or React Native.

'use strict'

import R from 'ramda'

import invariant from 'invariant'
import { warning } from '../impl/log'

import * as data from '../data'
import * as actions from '../action'
import { findParentEntry } from '../impl/cursor'

import { ActionRegistry } from '../registry'
/**
 * Main application reducer.
 *
 * @param config A configuration object passed from the Engine component
 * @param cursor The cursor representing the state.
 * @param action The action.
 * @returns {*} The new state represented by updated cursor.
 */
export const reducer = R.curry((config, cursor, action) => {
  // skip actions that are not for us
  if (!isApplicable(action)) return cursor

  invariant(
    cursor != null && cursor._keyPath != null,
    'The reducer is meant to work only with cursors'
  )

  const { keyPath: fromPath } = actions.actionMeta(action)
  const type = action.type
  const { registry } = config

  // handle global updates
  if (type.startsWith('.')) {
    const keyFn = el => ActionRegistry.keyFor(data.kindOf(el), type)

    const entry = findParentEntry(registry, keyFn, cursor.getIn(fromPath))
    if (entry != null) {
      const { element, entry: update } = entry
      return cursor.setIn(element._keyPath, update(element.deref(), action))
    }
    return cursor
  }

  // handle local updates
  const update = registry.get(ActionRegistry.keyFromAction(action))
  const element = cursor.getIn(fromPath)
  if (element) {
    if (update) {
      return cursor.setIn(fromPath, update(element.deref(), action))
    } else {
      return cursor
    }
  } else {
    warning(
      'Unable to perform local update, element has changed in meantime...'
    )
    return cursor
  }

  return cursor
})

const isApplicable = R.pipe(actions.actionMeta, R.complement(R.isNil))