mobx-keystone-yjs/src/binding/resolveYjsPath.ts

Yjs bindings for mobx-keystone

import * as Y from "yjs"
import { failure } from "../utils/error"
import { getOrCreateYjsCollectionAtom } from "../utils/getOrCreateYjsCollectionAtom"

/**
 * Resolves a path within a Yjs object structure.
 * Returns the Yjs container at the specified path.
 *
 * When a Y.Text is encountered during path resolution (either at the start
 * or mid-path), it is returned immediately since Y.Text doesn't support
 * nested path traversal.
 *
 * @param yjsObject The root Yjs object
 * @param path Array of keys/indices to traverse
 * @returns The Yjs container at the path, or Y.Text if encountered during traversal
 */
export function resolveYjsPath(
  yjsObject: Y.Map<unknown> | Y.Array<unknown> | Y.Text,
  path: readonly (string | number)[]
): unknown {
  let currentYjsObject: unknown = yjsObject

  let i = -1
  for (const pathPart of path) {
    i++
    // If we encounter a Y.Text during path resolution, return it immediately.
    // Y.Text objects don't support nested path traversal, and their updates
    // are handled separately by YjsTextModel's own synchronization mechanism.
    if (currentYjsObject instanceof Y.Text) {
      return currentYjsObject
    }

    if (currentYjsObject instanceof Y.Map) {
      getOrCreateYjsCollectionAtom(currentYjsObject).reportObserved()
      const key = String(pathPart)
      currentYjsObject = currentYjsObject.get(key)
    } else if (currentYjsObject instanceof Y.Array) {
      getOrCreateYjsCollectionAtom(currentYjsObject).reportObserved()
      const key = Number(pathPart)
      currentYjsObject = currentYjsObject.get(key)
    } else {
      throw failure(
        `Y.Map or Y.Array was expected at path ${JSON.stringify(
          path.slice(0, i)
        )} in order to resolve path ${JSON.stringify(path)}, but got ${currentYjsObject} instead`
      )
    }
  }

  return currentYjsObject
}