multi-framework-signals/src/ng-mock/js-land/connector/createSignalObjectForShape.ts

import updateShape from "src/ng-mock/wasm-land/updateShape";
import type { Connection, Diff, Scope, Shape } from "../types";
import requestShape from "src/ng-mock/wasm-land/requestShape";
import { applyDiff } from "./applyDiff";
import { deepSignal, watch, batch } from "alien-deepsignals";
import type { DeepPatch, DeepSignalObject } from "alien-deepsignals";
import type { CompactShapeType } from "node_modules/@ldo/ldo/dist/types/ShapeType";
import type { LdoCompactBase } from "@ldo/ldo";

interface PoolEntry<T extends LdoCompactBase> {
  key: string;
  shape: CompactShapeType<T>;
  scopeKey: string;
  signalObject: DeepSignalObject<T | {}>;
  refCount: number;
  stopListening: (() => void) | null;
  registerCleanup?: (fn: () => void) => void;
  connectionId?: string;
  ready: Promise<string>; // resolves to connectionId
  resolveReady: (id: string) => void;
  suspendDeepWatcher: boolean;
}

const pool = new Map<string, PoolEntry<any>>();

function canonicalScope(scope: Scope | undefined): string {
  if (scope == null) return "";
  return Array.isArray(scope) ? scope.slice().sort().join(",") : String(scope);
}

export function deepPatchesToDiff(patches: DeepPatch[]): Diff {
  return patches.map((patch) => {
    const path = "/" + patch.path.join("/");
    return { ...patch, path };
  }) as Diff;
}

export function createSignalObjectForShape<T extends LdoCompactBase>(
  shape: CompactShapeType<T>,
  scope?: Scope,
  poolSignal = true
) {
  const scopeKey = canonicalScope(scope);
  const key = `${shape}::${scopeKey}`;

  if (poolSignal) {
    const existing = pool.get(key);
    if (existing) {
      existing.refCount++;
      return buildReturn(existing);
    }
  }

  const signalObject = deepSignal<T | {}>({});
  let resolveReady!: (id: string) => void;
  const ready = new Promise<string>((res) => (resolveReady = res));
  const entry: PoolEntry<T> = {
    key,
    shape,
    scopeKey,
    signalObject,
    refCount: 1,
    stopListening: null,
    registerCleanup: undefined,
    connectionId: undefined,
    ready,
    resolveReady,
    suspendDeepWatcher: false,
  };
  if (poolSignal) pool.set(key, entry);

  const onUpdateFromDb = (diff: Diff, connectionId: Connection["id"]) => {
    console.debug("[shape][diff] applying", connectionId, diff);
    entry.suspendDeepWatcher = true;
    batch(() => applyDiff(signalObject, diff));
    queueMicrotask(() => {
      entry.suspendDeepWatcher = false;
    });
  };

  requestShape(shape, scope, onUpdateFromDb).then(
    ({ connectionId, shapeObject }) => {
      entry.connectionId = connectionId;
      entry.suspendDeepWatcher = true;
      batch(() => {
        for (const k of Object.keys(shapeObject)) {
          (signalObject as any)[k] = (shapeObject as any)[k];
        }
      });
      const watcher = watch(signalObject, ({ patches }) => {
        if (entry.suspendDeepWatcher || !patches.length) return;
        const diff = deepPatchesToDiff(patches);
        updateShape(connectionId as any, diff as any);
      });
      entry.stopListening = watcher.stopListening;
      entry.registerCleanup = watcher.registerCleanup;
      queueMicrotask(() => {
        entry.suspendDeepWatcher = false;
      });
      entry.resolveReady(connectionId);
    }
  );

  function buildReturn(entry: PoolEntry<T>) {
    const release = () => {
      if (entry.refCount > 0) entry.refCount--;
      if (entry.refCount === 0) {
        entry.stopListening?.();
        if (poolSignal) pool.delete(entry.key);
      }
    };
    return {
      signalObject: entry.signalObject,
      stop: release,
      ready: entry.ready, // Promise<string>
      get connectionId() {
        return entry.connectionId;
      },
      registerCleanup: entry.registerCleanup,
    };
  }

  return buildReturn(entry);
}