Object and other helpers (follow)

.gitignore

@@ -2,6 +2,9 @@ node_modules
 coverage
 dist
 *.dot
+*.png
 src/*.dot
+src/*.png
 README.html
 coverage
+.DS_Store

src/cell.ts

@@ -275,6 +275,9 @@ export class Cell<
   get name(): string {
     return this._sheet.name(this.id);
   }
+  get fullName(): string {
+    return this._sheet.name(this.id, true);
+  }
 
   /**
    * get the immediate cell value. or pointed value
@@ -522,7 +525,7 @@ export class Cell<
     // Invalidation for outdated computation
     if (computationRank < this._valueRank) {
       DEV &&
-        console.log(
+        console.warn(
           `Cell ${this.name}: `,
           `setting to ${newValue} has been invalidated`,
           {

src/cellify.test.ts

@@ -1,6 +1,12 @@
 import { expect, test } from "vitest";
 
-import { Cellified, Uncellified, _cellify, _uncellify } from "./cellify";
+import {
+  Cellified,
+  Uncellified,
+  _cellify,
+  _uncellify,
+  follow
+} from "./cellify";
 import { SheetProxy } from "./proxy";
 import { Sheet } from "./sheet";
 
@@ -45,3 +51,28 @@ test("_cellify one", async () => {
   const cell = await res.get();
   await expect(cell.a.get()).resolves.toBe(1);
 });
+
+test("follow", async () => {
+  const sheet = new Sheet();
+  const proxy = new SheetProxy(sheet);
+  const v = { a: [1, 2, 3], b: { c: { foo: 1, bar: 1 } } };
+  const cv = _cellify(proxy, v);
+  const f = follow(proxy, cv, ["a", 1]);
+  await expect(f.get()).resolves.toBe(2);
+  expect(sheet.stats).toEqual({ size: 12, count: 12 });
+
+  // update the cell directly
+  (await (await cv.get()).a.get())[1].set(4);
+  await expect(f.get()).resolves.toBe(4);
+  expect(sheet.stats).toEqual({ size: 12, count: 12 }); // unchanged
+
+  // prepend a new cell in array
+  (await cv.get()).a.update((l) => [proxy.new(0), ...l]);
+  await expect(f.get()).resolves.toBe(1);
+  expect(sheet.stats).toEqual({ size: 13, count: 14 }); // one new cell, update one pointer
+
+  // delete path, cell is error
+  (await cv.get()).a.set([]);
+  await expect(f.get()).resolves.toBeInstanceOf(Error);
+  expect(sheet.stats).toEqual({ size: 13, count: 14 }); // unchanged
+});

src/cellify.ts

@@ -1,4 +1,5 @@
-import { AnyCell, Cell, ValueCell } from "./cell";
+import { AnyCell, Cell, MapCell, ValueCell } from "./cell";
+import { collector } from "./gc";
 import { SheetProxy } from "./proxy";
 
 // Cellified computes a cellified type.
@@ -21,6 +22,13 @@ export type Uncellified<T> = T extends AnyCell<infer U>
     : U
   : T;
 
+// @todo is type only if true
+// exclude classes
+export const isObject = <K extends string | number | symbol>(
+  v: unknown
+): v is Record<K, unknown> =>
+  typeof v === "object" && v !== null && v.constructor?.name === "Object";
+
 /**
  * cellify converts any value to a Cellified value where each array or record
  * becomes a Cell in canonical form.
@@ -34,9 +42,7 @@ export const _cellify = <T>(proxy: SheetProxy, v: T): Cellified<T> => {
   return proxy.new(
     Array.isArray(v)
       ? v.map((vv) => _cellify(proxy, vv), "cellify.[]")
-      : typeof v === "object" &&
-          v !== null &&
-          v.constructor.prototype === Object.prototype // exclude classes
+      : isObject(v)
         ? Object.fromEntries(
             Object.entries(v).map(
               ([k, vv]) => [k, _cellify(proxy, vv)],
@@ -62,11 +68,7 @@ export const _uncellify = async <T>(
     return Promise.all(
       value.map(async (_element) => await _uncellify(_element))
     ) as Promise<Uncellified<T>>;
-  if (
-    typeof value === "object" &&
-    value !== null &&
-    value.constructor.prototype === Object.prototype // exclude classes
-  )
+  if (isObject(value))
     return Object.fromEntries(
       await Promise.all(
         Object.entries(value).map(async ([k, vv]) => [k, await _uncellify(vv)])
@@ -75,3 +77,33 @@ export const _uncellify = async <T>(
   // Classes, null or base types (string, number, ...)
   return value as Uncellified<T>;
 };
+
+export type Path = (string | number)[];
+
+/**
+ * follow a static path for a Cellified value.
+ */
+export const follow = (
+  proxy: SheetProxy,
+  v: Cellified<unknown>,
+  path: Path,
+  name = "follow"
+) => {
+  const aux = (v: Cellified<unknown>, path: Path, name: string) => {
+    // @todo multi collector?
+    const coll = collector<MapCell<unknown, false>>(proxy);
+    return proxy.map(
+      [v],
+      (_v) => {
+        const key = path[0];
+        const isContainer = Array.isArray(_v) || isObject(_v);
+        if (isContainer && _v[key])
+          return coll(aux(_v[key], path.slice(1), `${name}.${key}`));
+        if (isContainer) throw new Error(`path not found: ${key}`);
+        return _v; // pointer
+      },
+      name
+    );
+  };
+  return aux(v, path, name);
+};

src/index.ts

@@ -41,6 +41,16 @@ export {
   reduce,
   sort
 } from "./array";
+export {
+  _cellify,
+  _uncellify,
+  follow,
+  isObject,
+  type Cellified,
+  type Path,
+  type Uncellified
+} from "./cellify";
 export { Debugger } from "./debug";
 export { jsonStringify } from "./json";
 export { nextSubscriber } from "./next";
+export { asyncReduce, mapObject, reduceObject } from "./object";

src/object.test.ts

@@ -0,0 +1,91 @@
+import { writeFileSync } from "fs";
+import { expect, test } from "vitest";
+
+import { _cellify, _uncellify } from "./cellify";
+import { Debugger } from "./debug";
+import { isEqual } from "./isEqual.test";
+import { asyncReduce, mapObject, reduceObject } from "./object";
+import { delayed } from "./promise";
+import { SheetProxy } from "./proxy";
+import { Sheet } from "./sheet";
+
+test("mapObject", async () => {
+  const sheet = new Sheet();
+  const proxy = new SheetProxy(sheet);
+
+  const obj = _cellify(proxy, { a: 1, b: "foo", c: "bar" });
+  expect(sheet.stats).toEqual({ count: 4, size: 4 });
+  const m = mapObject(proxy, obj, (_k: string, _v: unknown): number =>
+    typeof _v === "string" ? _v.length : (_v as number)
+  );
+
+  // initial value
+  await expect(_uncellify(m)).resolves.toEqual({ a: 1, b: 3, c: 3 });
+  expect(sheet.stats).toEqual({ count: 8, size: 8 });
+
+  // update a field
+  (await (await obj.get()).a).set(4);
+  await expect(_uncellify(m)).resolves.toEqual({ a: 4, b: 3, c: 3 });
+  expect(sheet.stats).toEqual({ count: 8, size: 8 });
+
+  // add a field
+  obj.update((rec) => ({ ...rec, h: proxy.new("hello") }));
+  await expect(_uncellify(obj)).resolves.toEqual({
+    a: 4,
+    b: "foo",
+    c: "bar",
+    h: "hello"
+  });
+  console.log(await _uncellify(m));
+  await expect(_uncellify(m)).resolves.toEqual({ a: 4, b: 3, c: 3, h: 5 });
+  expect(sheet.stats).toEqual({ count: 10, size: 10 });
+
+  // delete a field
+  obj.update((rec) => {
+    const copy = { ...rec };
+    // biome-ignore lint/performance/noDelete: we don't want an undefined field
+    delete copy.a;
+    return copy;
+  });
+  await expect(_uncellify(m)).resolves.toEqual({ b: 3, c: 3, h: 5 });
+  expect(sheet.stats).toEqual({ count: 10, size: 9 }); // gc works
+});
+
+test("asyncReduce", async () => {
+  await expect(
+    asyncReduce([1, 2, 3], (acc, v) => delayed(acc + v, 10), 0)
+  ).resolves.toBe(6);
+});
+
+test(
+  "reduceObject",
+  async () => {
+    const sheet = new Sheet();
+    const debug = new Debugger(sheet);
+    const proxy = new SheetProxy(sheet);
+
+    const l = _cellify(proxy, { a: 1, b: 2, c: 3 });
+    const v = reduceObject(
+      proxy,
+      l,
+      async (acc, _key, v) => delayed(acc + (v as number), 1),
+      0
+    );
+    writeFileSync("reduceObject1.dot", debug.dot("reduceObject before"));
+    await expect(v.consolidatedValue).resolves.toBe(6);
+    expect(sheet.stats).toEqual({ count: 6, size: 6 }); // 3+1 array +1 sum +1 pointer
+
+    // update one cell
+    await (await l.get()).a.set(4);
+    await expect(v.consolidatedValue).resolves.toBe(9);
+    writeFileSync("reduceObject2.dot", debug.dot("reduceObject after update"));
+    expect(sheet.stats).toEqual({ count: 6, size: 6 }); // unchanged
+
+    // add one cell
+    l.update((obj) => ({ ...obj, d: proxy.new(5, "n:5") }));
+    await expect(v.consolidatedValue).resolves.toBe(14);
+    writeFileSync("reduceObject3.dot", debug.dot("reduceObject after add"));
+    expect(sheet.stats).toEqual({ count: 8, size: 7 }); // +1 cell, update pointer
+  },
+  { timeout: 1000 }
+);

src/object.ts

@@ -0,0 +1,106 @@
+import type { AnyCell, MapCell } from "./cell";
+import { collector } from "./gc";
+import type { SheetProxy } from "./proxy";
+
+// @todo introduce a type variable that is a sum type of all possible field types?
+export type CellObject<T> = AnyCell<Record<string, AnyCell<T>>>;
+
+/**
+ * mapObject applies a function to a CellObject.
+ */
+export const mapObject = <NF extends boolean = false>(
+  proxy: SheetProxy,
+  obj: CellObject<unknown>,
+  // @todo return type
+  fn: (
+    key: string,
+    value: unknown,
+    valueCell: AnyCell<unknown>
+  ) => unknown | Promise<unknown>,
+  name = "mapObject",
+  nf?: NF
+): MapCell<Record<string, AnyCell<unknown>>, NF> =>
+  proxy.map(
+    [obj],
+    (cells, prev) => {
+      const set = new Set(Object.keys(prev || {}));
+      const res = Object.fromEntries(
+        Object.entries(cells).map(([k, v]) => {
+          // we reuse a previous cell if the key is the same and still maps to same v
+          const reuse =
+            (prev?.[k] && prev[k].dependencies?.[0] === v.id) || false;
+          if (reuse) set.delete(k);
+          // console.log({ k, reuse, prev: prev?.[k]?.id });
+          return [
+            k,
+            reuse ? prev[k] : proxy.map([v], (_v) => fn(k, _v, v), `[${k}]µ`)
+          ];
+        })
+      );
+      // collect unused previously mapped cells
+      proxy._sheet.collect(...[...set].map((k) => prev[k]));
+      return res;
+    },
+    name,
+    nf
+  );
+
+export const asyncReduce = async <T, U>(
+  array: T[],
+  reducer: (
+    accumulator: U,
+    currentValue: T,
+    currentIndex: number,
+    array: T[]
+  ) => U | Promise<U>,
+  initialValue: U
+): Promise<U> => {
+  let acc: U = initialValue;
+  for (let index = 0; index < array.length; index++) {
+    acc = await reducer(acc, array[index], index, array);
+  }
+  return acc;
+};
+
+/**
+ * reduceObject applies the reducer function `fn` for each
+ * element in `obj`, starting from `init` value.
+ */
+export const reduceObject = <T, R, NF extends boolean = false>(
+  proxy: SheetProxy,
+  obj: CellObject<T>,
+  fn: (
+    acc: R,
+    key: string,
+    value: T,
+    cell?: AnyCell<T>,
+    index?: number
+  ) => R | Promise<R>,
+  init: R,
+  name = "reduceObject",
+  nf?: NF
+): MapCell<R, NF> => {
+  const coll = collector<MapCell<R, NF>>(proxy);
+  return proxy.mapNoPrevious(
+    [obj],
+    (cells) => {
+      const keys = Object.keys(cells);
+      const values = Object.values(cells);
+      // console.log({ reduce: keys, name, count: proxy._sheet.stats.count });
+      return coll(
+        proxy.mapNoPrevious(
+          values,
+          (..._cells) =>
+            asyncReduce(
+              _cells,
+              (acc, _cell, i) => fn(acc, keys[i], _cell, values[i], i),
+              init
+            ),
+          "_reduce"
+        )
+      );
+    },
+    name,
+    nf
+  );
+};