Deep utils (deepMerge, deepEquals, deepHash) (#11)

package.json

@@ -30,6 +30,7 @@
     "@types/react": "18.0.0",
     "react": "18.0.0",
     "bun-types": "1.0.21",
-    "typescript": "^5.3.3"
+    "typescript": "^5.3.3",
+    "fast-check": "^3.15.0"
   }
 }

src/plugin-sync.ts

@@ -45,7 +45,7 @@ export type SyncOptions<T extends AnyState, F extends SyncFunction<T>> = {
    *
    * Uses `JSON.stringify` by default.
    */
-  hash?: (state: T, ...extra: ExtraArgs<F>) => string;
+  hash?: (state: T, ...extra: ExtraArgs<F>) => string | number;
 };
 
 /** Configure how to pull a new state into the store. */
@@ -67,7 +67,7 @@ export type PullOptions<P extends PullFunction<any>> = {
    *
    * Uses `JSON.stringify` by default.
    */
-  hash?: (...args: Parameters<P>) => string;
+  hash?: (...args: Parameters<P>) => string | number;
 };
 
 /** Extracts a record of the user-defined sync functions from a setup object. */

src/util-cache.ts

@@ -1,17 +1,20 @@
 /** A function that returns a value. */
 export type ValueFactory<T> = () => T;
 
+/** A key to store a value under in the cache. */
+export type CacheKey = string | number;
+
 /** A function that returns a value from the cache. */
 export type CacheGetter<T> = {
   /** Gets the value from the cache, or `null` if it is not found. */
-  (key: string): T | null;
+  (key: CacheKey): T | null;
   /**
    * Gets the value from the cache, or creates (and stores) it if it is not found.
    * @param key The key of the value to get.
    * @param create A factory function that returns a value.
    * @param lifetime (Optionally) How long to keep the value in the cache, in milliseconds.
    */
-  (key: string, create: ValueFactory<T>, lifetime?: number): T;
+  (key: CacheKey, create: ValueFactory<T>, lifetime?: number): T;
 };
 
 /** A cache of values that can be either transient or permanent. */
@@ -28,15 +31,15 @@ export type Cache<T> = {
    * @param input A value, or a tuple of a value and a lifetime in milliseconds.
    * @param lifetime (Optionally) How long to keep the value in the cache, in milliseconds.
    */
-  set: (key: string, input: T, lifetime?: number) => T;
+  set: (key: CacheKey, input: T, lifetime?: number) => T;
   /**
    * Removes a value from the cache, optionally after a delay.
    * @param key The key of the value to evict.
    * @param delay (Optionally) How long to wait before evicting the value, in milliseconds.
    * If set to zero or less, evicts the value immediately (default)
    * If set to `Infinity`, makes the function no-op.
    */
-  evict: (key: string, delay?: number) => void;
+  evict: (key: CacheKey, delay?: number) => void;
 };
 
 /** Configure how to create a cache. */
@@ -64,10 +67,10 @@ export type CacheOptions = {
  * ```
  */
 export default function createCache<T>(options: CacheOptions = {}): Cache<T> {
-  const entries = new Map<string, T>();
+  const entries = new Map<CacheKey, T>();
   const defaultLifetime = options.lifetime ?? Infinity;
 
-  const set = (key: string, value: T, lifetime = defaultLifetime) => {
+  const set = (key: CacheKey, value: T, lifetime = defaultLifetime) => {
     if (lifetime > 0) {
       entries.set(key, value);
       evict(key, lifetime);
@@ -76,15 +79,15 @@ export default function createCache<T>(options: CacheOptions = {}): Cache<T> {
     return value;
   };
 
-  const get = ((key: string, create?: ValueFactory<T>, lifetime?: number) => {
+  const get = ((key: CacheKey, create?: ValueFactory<T>, lifetime?: number) => {
     const entry = entries.get(key);
 
     if (entry) return entry;
     else if (!create) return null;
     else return set(key, create(), lifetime);
   }) as CacheGetter<T>;
 
-  const evict = (key: string, delay?: number) => {
+  const evict = (key: CacheKey, delay?: number) => {
     if (delay === Infinity) return;
     if (!delay || delay < 0) entries.delete(key);
     else setTimeout(() => entries.delete(key), delay);

src/util-dedupe.ts

@@ -23,7 +23,7 @@ export type DedupeOptions<T extends AsyncFunction> = {
    *
    * Uses `JSON.stringify` by default.
    */
-  hash?: (...args: Parameters<T>) => string;
+  hash?: (...args: Parameters<T>) => string | number;
 };
 
 /**
@@ -44,7 +44,7 @@ export default function dedupe<T extends AsyncFunction<any>>(
   fn: T,
   options: DedupeOptions<T> = {}
 ): T {
-  let oldHash: string | undefined;
+  let oldHash: string | number | undefined;
   let promise: Promise<any> | undefined;
   let handle: any;
 

src/util-deep-equals.spec.ts

@@ -0,0 +1,80 @@
+import { test, expect, describe } from "bun:test";
+import deepEquals from "./util-deep-equals";
+
+describe("value equality", () => {
+  test("null", () => expect(deepEquals(null, null)).toBe(true));
+  test("undefined", () => expect(deepEquals(undefined, undefined)).toBe(true));
+  test("string", () => expect(deepEquals("a", "a")).toBe(true));
+  test("number", () => expect(deepEquals(1, 1)).toBe(true));
+  test("boolean", () => expect(deepEquals(true, true)).toBe(true));
+  test("empty array", () => expect(deepEquals([], [])).toBe(true));
+  test("empty object", () => expect(deepEquals({}, {})).toBe(true));
+});
+
+describe("value inequality", () => {
+  test("null vs undefined", () =>
+    expect(deepEquals(null, undefined)).toBe(false));
+  test("null vs string", () => expect(deepEquals(null, "a")).toBe(false));
+  test("null vs number", () => expect(deepEquals(null, 1)).toBe(false));
+  test("null vs boolean", () => expect(deepEquals(null, true)).toBe(false));
+  test("null vs array", () => expect(deepEquals(null, [])).toBe(false));
+  test("null vs object", () => expect(deepEquals(null, {})).toBe(false));
+  test("undefined vs string", () =>
+    expect(deepEquals(undefined, "a")).toBe(false));
+  test("undefined vs number", () =>
+    expect(deepEquals(undefined, 1)).toBe(false));
+  test("undefined vs boolean", () =>
+    expect(deepEquals(undefined, true)).toBe(false));
+  test("undefined vs array", () =>
+    expect(deepEquals(undefined, [])).toBe(false));
+  test("undefined vs object", () =>
+    expect(deepEquals(undefined, {})).toBe(false));
+  test("string vs number", () => expect(deepEquals("a", 1)).toBe(false));
+  test("string vs boolean", () => expect(deepEquals("a", true)).toBe(false));
+  test("string vs array", () => expect(deepEquals("a", [])).toBe(false));
+  test("string vs object", () => expect(deepEquals("a", {})).toBe(false));
+  test("number vs boolean", () => expect(deepEquals(1, true)).toBe(false));
+  test("number vs array", () => expect(deepEquals(1, [])).toBe(false));
+  test("number vs object", () => expect(deepEquals(1, {})).toBe(false));
+  test("boolean vs array", () => expect(deepEquals(true, [])).toBe(false));
+  test("boolean vs object", () => expect(deepEquals(true, {})).toBe(false));
+  test("array vs object", () => expect(deepEquals([], {})).toBe(false));
+});
+
+describe("array equality", () => {
+  test("single element", () => expect(deepEquals([1], [1])).toBe(true));
+  test("multiple elements", () =>
+    expect(deepEquals([1, 2, 3], [1, 2, 3])).toBe(true));
+  test("nested arrays", () =>
+    expect(deepEquals([1, [2, 3], 4], [1, [2, 3], 4])).toBe(true));
+});
+
+describe("array inequality", () => {
+  test("different lengths", () =>
+    expect(deepEquals([1, 2], [1, 2, 3])).toBe(false));
+  test("different elements", () =>
+    expect(deepEquals([1, 2, 3], [1, 2, 4])).toBe(false));
+  test("different nested arrays", () =>
+    expect(deepEquals([1, [2, 3], 4], [1, [2, 4], 4])).toBe(false));
+});
+
+describe("object equality", () => {
+  test("single key", () => expect(deepEquals({ a: 1 }, { a: 1 })).toBe(true));
+  test("multiple keys", () =>
+    expect(deepEquals({ a: 1, b: 2 }, { a: 1, b: 2 })).toBe(true));
+  test("nested objects", () =>
+    expect(deepEquals({ a: 1, b: { c: 2 } }, { a: 1, b: { c: 2 } })).toBe(
+      true
+    ));
+});
+
+describe("object inequality", () => {
+  test("different keys", () =>
+    expect(deepEquals({ a: 1 }, { b: 1 })).toBe(false));
+  test("different values", () =>
+    expect(deepEquals({ a: 1 }, { a: 2 })).toBe(false));
+  test("different nested objects", () =>
+    expect(deepEquals({ a: 1, b: { c: 2 } }, { a: 1, b: { c: 3 } })).toBe(
+      false
+    ));
+});

src/util-deep-equals.ts

@@ -0,0 +1,60 @@
+import isObject from "./util-is-object";
+
+/** An object that is either a plain array or plain object. */
+type Indexed = { [key: string | number]: any };
+
+/**
+ * Checks if the given values are equal.
+ *
+ * Note: Only plain objects and arrays are compared recursively.
+ * Classes and other objects are compared with `Object.is`.
+ * @param left The left value to compare.
+ * @param right The right value to compare.
+ * @example
+ * ```ts
+ * // Both true:
+ * deepEquals(
+ *  { a: 1 },
+ *  { a: 1 }
+ * )
+ * deepEquals(
+ *  { a: 1, b: { c: 2 } },
+ *  { a: 1, b: { c: 2 } }
+ * )
+ *
+ * // Both false:
+ * deepEquals(
+ *  { a: 1 },
+ *  { a: 2, b: 2 }
+ * )
+ * deepEquals(
+ *  { a: 1, b: { c: [] } },
+ *  { a: 1, b: { c: [] } }
+ * )
+ * ```
+ */
+const deepEquals = <T>(left: T, right: unknown): right is T => {
+  if (Object.is(left, right)) return true;
+  if (!isIndexed(left) || !isIndexed(right)) return false;
+  if (!isSamePrototype(left, right)) return false;
+
+  const leftKeys = Object.keys(left);
+  const rightKeys = Object.keys(right);
+
+  if (leftKeys.length !== rightKeys.length) return false;
+
+  for (const key of leftKeys) {
+    if (!(key in right)) return false;
+    if (!deepEquals(left[key], right[key])) return false;
+  }
+
+  return true;
+};
+
+const isIndexed = (value: unknown): value is Indexed =>
+  Array.isArray(value) || isObject(value);
+
+const isSamePrototype = <T>(left: T, right: unknown): right is T =>
+  Object.getPrototypeOf(left) === Object.getPrototypeOf(right);
+
+export default deepEquals;

src/util-deep-hash.spec.ts

@@ -0,0 +1,137 @@
+import { expect, test } from "bun:test";
+import fc from "fast-check";
+import deepHash from "./util-deep-hash";
+import { deepEquals } from "bun";
+
+const VERBOSE = false;
+const COLLISION_TEST = true;
+const ITERATIONS = process.env.CI ? 10_000 : 100_000;
+
+test("clones have the same hash", () => {
+  fc.assert(
+    fc.property(
+      fc.anything(),
+      (value) => deepHash(value) === deepHash(structuredClone(value))
+    )
+  );
+});
+
+test("true !== false", () => {
+  expect(deepHash(true)).not.toBe(deepHash(false));
+});
+
+test("null !== undefined", () => {
+  expect(deepHash(null)).not.toBe(deepHash(undefined));
+});
+
+test("increment changes", () => {
+  for (let i = -10000000; i < 10000000; i += 2) {
+    expect(deepHash(i)).not.toBe(deepHash(i + 1));
+  }
+});
+
+test.if(!process.env.CI)("16-bit range", () => {
+  const map = new Map<number, number>();
+
+  for (let i = -32768; i < -32767; i++) {
+    const hash = deepHash(i);
+    expect(map.has(hash)).toBe(false);
+    map.set(hash, i);
+  }
+});
+
+const fuzzTest = (arb: fc.Arbitrary<any>, count = 1) => {
+  return (name: string, runs: number) => {
+    test.skipIf(!COLLISION_TEST)(`hash ${name} (x${runs})`, () => {
+      let collisions = 0;
+      let identical = 0;
+
+      fc.assert(
+        fc.property(
+          fc.array(arb, { minLength: count, maxLength: count }),
+          fc.array(arb, { minLength: count, maxLength: count }),
+          (left, right) => {
+            if (deepEquals(left, right)) {
+              identical++;
+              if (VERBOSE) {
+                console.log("Identical:", left, "=", right);
+              }
+              return;
+            }
+
+            if (VERBOSE) {
+              console.log("Test:", left, "!==", right);
+            }
+
+            const leftHash = deepHash(...left);
+            const rightHash = deepHash(...right);
+
+            if (leftHash === rightHash) {
+              console.error("FAIL:", left, "===", right);
+              collisions++;
+            }
+          }
+        ),
+        {
+          numRuns: runs,
+          seed: Date.now(),
+          ignoreEqualValues: true,
+        }
+      );
+
+      console.log(
+        `Collisions: ${collisions}/${runs - identical}. ` +
+          `(${identical} identical)`
+      );
+      expect(collisions).toBe(0);
+    });
+  };
+};
+
+fuzzTest(fc.integer({ min: -25_000_000, max: 25_000_000 }))(
+  "reasonable integers",
+  ITERATIONS
+);
+
+fuzzTest(fc.double({ min: -25_000_000, max: 25_000_000 }))(
+  "reasonable doubles",
+  ITERATIONS
+);
+
+fuzzTest(fc.string({ minLength: 1, maxLength: 32 }), 10)(
+  "short strings",
+  ITERATIONS
+);
+
+fuzzTest(fc.string({ minLength: 32, maxLength: 256 }), 10)(
+  "long strings",
+  ITERATIONS
+);
+
+fuzzTest(fc.unicodeString({ minLength: 1, maxLength: 32 }), 10)(
+  "short unicode strings",
+  ITERATIONS
+);
+
+fuzzTest(fc.unicodeString({ minLength: 32, maxLength: 256 }), 10)(
+  "long unicode strings",
+  ITERATIONS
+);
+
+fuzzTest(
+  fc.record({
+    id: fc.uuid(),
+    email: fc.emailAddress({ size: "small" }),
+    username: fc.option(fc.asciiString({ minLength: 1, maxLength: 12 })),
+  })
+)("user states", ITERATIONS);
+
+fuzzTest(
+  fc.array(
+    fc.record({
+      id: fc.uuid(),
+      text: fc.string({ minLength: 1, maxLength: 32 }),
+      completed: fc.boolean(),
+    })
+  )
+)("todo lists", ITERATIONS);