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> Cacheble Utils

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`@cacheable/utils` is a collecton of utility functions, helpers, and types for `cacheable` and other caching libraries. It provides a robust set of features to enhance caching capabilities, including:

* Data Types for Caching Items
* Hash Functions for Key Generation
* Coalesce Async for Handling Multiple Promises
* Stats Helpers for Caching Statistics
* Sleep / Delay for Testing and Timing
* Memoization for wraping or get / set options
* Time to Live (TTL) Helpers

# Table of Contents
* [Getting Started](#getting-started)
* [Cacheable Types](#cacheable-types)
* [Coalesce Async](#coalesce-async)
* [Hash Functions](#hash-functions)
* [Shorthand Time Helpers](#shorthand-time-helpers)
* [Sleep Helper](#sleep-helper)
* [Stats Helpers](#stats-helpers)
* [Time to Live (TTL) Helpers](#time-to-live-ttl-helpers)
* [Run if Function Helper](#run-if-function-helper)
* [Less Than Helper](#less-than-helper)
* [Is Object Helper](#is-object-helper)
* [Wrap / Memoization for Sync and Async Functions](#wrap--memoization-for-sync-and-async-functions)
* [Get Or Set Memoization Function](#get-or-set-memoization-function)
* [How to Contribute](#how-to-contribute)
* [License and Copyright](#license-and-copyright)

# Getting Started

```bash
npm install @cacheable/utils --save
```

# Cacheable Types

The `@cacheable/utils` package provides various types that are used throughout the caching library. These types help in defining the structure of cached items, ensuring type safety and consistency across your caching operations.

```typescript

/**
 * CacheableItem
 * @typedef {Object} CacheableItem
 * @property {string} key - The key of the cacheable item
 * @property {any} value - The value of the cacheable item
 * @property {number|string} [ttl] - Time to Live - If you set a number it is miliseconds, if you set a string it is a human-readable
 * format such as `1s` for 1 second or `1h` for 1 hour. Setting undefined means that it will use the default time-to-live. If both are
 * undefined then it will not have a time-to-live.
 */
export type CacheableItem = {
	key: string;
	value: any;
	ttl?: number | string;
};

/**
 * CacheableStoreItem
 * @typedef {Object} CacheableStoreItem
 * @property {string} key - The key of the cacheable store item
 * @property {any} value - The value of the cacheable store item
 * @property {number} [expires] - The expiration time in milliseconds since epoch. If not set, the item does not expire.
 */
export type CacheableStoreItem = {
	key: string;
	value: any;
	expires?: number;
};
```

# Coalesce Async

The `coalesceAsync` function is a utility that allows you to handle multiple asynchronous operations efficiently. It was designed by `Douglas Cayers` https://github.com/douglascayers/promise-coalesce. It helps in coalescing multiple promises into a single promise, ensuring that only one operation is executed at a time for the same key.

```typescript
import { coalesceAsync } from '@cacheable/utils';

const fetchData = async (key: string) => {
  // Simulate an asynchronous operation
  return new Promise((resolve) => setTimeout(() => resolve(`Data for ${key}`), 1000));
};

const result = await Promise.all([
	coalesceAsync('my-key', fetchData),
	coalesceAsync('my-key', fetchData),
	coalesceAsync('my-key', fetchData),
]);
console.log(result); // Data for my-key only executed once
```

# Hash Functions

The `@cacheable/utils` package provides hash functions that can be used to generate unique keys for caching operations. These functions are useful for creating consistent and unique identifiers for cached items.

The hashing API provides both **async** (for cryptographic algorithms) and **sync** (for non-cryptographic algorithms) methods.

## Async Hashing (Cryptographic Algorithms)

Use `hash()` and `hashToNumber()` for cryptographic algorithms like SHA-256, SHA-384, and SHA-512:

```typescript
import { hash, hashToNumber, HashAlgorithm } from '@cacheable/utils';

// Hash using SHA-256 (default)
const key = await hash('my-cache-key');
console.log(key); // Unique hash for 'my-cache-key'

// Hash with specific algorithm
const sha512Hash = await hash('my-data', { algorithm: HashAlgorithm.SHA512 });

// Convert hash to number within range
const min = 0;
const max = 10;
const result = await hashToNumber({foo: 'bar'}, { min, max, algorithm: HashAlgorithm.SHA256 });
console.log(result); // A number between 0 and 10 based on the hash value
```

## Sync Hashing (Non-Cryptographic Algorithms)

Use `hashSync()` and `hashToNumberSync()` for faster, non-cryptographic algorithms like DJB2, FNV1, MURMER, and CRC32:

```typescript
import { hashSync, hashToNumberSync, HashAlgorithm } from '@cacheable/utils';

// Hash using DJB2 (default for sync)
const key = hashSync('my-cache-key');
console.log(key); // Unique hash for 'my-cache-key'

// Hash with specific algorithm
const fnv1Hash = hashSync('my-data', { algorithm: HashAlgorithm.FNV1 });

// Convert hash to number within range
const min = 0;
const max = 10;
const result = hashToNumberSync({foo: 'bar'}, { min, max, algorithm: HashAlgorithm.DJB2 });
console.log(result); // A number between 0 and 10 based on the hash value
```

## Available Hash Algorithms

**Cryptographic (Async):**
- `HashAlgorithm.SHA256` - SHA-256 (default for async methods)
- `HashAlgorithm.SHA384` - SHA-384
- `HashAlgorithm.SHA512` - SHA-512

**Non-Cryptographic (Sync):**
- `HashAlgorithm.DJB2` - DJB2 (default for sync methods)
- `HashAlgorithm.FNV1` - FNV-1
- `HashAlgorithm.MURMER` - Murmur hash
- `HashAlgorithm.CRC32` - CRC32

# Shorthand Time Helpers

The `@cacheable/utils` package provides a shorthand function to convert human-readable time strings into milliseconds. This is useful for setting time-to-live (TTL) values in caching operations.

You can also use the `shorthandToMilliseconds` function:

```typescript
import { shorthandToMilliseconds } from '@cacheable/utils';

const milliseconds = shorthandToMilliseconds('1h');
console.log(milliseconds); // 3600000
```

You can also use the `shorthandToTime` function to get the current date plus the shorthand time:

```typescript
import { shorthandToTime } from '@cacheable/utils';

const currentDate = new Date();
const timeInMs = shorthandToTime('1h', currentDate);
console.log(timeInMs); // Current date + 1 hour in milliseconds since epoch
```

# Sleep Helper

The `sleep` function is a utility that allows you to pause execution for a specified duration. This can be useful in testing scenarios or when you need to introduce delays in your code.

```typescript
import { sleep } from '@cacheable/utils';

await sleep(1000); // Pause for 1 second
console.log('Execution resumed after 1 second');
```

# Stats Helpers

The `@cacheable/utils` package provides statistics helpers that can be used to track and analyze caching operations. These helpers can be used to gather metrics such as hit rates, miss rates, and other performance-related statistics.

```typescript
import { stats } from '@cacheable/utils';

const cacheStats = stats();
cacheStats.incrementHits();
console.log(cacheStats.hits); // Get the hit rate of the cache
```

# Time to Live (TTL) Helpers

The `@cacheable/utils` package provides helpers for managing time-to-live (TTL) values for cached items. 

You can use the `calculateTtlFromExpiration` function to calculate the TTL based on an expiration date:

```typescript
import { calculateTtlFromExpiration } from '@cacheable/utils';

const expirationDate = new Date(Date.now() + 1000 * 60 * 5); // 5 minutes from now
const ttl = calculateTtlFromExpiration(Date.now(), expirationDate);
console.log(ttl); // 300000
```

You can also use `getTtlFromExpires` to get the TTL from an expiration date:

```typescript
import { getTtlFromExpires } from '@cacheable/utils';

const expirationDate = new Date(Date.now() + 1000 * 60 * 5); // 5 minutes from now
const ttl = getTtlFromExpires(expirationDate);
console.log(ttl); // 300000
```

You can use `getCascadingTtl` to get the TTL for cascading cache operations:

```typescript
import { getCascadingTtl } from '@cacheable/utils';
const cacheableTtl = 1000 * 60 * 5; // 5 minutes
const primaryTtl = 1000 * 60 * 2; // 2 minutes
const secondaryTtl = 1000 * 60; // 1 minute
const ttl = getCascadingTtl(cacheableTtl, primaryTtl, secondaryTtl);
```

# Run if Function Helper

The `runIfFn` utility function provides a convenient way to conditionally execute functions or return values based on whether the input is a function or not. This pattern is commonly used in UI libraries and configuration systems where values can be either static or computed.

```typescript
import { runIfFn } from '@cacheable/utils';

// Static value - returns the value as-is
const staticValue = runIfFn('hello world');
console.log(staticValue); // 'hello world'

// Function with no arguments - executes the function
const dynamicValue = runIfFn(() => new Date().toISOString());
console.log(dynamicValue); // Current timestamp

// Function with arguments - executes with provided arguments
const sum = runIfFn((a: number, b: number) => a + b, 5, 10);
console.log(sum); // 15

// Complex example with conditional logic
const getConfig = (isDevelopment: boolean) => ({
  apiUrl: isDevelopment ? 'http://localhost:3000' : 'https://api.example.com',
  timeout: isDevelopment ? 5000 : 30000
});

const config = runIfFn(getConfig, true);
console.log(config); // { apiUrl: 'http://localhost:3000', timeout: 5000 }
```

# Less Than Helper

The `lessThan` utility function provides a safe way to compare two values and determine if the first value is less than the second. It only performs the comparison if both values are valid numbers, returning `false` for any non-number inputs.

```typescript
import { lessThan } from '@cacheable/utils';

// Basic number comparisons
console.log(lessThan(1, 2)); // true
console.log(lessThan(2, 1)); // false
console.log(lessThan(1, 1)); // false

// Works with negative numbers
console.log(lessThan(-1, 0)); // true
console.log(lessThan(-2, -1)); // true

// Works with decimal numbers
console.log(lessThan(1.5, 2.5)); // true
console.log(lessThan(2.7, 2.7)); // false

// Safe handling of non-number values
console.log(lessThan("1", 2)); // false
console.log(lessThan(1, "2")); // false
console.log(lessThan(null, 1)); // false
console.log(lessThan(undefined, 1)); // false
console.log(lessThan(NaN, 1)); // false

// Useful in filtering and sorting operations
const numbers = [5, 2, 8, 1, 9];
const lessThanFive = numbers.filter(n => lessThan(n, 5));
console.log(lessThanFive); // [2, 1]

// Safe comparison in conditional logic
function processValue(a?: number, b?: number) {
  if (lessThan(a, b)) {
    return `${a} is less than ${b}`;
  }
  return 'Invalid comparison or a >= b';
}
```

This utility is particularly useful when dealing with potentially undefined or invalid numeric values, ensuring type safety in comparison operations.

# Is Object Helper

The `isObject` utility function provides a type-safe way to determine if a value is a plain object. It returns `true` for objects but `false` for arrays, `null`, functions, and primitive types. This function also serves as a TypeScript type guard.

```typescript
import { isObject } from '@cacheable/utils';

// Basic object detection
console.log(isObject({})); // true
console.log(isObject({ name: 'John', age: 30 })); // true
console.log(isObject(Object.create(null))); // true

// Arrays are not considered objects
console.log(isObject([])); // false
console.log(isObject([1, 2, 3])); // false

// null is not considered an object (despite typeof null === 'object')
console.log(isObject(null)); // false

// Primitive types return false
console.log(isObject('string')); // false
console.log(isObject(123)); // false
console.log(isObject(true)); // false
console.log(isObject(undefined)); // false

// Functions return false
console.log(isObject(() => {})); // false
console.log(isObject(Date)); // false

// Built-in object types return true
console.log(isObject(new Date())); // true
console.log(isObject(/regex/)); // true
console.log(isObject(new Error('test'))); // true
console.log(isObject(new Map())); // true

// TypeScript type guard usage
function processValue(value: unknown) {
  if (isObject<{ name: string; age: number }>(value)) {
    // TypeScript now knows value is an object with name and age properties
    console.log(`Name: ${value.name}, Age: ${value.age}`);
  }
}

// Useful for configuration validation
function validateConfig(config: unknown) {
  if (!isObject(config)) {
    throw new Error('Configuration must be an object');
  }
  
  // Safe to access object properties
  return config;
}

// Filtering arrays for objects only
const mixedArray = [1, 'string', {}, [], null, { valid: true }];
const objectsOnly = mixedArray.filter(isObject);
console.log(objectsOnly); // [{}', { valid: true }]
```

This utility is particularly useful for:
- **Type validation** - Ensuring values are objects before accessing properties
- **TypeScript type guarding** - Narrowing types in conditional blocks
- **Configuration parsing** - Validating that configuration values are objects
- **Data filtering** - Separating objects from other data types

# Wrap / Memoization for Sync and Async Functions

The `@cacheable/utils` package provides two main functions: `wrap` and `wrapSync`. These functions are used to memoize asynchronous and synchronous functions, respectively.

```javascript
import { Cacheable } from 'cacheable';
const asyncFunction = async (value: number) => {
  return Math.random() * value;
};

const cache = new Cacheable();
const options = {
  ttl: '1h', // 1 hour
  keyPrefix: 'p1', // key prefix. This is used if you have multiple functions and need to set a unique prefix.
  cache,
}
const wrappedFunction = wrap(asyncFunction, options);
console.log(await wrappedFunction(2)); // 4
console.log(await wrappedFunction(2)); // 4 from cache
```
With `wrap` we have also included stampede protection so that a `Promise` based call will only be called once if multiple requests of the same are executed at the same time. Here is an example of how to test for stampede protection:
  
```javascript
import { Cacheable } from 'cacheable';
const asyncFunction = async (value: number) => {
  return value;
};

const cache = new Cacheable();
const options = {
  ttl: '1h', // 1 hour
  keyPrefix: 'p1', // key prefix. This is used if you have multiple functions and need to set a unique prefix.
  cache,
}

const wrappedFunction = wrap(asyncFunction, options);
const promises = [];
for (let i = 0; i < 10; i++) {
  promises.push(wrappedFunction(i));
}

const results = await Promise.all(promises); // all results should be the same

console.log(results); // [0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
```

In this example we are wrapping an `async` function in a cache with a `ttl` of `1 hour`. This will cache the result of the function for `1 hour` and then expire the value. You can also wrap a `sync` function in a cache:

```javascript
import { CacheableMemory } from 'cacheable';
const syncFunction = (value: number) => {
  return value * 2;
};

const cache = new CacheableMemory();
const wrappedFunction = wrap(syncFunction, { ttl: '1h', key: 'syncFunction', cache });
console.log(wrappedFunction(2)); // 4
console.log(wrappedFunction(2)); // 4 from cache
```

In this example we are wrapping a `sync` function in a cache with a `ttl` of `1 hour`. This will cache the result of the function for `1 hour` and then expire the value. You can also set the `key` property in the `wrap()` options to set a custom key for the cache.

When an error occurs in the function it will not cache the value and will return the error. This is useful if you want to cache the results of a function but not cache the error. If you want it to cache the error you can set the `cacheError` property to `true` in the `wrap()` options. This is disabled by default.

```javascript
import { CacheableMemory } from 'cacheable';
const syncFunction = (value: number) => {
  throw new Error('error');
};

const cache = new CacheableMemory();
const wrappedFunction = wrap(syncFunction, { ttl: '1h', key: 'syncFunction', cacheError: true, cache });
console.log(wrappedFunction()); // error
console.log(wrappedFunction()); // error from cache
```

If you would like to generate your own key for the wrapped function you can set the `createKey` property in the `wrap()` options. This is useful if you want to generate a key based on the arguments of the function or any other criteria.

```javascript
  const cache = new Cacheable();
  const options: WrapOptions = {
    cache,
    keyPrefix: 'test',
    createKey: (function_, arguments_, options: WrapOptions) => `customKey:${options?.keyPrefix}:${arguments_[0]}`,
  };

  const wrapped = wrap((argument: string) => `Result for ${argument}`, options);

  const result1 = await wrapped('arg1');
  const result2 = await wrapped('arg1'); // Should hit the cache

  console.log(result1); // Result for arg1
  console.log(result2); // Result for arg1 (from cache)
```

We will pass in the `function` that is being wrapped, the `arguments` passed to the function, and the `options` used to wrap the function. You can then use these to generate a custom key for the cache.

# Get Or Set Memoization Function

The `getOrSet` method provides a convenient way to implement the cache-aside pattern. It attempts to retrieve a value from cache, and if not found, calls the provided function to compute the value and store it in cache before returning it. Here are the options:

```typescript
export type GetOrSetFunctionOptions = {
	ttl?: number | string;
	cacheErrors?: boolean;
	throwErrors?: boolean;
};
```

Here is an example of how to use the `getOrSet` method:

```javascript
import { Cacheable } from 'cacheable';
const cache = new Cacheable();
// Use getOrSet to fetch user data
const function_ = async () => Math.random() * 100;
const value = await getOrSet('randomValue', function_, { ttl: '1h', cache });
console.log(value); // e.g. 42.123456789
```

You can also use a function to compute the key for the function:

```javascript
import { Cacheable, GetOrSetOptions } from 'cacheable';
const cache = new Cacheable();

// Function to generate a key based on options
const generateKey = (options?: GetOrSetOptions) => {
  return `custom_key_:${options?.cacheId || 'default'}`;
};

const function_ = async () => Math.random() * 100;
const value = await getOrSet(generateKey(), function_, { ttl: '1h', cache });
```

# How to Contribute

You can contribute by forking the repo and submitting a pull request. Please make sure to add tests and update the documentation. To learn more about how to contribute go to our main README [https://github.com/jaredwray/cacheable](https://github.com/jaredwray/cacheable). This will talk about how to `Open a Pull Request`, `Ask a Question`, or `Post an Issue`.

# License and Copyright
[MIT © Jared Wray](./LICENSE)
