merge: Improved LRUCache (#953)

* feat: added new validation test casses & methods

* style: formated with standard

* feat: added parse method & test cases

* docs: added js docs

* chore: added default import export

Author: fahimfaisaal

Cache/LRUCache.js

@@ -1,40 +1,146 @@
 class LRUCache {
   // LRU Cache to store a given capacity of data
+  #capacity
+
+  /**
+   * @param {number} capacity - the capacity of LRUCache
+   * @returns {LRUCache} - sealed
+   */
   constructor (capacity) {
-    this.cache = new Map()
-    this.capacity = capacity
+    if (!Number.isInteger(capacity) || capacity < 0) {
+      throw new TypeError('Invalid capacity')
+    }
+
+    this.#capacity = ~~capacity
+    this.misses = 0
     this.hits = 0
-    this.miss = 0
+    this.cache = new Map()
+
+    return Object.seal(this)
+  }
+
+  get info () {
+    return Object.freeze({
+      misses: this.misses,
+      hits: this.hits,
+      capacity: this.capacity,
+      size: this.size
+    })
+  }
+
+  get size () {
+    return this.cache.size
   }
 
-  cacheInfo () {
-    // Return the details for the cache instance [hits, misses, capacity, current_size]
-    return `CacheInfo(hits=${this.hits}, misses=${this.miss}, capacity=${this.capacity}, current size=${this.cache.size})`
+  get capacity () {
+    return this.#capacity
   }
 
+  set capacity (newCapacity) {
+    if (newCapacity < 0) {
+      throw new RangeError('Capacity should be greater than 0')
+    }
+
+    if (newCapacity < this.capacity) {
+      let diff = this.capacity - newCapacity
+
+      while (diff--) {
+        this.#removeLeastRecentlyUsed()
+      }
+    }
+
+    this.#capacity = newCapacity
+  }
+
+  /**
+ * delete oldest key existing in map by the help of iterator
+ */
+  #removeLeastRecentlyUsed () {
+    this.cache.delete(this.cache.keys().next().value)
+  }
+
+  /**
+   * @param {string} key
+   * @returns {*}
+   */
+  has (key) {
+    key = String(key)
+
+    return this.cache.has(key)
+  }
+
+  /**
+   * @param {string} key
+   * @param {*} value
+   */
   set (key, value) {
+    key = String(key)
     // Sets the value for the input key and if the key exists it updates the existing key
-    if (this.cache.size === this.capacity) {
-      // delete oldest key existing in map
-      this.cache.delete(this.cache.keys().next().value)
+    if (this.size === this.capacity) {
+      this.#removeLeastRecentlyUsed()
     }
+
     this.cache.set(key, value)
   }
 
+  /**
+   * @param {string} key
+   * @returns {*}
+   */
   get (key) {
+    key = String(key)
     // Returns the value for the input key. Returns null if key is not present in cache
     if (this.cache.has(key)) {
       const value = this.cache.get(key)
+
       // refresh the cache to update the order of key
       this.cache.delete(key)
       this.cache.set(key, value)
-      this.hits += 1
+
+      this.hits++
       return value
-    } else {
-      this.miss += 1
-      return null
     }
+
+    this.misses++
+    return null
+  }
+
+  /**
+   * @param {JSON} json
+   * @returns {LRUCache}
+   */
+  parse (json) {
+    const { misses, hits, cache } = JSON.parse(json)
+
+    this.misses += misses ?? 0
+    this.hits += hits ?? 0
+
+    for (const key in cache) {
+      this.set(key, cache[key])
+    }
+
+    return this
+  }
+
+  /**
+   * @param {number} indent
+   * @returns {JSON} - string
+   */
+  toString (indent) {
+    const replacer = (_, value) => {
+      if (value instanceof Set) {
+        return [...value]
+      }
+
+      if (value instanceof Map) {
+        return Object.fromEntries(value)
+      }
+
+      return value
+    }
+
+    return JSON.stringify(this, replacer, indent)
   }
 }
 
-export { LRUCache }
+export default LRUCache

Cache/test/LRUCache.test.js

@@ -1,9 +1,19 @@
-import { LRUCache } from '../LRUCache'
+import LRUCache from '../LRUCache'
 import { fibonacciCache } from './cacheTest'
 
-describe('LRUCache', () => {
-  it('Example 1 (Small Cache, size=2)', () => {
-    const cache = new LRUCache(2)
+describe('Testing LRUCache', () => {
+  it('Testing with invalid capacity', () => {
+    expect(() => new LRUCache()).toThrow()
+    expect(() => new LRUCache('Invalid')).toThrow()
+    expect(() => new LRUCache(-1)).toThrow()
+    expect(() => new LRUCache(Infinity)).toThrow()
+  })
+
+  it('Example 1 (Small Cache, size = 2)', () => {
+    const cache = new LRUCache(1) // initially capacity
+
+    cache.capacity++ // now the capacity is increasing by one
+
     cache.set(1, 1)
     cache.set(2, 2)
 
@@ -24,14 +34,41 @@ describe('LRUCache', () => {
     expect(cache.get(3)).toBe(3)
     expect(cache.get(4)).toBe(4)
 
-    expect(cache.cacheInfo()).toBe('CacheInfo(hits=6, misses=3, capacity=2, current size=2)')
+    expect(cache.info).toEqual({
+      misses: 3,
+      hits: 6,
+      capacity: 2,
+      size: 2
+    })
+
+    const json = '{"misses":3,"hits":6,"cache":{"3":3,"4":4}}'
+    expect(cache.toString()).toBe(json)
+
+    // merge with json
+    cache.parse(json)
+
+    cache.capacity-- // now the capacity decreasing by one
+
+    expect(cache.info).toEqual({
+      misses: 6,
+      hits: 12,
+      capacity: 1,
+      size: 1
+    })
   })
 
-  it('Example 2 (Computing Fibonacci Series, size=100)', () => {
+  it('Example 2 (Computing Fibonacci Series, size = 100)', () => {
     const cache = new LRUCache(100)
+
     for (let i = 1; i <= 100; i++) {
       fibonacciCache(i, cache)
     }
-    expect(cache.cacheInfo()).toBe('CacheInfo(hits=193, misses=103, capacity=100, current size=98)')
+
+    expect(cache.info).toEqual({
+      misses: 103,
+      hits: 193,
+      capacity: 100,
+      size: 98
+    })
   })
 })