Guida TypeScript: Ottimizzazione delle Prestazioni con la Memoizzazione

1// Tipi per la funzione di memoizzazione
2type AnyFunction = (...args: unknown[]) => unknown;
3type MemoizedFunction<T extends AnyFunction> = T & {
4  clearCache: () => void;
5};
6
7// Tipo per le voci della cache
8interface CacheEntry<T> {
9  value: T;
10  timestamp: number;
11}
12
13// Funzione di memoizzazione base con tipizzazione stretta
14function memoize<T extends AnyFunction>(fn: T): MemoizedFunction<T> {
15  const cache = new Map<string, CacheEntry<ReturnType<T>>>();
16
17  const memoized = (...args: Parameters<T>): ReturnType<T> => {
18    const key = JSON.stringify(args);
19    const cached = cache.get(key);
20
21    if (cached) {
22      console.log(`Cache hit per la chiave: ${key}`);
23      return cached.value;
24    }
25
26    const result = fn(...args);
27    cache.set(key, {
28      value: result,
29      timestamp: Date.now(),
30    });
31    console.log(`Nuovo calcolo per la chiave: ${key}`);
32    return result;
33  };
34
35  // Aggiunta di un metodo per svuotare la cache
36  const memoizedWithClear = memoized as MemoizedFunction<T>;
37  memoizedWithClear.clearCache = () => cache.clear();
38
39  return memoizedWithClear;
40}

1// Tipi per le opzioni di configurazione
2interface MemoizeOptions {
3  maxCacheSize: number;
4  ttl: number; // Time To Live in millisecondi
5  cacheKeyGenerator?: <T extends unknown[]>(...args: T) => string;
6}
7
8// Tipo per le statistiche della cache
9interface CacheStats {
10  hits: number;
11  misses: number;
12  size: number;
13  averageAccessTime: number;
14}
15
16// Implementazione avanzata con gestione completa della cache
17function advancedMemoize<T extends AnyFunction>(
18  fn: T,
19  options: Partial<MemoizeOptions> = {},
20): MemoizedFunction<T> & { getStats: () => CacheStats } {
21  const {
22    maxCacheSize = 1000,
23    ttl = Infinity,
24    cacheKeyGenerator = JSON.stringify,
25  } = options;
26
27  const cache = new Map<string, CacheEntry<ReturnType<T>>>();
28  const stats = {
29    hits: 0,
30    misses: 0,
31    totalAccessTime: 0,
32    accessCount: 0,
33  };
34
35  const memoized = (...args: Parameters<T>): ReturnType<T> => {
36    const startTime = performance.now();
37    const key = cacheKeyGenerator(args);
38    const now = Date.now();
39    const cached = cache.get(key);
40
41    const updateStats = (hit: boolean): void => {
42      const accessTime = performance.now() - startTime;
43      stats.totalAccessTime += accessTime;
44      stats.accessCount += 1;
45      if (hit) stats.hits += 1;
46      else stats.misses += 1;
47    };
48
49    // Verifica della validità della cache
50    if (cached && now - cached.timestamp <= ttl) {
51      updateStats(true);
52      return cached.value;
53    }
54
55    // Rimozione delle voci scadute se necessario
56    if (cached) {
57      cache.delete(key);
58    }
59
60    // Gestione della dimensione della cache
61    if (cache.size >= maxCacheSize) {
62      const oldestKey = cache.keys().next().value;
63      cache.delete(oldestKey);
64    }
65
66    const result = fn(...args);
67    cache.set(key, { value: result, timestamp: now });
68    updateStats(false);
69    return result;
70  };
71
72  // Aggiunta dei metodi di utilità
73  const enhanced = memoized as MemoizedFunction<T> & {
74    getStats: () => CacheStats;
75  };
76  enhanced.clearCache = () => cache.clear();
77  enhanced.getStats = () => ({
78    hits: stats.hits,
79    misses: stats.misses,
80    size: cache.size,
81    averageAccessTime:
82      stats.accessCount > 0 ? stats.totalAccessTime / stats.accessCount : 0,
83  });
84
85  return enhanced;
86}

1type FibonacciFunction = (n: number) => number;
2
3const fibMemoized = memoize<FibonacciFunction>((n) => {
4  if (n <= 1) return n;
5  return fibMemoized(n - 1) + fibMemoized(n - 2);
6});

1interface User {
2  id: string;
3  name: string;
4  email: string;
5}
6
7type FetchUserFunction = (userId: string) => Promise<User>;
8
9const fetchUserDataMemoized = advancedMemoize<FetchUserFunction>(
10  async (userId) => {
11    const response = await fetch(`/api/users/${userId}`);
12    if (!response.ok) {
13      throw new Error(
14        `Impossibile recuperare l'utente: ${response.statusText}`,
15      );
16    }
17    return response.json();
18  },
19  {
20    ttl: 300000, // Cache di 5 minuti
21    maxCacheSize: 100,
22    cacheKeyGenerator: (args) => args[0], // Usa direttamente l'ID come chiave
23  },
24);

1interface DataTransformOptions {
2  format: 'json' | 'xml';
3  version: number;
4}
5
6type TransformFunction = (
7  data: Record<string, unknown>,
8  options: DataTransformOptions,
9) => string;
10
11const transformDataMemoized = advancedMemoize<TransformFunction>(
12  (data, options) => {
13    // Logica di trasformazione...
14    return JSON.stringify(data);
15  },
16  {
17    cacheKeyGenerator: (args) => {
18      const [data, options] = args;
19      return `${JSON.stringify(data)}-${options.format}-${options.version}`;
20    },
21  },
22);

1type MetricsWrapper<T extends AnyFunction> = T & {
2  getMetrics: () => {
3    totalCalls: number;
4    averageExecutionTime: number;
5    cacheEfficiency: number;
6  };
7};
8
9function withMetrics<T extends AnyFunction>(fn: T): MetricsWrapper<T> {
10  const metrics = {
11    calls: 0,
12    totalTime: 0,
13    cacheHits: 0,
14  };
15
16  const wrapped = (...args: Parameters<T>): ReturnType<T> => {
17    const start = performance.now();
18    const result = fn(...args);
19    metrics.totalTime += performance.now() - start;
20    metrics.calls += 1;
21
22    return result;
23  };
24
25  const enhanced = wrapped as MetricsWrapper<T>;
26  enhanced.getMetrics = () => ({
27    totalCalls: metrics.calls,
28    averageExecutionTime: metrics.totalTime / metrics.calls,
29    cacheEfficiency: metrics.cacheHits / metrics.calls,
30  });
31
32  return enhanced;
33}