Implementation of Redis-like cache - a key-value store with expiring keys. Data is stored in the Val Town SQLite database and shared between all your vals.

1. First you should decide on a name of a SQL table that will be used for storing cache data. It could something like cacheData or kv. Set that value to a new Environment Variable CACHE_TABLE_NAME.
2. Optionally you might add a new CACHE_DEFAULT_TTL Environment Variable. It's value should be set to a number of seconds that will be used when saving new values to the cache without providing the expiration time. By default it's 24h.
3. The setup() function should be ran before using the cache for the first time. You can do that by creating a small temporary Val:

   import { setup } from "https://esm.town/v/xkonti/cache";
   await setup();

4. Optionally create a scheduled val that will delete expired keys on some interval - 15 minutes can be a good start.

   import { deleteExpired } from "https://esm.town/v/xkonti/cache";
   export default async function cacheCleaner(interval: Interval) {
     await deleteExpired();
   }

After setting your cache up you can use it simply by importing functions from https://esm.town/v/xkonti/cache.

Set a value in the cache.

• key - the key to set the value for
• value - the value to set - it can be any value that can be serialized to JSON
• ttl - the time to live in seconds. In other words, after how many seconds the key will expire. If not set, the default TTL is used.
• returns the number of keys set: 1 if the key was inserted/updated, 0 if the ttl was 0 or invalid

// Set a value in the cache with a default TTL
await set("luckyNumber", 13);

// Set a value that will expire in 5 minutes
await set("product:344798", { name: "Audio Interface", price: 209.99}, 5 * 60);

Set a value in the cache until a specific date and time.

• key - the key to set the value for
• value - the value to set - it can be any value that can be serialized to JSON
• expiresAt - the expiration time as a UTC date string
• returns the number of keys set: 1 if the key was inserted/updated, 0 if the `expiresAt`` was in the past

// Set a value in the cache until 2024-01-01 16:23:05 UTC
await setUntil(
  "product:155392", 
  { name: "Audio Interface", price: 209.99 },
  new Date('2024-01-01T16:23:05Z').toISOString()
);

Update the expiration date of a cache entry based on TTL. If the key does not exist or is expired, nothing happens.

• key - the key of the cache entry to update
• ttl - the time to live in seconds from now. In other words, after how many seconds the key will expire. If not set, the default TTL is used.
• returns the number of keys updated: 1 if updated, 0 if not found or ttl was 0

// Set the expiration date in the cache with a default TTL
await setExpiration("luckyNumber");

// Set the expiration date in the cache for 5 minutes from now.
await setExpiration("luckyNumber", 5 * 60);

Update the expiration date of a cache entry to a specific UTC date and time. If the key does not exist or is expired, nothing happens.

• key - the key of the cache entry to update
• expiresAt - the expiration time as a UTC date string
• returns the number of keys updated: 1 if updated, 0 if not found or expiresAt was in the past

// Set the expiration date in the cache until 2024-01-01 16:23:05 UTC
await setExpirationUntil(
  "product:155392", 
  new Date('2024-01-01T16:23:05Z').toISOString()
);

Checks if the provided key exists (has value) in the cache. If the key is expired, it's considered non-existent.

• key - the key to check for existence

// Check if the key is present in the cache
const hasLuckyNumber: Boolean = await exists("luckyNumber");

Get a value from the cache by key. You can provide a type of the return value or it will default to unknown. If there is no value for the key or the value has expired, null is returned.

• key - the key to get the value for

// Get a value from the cache
const luckyNumber: number = await get<number>("luckyNumber");
const luckyNumber: number = await get("luckyNumber") as number; // same as above

Gets a list of all non-expired keys in the cache that match the prefix. If no prefix is provided, all keys are returned.

• prefix - the optional prefix to match keys against

// Get all keys from the cache
const keys: string[] = await listKeys();

// Get all keys from the cache that start with "product:"
const keys: string[] = await listKeys("product:");

Get many key-value pairs from the cache that match the given prefix.

• prefix - the optional prefix to match keys against. If not provided, all keys are considered.
• limit - the optional maximum number of key-value pairs to return. If 0, no limit is applied. Defaults to 0.
• returns An array of key-value pairs. Each pair is an object with key and value properties.

// Get all non-expired keys and their values
const everything = await getMany();

// Get all keys and values with a matching prefix
const allProducts = await getMany("product:");

// Get 5 keys and values with a matching prefix
const discountedProducts = await getMany("discounts:", 5);

Delete a key from the cache.

• key - the key to delete
• returns the number of keys deleted: 1 if the key was deleted, 0 if the key did not exist.

// Delete a key from the cache
await deleteKey("luckyNumber");

Delete all keys from the cache that match the prefix. If no prefix is provided, all keys in the cache are deleted.

• prefix - the optional prefix to match keys against
• returns the number of keys deleted

// Delete all keys from the cache
await deleteKeys();

// Delete all keys from the cache that start with "product:"
await deleteKeys("product:");

Delete all expired keys from the cache. Perfect for running on a schedule to keep the cache small and fast.

• returns the number of keys deleted

// Delete all expired keys from the cache
await deleteExpired();