In-Memory Key Value Store with Bun's SQLite implementation.

InMemoryKeyValueStore.ts

import { Database } from "bun:sqlite";

export class InMemoryKeyValueStore {
    private static instance: InMemoryKeyValueStore | null = null;
    private db: Database;

    // Private constructor to initialize the SQLite database
    private constructor() {
        this.db = new Database(":memory:"); // In-memory SQLite database
        this.initializeDatabase();
    }

    // Singleton pattern to ensure only one instance exists
    public static getInstance(): InMemoryKeyValueStore {
        if (InMemoryKeyValueStore.instance === null) {
            InMemoryKeyValueStore.instance = new InMemoryKeyValueStore();
        }
        return InMemoryKeyValueStore.instance;
    }

    // Initialize the key-value store table
    private initializeDatabase(): void {
        const createTableQuery = `
            CREATE TABLE IF NOT EXISTS InMemoryKeyValueStore (
                key TEXT PRIMARY KEY,
                value TEXT
            );
        `;
        this.db.run(createTableQuery);
    }

    // Set a value for a given key
    public set(key: string, value: any): void {
        const serializedValue = JSON.stringify(value); // Convert to JSON string
        const insertOrUpdateQuery = `
            INSERT INTO InMemoryKeyValueStore (key, value)
            VALUES (?, ?)
            ON CONFLICT(key) DO UPDATE SET value = excluded.value;
        `;
        this.db.run(insertOrUpdateQuery, [key, serializedValue]);
    }

    // Get a value for a given key
    public get<T = any>(key: string): T | null {
        const selectQuery = `SELECT value FROM InMemoryKeyValueStore WHERE key = ?;`;
        const row = this.db.query(selectQuery).get(key) as { value: string } | undefined;

        if (row && row.value) {
            try {
                return JSON.parse(row.value) as T; // Parse JSON string
            } catch {
                console.error(`Failed to parse value for key "${key}"`);
                return null;
            }
        }

        return null;
    }

    // Delete a key from the store
    public delete(key: string): void {
        const deleteQuery = `DELETE FROM InMemoryKeyValueStore WHERE key = ?;`;
        this.db.run(deleteQuery, [key]);
    }

    // Retrieve all keys in the store
    public getAllKeys(): string[] {
        const selectQuery = `SELECT key FROM InMemoryKeyValueStore;`;
        const rows = this.db.query(selectQuery).all() as { key: string }[];
        return rows.map(row => row.key);
    }

    // Clear the store
    public clear(): void {
        const clearQuery = `DELETE FROM InMemoryKeyValueStore;`;
        this.db.run(clearQuery);
    }
}

usage.txt

const store = InMemoryKeyValueStore.getInstance();

// Set some key-value pairs
store.set("user:1", { name: "Alice", age: 30 });
store.set("user:2", { name: "Bob", age: 25 });
store.set("appConfig", { theme: "dark", language: "en" });

// Retrieve values
const user1 = store.get("user:1");
console.log("User 1:", user1); // { name: "Alice", age: 30 }

const appConfig = store.get("appConfig");
console.log("App Config:", appConfig); // { theme: "dark", language: "en" }

// Delete a key
store.delete("user:2");

// Get all keys
const keys = store.getAllKeys();
console.log("All keys:", keys); // ["user:1", "appConfig"]

// Clear the store
store.clear();
console.log("Keys after clear:", store.getAllKeys()); // []