MCP Universal DB Client

import { PostgresDialect, MysqlDialect, SqliteDialect, Kysely } from "kysely"; import { createPool } from "mysql2"; import { Pool } from "pg"; import z from "zod"; import Database from "libsql"; export const dialectsSchema = z .enum(["psql", "mysql", "sqlite"]) .describe("The available database dialect (available: psql, mysql, sqlite)"); export const connectDatabaseInputSchema = z.object({ name: z .string() .describe("An unique name for this connection to be used as an ID"), dialect: dialectsSchema, connectionString: z .string() .describe( "The database connection string. e.g., postgresql://user:password@localhost:5432/dbname" ), }); type ConnectDatabaseInput = z.infer<typeof connectDatabaseInputSchema>; export const createDialect = (input: ConnectDatabaseInput) => { switch (input.dialect) { case "psql": return new PostgresDialect({ pool: new Pool({ connectionString: input.connectionString, }), }); case "mysql": return new MysqlDialect({ pool: createPool({ uri: input.connectionString, }), }); case "sqlite": return new SqliteDialect({ database: new Database(input.connectionString), }); default: throw new Error(`Unsupported dialect: ${input.dialect}`); } }; type Connection = { instance: Kysely<any>; dialect: z.infer<typeof dialectsSchema>; connectedAt: Date; }; /* * Manages multiple database connections identified by unique IDs. */ export class DatabaseConnections { private connections = new Map<string, Connection>(); /** * Add a new database connection and store it with a unique ID. */ public addConnection(input: ConnectDatabaseInput) { this.connections.set(input.name, { instance: new Kysely({ dialect: createDialect(input), }), dialect: input.dialect, connectedAt: new Date(), }); } /** * Retrieve a connection by its name. * * @throws when no connection is found with the given name. */ public getConnection(name: string) { const conn = this.connections.get(name); if (!conn) { throw new Error(`No active connection found for ID: ${name}`); } return conn; } /** * Delete a connection by its name and close the connection. */ public deleteConnection(name: string) { const conn = this.connections.get(name); if (conn) { conn.instance.destroy(); this.connections.delete(name); return true; } return false; } /** * Get all connections with their IDs, dialects, and connection times. */ public getAllConnections() { return Array.from(this.connections.entries()).map( ([connectionID, conn]) => ({ connectionID, dialect: conn.dialect, connectedAt: conn.connectedAt, }) ); } /** * Close all connections and clear the map. */ public async deleteAllConnections() { for (const [name, conn] of this.connections.entries()) { await conn.instance.destroy(); this.connections.delete(name); } } }