import { Service } from '../../../di/src/decorator/Service.ts'
import { Connection } from '../db/Connection.ts'
import PostgresConnection from '../db/PostgresConnection.ts'

/**
 * Error thrown if two connections with the same name are registered.
 * @extends Error
 */
export class DuplicateConnectionNameError extends Error {
    constructor(connection_name: string) {
        super(`A database connection with the name "${connection_name}" already exists.`)
    }
}

/**
 * Error thrown if a connection name is accessed when there is no corresponding connection registered.
 * @extends Error
 */
export class NoSuchDatabaseConnectionError extends Error {
    constructor(connection_name: string) {
        super(`No database connection exists with the name: "${connection_name}"`)
    }
}

/**
 * Service that manages and creates database connections.
 */
@Service()
export default class Database {
    /**
     * The created connections, keyed by name.
     * @type object
     */
    private connections: { [name: string]: Connection } = {}

    /**
     * Create a new PostgreSQL connection.
     * @param {string} name
     * @param {object} config
     * @return Promise<PostgresConnection>
     */
    async postgres(name: string, config: { [key: string]: any }): Promise<PostgresConnection> {
        if ( this.connections[name] )
            throw new DuplicateConnectionNameError(name)

        const conn = new PostgresConnection(name, config)
        this.connections[name] = conn
        await conn.init()
        return conn
    }

    /**
     * Get a connection by name.
     * @param name
     * @return Connection
     */
    connection(name: string): Connection {
        if ( !this.connections[name] )
            throw new NoSuchDatabaseConnectionError(name)

        return this.connections[name]
    }
}