import {Inject, Singleton} from "../../di";
import {DatabaseService} from "../DatabaseService";
import {PostgresConnection} from "../connection/PostgresConnection";
import {ErrorWithContext} from "../../util";
import {Unit} from "../../lifecycle/Unit";
import {Config} from "../../service/Config";
import {Logging} from "../../service/Logging";

/**
 * Application unit responsible for loading and creating database connections from config.
 */
@Singleton()
export class Database extends Unit {
    @Inject()
    protected readonly config!: Config;

    @Inject()
    protected readonly dbService!: DatabaseService;

    @Inject()
    protected readonly logging!: Logging;

    /**
     * Load the `database.connections` config and register Connection instances for each config.
     * Automatically initializes the connections.
     */
    public async up() {
        const connections = this.config.get('database.connections')
        const promises = []

        for ( const key in connections ) {
            if ( !connections.hasOwnProperty(key) ) continue
            const config = connections[key]

            this.logging.info(`Initializing database connection: ${key}`)
            this.logging.verbose(config)

            let conn
            if ( config?.dialect === 'postgres' ) {
                conn = <PostgresConnection> this.app().make(PostgresConnection, key, config)
            } else {
                const e = new ErrorWithContext(`Invalid or missing database dialect: ${config.dialect}. Should be one of: postgres`)
                e.context = { connectionName: key }
                throw e
            }

            this.dbService.register(key, conn)
            promises.push(conn.init())
        }

        await Promise.all(promises)
        this.logging.info('Database connections opened.')
    }

    /**
     * Close the configured connections cleanly before exit.
     */
    public async down() {
        await Promise.all(this.dbService.names()
            .map(name => this.dbService.get(name).close()))
    }
}