import * as moment from "moment";
import {Moment} from "moment";
import * as pgPromise from "pg-promise";

const readDelta = 1;

export function dbConfigCtor(pgPromise) {
  let settings: { databaseUrlRead: any, databaseUrlWrite: any, databaseUrlDelete: any, [name:string]: any };
  let dbProvider: any = null;
  let nextRead: Moment = moment().add(-readDelta, "minutes");

  return {
    async execute() {
      try {
        const now = moment();

        if (!dbProvider) {
          dbProvider = pgPromise()(process.env.DATABASE_URL_CONFIG);
        }

        if (!nextRead || nextRead <= now) {
          const defaultEnv = "dev";
          const configEnv = process.env.CONFIG_ENV || defaultEnv;
          const rows = await dbProvider.one(
            "SELECT settings FROM config WHERE env=$(CONFIG_ENV) AND effective < now() ORDER BY effective DESC LIMIT 1",
            {CONFIG_ENV: configEnv},
          );
          if (rows && rows.settings) {
            settings = rows.settings;
          } else {
            // noinspection ExceptionCaughtLocallyJS
            throw new Error(`Could not load config settings for environment ${configEnv}`);
          }
          nextRead = now.add(readDelta, "minutes");
        }

        return settings;
      } catch (e) {
        console.error(`unable to load dbConfig: ${e}`);
        throw e;
      }
    },
  };
}

export const dbConfig = dbConfigCtor(pgPromise).execute;