import extend from "extend";
import path from "path";

export class Config {
  public static getInstance() {
    if (!this.instance) {
      this.instance = this.readConfig(
        path.join(process.cwd(), "config"),
        `${process.env.NODE_ENV || "development"}`,
        "default"
      );
    }
    return this.instance;
  }

  private static instance: any;

  private static readConfig(dir: string, ...names: any[]) {
    if (dir.length < 1 || dir === null) {
      throw new Error("invalid directory parameter");
    }
    if (names.length === 0) {
      throw new Error("invalid name array parameter");
    }
    return names.reduce(
      (config, name) => {
        try {
          const newConfig = extend(
            true,
            config,
            require(path.join(dir, `${name}.json`))
          );
          newConfig.__envs.push(name);
          return newConfig;
        } catch (err) {
          throw err;
        }
      },
      {
        __envs: []
      }
    );
  }
}