Typescript Config Builder

configBuilder.ts

interface SsmParameter {
  ssmName: string;
  ssmType: "String" | "SecureString";
  configType?: "string" | "number" | "boolean";
}

class SsmConfig<Config, C extends Record<string, SsmParameter> = {}> {
  constructor(private config: C) {}
  static builder<Config>(): SsmConfig<Config, {}> {
    return new SsmConfig<Config, {}>({});
  }
  key<K extends keyof Config>(
    configName: K,
    ssmParameter: SsmParameter
  ): SsmConfig<Config, C & { [k in K]: SsmParameter }> {
    return new SsmConfig({
      ...this.config,
      ...({ [configName]: ssmParameter } as {
        [k in K]: SsmParameter;
      }),
    });
  }
  build(): { [K in keyof C]: C[K] } {
    return null as any;
  }
}

// usage

interface Config {
  bucketName: string;
  awsAccessKeyId: string;
  awsSecretKey: string;
  jwtSecret: string
}

const config: Config = SsmConfig.builder<Config>()
  .key("bucketName", { ssmName: "bucket-name-media", ssmType: "String" })
  .key("awsAccessKeyId", {ssmName: "/api/aws-access-key", ssmType: "String"})
  .key("awsSecretKey", {ssmName: "/api/aws-secret-key", ssmType: "SecureString"})
  .key("jwtSecret", {ssmName: "jwt-secret", ssmType: "SecureString"})
  .build();