import { ClassConstructor } from 'class-transformer';
import { ValidatorOptions } from 'class-validator';

declare type RawConfig = Record<string, any>;
declare type ConfigLoader = () => RawConfig;
interface TypedConfigOptions<T extends object> {
    /**
     * The root object for application configuration.
     */
    schema: ClassConstructor<T>;
    /**
     * Function(s) to load configurations, must be synchronous.
     */
    load: ConfigLoader | ConfigLoader[];
    /**
     * Custom function to validate configurations. It takes an object containing environment
     * variables as input and outputs validated configurations.
     * If exception is thrown in the function it would prevent the application from bootstrapping.
     */
    validate?: (config: Record<string, any>) => Record<string, any>;
    /**
     * Custom function to normalize configurations. It takes an object containing environment
     * variables as input and outputs normalized configurations.
     *
     * This function is executed before validation, and can be used to do type casting,
     * variable expanding, etc.
     */
    normalize?: (config: Record<string, any>) => Record<string, any>;
    /**
     * Options passed to validator during validation.
     * @see https://github.com/typestack/class-validator
     */
    validationOptions?: ValidatorOptions;
}

export { ConfigLoader, RawConfig, TypedConfigOptions };