import { IOptional, Either, Optional, type IEither, type ObjectFromList } from '@emprespresso/pengueno';

// type safe environment variables

export const getEnv = (name: string): IOptional<string> => Optional.from(process.env[name]);

export const getRequiredEnv = <V extends string>(name: V): IEither<Error, string> =>
    Either.fromFailable(() => getEnv(name).get()).mapLeft(
        () => new Error(`environment variable "${name}" is required D:`),
    );

export const getRequiredEnvVars = <V extends string>(vars: Array<V>): IEither<Error, ObjectFromList<typeof vars>> => {
    type Environment = ObjectFromList<typeof vars>;
    const emptyEnvironment = Either.right<Error, Environment>(<Environment>{});
    const addTo = (env: Environment, key: V, val: string) =>
        <Environment>{
            ...env,
            [key]: val,
        };
    return vars.reduce(
        (environment, key) =>
            environment.joinRight(getRequiredEnv(key), (value, environment) => addTo(environment, key, value)),
        emptyEnvironment,
    );
};