open dotenv.net
open Argu

type DotenvReader(?trimValues) =
    do DotEnv.Load(DotEnvOptions(?trimValues = trimValues))
    let envVars = DotEnv.Read()
    interface IConfigurationReader with
        member _.Name = "dotenv"
        member _.GetValue key = envVars.[key]

type Args =
    // Other arguments here...
    | [<NoCommandLine; CustomAppSettings "API_KEY">] ApiKey of string
    | [<NoCommandLine; CustomAppSettings "API_SECRET">] ApiSecret of string
    interface IArgParserTemplate with
        member self.Usage =
            // for brevity
            ""

let getToken (apiKey, apiSecret) =
    failwith "function that needs an API key and an API secret and returns a bearer token."

let main argv =
    let parser = ArgumentParser.Create(checkStructure = false, errorHandler = ProcessExiter())
    let result = parser.Parse(argv, DotenvReader(trimValues = true))

    let apiKey = result.GetResult <@ ApiKey @>
    let apiSecret = result.GetResult <@ ApiSecret @>
    let token = getToken (apiKey, apiSecret)

    // ...

    0