let interpret (past: Schema.schema) (input: string list): Schema.schema =

    let future: Schema.schema = { past with output = { past.output with main = "" } } in

    let say (message: string): Schema.schema =
        { future with output = { future.output with main = message }} in

    (*
       TODO: return a schema with orders, instead of calling side-effects
       directly, making this more of a parser and less of a glorified switch
    *)
    match input with
    | "pkg" :: tail -> System.Package.merge past tail
    | "os" :: _ -> say (System.File.read "/etc/os-release")
    | "user" :: _ -> say (System.Process.Reader.read [||] "whoami").output
    | "echo" :: tail -> say (String.concat " " tail)
    | ("version" | "-v" | "--version") :: _ ->
        say (Schema.format_version future.meta.version)
    | ("help" | "-h" | "--help") :: _ -> say future.meta.help.long
    | head :: _ ->
        { future with
            output = {
                future.output with main =
                    ("Unrecognized command: " ^ head ^ "\n"
                        ^ future.meta.help.short)
            };
            meta = { future.meta with status = 1 };
        }
    | _ -> future