Access checks

The middleware

SupporterMiddleware is a jda-commands middleware. It runs before every interaction, builds the subscription context and checks the interaction rules.

SubscriptionContextProvider contexts = new SubscriptionContextProvider() {
    @Override
    public ISubscriptionContext getSubscriptionContext(User user) {
        return () -> repository.user(user.getIdLong()).subscriptionIds();
    }

    @Override
    public ISubscriptionContext getSubscriptionContext(Guild guild) {
        return () -> repository.guild(guild.getIdLong()).subscriptions().stream()
                .map(Subscription::subscriptionId)
                .collect(Collectors.toSet());
    }
};

ISupporterErrorSupplier errors = new ISupporterErrorSupplier() {
    @Override
    public MessageCreateData getCommandError(AccessCheckResult result) {
        return MessageCreateData.fromContent("This command needs a subscription.");
    }

    @Override
    public String getAutoCompleteError() {
        return "This command needs a subscription.";
    }
};

JDACommands.builder(jda)
        .middleware(Priority.HIGH, new SupporterMiddleware<>(contexts, configuration, errors))
        .start();

ISubscriptionContext has a single method, enabledSubscriptions(), so a lambda that returns a Set<Long> is enough.

For each interaction the middleware:

collects the SKU ids of the Discord entitlements that come with the interaction,
adds the user's context, and in a guild the guild's context as well,
checks the command against the interaction rules.

So a rule or feature can list the subscription id, which your context provider returns, or a Discord SKU id, which Discord sends with the interaction.

When the check fails, a command is cancelled and the user gets the message from getCommandError. An autocomplete request gets a single choice with the text from getAutoCompleteError (at most 100 characters), or no choices when that text is blank.

Checking features in a command

When the check passes, the middleware puts two values into the interaction's key-value store:

Key	Value
`SupporterKeys.SUBSCRIPTION_VALIDATOR`	A `SupporterValidator` for your feature enum.
`SupporterKeys.SUBSCRIPTION_CONTEXT`	The `ISubscriptionContext` that was checked.

Use the validator to check a feature inside a command:

@Interaction
public class ProfileCommands {

    @Command("profile color")
    public void color(CommandEvent event, String color) {
        SupporterValidator<FeatureID> validator =
                event.kv().<SupporterValidator<FeatureID>>getOrThrow(SupporterKeys.SUBSCRIPTION_VALIDATOR);
        if (!validator.hasAccess(FeatureID.CUSTOM_PROFILE).hasAccess()) {
            event.reply("Custom colours need a subscription.");
            return;
        }
        event.reply("Your colour is now " + color + ".");
    }
}

hasAccess throws an IllegalArgumentException for a feature that is not in your configuration.

AccessCheckResult holds the feature that was checked and whether the context hasAccess. accessOrThrow(feature -> new MyException(feature)) throws your exception when access is denied.

You can also check a feature directly: context.hasAccess(configuration.feature(FeatureID.CUSTOM_PROFILE)).

The middleware​

Checking features in a command​

The middleware

Checking features in a command