Add cancellable GeneratorPreBuyEvent (#137)

[tastybento]

Closes #137

Problem

The existing GeneratorBuyEvent is fired after a purchase has completed, so listeners cannot use it to veto a purchase. Servers/plugins that want to add their own requirements to the buying process have no hook.

Change

Adds a new cancellable GeneratorPreBuyEvent, fired at the very start of StoneGeneratorManager.purchaseGenerator(...) — before any money is withdrawn and before the existing GeneratorBuyEvent fires. If a listener cancels it, the purchase is aborted (no withdrawal, no tier granted, no post-buy event).

The existing GeneratorBuyEvent is unchanged, so this is fully backwards compatible.

API

@EventHandler
public void onPreBuy(GeneratorPreBuyEvent e) {
    if (someCustomRequirementNotMet(e.getTargetPlayer(), e.getGeneratorID())) {
        e.setCancelled(true);
    }
}

Tests

• GeneratorPreBuyEventTest — field population, cancellable contract, handlers.
• StoneGeneratorManagerTest:
  • testPurchaseGeneratorFiresPreBuyEvent — event is fired on purchase.
  • testPurchaseGeneratorCancelledPreBuyEventStopsPurchase — cancelling aborts the purchase (tier not added, GeneratorBuyEvent not fired).

All 58 tests in the affected classes pass.

🤖 Generated with Claude Code

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud