Adding Effects to Pokestar

Quick Reference

Files to modify:

•src/enums/battleEnums.js - Add effectIdEnum.YOUR_EFFECT entry (ONLY if not exists)
•src/battle/data/effects.js - Add the effect implementation

DO NOT modify other effects or battleConfig.js unless explicitly asked.

Effect Structure

javascript

[effectIdEnum.EFFECT_NAME]: new Effect({
  id: effectIdEnum.EFFECT_NAME,
  name: "Effect Name",
  description: "Description of the effect",
  type: effectTypes.BUFF,        // BUFF, DEBUFF, or NEUTRAL
  dispellable: true,             // Can it be removed by dispell effects?
  effectAdd({ battle, target, source, initialArgs }) {
    // Called when effect is applied
    // initialArgs contains arguments passed when applying the effect
    return {
      // Properties to store for later use in effectRemove
    };
  },
  effectRemove({ battle, target, source, properties, initialArgs }) {
    // Called when effect expires or is removed
    // properties contains what effectAdd returned
    // Clean up any listeners or state here
  },
  tags: [],                      // Optional: ["hazard", "test"]
}),

Properties Pattern

The most important pattern is the properties pattern - return state from effectAdd that you'll need in effectRemove:

javascript

effectAdd({ battle, target, source, initialArgs }) {
  return {
    listenerId: battle.registerListenerFunction({...}),
    originalValue: target.getStat("atk"),
    counter: 0,
  };
},
effectRemove({ battle, target, properties }) {
  battle.unregisterListener(properties.listenerId);
}

Event Listener Registration

Use battle.registerListenerFunction for effects (effects don't have a class-level helper):

javascript

effectAdd({ battle, target }) {
  return {
    listenerId: battle.registerListenerFunction({
      eventName: battleEventEnum.BEFORE_DAMAGE,
      callback: (args) => {
        // Modify damage or perform logic
        return { damage: Math.floor(args.damage * 0.5) };
      },
      conditionCallback: getIsTargetPokemonCallback(target),
    }),
  };
},
effectRemove({ battle, properties }) {
  battle.unregisterListener(properties.listenerId);
}

Effect Types

Type	Description
`effectTypes.BUFF`	Positive effect, can be dispelled by debuff-removing abilities
`effectTypes.DEBUFF`	Negative effect, can be dispelled by buff-removing abilities
`effectTypes.NEUTRAL`	Neither buff nor debuff, special handling

Using initialArgs

Effects can receive arguments when applied. Access them in both add and remove:

javascript

effectAdd({ battle, target, initialArgs }) {
  const { shield } = initialArgs;
  battle.addToLog(`${target.name} is shielded for ${shield} damage!`);
  return { shieldAmount: shield };
},
effectRemove({ battle, target, initialArgs }) {
  const { shield } = initialArgs;
  // initialArgs persists through the effect's lifetime
}

Common Gotchas

•
Always Clean Up Listeners: Failing to unregister listeners causes memory leaks and incorrect behavior.
•
Event Argument Modification: Return modified values from callbacks to change event behavior:
javascript
```
callback: (args) => {
  return { damage: Math.floor(args.damage * 0.5) };
};
```
•
State Management: Properties can be mutated during runtime - be careful with shared references.
•
Dispellable Flag: Set dispellable: false for effects that should persist through dispell abilities.

References

•references/pattern-*.md - Common effect implementation patterns
•add-event-listener skill - Common event types and condition callbacks