Added ComboDice modifier for dice rolls

module/dice/_module.mjs

@@ -4,4 +4,5 @@ export { default as DamageRoll } from './damageRoll.mjs';
 export { default as DHRoll } from './dhRoll.mjs';
 export { default as DualityRoll } from './dualityRoll.mjs';
 export { default as FateRoll } from './fateRoll.mjs';
+export { BaseDie } from './die/_module.mjs';
 export { diceTypes } from './die/_module.mjs';

module/dice/die/_module.mjs

@@ -3,6 +3,7 @@ import HopeDie from './hopeDie.mjs';
 import FearDie from './fearDie.mjs';
 import AdvantageDie from './advantageDie.mjs';
 import DisadvantageDie from './disadvantageDie.mjs';
+export { default as BaseDie } from './baseDie.mjs';
 
 export const diceTypes = {
     DualityDie,

module/dice/die/advantageDie.mjs

@@ -1,4 +1,6 @@
-export default class AdvantageDie extends foundry.dice.terms.Die {
+import BaseDie from './baseDie.mjs';
+
+export default class AdvantageDie extends BaseDie {
     constructor(options) {
         super(options);
 

module/dice/die/baseDie.mjs

@@ -0,0 +1,31 @@
+import { adjustDice } from '../../helpers/utils.mjs';
+
+export default class BaseDie extends foundry.dice.terms.Die {
+    static MODIFIERS = {
+        ...foundry.dice.terms.Die.MODIFIERS,
+        c: 'comboDice'
+    };
+
+    async comboDice(modifier) {
+        /* ComboDice only works with exactly two dice and both have to be the same denomination */
+        if (this.number !== 2) return false;
+
+        const maxIncreasesDiceSize = modifier.endsWith('1');
+        return this.continueCombo(maxIncreasesDiceSize);
+    }
+
+    async continueCombo(maxIncreasesDiceSize) {
+        const lastIndex = this.results.length - 1;
+
+        /* The Combo only continues if the latest roll was higher than the previous */
+        if (this.results[lastIndex].result <= this.results[lastIndex - 1].result) return false;
+
+        const increaseDiceSize = maxIncreasesDiceSize && this.results[lastIndex].result === this.faces;
+        const denomination = increaseDiceSize ? adjustDice(this.denomination, false) : this.denomination;
+        const newRoll = await (new Roll(`1${denomination}`)).evaluate();
+        this.results.push({ result: newRoll.total, active: true });
+        this.number += 1;
+
+        return this.continueCombo();
+    }
+}

module/dice/die/disadvantageDie.mjs

@@ -1,4 +1,6 @@
-export default class DisadvantageDie extends foundry.dice.terms.Die {
+import BaseDie from './baseDie.mjs';
+
+export default class DisadvantageDie extends BaseDie {
     constructor(options) {
         super(options);
 

module/dice/die/dualityDie.mjs

@@ -1,6 +1,7 @@
 import { updateResourcesForDualityReroll } from '../helpers.mjs';
+import BaseDie from './baseDie.mjs';
 
-export default class DualityDie extends foundry.dice.terms.Die {
+export default class DualityDie extends BaseDie {
     constructor(options) {
         super(options);