Add slying dice modifier to DicePool

src/module/ds4.ts

@@ -1,15 +1,16 @@
 import { DS4Actor } from "./actor/actor";
-import { DS4Item } from "./item/item";
-import { DS4ItemSheet } from "./item/item-sheet";
-import { DS4 } from "./config";
-import { DS4Check } from "./rolls/check";
 import { DS4CharacterActorSheet } from "./actor/sheets/character-sheet";
 import { DS4CreatureActorSheet } from "./actor/sheets/creature-sheet";
-import { createCheckRoll } from "./rolls/check-factory";
+import { DS4 } from "./config";
-import { registerSystemSettings } from "./settings";
-import { migration } from "./migrations";
 import registerHandlebarsHelpers from "./handlebars/handlebars-helpers";
 import registerHandlebarsPartials from "./handlebars/handlebars-partials";
+import { DS4Item } from "./item/item";
+import { DS4ItemSheet } from "./item/item-sheet";
+import { migration } from "./migrations";
+import { DS4Check } from "./rolls/check";
+import { createCheckRoll } from "./rolls/check-factory";
+import registerSlayingDiceModifier from "./rolls/slaying-dice-modifier";
+import { registerSystemSettings } from "./settings";
 
 Hooks.once("init", async () => {
     console.log(`DS4 | Initializing the DS4 Game System\n${DS4.ASCII}`);
@@ -33,6 +34,8 @@ Hooks.once("init", async () => {
     CONFIG.Dice.types.push(DS4Check);
     CONFIG.Dice.terms.s = DS4Check;
 
+    registerSlayingDiceModifier();
+
     registerSystemSettings();
 
     Actors.unregisterSheet("core", ActorSheet);

src/module/rolls/check.ts

@@ -1,28 +1,22 @@
 import evaluateCheck, { getRequiredNumberOfDice } from "./check-evaluation";
 
-interface DS4CheckTermData extends DiceTerm.TermData {
-    canFumble: boolean;
-}
-
 /**
  * Implements DS4 Checks as an emulated "dice throw".
  *
  * @example
  * - Roll a check against a Check Target Number (CTN) of 18: `/r dsv18`
  * - Roll a check with multiple dice against a CTN of 34: `/r dsv34`
- * - Roll a check with a racial ability that makes `2` a coup and `19` a fumble: `/r dsv19c2,19`
+ * - Roll a check with a racial ability that makes `2` a coup and `19` a fumble: `/r dsv19c2:19`
  * - Roll a check with a racial ability that makes `5` a coup and default fumble: `/r dsv19c5`
  */
 export class DS4Check extends DiceTerm {
-    constructor({ modifiers = [], options = {}, canFumble = true }: Partial<DS4CheckTermData> = {}) {
+    constructor({ modifiers = [], options }: Partial<DiceTerm.TermData> = {}) {
         super({
             faces: 20,
             modifiers: modifiers,
             options: options,
         });
 
-        this.canFumble = canFumble;
-
         // Parse and store check target number
         const checkTargetNumberModifier = this.modifiers.filter((m) => m[0] === "v")[0];
         const ctnRgx = new RegExp("v([0-9]+)?");
@@ -38,10 +32,11 @@ export class DS4Check extends DiceTerm {
 
         // Parse and store maximumCoupResult and minimumFumbleResult
         const coupFumbleModifier = this.modifiers.filter((m) => m[0] === "c")[0];
-        const cfmRgx = new RegExp("c([0-9]+)?,([0-9]+)?");
+        const cfmRgx = new RegExp("c([0-9]+)?(:([0-9]+))?");
         const cfmMatch = coupFumbleModifier?.match(cfmRgx);
         if (cfmMatch) {
-            const [parseMaximumCoupResult, parseMinimumFumbleResult] = cfmMatch.slice(1);
+            const parseMaximumCoupResult = cfmMatch[1];
+            const parseMinimumFumbleResult = cfmMatch[3];
             this.maximumCoupResult = parseMaximumCoupResult
                 ? parseInt(parseMaximumCoupResult)
                 : DS4Check.DEFAULT_MAXIMUM_COUP_RESULT;
@@ -51,11 +46,17 @@ export class DS4Check extends DiceTerm {
             if (this.minimumFumbleResult <= this.maximumCoupResult)
                 throw new SyntaxError(game.i18n.localize("DS4.ErrorDiceCritOverlap"));
         }
+
+        // Parse and store no fumble
+        const noFumbleModifier = this.modifiers.filter((m) => m[0] === "n")[0];
+        if (noFumbleModifier) {
+            this.canFumble = false;
+        }
     }
 
     coup: boolean | null = null;
     fumble: boolean | null = null;
-    canFumble: boolean;
+    canFumble = true;
     checkTargetNumber = DS4Check.DEFAULT_CHECK_TARGET_NUMBER;
     minimumFumbleResult = DS4Check.DEFAULT_MINIMUM_FUMBLE_RESULT;
     maximumCoupResult = DS4Check.DEFAULT_MAXIMUM_COUP_RESULT;
@@ -107,7 +108,7 @@ export class DS4Check extends DiceTerm {
     /**
      * @override
      */
-    static fromResults(options: Partial<DS4CheckTermData>, results: DiceTerm.Result[]): DS4Check {
+    static fromResults(options: Partial<DiceTerm.TermData>, results: DiceTerm.Result[]): DS4Check {
         const term = new this(options);
         term.results = results;
         term.evaluateResults();
@@ -122,5 +123,6 @@ export class DS4Check extends DiceTerm {
     static MODIFIERS = {
         c: (): void => undefined, // Modifier is consumed in constructor for maximumCoupResult / minimumFumbleResult
         v: (): void => undefined, // Modifier is consumed in constructor for checkTargetNumber
+        n: (): void => undefined, // Modifier is consumed in constructor for canFumble
     };
 }

src/module/rolls/slaying-dice-modifier.ts

@@ -0,0 +1,29 @@
+import { DS4Check } from "./check";
+
+export default function registerSlayingDiceModifier(): void {
+    // TODO(types): Adjust types to allow extension of DiceTerm.MODIFIERS
+    // eslint-disable-next-line
+    // @ts-ignore
+    DicePool.MODIFIERS.x = slay;
+    DicePool.POOL_REGEX = /^{([^}]+)}([A-z]([A-z0-9<=>]+)?)?$/;
+}
+
+function slay(this: DicePool, modifier: string): void {
+    const rgx = /[xX]/;
+    const match = modifier.match(rgx);
+    if (!match || !this.rolls) return;
+
+    let checked = 0;
+    while (checked < (this.dice.length ?? 0)) {
+        const diceTerm = this.dice[checked];
+        checked++;
+        if (diceTerm instanceof DS4Check && diceTerm.coup) {
+            const formula = `dsv${diceTerm.checkTargetNumber}c${diceTerm.maximumCoupResult}:${diceTerm.minimumFumbleResult}n`;
+            const additionalRoll = Roll.create(formula).evaluate();
+
+            this.rolls.push(additionalRoll);
+            this.results.push({ result: additionalRoll.total ?? 0, active: true });
+        }
+        if (checked > 1000) throw new Error(game.i18n.localize("DS4.ErrorExplodingRecursionLimitExceeded"));
+    }
+}