Add function to assign sub checks to dice

src/module/rolls/check-evaluation.ts

@@ -0,0 +1,57 @@
+export function assignSubChecksToDice(
+    dice: number[],
+    checkTargetNumber: number,
+    {
+        maximumCoupResult = 1,
+    }: {
+        maximumCoupResult?: number;
+    } = {},
+): { result: number; checkTargetNumber: number }[] {
+    const requiredNumberOfDice = Math.ceil(checkTargetNumber / 20);
+    if (dice.length !== requiredNumberOfDice || requiredNumberOfDice < 1) {
+        throw new Error(game.i18n.localize("DS4.ErrorInvalidNumberOfDice")); // TODO: add i18n
+    }
+
+    const checkTargetNumberForLastSubCheck = checkTargetNumber - 20 * (requiredNumberOfDice - 1);
+
+    const indexOfSmallestNonCoup = findIndexOfSmallestNonCoup(dice, maximumCoupResult);
+    const indexOfFirstCoup = dice.findIndex((die) => die <= maximumCoupResult);
+    const indexForLastSubCheck = shouldUseCoupForLastSubCheck(
+        indexOfSmallestNonCoup,
+        indexOfFirstCoup,
+        dice,
+        checkTargetNumberForLastSubCheck,
+    )
+        ? indexOfFirstCoup
+        : indexOfSmallestNonCoup;
+
+    return dice.map((die, index) => ({
+        result: die,
+        checkTargetNumber: index === indexForLastSubCheck ? checkTargetNumberForLastSubCheck : 20,
+    }));
+}
+
+function findIndexOfSmallestNonCoup(dice: number[], maximumCoupResult: number): number {
+    return dice
+        .map((die, index) => [die, index])
+        .filter((indexedDie) => indexedDie[0] > maximumCoupResult)
+        .reduce(
+            (smallestIndexedDie, indexedDie) =>
+                indexedDie[0] < smallestIndexedDie[0] ? indexedDie : smallestIndexedDie,
+            [Infinity, -1],
+        )[1];
+}
+
+function shouldUseCoupForLastSubCheck(
+    indexOfSmallestNonCoup: number,
+    indexOfFirstCoup: number,
+    dice: number[],
+    checkTargetNumberForLastSubCheck: number,
+) {
+    return (
+        indexOfFirstCoup !== -1 &&
+        (indexOfSmallestNonCoup === -1 ||
+            (dice[indexOfSmallestNonCoup] > checkTargetNumberForLastSubCheck &&
+                dice[indexOfSmallestNonCoup] + checkTargetNumberForLastSubCheck > 20))
+    );
+}