Progress on action choices

app/imports/api/engine/action/functions/userInput/getDeterministicDiceRoller.ts

@@ -0,0 +1,28 @@
+import Alea from 'alea';
+
+/**
+ * Return a function that can be be used as InputProvider.rollDice
+ * this function instance must be used for the entire action
+ */
+export default function getDeterministicDiceRoller(
+  actionId: string
+): (dice: { number: number, diceSize: number }[]) => Promise<number[][]> {
+  // Create a random number generator seeded on the ID of the action
+  if (!actionId) throw new Meteor.Error('Id Required', 'action ID can not be ' + actionId)
+  const randFrac = Alea(actionId);
+  return (dice) => {
+    const results: number[][] = [];
+    for (const diceRoll of dice) {
+      const values: number[] = [];
+      if (diceRoll.number > 100) {
+        throw new Meteor.Error('Too many dice', 'can only roll up to 100 dice at once');
+      }
+      for (let i = 0; i < diceRoll.number; i++) {
+        const rolledValue = ~~(randFrac() * diceRoll.diceSize) + 1
+        values.push(rolledValue);
+      }
+      results.push(values);
+    }
+    return Promise.resolve(results);
+  }
+}