Initial commit

src/dice/effect-mods.ts

@@ -0,0 +1,52 @@
+/**
+ * Active-Effect-driven roll modifier collection.
+ * Reads `flags.hbm.*` metadata from the actor's currently-applied effects
+ * (`actor.appliedEffects` in v13) and aggregates threshold steps + blocked tags.
+ */
+
+import { SkillTag } from '../constants';
+
+export interface RollModifiers {
+  thresholdSteps: number;
+  requiredSteps: number;
+  /** First blocked condition encountered, for friendly error message. */
+  blockedBy?: { conditionLabel: string; tag: SkillTag };
+}
+
+export function collectRollModifiers(actor: any, tags: readonly SkillTag[]): RollModifiers {
+  const result: RollModifiers = { thresholdSteps: 0, requiredSteps: 0 };
+  const effects = (actor?.appliedEffects ?? actor?.effects ?? []) as Iterable<any>;
+  for (const ef of effects) {
+    if (ef?.disabled) continue;
+    const hbm = ef?.flags?.hbm;
+    if (!hbm) continue;
+
+    // Threshold step modifiers — keys may be tag names or 'all'
+    const ts = hbm.thresholdSteps as Record<string, number> | undefined;
+    if (ts && typeof ts === 'object') {
+      if (typeof ts['all'] === 'number') result.thresholdSteps += ts['all'];
+      for (const t of tags) {
+        if (typeof ts[t] === 'number') result.thresholdSteps += ts[t]!;
+      }
+    }
+    if (typeof hbm.requiredSteps === 'number') result.requiredSteps += hbm.requiredSteps;
+
+    // Blocked tags
+    const blocked = (hbm.blocksTags ?? []) as SkillTag[];
+    if (Array.isArray(blocked) && !result.blockedBy) {
+      for (const t of tags) {
+        if (blocked.includes(t)) {
+          result.blockedBy = { conditionLabel: ef?.name ?? ef?.label ?? '?', tag: t };
+          break;
+        }
+      }
+    }
+  }
+  return result;
+}
+
+export class RollBlockedError extends Error {
+  constructor(public conditionLabel: string, public tag: SkillTag) {
+    super(`Roll blocked by ${conditionLabel} (${tag})`);
+  }
+}