Implement the 026-roll-initiative feature that adds d20 roll buttons for bestiary combatants' initiative using a click-to-edit pattern (d20 icon when empty, plain text when set), plus a Roll All button in the top bar that batch-rolls for all unrolled bestiary combatants, with randomness confined to the adapter layer and the domain receiving pre-resolved dice values

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/application/src/roll-initiative-use-case.ts

@@ -0,0 +1,67 @@
+import {
+	type CombatantId,
+	type Creature,
+	type CreatureId,
+	calculateInitiative,
+	type DomainError,
+	type DomainEvent,
+	isDomainError,
+	rollInitiative,
+	setInitiative,
+} from "@initiative/domain";
+import type { EncounterStore } from "./ports.js";
+
+export function rollInitiativeUseCase(
+	store: EncounterStore,
+	combatantId: CombatantId,
+	diceRoll: number,
+	getCreature: (id: CreatureId) => Creature | undefined,
+): DomainEvent[] | DomainError {
+	const encounter = store.get();
+	const combatant = encounter.combatants.find((c) => c.id === combatantId);
+
+	if (!combatant) {
+		return {
+			kind: "domain-error",
+			code: "combatant-not-found",
+			message: `No combatant found with ID "${combatantId}"`,
+		};
+	}
+
+	if (!combatant.creatureId) {
+		return {
+			kind: "domain-error",
+			code: "no-creature-link",
+			message: `Combatant "${combatant.name}" has no linked creature`,
+		};
+	}
+
+	const creature = getCreature(combatant.creatureId);
+	if (!creature) {
+		return {
+			kind: "domain-error",
+			code: "creature-not-found",
+			message: `Creature not found for ID "${combatant.creatureId}"`,
+		};
+	}
+
+	const { modifier } = calculateInitiative({
+		dexScore: creature.abilities.dex,
+		cr: creature.cr,
+		initiativeProficiency: creature.initiativeProficiency,
+	});
+	const value = rollInitiative(diceRoll, modifier);
+
+	if (isDomainError(value)) {
+		return value;
+	}
+
+	const result = setInitiative(encounter, combatantId, value);
+
+	if (isDomainError(result)) {
+		return result;
+	}
+
+	store.save(result.encounter);
+	return result.events;
+}