Add min/max hit point variants for D&D creatures

A D&D stat block opened for a combatant now offers a Min/Avg/Max toggle below the Hit Points line, deriving both ends from the Hit Dice formula (3d6 + 6 -> 9 / 16 / 24). The switch is applied as a delta, so manual HP edits and damage already taken survive it. Unlike the PF2e weak/elite adjustment this is a convenience tool, not a rules mechanic: nothing but HP changes and the combatant is not renamed. The toggle is hidden when the HP field carries prose instead of a dice pool. Also extracts a SegmentedControl primitive. Game system, theme and the PF2e weak/elite toggle were three hand-rolled copies of the same markup, which is why the D&D toggle first came out chunkier and in the wrong accent color. All four now share one definition, and segments expose aria-pressed instead of signalling the active state by color alone. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
2026-08-05 17:06:01 +02:00
parent 7b599e9ad9
commit be3778a0c9
22 changed files with 942 additions and 88 deletions
@@ -0,0 +1,73 @@
+import type { DomainEvent } from "./events.js";
+import { type HpRange, type HpVariant, hpForVariant } from "./hp-range.js";
+import {
+	type CombatantId,
+	type DomainError,
+	type Encounter,
+	findCombatant,
+	isDomainError,
+} from "./types.js";
+
+export interface SetHpVariantSuccess {
+	readonly encounter: Encounter;
+	readonly events: DomainEvent[];
+}
+
+/**
+ * Switches a combatant's max HP between the minimum, average and maximum roll
+ * of its Hit Dice.
+ *
+ * The shift is applied as a delta so manual HP edits and damage already taken
+ * survive the switch: a creature missing 5 HP still misses 5 HP afterwards.
+ */
+export function setHpVariant(
+	encounter: Encounter,
+	combatantId: CombatantId,
+	variant: HpVariant | undefined,
+	range: HpRange,
+): SetHpVariantSuccess | DomainError {
+	const found = findCombatant(encounter, combatantId);
+	if (isDomainError(found)) return found;
+
+	const { combatant } = found;
+	if (combatant.hpVariant === variant) {
+		return { encounter, events: [] };
+	}
+
+	const delta =
+		hpForVariant(range, variant) - hpForVariant(range, combatant.hpVariant);
+
+	const newMaxHp =
+		combatant.maxHp === undefined
+			? undefined
+			: Math.max(1, combatant.maxHp + delta);
+	const newCurrentHp =
+		combatant.currentHp === undefined || newMaxHp === undefined
+			? combatant.currentHp
+			: Math.max(0, Math.min(combatant.currentHp + delta, newMaxHp));
+
+	return {
+		encounter: {
+			...encounter,
+			combatants: encounter.combatants.map((c) =>
+				c.id === combatantId
+					? {
+							...c,
+							maxHp: newMaxHp,
+							currentHp: newCurrentHp,
+							hpVariant: variant,
+						}
+					: c,
+			),
+		},
+		events: [
+			{
+				type: "HpVariantSet",
+				combatantId,
+				variant,
+				previousMaxHp: combatant.maxHp,
+				newMaxHp,
+			},
+		],
+	};
+}