Multiple healths as shields

src/common/rpg/components/stat.ts

@@ -65,7 +65,10 @@ export class Stat<T = {}> extends Component<StatState & T> {
 }
 
 @component
-export class Health extends Stat {
+export class Health extends Stat<{ damageTypes?: string[]; priority?: number }> {
+    get damageTypes(): readonly string[] { return this.state.damageTypes ?? []; }
+    get priority(): number { return this.state.priority ?? 0; }
+
     @action
     kill() {
         this.set(0);

src/common/rpg/systems/combat.ts

@@ -18,8 +18,8 @@ export class CombatSystem extends System {
         let random: Random | undefined;
 
         for (const [target] of world.query(Attacked)) {
-            const health = target.get(Health);
+            const healths = target.getAll(Health).sort((a, b) => b.priority - a.priority);
-            if (!health) {
+            if (healths.length === 0) {
                 console.warn(`[CombatSystem] Target ${target.id} has no Health component`);
                 for (const attack of target.getAll(Attacked)) target.remove(attack);
                 continue;
@@ -116,14 +116,43 @@ export class CombatSystem extends System {
 
             if (damageSum === 0) continue;
 
-            const wasAlive = health.value > 0;
+            let totalBefore = 0;
-            health.update(-damageSum);
+            for (const pool of healths) totalBefore += pool.value;
+
+            for (const hit of hitEvents) {
+                let remaining = hit.amount;
+
+                if (hit.damageType) {
+                    for (const pool of healths) {
+                        if (remaining <= 0) break;
+                        if (pool.value <= 0) continue;
+                        if (!pool.damageTypes.includes(hit.damageType)) continue;
+                        const take = Math.min(pool.value, remaining);
+                        pool.update(-take);
+                        remaining -= take;
+                    }
+                }
+
+                if (remaining > 0) {
+                    for (const pool of healths) {
+                        if (remaining <= 0) break;
+                        if (pool.value <= 0) continue;
+                        if (pool.damageTypes.length > 0) continue;
+                        const take = Math.min(pool.value, remaining);
+                        pool.update(-take);
+                        remaining -= take;
+                    }
+                }
+            }
 
             for (const info of hitEvents) {
                 target.emit('Combat.hit', info);
             }
 
-            if (wasAlive && health.value <= 0 && lastHit) {
+            let totalAfter = 0;
+            for (const pool of healths) totalAfter += pool.value;
+
+            if (totalBefore > 0 && totalAfter <= 0 && lastHit) {
                 target.emit('Combat.killed', lastHit);
             }
         }