feat: add getEffectiveStat helper for computed stat values

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

server/src/systems/__tests__/statHelpers.test.ts

@@ -0,0 +1,82 @@
+import { describe, it, expect } from 'vitest';
+import { World } from '../../ecs/World.js';
+import { getEffectiveStat } from '../statHelpers.js';
+import type { Stats, StatModifiers } from '@dflike/shared';
+
+function addStats(world: World, entity: number, overrides: Partial<Stats> = {}): void {
+  const base: Stats = {
+    strength: 10, dexterity: 10, constitution: 10, intelligence: 10, perception: 10,
+    sociability: 10, courage: 10, curiosity: 10, empathy: 10, temperament: 10,
+    ...overrides,
+  };
+  world.addComponent<Stats>(entity, 'stats', base);
+}
+
+describe('getEffectiveStat', () => {
+  it('returns base stat when no modifiers', () => {
+    const world = new World();
+    const e = world.createEntity();
+    addStats(world, e, { strength: 14 });
+    expect(getEffectiveStat(world, e, 'strength')).toBe(14);
+  });
+
+  it('adds positive modifier', () => {
+    const world = new World();
+    const e = world.createEntity();
+    addStats(world, e, { empathy: 12 });
+    world.addComponent<StatModifiers>(e, 'statModifiers', {
+      modifiers: [{ stat: 'empathy', value: 2, remaining: 50 }],
+    });
+    expect(getEffectiveStat(world, e, 'empathy')).toBe(14);
+  });
+
+  it('adds negative modifier', () => {
+    const world = new World();
+    const e = world.createEntity();
+    addStats(world, e, { intelligence: 10 });
+    world.addComponent<StatModifiers>(e, 'statModifiers', {
+      modifiers: [{ stat: 'intelligence', value: -2, remaining: 50 }],
+    });
+    expect(getEffectiveStat(world, e, 'intelligence')).toBe(8);
+  });
+
+  it('clamps to minimum 3', () => {
+    const world = new World();
+    const e = world.createEntity();
+    addStats(world, e, { dexterity: 4 });
+    world.addComponent<StatModifiers>(e, 'statModifiers', {
+      modifiers: [{ stat: 'dexterity', value: -5, remaining: 50 }],
+    });
+    expect(getEffectiveStat(world, e, 'dexterity')).toBe(3);
+  });
+
+  it('clamps to maximum 18', () => {
+    const world = new World();
+    const e = world.createEntity();
+    addStats(world, e, { strength: 17 });
+    world.addComponent<StatModifiers>(e, 'statModifiers', {
+      modifiers: [{ stat: 'strength', value: 5, remaining: 50 }],
+    });
+    expect(getEffectiveStat(world, e, 'strength')).toBe(18);
+  });
+
+  it('sums multiple modifiers for same stat', () => {
+    const world = new World();
+    const e = world.createEntity();
+    addStats(world, e, { sociability: 10 });
+    world.addComponent<StatModifiers>(e, 'statModifiers', {
+      modifiers: [
+        { stat: 'sociability', value: 2, remaining: 50 },
+        { stat: 'sociability', value: -1, remaining: 30 },
+      ],
+    });
+    expect(getEffectiveStat(world, e, 'sociability')).toBe(11);
+  });
+
+  it('floors float base stats to integer', () => {
+    const world = new World();
+    const e = world.createEntity();
+    addStats(world, e, { courage: 10.7 });
+    expect(getEffectiveStat(world, e, 'courage')).toBe(10);
+  });
+});

server/src/systems/statHelpers.ts

@@ -0,0 +1,15 @@
+import type { Stats, StatName, StatModifiers } from '@dflike/shared';
+import type { World } from '../ecs/World.js';
+
+export function getEffectiveStat(world: World, entity: number, stat: StatName): number {
+  const base = world.getComponent<Stats>(entity, 'stats');
+  if (!base) return 10; // fallback for entities without stats
+  let value = base[stat];
+  const mods = world.getComponent<StatModifiers>(entity, 'statModifiers');
+  if (mods) {
+    for (const m of mods.modifiers) {
+      if (m.stat === stat) value += m.value;
+    }
+  }
+  return Math.max(3, Math.min(18, Math.floor(value)));
+}