feat: implement NPC systems (needs decay, brain, movement)

Add three ECS systems for NPC simulation: - needsDecaySystem: decrements hunger/energy each tick, clamped at 0 - npcBrainSystem: goal selection based on need thresholds with pathfinding - movementSystem: advances entities along computed paths Includes 8 passing tests covering decay, goal prioritization, and movement. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
2026-03-06 18:19:07 -05:00
parent 30ea2f42c2
commit 83660609fc
4 changed files with 229 additions and 0 deletions
@@ -0,0 +1,75 @@
+import {
+  HUNGER_THRESHOLD, ENERGY_THRESHOLD,
+  type Needs, type Movement, type NPCBrain, type Position,
+} from '@dflike/shared';
+import type { World } from '../ecs/World.js';
+import type { GameMap } from '../map/GameMap.js';
+import { findPath } from '../map/pathfinding.js';
+
+function closestPOI(map: GameMap, from: Position, type: 'food' | 'rest'): Position | null {
+  const pois = map.getPointsOfInterest(type);
+  if (pois.length === 0) return null;
+  let best = pois[0].position;
+  let bestDist = Math.abs(from.x - best.x) + Math.abs(from.y - best.y);
+  for (let i = 1; i < pois.length; i++) {
+    const d = Math.abs(from.x - pois[i].position.x) + Math.abs(from.y - pois[i].position.y);
+    if (d < bestDist) { best = pois[i].position; bestDist = d; }
+  }
+  return best;
+}
+
+function directionTo(from: Position, to: Position): number {
+  const dx = to.x - from.x;
+  const dy = to.y - from.y;
+  if (Math.abs(dx) > Math.abs(dy)) return dx > 0 ? 2 : 1; // RIGHT : LEFT
+  return dy > 0 ? 0 : 3; // DOWN : UP
+}
+
+export function npcBrainSystem(world: World, map: GameMap): void {
+  for (const entity of world.query('npcBrain', 'needs', 'movement', 'position')) {
+    const brain = world.getComponent<NPCBrain>(entity, 'npcBrain')!;
+    const needs = world.getComponent<Needs>(entity, 'needs')!;
+    const movement = world.getComponent<Movement>(entity, 'movement')!;
+    const pos = world.getComponent<Position>(entity, 'position')!;
+
+    // Skip if currently walking toward a goal
+    if (movement.state === 'walking' && movement.path.length > 0) continue;
+
+    // Check if at goal destination — recover needs
+    if (brain.currentGoal === 'eat' && movement.state === 'idle') {
+      needs.hunger = Math.min(100, needs.hunger + 20);
+      brain.currentGoal = null;
+    }
+    if (brain.currentGoal === 'rest' && movement.state === 'idle') {
+      needs.energy = Math.min(100, needs.energy + 20);
+      brain.currentGoal = null;
+    }
+
+    // Determine new goal based on needs priority
+    let goal: 'rest' | 'eat' | 'wander' = 'wander';
+    if (needs.energy < ENERGY_THRESHOLD) goal = 'rest';
+    else if (needs.hunger < HUNGER_THRESHOLD) goal = 'eat';
+
+    brain.currentGoal = goal;
+
+    // Pick target based on goal
+    let target: Position | null = null;
+    if (goal === 'eat') {
+      target = closestPOI(map, pos, 'food');
+    } else if (goal === 'rest') {
+      target = closestPOI(map, pos, 'rest');
+    }
+    if (!target) {
+      target = map.getRandomWalkable();
+    }
+
+    // Pathfind to target
+    const path = findPath(map, pos, target);
+    if (path && path.length > 0) {
+      movement.state = 'walking';
+      movement.target = target;
+      movement.path = path;
+      movement.direction = directionTo(pos, path[0]);
+    }
+  }
+}