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>
This commit is contained in:
2026-03-06 18:19:07 -05:00
parent 30ea2f42c2
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import { describe, it, expect } from 'vitest';
import { World } from '../../ecs/World.js';
import { GameMap } from '../../map/GameMap.js';
import { needsDecaySystem } from '../needsDecaySystem.js';
import { npcBrainSystem } from '../npcBrainSystem.js';
import { movementSystem } from '../movementSystem.js';
import type { Needs, Movement, NPCBrain, Position } from '@dflike/shared';
import { HUNGER_DECAY_PER_TICK, ENERGY_DECAY_PER_TICK } from '@dflike/shared';
function createNPC(world: World, x: number, y: number, hunger = 80, energy = 80) {
const e = world.createEntity();
world.addComponent<Position>(e, 'position', { x, y });
world.addComponent<Needs>(e, 'needs', { hunger, energy });
world.addComponent<Movement>(e, 'movement', { state: 'idle', target: null, path: [], direction: 0 });
world.addComponent<NPCBrain>(e, 'npcBrain', { currentGoal: null, goalQueue: [] });
return e;
}
describe('needsDecaySystem', () => {
it('decays hunger and energy each tick', () => {
const world = new World();
const e = createNPC(world, 0, 0, 50, 50);
needsDecaySystem(world);
const needs = world.getComponent<Needs>(e, 'needs')!;
expect(needs.hunger).toBeCloseTo(50 - HUNGER_DECAY_PER_TICK);
expect(needs.energy).toBeCloseTo(50 - ENERGY_DECAY_PER_TICK);
});
it('clamps needs at 0', () => {
const world = new World();
const e = createNPC(world, 0, 0, 0.01, 0.01);
needsDecaySystem(world);
const needs = world.getComponent<Needs>(e, 'needs')!;
expect(needs.hunger).toBeGreaterThanOrEqual(0);
expect(needs.energy).toBeGreaterThanOrEqual(0);
});
});
describe('npcBrainSystem', () => {
it('sets wander goal when needs are satisfied', () => {
const world = new World();
const map = new GameMap(10, 10);
const e = createNPC(world, 5, 5, 80, 80);
npcBrainSystem(world, map);
const brain = world.getComponent<NPCBrain>(e, 'npcBrain')!;
expect(brain.currentGoal).toBe('wander');
});
it('sets eat goal when hunger is low', () => {
const world = new World();
const map = new GameMap(10, 10);
map.addPointOfInterest({ type: 'food', position: { x: 3, y: 3 } });
const e = createNPC(world, 5, 5, 15, 80);
npcBrainSystem(world, map);
const brain = world.getComponent<NPCBrain>(e, 'npcBrain')!;
expect(brain.currentGoal).toBe('eat');
});
it('sets rest goal when energy is low', () => {
const world = new World();
const map = new GameMap(10, 10);
map.addPointOfInterest({ type: 'rest', position: { x: 7, y: 7 } });
const e = createNPC(world, 5, 5, 80, 10);
npcBrainSystem(world, map);
const brain = world.getComponent<NPCBrain>(e, 'npcBrain')!;
expect(brain.currentGoal).toBe('rest');
});
it('prioritizes energy over hunger', () => {
const world = new World();
const map = new GameMap(10, 10);
map.addPointOfInterest({ type: 'food', position: { x: 3, y: 3 } });
map.addPointOfInterest({ type: 'rest', position: { x: 7, y: 7 } });
const e = createNPC(world, 5, 5, 15, 10);
npcBrainSystem(world, map);
const brain = world.getComponent<NPCBrain>(e, 'npcBrain')!;
expect(brain.currentGoal).toBe('rest');
});
});
describe('movementSystem', () => {
it('moves entity along path', () => {
const world = new World();
const e = world.createEntity();
world.addComponent<Position>(e, 'position', { x: 0, y: 0 });
world.addComponent<Movement>(e, 'movement', {
state: 'walking',
target: { x: 2, y: 0 },
path: [{ x: 1, y: 0 }, { x: 2, y: 0 }],
direction: 2, // RIGHT
});
movementSystem(world);
const pos = world.getComponent<Position>(e, 'position')!;
expect(pos).toEqual({ x: 1, y: 0 });
});
it('sets idle when path is exhausted', () => {
const world = new World();
const e = world.createEntity();
world.addComponent<Position>(e, 'position', { x: 1, y: 0 });
world.addComponent<Movement>(e, 'movement', {
state: 'walking',
target: { x: 1, y: 0 },
path: [],
direction: 2,
});
movementSystem(world);
const mov = world.getComponent<Movement>(e, 'movement')!;
expect(mov.state).toBe('idle');
expect(mov.target).toBeNull();
});
});
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import { Direction, type Movement, type Position } from '@dflike/shared';
import type { World } from '../ecs/World.js';
function directionFromDelta(dx: number, dy: number): number {
if (Math.abs(dx) > Math.abs(dy)) return dx > 0 ? Direction.RIGHT : Direction.LEFT;
return dy > 0 ? Direction.DOWN : Direction.UP;
}
export function movementSystem(world: World): void {
for (const entity of world.query('position', 'movement')) {
const movement = world.getComponent<Movement>(entity, 'movement')!;
const pos = world.getComponent<Position>(entity, 'position')!;
if (movement.state !== 'walking' || movement.path.length === 0) {
if (movement.state === 'walking' && movement.path.length === 0) {
movement.state = 'idle';
movement.target = null;
}
continue;
}
const next = movement.path.shift()!;
movement.direction = directionFromDelta(next.x - pos.x, next.y - pos.y);
pos.x = next.x;
pos.y = next.y;
if (movement.path.length === 0) {
movement.state = 'idle';
movement.target = null;
}
}
}
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import { HUNGER_DECAY_PER_TICK, ENERGY_DECAY_PER_TICK, type Needs } from '@dflike/shared';
import type { World } from '../ecs/World.js';
export function needsDecaySystem(world: World): void {
for (const entity of world.query('needs')) {
const needs = world.getComponent<Needs>(entity, 'needs')!;
needs.hunger = Math.max(0, needs.hunger - HUNGER_DECAY_PER_TICK);
needs.energy = Math.max(0, needs.energy - ENERGY_DECAY_PER_TICK);
}
}
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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]);
}
}
}