feuerwerk/src/runtime/systems/behaviorContext.ts

/**
 * What a behavior's graph reaches of the running game, as the `NodeContext` its nodes are handed:
 * the world, the keyboard, collisions and rays, physics, sound, the clock and the shared values.
 * Handles arriving from a graph are resolved to the world's entities here, so no node holds one.
 */
import type { EntityHandle, NodeContext, PhysicsControl, SharedState } from '../../core/graph';
import { keyName } from '../../core/keys';
import { collisionFilterOf } from '../../core/model/collisionLayers';
import type { Vec2 } from '../../core/model/Properties';
import { JOINT_CONNECTED_KEY } from '../../core/model/joint';
import { objectReference } from '../../core/model/objectRefs';
import { findAsset, findAssetOf, findScene, type Project } from '../../core/model/Project';
import { soundFileOf } from '../../core/model/sound';
import { resolveAssetProps } from '../../core/properties/resolve';
import { loopsOf, volumeOf } from '../../core/properties/sounds';
import type { Entity } from '../Entity';
import { PhysicsSystem } from '../physics/PhysicsSystem';
import type { World } from '../World';
import type { AudioSink } from './Audio';
import type { Instance } from './behaviorPulses';
import type { Input } from './Input';
import { bodyOf, type CollisionSource, layerHolderOf, NOT_BLOCKED } from './solids';

export interface TimeScaled {
  scale: number;
}

/** What the running `BehaviorSystem` lends every context it makes. */
export interface ContextSources {
  project: Project;
  input: Input;
  collisions: CollisionSource | null;
  audio: AudioSink;
  clock: TimeScaled | null;
  shared: SharedState;
  /** A graph moved one of this instance's machines; its events follow between exec flows. */
  stateChanged(machineId: string, from: string, to: string): void;
}

const NO_DYNAMIC_BODY =
  'has no dynamic rigidbody, so Apply force, Apply impulse and Set velocity do nothing on it.';

export function behaviorContext(
  instance: Instance,
  world: World,
  dt: number,
  run: ContextSources,
): NodeContext {
  const { entity, states } = instance;
  const { project, collisions, clock } = run;
  // Handles arriving from the graph are the entities themselves, or test doubles with the same id.
  const resolve = (handle: EntityHandle | null): Entity | undefined =>
    handle ? world.entities.find((e) => e === handle || e.id === handle.id) : undefined;
  return {
    self: entity,
    owner: entity.parent,
    variables: instance.variables ?? entity.props,
    states,
    shared: run.shared,
    stateChanged: (machineId, from, to) => run.stateChanged(machineId, from, to),
    time: world.time,
    dt,
    findByName: (name) => world.findByName(name) ?? null,
    // By identity, not by id: a restarted scene builds new entities under the same ids.
    isAlive: (target) => world.entities.some((e) => e === target),
    findReferenced: (from, ref) => {
      const found = resolve(from);
      return (found && world.findReferenced(found, ref)) ?? null;
    },
    childByName: (parent, name) => {
      const found = resolve(parent);
      return (found && world.childByName(found, name)) ?? null;
    },
    objects: () => world.entities,
    isKeyDown: (key) => run.input.isDown(key),
    wasKeyPressed: (key) => run.input.justPressed.has(keyName(key)),
    wasKeyReleased: (key) => run.input.justReleased.has(keyName(key)),
    pointer: world.pointer,
    hitTest: (target, x, y) => {
      const found = resolve(target);
      return Boolean(found && world.hitTest(found, x, y));
    },
    isTouching: (a, b) => {
      const ea = resolve(a);
      const eb = resolve(b);
      return Boolean(collisions && ea && eb && collisions.touching(world, ea, eb));
    },
    moveAndSlide: (target, dx, dy) => {
      const found = resolve(target);
      if (!found) return NOT_BLOCKED;
      if (collisions) return collisions.moveAndSlide(world, found, dx, dy);
      found.x += dx;
      found.y += dy;
      return NOT_BLOCKED;
    },
    raycast: (from, direction, length, { ignore, triggers, layers }) => {
      const hit = collisions?.raycast(world, from, direction, length, {
        ignore: resolve(ignore) ?? null,
        triggers,
        layers,
      });
      world.noteRay(from, hit?.point ?? pointAlong(from, direction, length), Boolean(hit));
      return hit ? { ...hit, object: bodyOf(hit.collider) } : null;
    },
    raycastAll: (from, direction, length, { ignore, triggers, layers, maxHits }) => {
      const hits =
        collisions?.raycastAll(
          world,
          from,
          direction,
          length,
          { ignore: resolve(ignore) ?? null, triggers, layers },
          maxHits,
        ) ?? [];
      // Drawn to the last thing it met, not to the first: that is how far this ray looked.
      const last = hits[hits.length - 1];
      const end = last ? last.point : pointAlong(from, direction, length);
      world.noteRay(from, end, hits.length > 0);
      return hits.map((hit) => ({ ...hit, object: bodyOf(hit.collider) }));
    },
    collisionLayerOf: (target) => {
      const found = resolve(target);
      const holder = found && layerHolderOf(world, found);
      return holder ? collisionFilterOf(holder.props).layer : null;
    },
    ignoreOneWay: (target, seconds) => {
      const found = resolve(target);
      if (found) world.ignoreOneWay(found, seconds);
    },
    isTilemap: (target) => {
      const found = resolve(target);
      return found ? world.isTilemap(found) : false;
    },
    tileAt: (target, layer, cell) => {
      const found = resolve(target);
      return found ? world.tileAt(found, layer, cell) : null;
    },
    setTile: (target, layer, cell, tileId) => {
      const found = resolve(target);
      return found ? world.setTile(found, layer, cell, tileId) : false;
    },
    physics: collisions instanceof PhysicsSystem ? physicsControl(world, collisions, resolve) : undefined,
    log: (message) => {
      world.log.push(message);
      // The `Log` node's whole purpose: the author wants this in the browser console.
      // eslint-disable-next-line no-console
      console.log(`[behavior ${entity.name}]`, message);
    },
    playSound: (assetId, volume, loop, detached) =>
      playSound(run, assetId, volume, loop, detached ? '' : entity.id),
    // An id nothing resolves stops nothing, rather than silencing the whole run by accident;
    // only the empty id means "everything", which is what the node promises.
    stopSound: (assetId) => {
      const file = assetId === '' ? '' : soundFileOf(project, assetId);
      if (assetId === '' || file) run.audio.stop(file);
    },
    spawn: (assetId, position, parent) => world.spawn(assetId, position, resolve(parent) ?? null),
    addJoint: (assetId, owner, connected, at) => {
      const on = resolve(owner);
      if (!on || findAsset(project, assetId)?.type !== 'joint') return null;
      const joint = world.spawn(assetId, { ...at, z: 0 }, on);
      const to = resolve(connected);
      // By id, as a pick in the inspector stores it: the scene view of the run then draws the link too.
      if (joint && to) joint.props[JOINT_CONNECTED_KEY] = objectReference(to.objectId);
      return joint;
    },
    destroy: (target, keepChildren) => {
      const found = resolve(target);
      if (!found) return [];
      if (keepChildren) return world.removeKeepingChildren(found);
      world.remove(found);
      return [];
    },
    loadScene: (sceneId) => {
      // An id naming no scene is dropped here rather than half way through the swap, where the
      // run would already have torn down the world it is still standing in.
      if (findScene(project, sceneId)) world.loadSceneRequested = sceneId;
      else world.log.push(`Load scene: no scene ${sceneId}`);
    },
    stop: () => {
      world.stopRequested = true;
    },
    restart: () => {
      world.restartRequested = true;
    },
    timeScale: () => clock?.scale ?? 1,
    setTimeScale: (scale) => {
      if (clock) clock.scale = scale;
      else world.log.push(`Set time scale is ignored in the editor run (${scale})`);
    },
    isPaused: () => world.paused,
    setPaused: (paused) => {
      world.paused = paused;
    },
  };
}

/**
 * What the graph asked for, as the sink understands it: the asset's own volume scaled by the
 * node's, and its loop flag unless the node overrules it either way. The asset is what a sound
 * *is* – a node that says nothing therefore plays it as the project describes it.
 */
function playSound(
  { project, audio }: ContextSources,
  assetId: string,
  volume: number,
  loop: boolean | undefined,
  owner: string,
): void {
  const asset = findAssetOf(project, assetId, 'sound');
  if (!asset?.file) return;
  const props = resolveAssetProps(project, asset);
  const level = Math.max(0, Math.min(1, volumeOf(props) * volume));
  audio.play(asset.file, level, loop ?? loopsOf(props), owner);
}

/** Where a ray of that length ends; where it has no direction, where it starts. */
function pointAlong(from: Vec2, direction: Vec2, length: number): Vec2 {
  const d = Math.hypot(direction.x, direction.y);
  if (!(d > 0) || !(length > 0)) return from;
  return { x: from.x + (direction.x / d) * length, y: from.y + (direction.y / d) * length };
}

/** The physics nodes' way into the played game's engine, with the handles of the graph resolved. */
function physicsControl(
  world: World,
  physics: PhysicsSystem,
  resolve: (handle: EntityHandle | null) => Entity | undefined,
): PhysicsControl {
  const act = (handle: EntityHandle, action: (entity: Entity) => boolean): boolean => {
    const found = resolve(handle);
    if (!found) return false;
    if (action(found)) return true;
    physics.hint(world, found, NO_DYNAMIC_BODY);
    return false;
  };
  return {
    velocityOf: (handle) => {
      const found = resolve(handle);
      const v = found ? physics.velocityOf(found) : null;
      return found && v ? { ...v, angular: physics.angularVelocityOf(found) ?? 0 } : null;
    },
    setVelocity: (handle, x, y) => act(handle, (e) => physics.setVelocity(e, { x, y })),
    setAngularVelocity: (handle, degrees) => act(handle, (e) => physics.setAngularVelocity(e, degrees)),
    applyImpulse: (handle, x, y) => act(handle, (e) => physics.applyImpulse(e, { x, y })),
    setGravity: (x, y) => physics.setGravity(world, { x, y }),
  };
}