import { isHandleEnabled } from '../../core/graph';
import { animationFrameAt } from '../../core/model/animation';
import { textOf } from '../../core/model/Properties';
import { findAssetOf } from '../../core/model/Project';
import type { Entity } from '../Entity';
import type { World } from '../World';
import type { System } from './System';

export interface AnimationFinish {
  entity: Entity;
  animationId: string;
}

/**
 * Advances every sprite wearing an animation. A different animation starts over; the same one set
 * again runs on, so a graph may set it every frame. Runs before the BehaviorSystem, which reports
 * this frame's `finished`.
 */
export class AnimationSystem implements System {
  finished: AnimationFinish[] = [];

  update(world: World, dt: number): void {
    this.finished = [];
    for (const entity of world.entities) {
      if (entity.type !== 'sprite') continue;
      const id = textOf(entity.props.texture ?? '');
      const asset = findAssetOf(world.project, id, 'animation');
      if (!asset) {
        delete entity.animation;
        continue;
      }
      const clock = entity.animation;
      if (!clock || clock.id !== id) {
        entity.animation = { id, time: 0, finished: false };
        continue;
      }
      if (!isHandleEnabled(entity)) continue;
      clock.time += dt;
      if (!clock.finished && animationFrameAt(asset, clock.time).finished) {
        clock.finished = true;
        this.finished.push({ entity, animationId: id });
      }
    }
  }

  stop(): void {
    this.finished = [];
  }
}

/** Seconds into the animation the entity wears – 0 for one it was given since the last tick. */
export function animationTime(entity: Entity): number {
  const clock = entity.animation;
  return clock && clock.id === textOf(entity.props.texture ?? '') ? clock.time : 0;
}