import type { Stage } from './scenes/stage';
import { FLOOR_Y } from './scenes/stage';

/**
 * Dev harness — toastsim's single most valuable organ, transplanted.
 *
 * Drives the REAL sim deterministically at a fixed dt so "does it actually work"
 * is answered by measured numbers, not by squinting. Every helper returns a
 * stats object. Installed on window.__s in dev builds. Milestones add verbs;
 * nothing ships without a harness number behind it.
 */
const STAGE_UNIT = 40; // px per "stage-unit" — the walk bar is measured in these
const HOME_X = 400;

export function installHarness(stage: Stage): void {
  const p = () => stage.puppet;
  const M = () => stage.matter.body;

  const step = (frames: number, dt = 1000 / 60): void => {
    stage.auto = false;
    for (let i = 0; i < frames; i++) stage.stepSim(dt);
  };

  /** Hold the bar at (x,y) for `frames`, stepping each frame (no tilt). */
  const hold = (x: number, y: number, frames: number, grip = false): void => {
    stage.auto = false;
    for (let i = 0; i < frames; i++) {
      p().setBar(x, y, 0);
      p().setGrip(grip);
      stage.stepSim();
    }
  };

  /** Frames until the swing steadies. Soft strings keep a marionette gently
   *  alive forever, so "settled" means the energy has plateaued (stopped
   *  falling), not literal zero. Returns frames-to-steady. */
  const settle = (maxFrames = 600): number => {
    stage.auto = false;
    let f = 0, low = Infinity, plateau = 0;
    for (; f < maxFrames; f++) {
      stage.stepSim();
      const v = p().restSpeed();
      if (v < low - 0.02) { low = v; plateau = 0; } else if (++plateau > 45) break;
      if (v < 0.15) break;
    }
    return f;
  };

  const placeCrate = (x: number): void => {
    M().setPosition(stage.crate, { x, y: FLOOR_Y - 16 }, false);
    M().setAngle(stage.crate, 0, false);
    M().setVelocity(stage.crate, { x: 0, y: 0 });
    M().setAngularVelocity(stage.crate, 0);
  };

  const s = {
    stage,
    step,
    settle,
    pose: () => p().pose(),

    /** Set the control bar to an absolute position and step one frame. */
    bar(x: number, y = p().barHomeY) {
      stage.auto = false;
      p().setBar(x, y, 0);
      stage.stepSim();
      return p().pose();
    },

    grip(on: boolean) {
      stage.auto = false;
      p().setGrip(on);
      stage.stepSim();
      return { gripping: p().gripping, hands: p().handWorld() };
    },

    /** Oscillate the bar around home: freq Hz, amp px, for secs seconds. */
    sway(freq = 1.2, amp = 90, secs = 3) {
      stage.auto = false;
      const frames = Math.round(secs * 60);
      for (let i = 0; i < frames; i++) {
        const x = HOME_X + amp * Math.sin((2 * Math.PI * freq * i) / 60);
        p().applyInput(x, p().barHomeY, false, false);
        stage.stepSim();
      }
      return p().pose();
    },

    /** THE DANGLE (M1 feel gate): yank the bar aside, let go, measure the swing
     *  home. Long settle + a clean decay = a puppet that has real pendulum. */
    dangle() {
      hold(HOME_X, p().barHomeY, 30); // start at rest
      hold(HOME_X + 220, p().barHomeY, 12); // yank right
      p().setBar(HOME_X, p().barHomeY, 0); // release to home
      const frames = settle();
      return { settleFrames: frames, ...p().pose() };
    },

    /** THE WALK (M1 exit-bar): a rhythmic sway whose centre drifts `dir`, so the
     *  legs swing and the puppet is dragged along. Reports units travelled and
     *  whether it stayed upright the whole way. */
    walk(dir = 1, secs = 8, freq = 1.2, amp = 45, advance = 460) {
      hold(HOME_X, p().barHomeY, 20);
      const x0 = p().torsoX;
      const frames = Math.round(secs * 60);
      let upright = true;
      for (let i = 0; i < frames; i++) {
        const center = HOME_X + dir * advance * (i / frames);
        const x = center + amp * Math.sin((2 * Math.PI * freq * i) / 60);
        p().applyInput(x, p().barHomeY, false, false);
        stage.stepSim();
        if (!p().pose().upright) upright = false;
      }
      const dx = p().torsoX - x0;
      return {
        units: +(dx / STAGE_UNIT).toFixed(2),
        dx: +dx.toFixed(1),
        upright,
        faceplant: !upright,
        lean: p().pose().lean,
      };
    },

    /** Reach down over the crate, grip, lift — did the crate leave the floor? */
    pickup(crateX = 470) {
      placeCrate(crateX);
      // hover the hands over the crate, then reach + grip
      hold(crateX, p().barHomeY, 25);
      hold(crateX, p().barHomeY + 130, 30, true); // reach + clamp
      const grabbedY = stage.crate.position.y;
      hold(crateX, p().barHomeY - 40, 40, true); // lift
      const lift = grabbedY - stage.crate.position.y;
      const held = stage.crate.position.y < FLOOR_Y - 40;
      p().setGrip(false);
      return { lift: +lift.toFixed(1), crateY: +stage.crate.position.y.toFixed(1), held };
    },

    /** Grip must lift the crate 10/10. Vary the crate x each trial. */
    pickupTest(n = 10) {
      let ok = 0;
      const lifts: number[] = [];
      for (let i = 0; i < n; i++) {
        stage.auto = false;
        hold(HOME_X, p().barHomeY, 25); // re-dangle to home between trials
        const r = this.pickup(440 + (i % 5) * 15);
        if (r.held) ok++;
        lifts.push(r.lift);
      }
      return { ok, n, rate: `${ok}/${n}`, lifts };
    },
  };

  (window as { __s?: typeof s }).__s = s;
  // eslint-disable-next-line no-console
  console.log('[dev] __s ready — __s.dangle() __s.walk() __s.pickupTest()');
}