// static/physics.js
// Pure pulse-engine math. No DOM. app.js drives the DOM from these numbers.
// Everything here is a function of the live VADUGWI mood — animation READS the
// soul; it never invents motion the soul didn't justify.
'use strict';

(function (global) {

  function springStep(state, target, dt, k, c) {
    const x = state.pos, v = state.vel;
    const a = -k * (x - target) - c * v;
    const nv = v + a * dt;
    const nx = x + nv * dt;
    return { pos: nx, vel: nv };
  }

  function breath(phase, mood) {
    const a = mood[1] ?? 128;
    const depth = 0.012 + (a / 255) * 0.05;
    return 1 + Math.sin(phase) * depth;
  }

  function breathRate(mood) {
    const a = mood[1] ?? 128;
    return 0.6 + (a / 255) * 3.2;
  }

  function behaviorFor(mood) {
    const a = mood[1] ?? 128, u = mood[3] ?? 0;
    if (a < 70 && u < 60) return 'sleep';
    if (a >= 195)         return 'excited';
    if (a >= 150)         return 'roam';
    if (a < 120)          return 'calm';
    return 'idle';
  }

  function sway(phase, mood) {
    const a = mood[1] ?? 128, i = mood[6] ?? 128;
    const amp = 1.5 + (a / 255) * 5.0;
    const bias = (i - 128) / 128 * 2.0;
    return Math.sin(phase * 0.6) * amp + bias;
  }

  global.ClankerPhysics = { springStep, breath, breathRate, behaviorFor, sway };

})(window);