/* springslab.jsx — SpringsTutor: the mass-on-a-spring bench, in TRUE 3-D. Built on window.BenchKit
   (harness + 3-D SVG toolkit) + window.BenchFields (shared field math), so this file is just the FIGURE.
   computeFields = window.BenchFields.springs — the SAME function server/benches/springs.js calls, so
   client and server fields are identical by construction. A real 3-D helical coil hangs from a ceiling
   with a mass at its end; stretch/compress it (x) and watch the restoring force F = −kx, the elastic
   PE = ½kx² and the period T = 2π√(m/k) respond. Drag to orbit. 3-D method: docs/samples/triple-integral-svg.html. */
(function () {
  const { useState, useMemo, useEffect } = React;
  const K = window.BenchKit, C = K.C, fmt = K.fmt, V3 = K.V3;
  const TaskStrip = K.TaskStrip, StatMeter = K.StatMeter, Scene3D = K.Scene3D;
  const compute = (s) => window.BenchFields.springs(s);

  function Slider({ label, value, set, min, max, step, unit, color, onUp }) {
    return (
      <div style={{ display: "flex", alignItems: "center", gap: 10, marginTop: 9 }}>
        <span style={{ fontSize: 12, color: C.mute, width: 116 }}><K.T>{label}</K.T></span>
        <input type="range" min={min} max={max} step={step} value={value} onChange={(e) => set(parseFloat(e.target.value))} onPointerUp={onUp} style={{ flex: 1 }} />
        <span style={{ color: color || C.amber, width: 64, textAlign: "right" }}>{value}{unit ? ` ${unit}` : ""}</span>
      </div>
    );
  }

  function SpringsFig({ task, setTask, tasks, report, event, done }) {
    const [springK, setSpringK] = useState(200);
    const [displacement, setDisplacement] = useState(0.1);
    const [mass, setMass] = useState(0.5);
    const [az, setAz] = useState(26);
    const [el, setEl] = useState(12);
    const fld = useMemo(() => compute({ springK, displacement, mass }), [springK, displacement, mass]);
    useEffect(() => { report(fld); }, [springK, displacement, mass]); // eslint-disable-line

    // world: z is UP; the coil hangs from the ceiling at z=0 down to z=−springLen, then the mass.
    const R = 0.6, COILS = 7, EQ = 3;
    const springLen = EQ + (displacement / 0.3) * 1.5;     // stretched (x>0) longer, compressed shorter
    const bw = 0.5 + Math.min(1.0, mass * 0.22), bh = 0.5 + Math.min(1.2, mass * 0.25);
    const zBlockTop = -springLen, zBlockBot = zBlockTop - bh;
    const stretched = displacement > 0.005, compressed = displacement < -0.005;
    const coilColor = stretched ? "rgba(255,122,107,.95)" : compressed ? "rgba(108,182,255,.95)" : "rgba(84,242,178,.95)";

    const fit = [];
    for (const x of [-1.4, 1.4]) for (const y of [-1.4, 1.4]) { fit.push([x, y, 0]); fit.push([x, y, -EQ]); }
    fit.push([0, 0, zBlockBot - 0.3], [bw, bw, zBlockBot], [-bw, -bw, zBlockTop]);

    const build = (screen) => {
      let out = "";
      // ceiling (anchor plane) at z=0 with hatching
      out += K.poly3d(screen, [[-1.1, -1.1, 0], [1.1, -1.1, 0], [1.1, 1.1, 0], [-1.1, 1.1, 0]], "rgba(159,182,198,0.10)", C.faint, 1);
      for (let i = -1; i <= 1; i += 0.5) out += K.seg3d(screen, [i, -1.1, 0], [i - 0.25, -1.1, 0.35], C.faint, 0.8);
      // equilibrium reference plane (dashed square) at z=−EQ
      out += K.poly3d(screen, [[-1.4, -1.4, -EQ], [1.4, -1.4, -EQ], [1.4, 1.4, -EQ], [-1.4, 1.4, -EQ]], "rgba(108,182,255,0.05)", C.line, 0.8);
      out += K.text3d(screen, [1.7, 1.4, -EQ], "equilibrium", C.faint, 10);
      // central z axis (dashed)
      out += K.seg3d(screen, [0, 0, 0.3], [0, 0, zBlockBot - 0.4], C.faint, 0.7, "3 3");
      // the helix — sample the coil, draw as one polyline
      const N = COILS * 22, pts = [];
      for (let i = 0; i <= N; i++) { const t = i / N, th = t * COILS * 2 * Math.PI; pts.push(screen([R * Math.cos(th), R * Math.sin(th), -t * springLen])); }
      out += `<polyline points="${pts.map((p) => `${p.x.toFixed(1)},${p.y.toFixed(1)}`).join(" ")}" fill="none" stroke="${coilColor}" stroke-width="2.4" stroke-linejoin="round" stroke-linecap="round"/>`;
      // the mass block (a shaded 3-D cube)
      out += K.paint3d(K.boxFaces3d(screen, -bw, bw, -bw, bw, zBlockBot, zBlockTop, [227, 179, 65]));
      out += K.text3d(screen, [0, 0, (zBlockTop + zBlockBot) / 2], `${fmt(mass)} kg`, "#241a00", 11);
      // restoring-force vector beside the block: stretched ⇒ up (+z), compressed ⇒ down
      if (Math.abs(fld.force) > 0.5) {
        const L = Math.min(1.6, Math.abs(fld.force) / 60), dir = displacement > 0 ? 1 : -1, zc = (zBlockTop + zBlockBot) / 2;
        out += K.vec3d(screen, [bw + 0.35, 0, zc], [bw + 0.35, 0, zc + dir * L], C.crimson, 2.6);
        out += K.text3d(screen, [bw + 0.9, 0, zc + dir * L], `F = ${fmt(fld.force)} N`, C.crimson, 11);
      }
      return out;
    };

    const t = tasks.find((x) => x.id === task) || tasks[0];

    return (
      <>
        <TaskStrip tasks={tasks} cur={task} setCur={setTask} done={done} goal={t && t.goal} />
        <Scene3D az={az} el={el} setAz={setAz} setEl={setEl} fit={fit} width={600} height={320} build={build}
          onUp={() => event("rotated", `View az ${Math.round(az)}° · el ${Math.round(el)}°`, { response: `F ${fmt(fld.force)} N` }, C.blue)} />
        <div style={{ display: "flex", justifyContent: "space-between", alignItems: "center", marginTop: 8, fontSize: 11.5, color: C.faint, fontFamily: "monospace" }}>
          <span><K.T>drag to orbit</K.T> · k = {Math.round(springK)} N/m · x = {fmt(displacement)} m · m = {fmt(mass)} kg</span>
          <span><span style={{ color: C.crimson }}>F = {fmt(fld.force)} N</span> · T = {fmt(fld.period)} s</span>
        </div>
        <div style={{ marginTop: 10, padding: "8px 12px", borderRadius: 6, background: C.panel, border: `1px solid ${C.line}`, color: C.mute, fontSize: 12.5 }}>
          F = −kx = {fmt(fld.force)} N · PE = ½kx² = {fmt(fld.peSpring)} J · T = 2π√(m/k) = {fmt(fld.period)} s. {fld.atRest ? <K.T>At equilibrium (x ≈ 0).</K.T> : <K.T>Displace x, stiffen k, or change m and watch the restoring force and period respond.</K.T>}
        </div>
        <Slider label="spring constant k" value={springK} set={setSpringK} min={10} max={1000} step={10} unit="N/m" color={C.teal} onUp={() => event("adjusted", `Set k = ${Math.round(springK)} N/m`, { response: `F ${fmt(fld.force)} N` }, C.teal)} />
        <Slider label="displacement x" value={displacement} set={setDisplacement} min={-0.3} max={0.3} step={0.01} unit="m" color={C.crimson} onUp={() => event("adjusted", `Set x = ${fmt(displacement)} m`, { response: `F ${fmt(fld.force)} N` }, C.crimson)} />
        <Slider label="mass m" value={mass} set={setMass} min={0.1} max={5} step={0.1} unit="kg" color={C.gold} onUp={() => event("adjusted", `Set m = ${fmt(mass)} kg`, { response: `T ${fmt(fld.period)} s` }, C.gold)} />
        <div style={{ display: "grid", gridTemplateColumns: "repeat(4,1fr)", gap: 8, marginTop: 12 }}>
          <StatMeter label="force F" v={fld.force} d={1} unit="N" color={C.crimson} />
          <StatMeter label="elastic PE" v={fld.peSpring} unit="J" color={C.blue} />
          <StatMeter label="period T" v={fld.period} unit="s" color={C.teal} />
          <StatMeter label="frequency f" v={fld.freq} unit="Hz" color={C.amber} />
        </div>
      </>
    );
  }

  window.SpringsTutor = K.makeTutor(SpringsFig, { moduleLabel: "Springs bench", benchId: "springs" });
})();