/* kinematicslab.jsx — KinematicsTutor: the 1-D motion (dragster) bench. Built on
   window.BenchKit (harness) + window.BenchFields (shared field math), so this file is just
   the FIGURE. compute = window.BenchFields.kinematics — the SAME function
   server/benches/kinematics.js calls, so client and server fields are identical by
   construction. Follows the gas-laws TEMPLATE: sliders → BenchFields.fn(state) → report + meters. */
(function () {
  const { useState, useMemo, useEffect } = React;
  const K = window.BenchKit, C = K.C, SVG_BG = K.SVG_BG, fmt = K.fmt;
  const TaskStrip = K.TaskStrip, StatMeter = K.StatMeter;
  const compute = (s) => window.BenchFields.kinematics(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 }}>{label}</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 KinematicsFig({ task, setTask, tasks, report, event, done }) {
    const [v0, setV0] = useState(0);
    const [accel, setAccel] = useState(3);
    const [time, setTime] = useState(4);
    const fld = useMemo(() => compute({ v0, accel, time }), [v0, accel, time]);
    useEffect(() => { report(fld); }, [v0, accel, time]); // eslint-disable-line

    // track: displacement maps along X; v–t graph in a side panel.
    const X0 = 50, X1 = 360, TY = 110;                 // track line
    const dispMax = 120;                                // m mapped across the track
    const carX = X0 + Math.max(0, Math.min(1, fld.displacement / dispMax)) * (X1 - X0);
    // v–t graph box
    const GX0 = 400, GX1 = 560, GY0 = 50, GY1 = 250;
    const vAbsMax = 25;                                 // m/s mapped on the v axis
    const tMax = 15;                                    // s mapped on the t axis
    const vToY = (v) => GY0 + (GY1 - GY0) * (1 - (v + vAbsMax) / (2 * vAbsMax));
    const tToX = (t) => GX0 + (GX1 - GX0) * (t / tMax);
    const zeroY = vToY(0);
    const gx0 = tToX(0), gy0 = vToY(v0);
    const gx1 = tToX(time), gy1 = vToY(fld.velocity);

    const t = tasks.find((x) => x.id === task) || tasks[0];
    const vel = fld.velocity, dec = fld.isDecelerating;

    return (
      <>
        <TaskStrip tasks={tasks} cur={task} setCur={setTask} done={done} goal={t && t.goal} />
        <svg viewBox="0 0 600 300" style={{ width: "100%", background: SVG_BG, border: `1px solid ${C.line}`, borderRadius: 8 }}>
          {/* track */}
          <line x1={X0} y1={TY} x2={X1} y2={TY} stroke={C.faint} strokeWidth="2" />
          <line x1={X0} y1={TY - 8} x2={X0} y2={TY + 8} stroke={C.mute} strokeWidth="1.5" />
          <line x1={X1} y1={TY - 8} x2={X1} y2={TY + 8} stroke={C.mute} strokeWidth="1.5" />
          {/* dragster marker */}
          <rect x={carX - 10} y={TY - 8} width={20} height={12} rx={2} fill={dec ? C.crimson : C.teal} opacity="0.9" />
          <circle cx={carX - 5} cy={TY + 6} r={3} fill={C.ink} />
          <circle cx={carX + 5} cy={TY + 6} r={3} fill={C.ink} />
          {/* velocity arrow */}
          <line x1={carX} y1={TY - 16} x2={carX + Math.max(-40, Math.min(40, vel * 2))} y2={TY - 16} stroke={C.gold} strokeWidth="3" />
          <text x={X0} y={TY + 34} fill={C.mute} fontSize="11" fontFamily="monospace">x = {fmt(fld.displacement)} m</text>
          <text x={X0} y={TY - 30} fill={C.ink} fontSize="13" fontFamily="monospace">v = {fmt(vel)} m/s · a = {fmt(fld.accel)} m/s²</text>
          {/* v–t graph */}
          <rect x={GX0} y={GY0} width={GX1 - GX0} height={GY1 - GY0} fill="none" stroke={C.faint} strokeWidth="1.5" rx="4" />
          <line x1={GX0} y1={zeroY} x2={GX1} y2={zeroY} stroke={C.line} strokeWidth="1" />
          <line x1={gx0} y1={gy0} x2={gx1} y2={gy1} stroke={dec ? C.crimson : C.blue} strokeWidth="2.5" />
          <circle cx={gx0} cy={gy0} r={3} fill={C.mute} />
          <circle cx={gx1} cy={gy1} r={3.5} fill={dec ? C.crimson : C.blue} />
          <text x={GX0 + 4} y={GY0 - 6} fill={C.mute} fontSize="11" fontFamily="monospace">v–t (slope = a)</text>
          <text x={GX0 + 4} y={GY1 + 14} fill={C.mute} fontSize="10" fontFamily="monospace">t = {fmt(fld.time)} s</text>
        </svg>
        <div style={{ marginTop: 10, padding: "8px 12px", borderRadius: 6, background: C.panel, border: `1px solid ${dec ? C.crimson : C.line}`, color: dec ? C.crimson : C.mute, fontSize: 12.5 }}>
          v = v₀ + at = {fmt(vel)} m/s · x = v₀t + ½at² = {fmt(fld.displacement)} m. {dec ? "⚠ decelerating (a opposes v₀)." : "Raise a or t to gain speed; point a against v₀ to brake."}
        </div>
        <Slider label="initial velocity v₀" value={v0} set={setV0} min={-20} max={20} step={1} unit="m/s" color={C.blue} onUp={() => event("adjusted", `Set v₀ = ${fmt(v0)} m/s`, { response: `v ${fmt(fld.velocity)} m/s` }, C.blue)} />
        <Slider label="acceleration a" value={accel} set={setAccel} min={-10} max={10} step={0.5} unit="m/s²" color={C.crimson} onUp={() => event("adjusted", `Set a = ${fmt(accel)} m/s²`, { response: `v ${fmt(fld.velocity)} m/s` }, C.crimson)} />
        <Slider label="time t" value={time} set={setTime} min={0} max={15} step={0.5} unit="s" color={C.gold} onUp={() => event("adjusted", `Set t = ${fmt(time)} s`, { response: `x ${fmt(fld.displacement)} m` }, C.gold)} />
        <div style={{ display: "grid", gridTemplateColumns: "repeat(4,1fr)", gap: 8, marginTop: 12 }}>
          <StatMeter label="velocity v" v={fld.velocity} d={2} unit="m/s" color={dec ? C.crimson : C.teal} />
          <StatMeter label="displacement x" v={fld.displacement} d={1} unit="m" color={C.blue} />
          <StatMeter label="avg velocity" v={fld.avgVelocity} d={2} unit="m/s" color={C.amber} />
          <StatMeter label="acceleration a" v={fld.accel} d={2} unit="m/s²" color={C.crimson} />
        </div>
      </>
    );
  }

  window.KinematicsTutor = K.makeTutor(KinematicsFig, { moduleLabel: "Kinematics bench", benchId: "kinematics" });
})();