/**
 * The 3D hero view of the line.
 *
 * No external assets are loaded anywhere in this scene - no HDRI environment, no
 * CDN font, no texture. Everything is primitives and analytic lights, because the
 * demo has to survive a room with no working wifi.
 */

import { Suspense } from 'react';
import { Canvas } from '@react-three/fiber';
import { OrbitControls, ContactShadows } from '@react-three/drei';
import { useStore } from '../store.js';
import { Station } from './Station.jsx';
import { Belt, QueueBoxes, FlowBoxes } from './Conveyor.jsx';
import { stateMeta } from '../lib/format.js';

/** Station centres, evenly spaced along the line. */
const SPACING = 4.3;
const stationX = (i, n) => (i - (n - 1) / 2) * SPACING;

function Floor() {
  return (
    <>
      <mesh position={[0, -0.02, 0]} rotation={[-Math.PI / 2, 0, 0]} receiveShadow>
        <planeGeometry args={[60, 26]} />
        <meshStandardMaterial color="#161513" roughness={0.95} metalness={0} />
      </mesh>
      {/* aisle markings, purely to give the eye a ground plane to read depth from */}
      {[-3.2, 3.2].map((z) => (
        <mesh key={z} position={[0, 0, z]} rotation={[-Math.PI / 2, 0, 0]}>
          <planeGeometry args={[26, 0.06]} />
          <meshBasicMaterial color="#3a3830" />
        </mesh>
      ))}
    </>
  );
}

function LineContent() {
  const frame = useStore((s) => s.frame);
  const meta = useStore((s) => s.meta);
  const selected = useStore((s) => s.selected);
  const select = useStore((s) => s.select);

  if (!frame || !meta) return null;
  const n = frame.stations.length;

  return (
    <group>
      {frame.stations.map((st, i) => (
        <Station
          key={st.id}
          station={st}
          spec={meta.stations.find((x) => x.id === st.id)}
          x={stationX(i, n)}
          selected={selected === st.id}
          onSelect={select}
        />
      ))}

      {frame.buffers.map((level, i) => {
        const x = (stationX(i, n) + stationX(i + 1, n)) / 2;
        const width = SPACING - 2.15;
        const upstream = frame.stations[i];
        return (
          <group key={i}>
            <Belt x={x} width={width} />
            <QueueBoxes
              x={x}
              width={width}
              count={level}
              full={level >= frame.bufferCapacity}
            />
            <FlowBoxes
              x={x}
              width={width}
              active={upstream.state === 'running'}
              rate={frame.controls.lineSpeedPct / 100}
            />
          </group>
        );
      })}
    </group>
  );
}

export function Scene() {
  const frame = useStore((s) => s.frame);
  const connected = useStore((s) => s.connected);

  const worstState = frame
    ? (frame.stations.find((s) => s.state === 'fault' || s.state === 'down')
      || frame.stations.find((s) => s.state === 'blocked'))
    : null;

  return (
    <div className="scene">
      <Canvas
        shadows
        dpr={[1, 1.75]}
        camera={{ position: [11, 8.5, 13], fov: 40 }}
        gl={{ antialias: true }}
      >
        <color attach="background" args={['#121211']} />
        <fog attach="fog" args={['#121211', 26, 52]} />

        {/* Analytic lights only - an HDRI would be a network fetch. */}
        <hemisphereLight args={['#8fa4b8', '#2a2620', 0.55]} />
        <directionalLight
          position={[9, 14, 8]}
          intensity={1.7}
          castShadow
          shadow-mapSize={[1024, 1024]}
          shadow-camera-left={-16}
          shadow-camera-right={16}
          shadow-camera-top={12}
          shadow-camera-bottom={-12}
        />
        <directionalLight position={[-10, 6, -8]} intensity={0.45} color="#7fa8d0" />

        <Suspense fallback={null}>
          <Floor />
          <LineContent />
          <ContactShadows
            position={[0, 0.01, 0]}
            opacity={0.5}
            scale={40}
            blur={2.4}
            far={5}
            resolution={512}
            color="#000000"
          />
        </Suspense>

        <OrbitControls
          target={[0, 1.1, 0]}
          enablePan
          minDistance={7}
          maxDistance={34}
          minPolarAngle={0.15}
          maxPolarAngle={Math.PI / 2.15}
        />
      </Canvas>

      <div className="scene-overlay">
        <span className="ttl">LINE-1 · Assembly &amp; Cure</span>
        <span className="sub">
          {connected ? 'Live twin' : 'Disconnected'}
          {worstState ? ` · ${worstState.id} ${stateMeta(worstState.state).label.toLowerCase()}` : ' · all stations nominal'}
        </span>
      </div>

      {/* Legend pairs every status colour with its word. */}
      <div className="scene-legend">
        {['running', 'microstop', 'blocked', 'fault'].map((s) => {
          const sm = stateMeta(s);
          return (
            <span className="legend-item" key={s}>
              <span className="dot" style={{
                width: 7, height: 7, borderRadius: '50%', background: sm.color, display: 'inline-block',
              }} />
              {sm.label}
            </span>
          );
        })}
      </div>

      <div className="scene-hint">Drag to orbit · scroll to zoom · click a machine to inspect</div>
    </div>
  );
}