/**
 * CircuitField.tsx
 * ---------------------------------------------------------------------------
 * The Professional page's counterpart to ConstellationField. It draws a faint
 * circuit-board pattern — orthogonal traces connecting node pads, with a slow
 * "signal pulse" traveling the traces — instead of stars and constellations.
 *
 * Crucially it carries the SAME `view-transition-name` ("sky") as the star
 * fields on other pages. So when you navigate from, say, the Home hero
 * (ConstellationField / AnimatedBackground) to the Professional page, the
 * browser's View Transition morphs the star field into the circuit field as
 * one element — constellations visibly transform into circuitry.
 *
 * Honors prefers-reduced-motion (renders a static board) and pauses off-screen.
 */
import { useEffect, useRef } from 'react';

interface Props {
  /**
   * Tailwind/className passthrough. The .astro call site includes `vt-sky` when
   * this element should carry the view-transition morph. Not computed here to
   * avoid a server/client hydration mismatch (see AnimatedBackground).
   */
  className?: string;
}

interface Trace {
  x1: number;
  y1: number;
  x2: number;
  y2: number;
}
interface Node {
  x: number;
  y: number;
}

export default function CircuitField({
  className = '',
}: Props) {
  const canvasRef = useRef<HTMLCanvasElement>(null);

  useEffect(() => {
    const canvas = canvasRef.current;
    if (!canvas) return;
    const ctx = canvas.getContext('2d');
    if (!ctx) return;

    const reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
    const dpr = Math.min(window.devicePixelRatio || 1, 2);
    let raf = 0;
    let width = 0;
    let height = 0;
    let t0 = performance.now();

    let traces: Trace[] = [];
    let nodes: Node[] = [];

    const gold = '#c9a24a';
    const violet = '#6a2fe0';
    const teal = '#2bc2b7';

    function build() {
      if (!canvas || !ctx) return;
      const rect = canvas.getBoundingClientRect();
      width = rect.width;
      height = rect.height;
      canvas.width = Math.floor(width * dpr);
      canvas.height = Math.floor(height * dpr);
      ctx.setTransform(dpr, 0, 0, dpr, 0, 0);

      // Build a clean, ALIGNED orthogonal circuit on a grid: pads sit exactly at
      // grid intersections (no jitter) and traces connect them in straight
      // right-angle lines. Reads as an orderly schematic / PCB layout.
      const step = 64;
      const cols = Math.ceil(width / step) + 1;
      const rows = Math.ceil(height / step) + 1;
      const present: boolean[][] = [];
      nodes = [];
      for (let r = 0; r < rows; r++) {
        present[r] = [];
        for (let c = 0; c < cols; c++) {
          // ~62% of intersections get a pad.
          present[r][c] = Math.random() < 0.62;
          if (present[r][c]) {
            // Snapped to the grid — no jitter, so traces land flush on pads.
            nodes.push({ x: c * step, y: r * step });
          }
        }
      }
      traces = [];
      for (let r = 0; r < rows; r++) {
        for (let c = 0; c < cols; c++) {
          if (!present[r][c]) continue;
          const here = { x: c * step, y: r * step };
          // Right neighbor.
          if (c + 1 < cols && present[r][c + 1] && Math.random() < 0.7) {
            traces.push({ x1: here.x, y1: here.y, x2: (c + 1) * step, y2: r * step });
          }
          // Down neighbor.
          if (r + 1 < rows && present[r + 1][c] && Math.random() < 0.7) {
            traces.push({ x1: here.x, y1: here.y, x2: c * step, y2: (r + 1) * step });
          }
        }
      }
    }

    function frame(now: number) {
      if (!ctx) return;
      const dt = Math.min(0.05, (now - t0) / 1000);
      t0 = now;
      ctx.clearRect(0, 0, width, height);

      // Traces. A signal pulse brightens a moving window along each trace, with
      // traces staggered so pulses are distributed across the board over time.
      for (let i = 0; i < traces.length; i++) {
        const t = traces[i];
        // Base trace — clearly visible violet conductor line.
        ctx.strokeStyle = 'rgba(43, 194, 183, 0.55)';
        ctx.lineWidth = 1.4;
        ctx.beginPath();
        ctx.moveTo(t.x1, t.y1);
        ctx.lineTo(t.x2, t.y2);
        ctx.stroke();

        // Pulse: a bright gold "signal" traveling the trace. position 0..1,
        // looping, with traces staggered so pulses spread across the board.
        const period = 6 + (i % 7);
        const phase = ((now / 1000) % period) / period;
        const px = t.x1 + (t.x2 - t.x1) * phase;
        const py = t.y1 + (t.y2 - t.y1) * phase;
        ctx.strokeStyle = gold;
        ctx.globalAlpha = 0.95;
        ctx.lineWidth = 2.2;
        ctx.shadowBlur = 10;
        ctx.shadowColor = gold;
        ctx.beginPath();
        ctx.moveTo(px - (t.x2 - t.x1) * 0.08, py - (t.y2 - t.y1) * 0.08);
        ctx.lineTo(px, py);
        ctx.stroke();
        // Bright pulse head dot.
        ctx.globalAlpha = 1;
        ctx.fillStyle = '#fbf3dc';
        ctx.beginPath();
        ctx.arc(px, py, 1.8, 0, Math.PI * 2);
        ctx.fill();
        ctx.globalAlpha = 1;
        ctx.shadowBlur = 0;
      }

      // Node pads — solid teal fill with a brighter violet ring (solder pad).
      for (const n of nodes) {
        ctx.beginPath();
        ctx.fillStyle = teal;
        ctx.globalAlpha = 0.95;
        ctx.arc(n.x, n.y, 2.4, 0, Math.PI * 2);
        ctx.fill();
        ctx.globalAlpha = 0.85;
        ctx.strokeStyle = violet;
        ctx.lineWidth = 1.4;
        ctx.beginPath();
        ctx.arc(n.x, n.y, 4.5, 0, Math.PI * 2);
        ctx.stroke();
      }
      ctx.globalAlpha = 1;

      void dt;
      raf = requestAnimationFrame(frame);
    }

    function drawStatic() {
      if (!ctx) return;
      ctx.clearRect(0, 0, width, height);
      for (const t of traces) {
        ctx.strokeStyle = 'rgba(43, 194, 183, 0.5)';
        ctx.lineWidth = 1.4;
        ctx.beginPath();
        ctx.moveTo(t.x1, t.y1);
        ctx.lineTo(t.x2, t.y2);
        ctx.stroke();
      }
      for (const n of nodes) {
        ctx.fillStyle = teal;
        ctx.globalAlpha = 0.95;
        ctx.beginPath();
        ctx.arc(n.x, n.y, 2.4, 0, Math.PI * 2);
        ctx.fill();
      }
      ctx.globalAlpha = 1;
    }

    build();
    if (reduce) {
      drawStatic();
    } else {
      t0 = performance.now();
      raf = requestAnimationFrame(frame);
    }
    const onResize = () => {
      build();
      if (reduce) drawStatic();
    };
    window.addEventListener('resize', onResize);

    const io = new IntersectionObserver((entries) => {
      if (reduce) return;
      for (const e of entries) {
        if (e.isIntersecting) {
          if (!raf) {
            t0 = performance.now();
            raf = requestAnimationFrame(frame);
          }
        } else {
          cancelAnimationFrame(raf);
          raf = 0;
        }
      }
    });
    io.observe(canvas);

    return () => {
      cancelAnimationFrame(raf);
      window.removeEventListener('resize', onResize);
      io.disconnect();
    };
  }, []);

  return (
    // Root container mirrors AnimatedBackground's structure (gradient layers +
    // canvas all INSIDE the named element) so the view-transition morph from a
    // star hero into this circuit field is element-to-element equivalent and
    // nothing flashes separately. The `vt-sky`/opacity classes are passed via
    // className from the .astro call site.
    <div
      className={`pointer-events-none absolute inset-0 -z-10 overflow-hidden ${className}`}
      aria-hidden="true"
    >
      {/* Base gradient — IDENTICAL colors to AnimatedBackground's night sky so
          the morph between star field and circuit field is color-consistent.
          No nebula radials here (the user asked to keep the circuit style only);
          just the clean deep-blue sky base. */}
      <div
        className="absolute inset-0"
        style={{
          background:
            'linear-gradient(180deg, #080c14 0%, #0b111c 32%, #0e1522 58%, #131c2b 82%, #1a2a3a 100%)',
        }}
      />
      {/* Circuit traces + nodes + signal pulses. */}
      <canvas ref={canvasRef} className="absolute inset-0 h-full w-full" />
    </div>
  );
}