"use client";

import { useEffect, useRef } from "react";
import { cn } from "@/lib/utils";

type AgentWorkflowParticleScatterProps = {
  className?: string;
  density?: "low" | "medium" | "high";
};

type Particle = {
  x: number;
  y: number;
  radius: number;
  speed: number;
  drift: number;
  alpha: number;
  hue: number;
  phase: number;
  swing: number;
  depth: number;
};

const PARTICLE_DENSITY_MULTIPLIER = {
  low: 0.75,
  medium: 1,
  high: 1.35,
} as const;

function randomBetween(min: number, max: number) {
  return min + Math.random() * (max - min);
}

export function AgentWorkflowParticleScatter({
  className,
  density = "medium",
}: AgentWorkflowParticleScatterProps) {
  const canvasRef = useRef<HTMLCanvasElement | null>(null);

  useEffect(() => {
    const canvas = canvasRef.current;
    if (!canvas) {
      return;
    }

    const context = canvas.getContext("2d");
    if (!context) {
      return;
    }

    const reducedMotionQuery = window.matchMedia("(prefers-reduced-motion: reduce)");
    let width = 0;
    let height = 0;
    let animationFrameId = 0;
    let particles: Particle[] = [];

    const buildParticle = (): Particle => {
      const depth = randomBetween(0.65, 1.15);
      const spread = width * randomBetween(0.16, 0.48);
      const originX = width / 2 + randomBetween(-spread, spread);
      const originY = height * randomBetween(0.56, 1.06);

      return {
        x: originX,
        y: originY,
        radius: randomBetween(0.9, 2.8) * depth,
        speed: randomBetween(0.08, 0.34) * depth,
        drift: randomBetween(0.12, 0.38) * (Math.random() > 0.5 ? 1 : -1),
        alpha: randomBetween(0.16, 0.84),
        hue: Math.random() > 0.7 ? 0 : 160,
        phase: randomBetween(0, Math.PI * 2),
        swing: randomBetween(10, 42),
        depth,
      };
    };

    const resetParticle = (particle: Particle, respawnNearBottom = false) => {
      const next = buildParticle();
      particle.x = next.x;
      particle.y = respawnNearBottom ? height * randomBetween(0.72, 1.04) : next.y;
      particle.radius = next.radius;
      particle.speed = next.speed;
      particle.drift = next.drift;
      particle.alpha = next.alpha;
      particle.hue = next.hue;
      particle.phase = next.phase;
      particle.swing = next.swing;
      particle.depth = next.depth;
    };

    const resize = () => {
      const bounds = canvas.getBoundingClientRect();
      const pixelRatio = Math.min(window.devicePixelRatio || 1, 2);
      width = Math.max(1, bounds.width);
      height = Math.max(1, bounds.height);
      canvas.width = Math.round(width * pixelRatio);
      canvas.height = Math.round(height * pixelRatio);
      context.setTransform(pixelRatio, 0, 0, pixelRatio, 0, 0);

      const baseCount = Math.round((width / 12) * PARTICLE_DENSITY_MULTIPLIER[density]);
      particles = Array.from(
        { length: Math.max(56, Math.min(220, baseCount)) },
        () => buildParticle()
      );
    };

    const drawGlow = (x: number, y: number, radius: number, alpha: number, hue: number) => {
      const gradient = context.createRadialGradient(x, y, 0, x, y, radius * 5.5);
      if (hue === 160) {
        gradient.addColorStop(0, `rgba(110, 255, 217, ${alpha})`);
        gradient.addColorStop(0.35, `rgba(26, 214, 168, ${alpha * 0.7})`);
        gradient.addColorStop(1, "rgba(26, 214, 168, 0)");
      } else {
        gradient.addColorStop(0, `rgba(255, 255, 255, ${alpha})`);
        gradient.addColorStop(0.42, `rgba(209, 255, 244, ${alpha * 0.45})`);
        gradient.addColorStop(1, "rgba(255, 255, 255, 0)");
      }
      context.fillStyle = gradient;
      context.beginPath();
      context.arc(x, y, radius * 5.5, 0, Math.PI * 2);
      context.fill();
    };

    const render = (time: number) => {
      context.clearRect(0, 0, width, height);

      const bottomGlow = context.createRadialGradient(
        width / 2,
        height * 0.92,
        0,
        width / 2,
        height * 0.92,
        width * 0.42
      );
      bottomGlow.addColorStop(0, "rgba(19, 221, 179, 0.18)");
      bottomGlow.addColorStop(0.5, "rgba(19, 221, 179, 0.08)");
      bottomGlow.addColorStop(1, "rgba(19, 221, 179, 0)");
      context.fillStyle = bottomGlow;
      context.fillRect(0, 0, width, height);

      particles.forEach((particle) => {
        particle.phase += 0.012;
        particle.y -= particle.speed;
        particle.x += Math.sin(time * 0.00032 + particle.phase) * particle.drift;

        const waveOffset =
          Math.sin(time * 0.001 + particle.phase * 2.4) * particle.swing * 0.018;
        const pulseAlpha =
          particle.alpha * (0.7 + 0.3 * Math.sin(time * 0.0016 + particle.phase));
        const renderX = particle.x + waveOffset;
        const renderY = particle.y;

        if (renderY < -24 || renderX < -32 || renderX > width + 32) {
          resetParticle(particle, true);
        }

        drawGlow(renderX, renderY, particle.radius, pulseAlpha * 0.68, particle.hue);

        context.beginPath();
        context.fillStyle =
          particle.hue === 160
            ? `rgba(155, 255, 230, ${pulseAlpha})`
            : `rgba(255, 255, 255, ${pulseAlpha})`;
        context.arc(renderX, renderY, particle.radius, 0, Math.PI * 2);
        context.fill();
      });

      if (!reducedMotionQuery.matches) {
        animationFrameId = window.requestAnimationFrame(render);
      }
    };

    resize();

    const handleResize = () => {
      resize();
    };

    window.addEventListener("resize", handleResize);

    if (reducedMotionQuery.matches) {
      render(0);
    } else {
      animationFrameId = window.requestAnimationFrame(render);
    }

    return () => {
      window.removeEventListener("resize", handleResize);
      if (animationFrameId) {
        window.cancelAnimationFrame(animationFrameId);
      }
    };
  }, [density]);

  return (
    <div
      className={cn(
        "pointer-events-none absolute inset-x-0 bottom-0 overflow-hidden",
        className
      )}
    >
      <canvas
        ref={canvasRef}
        className="h-full w-full [mask-image:linear-gradient(to_top,black_58%,transparent_100%)]"
      />
    </div>
  );
}