'use client'

import React, { useEffect, useRef } from 'react'

interface OKLCHColor {
  l: number
  c: number
  h: number
}

// Monochromes Farbkonzept im OKLCH-Raum
const BASE_BG = { l: 0.145, c: 0.01, h: 148 }
const BASE_DIM = { l: 0.50, c: 0.01, h: 148 }
const HIGHLIGHT_BRIGHT = { l: 0.95, c: 0.01, h: 148 }

function lerp(a: number, b: number, t: number): number {
  return a + (b - a) * t
}

function lerpOKLCH(c1: OKLCHColor, c2: OKLCHColor, t: number): OKLCHColor {
  return {
    l: lerp(c1.l, c2.l, t),
    c: lerp(c1.c, c2.c, t),
    h: lerp(c1.h, c2.h, t)
  }
}

export function AsciiShaderBackground({ className = '' }: { className?: string }) {
  const canvasRef = useRef<HTMLCanvasElement | null>(null)

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

    const ctx = canvas.getContext('2d')
    if (!ctx) return

    let animationFrameId: number

    // Minimalistisches, ruhiges ASCII-Array
    const chars = ['•', '∘', '+', '▪', '▫', ' ']
    const fontSize = 18
    let cols = 0
    let rows = 0

    const mouse = { x: 0, y: 0, targetX: 0, targetY: 0 }
    let scrollProgress = 0
    let targetScrollProgress = 0

    const resize = () => {
      const width = window.innerWidth
      const height = window.innerHeight
      const dpr = window.devicePixelRatio || 1

      canvas.width = width * dpr
      canvas.height = height * dpr
      ctx.scale(dpr, dpr)

      cols = Math.ceil(width / fontSize)
      rows = Math.ceil(height / fontSize)

      if (mouse.x === 0 && mouse.y === 0) {
        mouse.x = width / 2
        mouse.y = height / 2
        mouse.targetX = width / 2
        mouse.targetY = height / 2
      }
    }

    const onPointerMove = (e: PointerEvent) => {
      mouse.targetX = e.clientX
      mouse.targetY = e.clientY
    }

    const onScroll = () => {
      const maxScroll = Math.max(
        document.body.scrollHeight - window.innerHeight,
        1
      )
      targetScrollProgress = Math.min(Math.max(window.scrollY / maxScroll, 0), 1)
    }

    resize()
    window.addEventListener('resize', resize)
    window.addEventListener('pointermove', onPointerMove)
    window.addEventListener('scroll', onScroll, { passive: true })

    const render = (time: number) => {
      mouse.x += (mouse.targetX - mouse.x) * 0.05
      mouse.y += (mouse.targetY - mouse.y) * 0.05
      scrollProgress += (targetScrollProgress - scrollProgress) * 0.05

      ctx.clearRect(0, 0, canvas.width, canvas.height)

      // Beim Scrollen sofort ausblenden (vollständig weg ab 150px Scroll-Tiefe)
      const scrollFade = Math.max(1 - (window.scrollY / 150), 0)
      if (scrollFade <= 0) {
        animationFrameId = requestAnimationFrame(render)
        return
      }

      // Scroll-gesteuerter Dimmer
      const scrollDimFactor = (1 - scrollProgress * 0.4) * scrollFade
      const currentDimColor = {
        ...BASE_DIM,
        l: BASE_DIM.l * scrollDimFactor
      }

      ctx.font = `${fontSize}px monospace`
      ctx.textAlign = 'center'
      ctx.textBaseline = 'middle'

      const timeSec = time * 0.001

      for (let r = 0; r < rows; r++) {
        for (let c = 0; c < cols; c++) {
          const x = c * fontSize + fontSize / 2
          const y = r * fontSize + fontSize / 2

          // Abstandsvektor zur gedämpften Mausposition
          const dx = x - mouse.x
          const dy = y - mouse.y
          const dist = Math.sqrt(dx * dx + dy * dy)

          // Maus-Störung (Vektorfeld-Ablenkung): Phase & Amplitude lokal beeinflussen
          const mouseInfluence = Math.exp(-dist / 250)
          const mouseDistortion = (Math.atan2(dy, dx) + (dx + dy) * 0.003) * mouseInfluence * 3.0

          // Diagonale 2D-Strömung / Wellen-Synthese aus Sinus & Kosinus
          const waveX = Math.sin(c * 0.08 + timeSec * 0.8 + mouseDistortion)
          const waveY = Math.cos(r * 0.08 + timeSec * 0.6 + mouseDistortion)
          const flowValue = Math.sin(waveX + waveY + (c + r) * 0.04 + timeSec * 0.4)

          // Zeichenauswahl basierend auf Strömungsfeld
          const normalizedFlow = (flowValue + 1) * 0.5 // Range 0..1
          const charIndex = Math.floor(normalizedFlow * chars.length) % chars.length
          const char = chars[charIndex]

          // Leerzeichen für ruhiges Raster überspringen
          if (char === ' ') continue

          // Helligkeits-Highlighting durch Maus-Störung und Wellenkamm
          const blendFactor = Math.min(Math.max(mouseInfluence * 0.85 + normalizedFlow * 0.15, 0), 1)
          const currentColor = lerpOKLCH(currentDimColor, HIGHLIGHT_BRIGHT, blendFactor)

          // Stärkerer Kontrast: min 0.35, max 0.95 Deckkraft
          const alpha = (0.35 + blendFactor * 0.6) * scrollDimFactor

          ctx.fillStyle = `oklch(${currentColor.l.toFixed(3)} ${currentColor.c.toFixed(3)} ${currentColor.h.toFixed(1)} / ${alpha.toFixed(2)})`
          ctx.fillText(char, x, y)
        }
      }

      animationFrameId = requestAnimationFrame(render)
    }

    animationFrameId = requestAnimationFrame(render)

    return () => {
      window.removeEventListener('resize', resize)
      window.removeEventListener('pointermove', onPointerMove)
      window.removeEventListener('scroll', onScroll)
      cancelAnimationFrame(animationFrameId)
    }
  }, [])

  return (
    <div
      className={`absolute top-0 left-0 right-0 h-[500px] z-0 overflow-hidden bg-background pointer-events-none ${className}`}
      style={{
        maskImage: 'linear-gradient(to bottom, rgba(0,0,0,1) 0%, rgba(0,0,0,1) 250px, rgba(0,0,0,0) 500px)',
        WebkitMaskImage: 'linear-gradient(to bottom, rgba(0,0,0,1) 0%, rgba(0,0,0,1) 250px, rgba(0,0,0,0) 500px)'
      }}
    >
      <canvas
        ref={canvasRef}
        className="absolute inset-0 w-full h-full block will-change-transform pointer-events-none"
      />
      <div
        className="absolute inset-0 w-full h-full pointer-events-none opacity-60"
        style={{
          backgroundSize: '40px 40px',
          backgroundImage: `
            linear-gradient(to right, oklch(0.31 0.012 148 / 0.4) 1px, transparent 1px),
            linear-gradient(to bottom, oklch(0.31 0.012 148 / 0.4) 1px, transparent 1px)
          `
        }}
      />
    </div>
  )
}