"use client"

import { useEffect, useRef } from "react"

import {
  INTRO_CLASS,
  INTRO_END_EVENT,
  INTRO_STORAGE_KEY,
  isIntroRunning,
} from "@/modules/shared/lib/intro"

const COUNT_DURATION_MS = 1600
const CURTAIN_DURATION_MS = 1000
// The hero starts animating while the curtain is still moving up
const HERO_START_OFFSET_MS = 250

// Fast start, dramatic hold near 100
function easeCount(t: number) {
  return t < 0.7 ? (t / 0.7) * 0.86 : 0.86 + (1 - Math.pow(1 - (t - 0.7) / 0.3, 3)) * 0.14
}

export function Preloader() {
  const rootRef = useRef<HTMLDivElement>(null)
  const countRef = useRef<HTMLSpanElement>(null)
  const barRef = useRef<HTMLDivElement>(null)

  useEffect(() => {
    const root = rootRef.current
    if (!root || !isIntroRunning()) return

    const timers: number[] = []
    let frame = 0
    const start = performance.now()

    const finish = () => {
      root.dataset.state = "leaving"
      timers.push(
        window.setTimeout(() => {
          document.documentElement.classList.remove(INTRO_CLASS)
          try {
            sessionStorage.setItem(INTRO_STORAGE_KEY, "1")
          } catch {
            // Storage blocked: the intro simply plays again next time
          }
          window.dispatchEvent(new Event(INTRO_END_EVENT))
        }, HERO_START_OFFSET_MS),
        window.setTimeout(() => {
          root.dataset.state = "done"
        }, CURTAIN_DURATION_MS)
      )
    }

    const tick = (now: number) => {
      const t = Math.min((now - start) / COUNT_DURATION_MS, 1)
      const value = easeCount(t)
      if (countRef.current) {
        countRef.current.textContent = String(Math.round(value * 100)).padStart(3, "0")
      }
      if (barRef.current) barRef.current.style.scale = `${value} 1`

      if (t < 1) frame = requestAnimationFrame(tick)
      else finish()
    }

    frame = requestAnimationFrame(tick)

    return () => {
      cancelAnimationFrame(frame)
      timers.forEach(window.clearTimeout)
    }
  }, [])

  return (
    <div
      ref={rootRef}
      aria-hidden="true"
      className="preloader fixed inset-0 z-[var(--z-preloader)] flex-col justify-between bg-black p-gutter text-white"
    >
      <div className="flex items-start justify-between font-mono text-label text-ink-400">
        <span>Digitalagentur</span>
        <span>Steinfurt, DE</span>
      </div>

      <p className="self-center font-mono text-2xl sm:text-4xl">
        <span className="text-ink-500">&lt;</span>since3
        <span className="text-ink-500">&gt;</span>
      </p>

      <div className="flex flex-col gap-4">
        <div className="flex items-end justify-between">
          <span className="font-mono text-label text-ink-400">Lädt Erlebnis</span>
          <span
            ref={countRef}
            className="text-mega leading-none tabular-nums type-poster"
          >
            000
          </span>
        </div>
        <div className="h-px w-full bg-white/15">
          <div ref={barRef} className="h-full origin-left bg-white [scale:0_1]" />
        </div>
      </div>
    </div>
  )
}