'use client'

import { useEffect, useRef, useState } from 'react'
import { ArrowDown, ArrowLeft, ArrowRight, ArrowUp, CornerDownLeft, Sparkles } from 'lucide-react'

/**
 * A three-up feature carousel on a ruled grid.
 *
 * Same scroll-snap mechanics as the two-up variant — see the note there for why
 * it is not a transform track. The difference is the framing: dashed vertical
 * rules run the full height of the row, so the cells read as panels cut out of
 * a sheet rather than as cards floating on it.
 */

function useReducedMotion() {
  const [reduce, setReduce] = useState(false)
  useEffect(() => {
    const mq = window.matchMedia('(prefers-reduced-motion: reduce)')
    setReduce(mq.matches)
    const onChange = () => setReduce(mq.matches)
    mq.addEventListener('change', onChange)
    return () => mq.removeEventListener('change', onChange)
  }, [])
  return reduce
}

const SUGGESTIONS = [
  { text: '…authentication with OAuth 2.0?', hint: true },
  { text: '…a dark mode toggle in React?' },
  { text: '…caching for API responses?' },
]

function CompletionMock() {
  return (
    <div className="w-full max-w-[19rem]">
      <div className="rounded-xl border border-gray-200 bg-white px-3.5 py-3 shadow-[0_1px_2px_rgb(15_23_42_/_0.05)] dark:border-white/10 dark:bg-gray-900">
        <p className="text-[13.5px] text-gray-900 dark:text-white">
          How do I implement
          {/* A caret drawn as a box, so there is no animation to distract and no
              blinking element for anyone sensitive to motion. */}
          <span
            aria-hidden
            className="ml-0.5 inline-block h-[1.05em] w-px translate-y-[0.15em] bg-gray-900 dark:bg-white"
          />
        </p>
      </div>

      <div className="mt-2 overflow-hidden rounded-xl border border-gray-200 bg-white shadow-[0_12px_32px_-12px_rgb(15_23_42_/_0.18)] dark:border-white/10 dark:bg-gray-900">
        <p className="flex items-center gap-2 bg-indigo-50/70 px-3.5 py-2.5 text-[12.5px] font-semibold text-indigo-700 dark:bg-indigo-500/10 dark:text-indigo-300">
          <Sparkles aria-hidden="true" className="size-3.5" />
          AI Suggestions
        </p>
        <ul className="divide-y divide-gray-100 dark:divide-white/[0.06]">
          {SUGGESTIONS.map((s) => (
            <li
              key={s.text}
              className="flex items-center justify-between gap-3 px-3.5 py-2.5 text-[13px] text-gray-700 dark:text-gray-300"
            >
              {s.text}
              {s.hint && (
                <span className="inline-flex shrink-0 items-center gap-1 rounded-md border border-gray-200 px-1.5 py-0.5 font-mono text-[10.5px] text-gray-500 dark:border-white/15 dark:text-gray-400">
                  <CornerDownLeft aria-hidden="true" className="size-3" />
                  Tab
                </span>
              )}
            </li>
          ))}
        </ul>
      </div>

      <div className="mt-2.5 flex items-center justify-between text-[12px] text-gray-500 dark:text-gray-400">
        <span>3 suggestions</span>
        <span className="flex items-center gap-1.5">
          <Key>
            <ArrowUp aria-hidden="true" className="size-3" />
          </Key>
          <Key>
            <ArrowDown aria-hidden="true" className="size-3" />
          </Key>
          to navigate
        </span>
      </div>
    </div>
  )
}

function Key({ children }: { children: React.ReactNode }) {
  return (
    <span className="inline-flex size-[18px] items-center justify-center rounded border border-gray-200 text-gray-500 dark:border-white/15 dark:text-gray-400">
      {children}
    </span>
  )
}

function UsageMock() {
  return (
    <div className="w-full max-w-[19rem] rounded-2xl border border-gray-200 bg-white p-4 shadow-[0_12px_32px_-12px_rgb(15_23_42_/_0.18)] dark:border-white/10 dark:bg-gray-900">
      <p className="text-[14px] font-semibold text-gray-900 dark:text-white">Usage</p>

      <div className="mt-3 rounded-xl border border-gray-200 p-4 dark:border-white/10">
        <div className="flex items-baseline justify-between gap-3">
          <p className="text-[14px] font-semibold text-gray-900 dark:text-white">
            User prompt tokens
          </p>
          <p className="text-[13px] font-semibold text-gray-900 tabular-nums dark:text-white">
            43%
          </p>
        </div>
        <p className="mt-1.5 text-[12.5px]/[1.5] text-gray-500 dark:text-gray-400">
          Using a premium model costs one prompt credit per use.
        </p>

        <div className="mt-3 h-1.5 overflow-hidden rounded-full bg-gray-100 dark:bg-white/10">
          <div className="h-full w-[43%] rounded-full bg-gradient-to-r from-emerald-400 to-sky-400" />
        </div>
        <div className="mt-2 flex items-baseline justify-between text-[12px]">
          <span className="text-gray-500 tabular-nums dark:text-gray-400">
            550 / 1,500 tokens
          </span>
          <span className="font-semibold text-emerald-600 tabular-nums dark:text-emerald-400">
            950 left
          </span>
        </div>

        {/* Clipped by the panel, which implies the list continues. A fade would
            need a background colour that breaks in dark mode; overflow does not. */}
        <div className="mt-3 grid grid-cols-2 gap-2.5">
          {[
            ['Est. Cost', '$0.25'],
            ['Requests', '48'],
          ].map(([label, value]) => (
            <div
              key={label}
              className="rounded-lg border border-gray-200 px-3 py-2 dark:border-white/10"
            >
              <p className="text-[11.5px] text-gray-400 dark:text-gray-500">{label}</p>
              <p className="text-[13px] font-semibold text-gray-900 tabular-nums dark:text-white">
                {value}
              </p>
            </div>
          ))}
        </div>
      </div>
    </div>
  )
}

function TranslationMock() {
  return (
    <div className="w-full max-w-[19rem]">
      <p className="text-[13.5px]/[1.6] text-gray-300 dark:text-gray-600">
        Corporis voluptates voluptatem atque excepturi, tempore dolor distinctio libero
        dicta vel, nihil rem consequatur esse aspernatur nostrum.
      </p>
      <p className="mt-3 text-[13.5px] font-medium text-indigo-600 dark:text-indigo-400">
        Auto translated from English
      </p>
      <div className="mt-2.5 rounded-xl border border-indigo-200 bg-white p-4 shadow-[0_12px_32px_-12px_rgb(79_70_229_/_0.22)] dark:border-indigo-500/30 dark:bg-gray-900">
        <p className="text-[12px] text-gray-500 dark:text-gray-400">Spanish</p>
        <p className="mt-1.5 text-[13.5px]/[1.6] text-gray-900 dark:text-white">
          Hola, ¿cómo puedo ayudarte hoy? Estoy aquí para responder cualquier pregunta que
          tengas sobre nuestros servicios y productos.
        </p>
      </div>
    </div>
  )
}

const SLIDES = [
  {
    mock: <CompletionMock />,
    lead: 'Intelligent code completion',
    body: 'that understands your codebase and suggests context-aware snippets.',
  },
  {
    mock: <UsageMock />,
    lead: 'Usage analytics',
    body: 'with detailed token tracking, cost estimation, and budget alerts.',
  },
  {
    mock: <TranslationMock />,
    lead: 'Real-time translation',
    body: 'across 50+ languages with natural-sounding output and dialect support.',
  },
  {
    mock: <CompletionMock />,
    lead: 'Inline refactors',
    body: 'proposed as a diff you accept or reject, never applied behind your back.',
  },
]

export default function CarouselThreeUp({
  title = 'Build modern AI\ndevelopment tools',
}: {
  title?: string
}) {
  const trackRef = useRef<HTMLDivElement>(null)
  const [atStart, setAtStart] = useState(true)
  const [atEnd, setAtEnd] = useState(false)
  const reduce = useReducedMotion()

  function sync() {
    const el = trackRef.current
    if (!el) return
    setAtStart(el.scrollLeft <= 2)
    setAtEnd(el.scrollLeft + el.clientWidth >= el.scrollWidth - 2)
  }

  useEffect(() => {
    sync()
    const onResize = () => sync()
    window.addEventListener('resize', onResize)
    return () => window.removeEventListener('resize', onResize)
  }, [])

  function page(direction: 1 | -1) {
    const el = trackRef.current
    if (!el) return
    const card = el.firstElementChild as HTMLElement | null
    const step = card ? card.offsetWidth : el.clientWidth
    el.scrollBy({ left: direction * step, behavior: reduce ? 'auto' : 'smooth' })
  }

  return (
    <section className="bg-white py-20 sm:py-28 dark:bg-gray-950">
      <div className="mx-auto max-w-7xl px-6">
        <div className="flex items-start justify-between gap-8">
          <h2 className="max-w-xl text-[2rem] leading-[1.1] font-semibold tracking-[-0.025em] whitespace-pre-line text-gray-900 sm:text-[3rem] dark:text-white">
            {title}
          </h2>
          <div className="hidden shrink-0 items-center gap-2 pt-3 sm:flex">
            <ArrowButton label="Previous features" disabled={atStart} onClick={() => page(-1)}>
              <ArrowLeft aria-hidden="true" className="size-4" />
            </ArrowButton>
            <ArrowButton label="Next features" disabled={atEnd} onClick={() => page(1)}>
              <ArrowRight aria-hidden="true" className="size-4" />
            </ArrowButton>
          </div>
        </div>
      </div>

      {/* The ruled band is full-bleed and the track sits inside it, so the dashed
          rules read as part of the page rather than as cell borders. */}
      <div className="mt-14 border-y border-dashed border-gray-200 dark:border-white/10">
        <div className="mx-auto max-w-7xl">
          <div
            ref={trackRef}
            onScroll={sync}
            className="flex snap-x snap-mandatory overflow-x-auto [-ms-overflow-style:none] [scrollbar-width:none] [&::-webkit-scrollbar]:hidden"
          >
            {SLIDES.map((slide, i) => (
              <article
                key={i}
                className="flex w-[88%] shrink-0 snap-start flex-col border-r border-dashed border-gray-200 px-6 py-10 sm:w-1/2 lg:w-1/3 dark:border-white/10"
              >
                {/* The product mock is a drawing of an app, not an app: fake rows,
                invented dates, no behaviour. aria-hidden so a screen reader does
                not read the chrome out as page content, and so its deliberately
                low-contrast styling stops being a text-contrast failure. Nothing
                inside is focusable, which is what makes hiding it safe. */}
                <div aria-hidden="true" className="flex min-h-[15rem] flex-1 items-start">{slide.mock}</div>
                <p className="mt-10 text-[15px]/[1.6] text-gray-500 dark:text-gray-400">
                  <span className="font-semibold text-gray-900 dark:text-white">
                    {slide.lead}
                  </span>{' '}
                  {slide.body}
                </p>
              </article>
            ))}
          </div>
        </div>
      </div>
    </section>
  )
}

function ArrowButton({
  label,
  disabled,
  onClick,
  children,
}: {
  label: string
  disabled: boolean
  onClick: () => void
  children: React.ReactNode
}) {
  return (
    <button
      type="button"
      onClick={onClick}
      disabled={disabled}
      aria-label={label}
      className="inline-flex size-11 items-center justify-center rounded-full border border-gray-200 bg-white text-gray-700 shadow-[0_1px_2px_rgb(15_23_42_/_0.06)] transition-all duration-200 hover:bg-gray-50 active:scale-[0.96] disabled:pointer-events-none disabled:opacity-35 dark:border-white/15 dark:bg-white/5 dark:text-gray-200 dark:hover:bg-white/10"
    >
      {children}
    </button>
  )
}
Feature Sections

Three column with icons

Alternating with screenshots

With feature tabs

Carousel, two up

Carousel, three up

Expandable with tabbed card

Tabbed split panels

Expandable pills with diagram

Headline with inline icons
