'use client'

import { useEffect, useState, type CSSProperties } from 'react'
import { PageBlockView, IntentBadge } from '@/components/interactive-page/page-blocks'
import { PageMd } from '@/components/interactive-page/page-md'
import { PageStickyNav } from '@/components/interactive-page/page-sticky-nav'
import type { PageSpecV1 } from '@/lib/interactive-page'
import { cn } from '@/lib/utils'

export type PageViewProps = {
  page: PageSpecV1
  /** interactive = hydrate demo players; static = final-state only (SSR/noscript) */
  demoMode?: 'interactive' | 'static'
  className?: string
  paper?: boolean
}

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

function useScrollReveal(enabled: boolean) {
  useEffect(() => {
    if (!enabled) {
      document
        .querySelectorAll<HTMLElement>('[data-scroll-init]')
        .forEach((el) => el.setAttribute('data-scroll-visible', 'true'))
      return
    }
    const nodes = Array.from(
      document.querySelectorAll<HTMLElement>('[data-scroll-init]')
    )
    const obs = new IntersectionObserver(
      (entries) => {
        for (const e of entries) {
          if (e.isIntersecting) {
            e.target.setAttribute('data-scroll-visible', 'true')
            obs.unobserve(e.target)
          }
        }
      },
      { rootMargin: '0px 0px -8% 0px', threshold: 0.12 }
    )
    nodes.forEach((n) => obs.observe(n))
    return () => obs.disconnect()
  }, [enabled])
}

/**
 * PageView — Kimi/AttnRes-style explainer page.
 * Design tokens replicated from the reference page (paper, plum accent,
 * mono labels, formula left-bar, stat cards) with dark-mode adaptation.
 */
export function PageView({
  page,
  demoMode = 'interactive',
  className,
  paper = true,
}: PageViewProps) {
  const reducedMotion = usePrefersReducedMotion()
  useScrollReveal(!reducedMotion)

  const paperStyle = {
    '--page-paper': paper ? 'var(--pp-paper)' : 'var(--background)',
  } as CSSProperties

  return (
    <article
      className={cn('interactive-page min-h-screen', paper && 'page-paper', className)}
      data-page-id={page.id}
      style={paperStyle}
    >
      <style>{`
        @media (prefers-reduced-motion: no-preference) {
          html { scroll-behavior: smooth; }
        }
        .interactive-page {
          --pp-paper: #F4F0E8;
          --pp-paper-deep: #EAE4D9;
          --pp-card: #FFFDF8;
          --pp-ink: #242422;
          --pp-muted: #686762;
          --pp-line: #D6D0C6;
          --pp-plum: #9F3F70;
          --pp-plum-soft: #F2DCE8;
          --pp-blue: #3F6F9F;
          --pp-mono: ui-monospace, "SF Mono", Menlo, Consolas, monospace;
          color: var(--pp-ink);
        }
        .dark .interactive-page {
          --pp-paper: #17140F;
          --pp-paper-deep: #201C15;
          --pp-card: #221E17;
          --pp-ink: #EDE7DB;
          --pp-muted: #A39C8D;
          --pp-line: #3B352A;
          --pp-plum: #D07AA6;
          --pp-plum-soft: #3A2530;
          --pp-blue: #7FA8CC;
        }
        .interactive-page.page-paper {
          background-color: var(--pp-paper);
          background-image: radial-gradient(
            color-mix(in oklab, var(--pp-ink) 7%, transparent) 0.7px,
            transparent 0.7px
          );
          background-size: 18px 18px;
        }
        .pp-card {
          background: var(--pp-card);
          border: 1px solid var(--pp-line);
          border-radius: 14px;
        }
        .pp-mono {
          font-family: var(--pp-mono);
        }
        .interactive-page [data-scroll-init]:not([data-scroll-visible]) {
          opacity: 0;
          transform: translateY(12px);
        }
        .interactive-page [data-scroll-init] {
          transition: opacity 420ms ease, transform 420ms ease;
          will-change: opacity, transform;
        }
        .interactive-page [data-scroll-visible] {
          opacity: 1;
          transform: none;
        }
        @media (prefers-reduced-motion: reduce) {
          .interactive-page [data-scroll-init] {
            opacity: 1 !important;
            transform: none !important;
            transition: none !important;
          }
        }
      `}</style>
      {/* Without JS the scroll-reveal never fires — show everything */}
      <noscript>
        <style>{`
          .interactive-page [data-scroll-init] {
            opacity: 1 !important;
            transform: none !important;
          }
        `}</style>
      </noscript>

      {/* ── Hero (kicker / 800 title / ink subtitle / mono meta) ── */}
      <header className="mx-auto max-w-[1100px] px-5 pb-8 pt-12 md:pt-16">
        <p
          className="pp-mono mb-2.5 text-xs uppercase"
          style={{ letterSpacing: '0.14em', color: 'var(--pp-plum)' }}
        >
          {page.hero.kicker}
        </p>
        <h1
          className="max-w-[22ch] font-extrabold leading-[1.14] tracking-[-0.015em]"
          style={{ fontSize: 'clamp(26px, 3.4vw, 44px)' }}
        >
          {page.hero.title}
        </h1>
        {page.hero.subtitle ? (
          <p
            className="mt-2.5 font-semibold"
            style={{ fontSize: 'clamp(16px, 1.6vw, 21px)' }}
          >
            {page.hero.subtitle}
          </p>
        ) : null}
        {page.hero.meta ? (
          <p
            className="pp-mono mt-3 leading-relaxed"
            style={{ fontSize: '12.5px', color: 'var(--pp-muted)' }}
          >
            {page.hero.meta}
          </p>
        ) : null}
      </header>

      <PageStickyNav page={page} />

      <div className="mx-auto max-w-[1100px] px-5 pb-24 pt-10">
        {/* ── One-minute overview ── */}
        {page.overview ? (
          <section className="pp-card mb-20 p-6 shadow-sm md:p-8" data-scroll-init>
            <p
              className="pp-mono mb-3 text-[11px] uppercase"
              style={{ letterSpacing: '0.14em', color: 'var(--pp-muted)' }}
            >
              {page.lang.startsWith('fr')
                ? 'L’essentiel en une minute'
                : 'One-minute overview'}
            </p>
            <PageMd
              md={page.overview.lead}
              className="max-w-[75ch] text-lg leading-relaxed [&_p]:my-0"
            />
            <div className="mt-5 grid gap-3.5 sm:grid-cols-2 lg:grid-cols-3">
              {page.overview.cards.map((card) => (
                <div
                  key={card.badge + card.title}
                  className="rounded-xl border p-4"
                  style={{
                    background: 'var(--pp-paper)',
                    borderColor: 'var(--pp-line)',
                  }}
                >
                  <IntentBadge label={card.badge} intent={card.intent} />
                  <h3 className="mt-3 text-base font-semibold tracking-tight">
                    {card.title}
                  </h3>
                  <PageMd
                    md={card.body}
                    className="mt-1.5 text-sm text-muted-foreground [&_p]:my-0"
                  />
                </div>
              ))}
            </div>
          </section>
        ) : null}

        {/* ── Sections ── */}
        <div className="space-y-20">
          {page.sections.map((section, i) => (
            <section
              key={section.id}
              id={section.id}
              className="scroll-mt-28"
              data-scroll-init
            >
              <h2 className="mb-6 flex items-baseline gap-3 text-2xl font-extrabold tracking-tight md:text-[28px]">
                <span
                  className="pp-mono text-sm font-semibold"
                  style={{ color: 'var(--pp-plum)' }}
                >
                  {String(i + 1).padStart(2, '0')}
                </span>
                {section.title}
              </h2>
              <div>
                {section.blocks.map((block, bi) => {
                  const narrow =
                    block.type === 'prose' ||
                    block.type === 'formula' ||
                    block.type === 'callout'
                  return (
                    <div
                      key={`${section.id}-${bi}`}
                      className={narrow ? 'max-w-[75ch]' : 'max-w-[880px]'}
                    >
                      <PageBlockView
                        block={block}
                        demoMode={demoMode}
                        lang={page.lang}
                      />
                    </div>
                  )
                })}
              </div>
            </section>
          ))}
        </div>

        {page.footer ? (
          <footer
            className="pp-mono mt-16 border-t pt-5 text-xs italic"
            style={{ borderColor: 'var(--pp-line)', color: 'var(--pp-muted)' }}
          >
            {page.footer}
          </footer>
        ) : null}
      </div>
    </article>
  )
}