'use client';

import { useEffect, useRef } from 'react';
import { motion } from 'framer-motion';
import { Wordmark } from '@/components/primitives/Wordmark';
import { fadeInUp } from '@/lib/motion';

// One exchange of the page's conversation: the reader's situation, then what
// creeer does about it. The answer arrives as you scroll into the pair — its
// gold rule draws down and the block comes up to full contrast — so the section
// reads as being answered rather than as a list that happens to have answers.
//
// The sides never swap from one pair to the next. Each voice keeps its own
// margin, the way a conversation reads on a page; what alternates going down is
// situación → respuesta, not left → right. Flipping sides per pair would cost
// the reader the one cue that tells them who is speaking.
//
// Three cues carry that distinction, never colour alone: the speaker label, the
// column, and the rule hanging off each block.
//
// The answer text is in the DOM at all times, at every breakpoint — opacity,
// never `display: none` or `hidden`, so screen readers still announce it and
// the static export still ships it to search engines.
//
// `activo` latches: the section turns it on when the reader reaches the pair
// and never turns it off again. An answer that faded back out once you scrolled
// past would leave the page emptier the further you read, and would re-create
// the failure this project has already hit twice — content stranded at opacity
// zero with every test green, because jsdom has no layout and no scrolling.
//
// No motion.li here on purpose: Framer propagates variants through React
// context, so the two motion.div children still inherit the stagger from the
// <ul> the section wraps them in, even across this plain <li>.

export function ParDialogo({
  n,
  name,
  situacion,
  respuesta,
  activo,
  reducido,
  onActivar,
}: {
  n: number;
  name: string;
  situacion: string;
  respuesta: string;
  activo: boolean;
  reducido: boolean;
  onActivar: (n: number) => void;
}) {
  const ref = useRef<HTMLLIElement>(null);

  // The pair crossing the middle of the viewport is the one being answered.
  // The negative margins collapse the root to a band across the centre, so
  // "in view" means "where the reader is actually looking", not "anywhere on
  // screen" — which with six pairs would fire all of them at once.
  useEffect(() => {
    const el = ref.current;
    if (!el || reducido) return;
    const observer = new IntersectionObserver(
      ([entrada]) => {
        if (entrada.isIntersecting) onActivar(n);
      },
      { rootMargin: '-45% 0px -45% 0px' },
    );
    observer.observe(el);
    return () => observer.disconnect();
  }, [n, reducido, onActivar]);

  // Reduced motion gets the resolved state outright: everything at full
  // contrast, every rule drawn. Never the dimmed half of an animation that
  // will not run.
  const resuelto = reducido || activo;

  return (
    <li
      ref={ref}
      data-activo={resuelto ? 'true' : 'false'}
      onMouseEnter={() => onActivar(n)}
      onFocus={() => onActivar(n)}
      className="grid gap-5 md:grid-cols-2 md:gap-12"
    >
      {/* Two nested layers on purpose, and they must stay nested. Framer writes
          the resolved variant into the inline `style` — `opacity: 1` — and an
          inline style beats a Tailwind class. Putting the reveal on the same
          element as `variants` looked right in the markup and did nothing in the
          browser: the answers were readable from the moment the section entered,
          and only the gold rule, a transform Framer never touches, animated.
          So: motion.div owns the entrance, the plain child owns the reveal. */}
      <motion.div variants={fadeInUp}>
        <div
          className={`border-l-2 border-azul-profundo/25 pl-5 transition-opacity duration-500 motion-reduce:transition-none ${
            resuelto ? 'opacity-100' : 'opacity-55'
          }`}
        >
          <p className="text-xs font-black uppercase tracking-[0.2em] text-dorado">
            {String(n).padStart(2, '0')} · {name}
          </p>
          <p className="mt-3 font-sans font-bold text-xl md:text-2xl text-azul-profundo leading-snug">
            «{situacion}»
          </p>
        </div>
      </motion.div>

      <motion.div variants={fadeInUp} className="md:mt-10">
        <div
          tabIndex={0}
          aria-label={`Respuesta de creeer a: ${name}`}
          className={`relative pl-5 transition-opacity duration-500 motion-reduce:transition-none ${
            resuelto ? 'opacity-100' : 'opacity-0'
          }`}
        >
          {/* The rule draws itself down as the answer arrives. A transform, not
              a stroke: a dash pattern on a non-uniformly scaled SVG is exactly
              what broke the hilo conductor, and this has to survive any
              container it lands in. */}
          <span
            aria-hidden="true"
            className={`absolute left-0 top-0 h-full w-0.5 bg-dorado origin-top transition-transform duration-700 ease-out motion-reduce:transition-none ${
              resuelto ? 'scale-y-100' : 'scale-y-0'
            }`}
          />
          <Wordmark size="sm" />
          <p className="mt-3 text-gris-medio leading-relaxed">{respuesta}</p>
        </div>
      </motion.div>
    </li>
  );
}